fix(esbuild): Avoid warning when entry point has no default export#901

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fix(esbuild): Avoid warning when entry point has no default export #901

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70c696b
fix(esbuild): Avoid "Import 'default' will always be undefined" warning
queelius Mar 25, 2026
71b4e79
style: Fix formatting in esbuild default export warning test
queelius Mar 25, 2026
98321cb
Merge branch 'main' into fix/747-esbuild-default-export-warning
timfish Mar 28, 2026
2bec1be
Merge branch 'main' into fix/747-esbuild-default-export-warning
timfish Apr 20, 2026
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9 changes: 7 additions & 2 deletions packages/esbuild-plugin/src/index.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
return {
loader: "js",
pluginName,
// We wrap the default export access in a function call to prevent esbuild's
// static analysis from generating an "Import 'default' will always be undefined"
// warning when the original module has no default export. The function wrapper
// is transparent and correctly forwards the default export when it exists.
contents: `
import "_sentry-debug-id-injection-stub";
import * as OriginalModule from ${JSON.stringify(originalPath)};
export default OriginalModule.default;
import * as _sentry_original_module from ${JSON.stringify(originalPath)};
var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
export { _sentry_default_export as default };
export * from ${JSON.stringify(originalPath)};`,
resolveDir: originalResolveDir,
};
Expand Down
134 changes: 134 additions & 0 deletions packages/esbuild-plugin/test/no-default-export-warning.test.ts
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
let tmpDir: string;

beforeAll(() => {
tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
});

afterAll(() => {
fs.rmSync(tmpDir, { recursive: true, force: true });
Comment on lines +9 to +16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change
lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}

Copilot uses AI. Check for mistakes.
});

it("should build successfully without warnings when entry point has no default export", async () => {
const inputFile = path.join(tmpDir, "no-default.ts");
fs.writeFileSync(
inputFile,
[
'import * as path from "path";',
'console.log("No default export here", path.sep);',
"",
].join("\n")
);

const outDir = path.join(tmpDir, "out-no-default");
const result = await esbuild.build({
entryPoints: [inputFile],
sourcemap: true,
bundle: true,
outdir: outDir,
platform: "node",
plugins: [
sentryEsbuildPlugin({
telemetry: false,
release: { name: "test-release", create: false },
}),
],
write: true,
});

// If esbuild version is new enough, warnings about "Import 'default' will always be
// undefined" will be captured in result.warnings. On older esbuild versions this array
// may be empty regardless, so the test at least verifies no build errors occur.
const importUndefinedWarnings = (result.warnings || []).filter(
(w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
);

expect(importUndefinedWarnings).toHaveLength(0);
});

it("should preserve default export when the entry point has one", async () => {
const inputFile = path.join(tmpDir, "with-default.ts");
fs.writeFileSync(
inputFile,
["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
"\n"
)
);

const outDir = path.join(tmpDir, "out-with-default");
const result = await esbuild.build({
entryPoints: [inputFile],
sourcemap: true,
bundle: true,
outdir: outDir,
platform: "node",
format: "esm",
plugins: [
sentryEsbuildPlugin({
telemetry: false,
release: { name: "test-release", create: false },
}),
],
write: true,
});

// Should produce no warnings
const importUndefinedWarnings = (result.warnings || []).filter(
(w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
);
expect(importUndefinedWarnings).toHaveLength(0);

// Verify the output contains the default export function
const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
expect(outputFiles.length).toBeGreaterThan(0);

const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
expect(outputContent).toContain("main");
});

it("should preserve named exports when the entry point has no default export", async () => {
const inputFile = path.join(tmpDir, "named-only.ts");
fs.writeFileSync(
inputFile,
["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
);

const outDir = path.join(tmpDir, "out-named-only");
const result = await esbuild.build({
entryPoints: [inputFile],
sourcemap: true,
bundle: true,
outdir: outDir,
platform: "node",
format: "esm",
plugins: [
sentryEsbuildPlugin({
telemetry: false,
release: { name: "test-release", create: false },
}),
],
write: true,
});

// Should produce no warnings
const importUndefinedWarnings = (result.warnings || []).filter(
(w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
);
expect(importUndefinedWarnings).toHaveLength(0);

// Verify the output contains the named exports
const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
expect(outputFiles.length).toBeGreaterThan(0);

const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
expect(outputContent).toContain("foo");
expect(outputContent).toContain("bar");
});
});
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fix(esbuild): Avoid warning when entry point has no default export#901

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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
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if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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fix(esbuild): Avoid warning when entry point has no default export#901

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#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

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+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
fix(esbuild): Avoid warning when entry point has no default export#901

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queelius
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4
commits into

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Choose a base branch

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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(esbuild): Avoid warning when entry point has no default export#901

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 Open

queelius
wants to merge
4
commits into

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Choose a base branch

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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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The reason will be displayed to describe this comment to others. Learn more.

afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
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fix(esbuild): Avoid warning when entry point has no default export#901

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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
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if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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fix(esbuild): Avoid warning when entry point has no default export#901

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 Open

queelius
wants to merge
4
commits into

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Choose a base branch

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+141

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fix(esbuild): Avoid warning when entry point has no default export
#901
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70c696b

fix(esbuild): Avoid "Import 'default' will always be undefined" warning


queelius Mar 25, 2026
71b4e79

style: Fix formatting in esbuild default export warning test


queelius Mar 25, 2026
98321cb

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Mar 28, 2026
2bec1be

Merge branch 'main' into fix/747-esbuild-default-export-warning


timfish Apr 20, 2026

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9 changes: 7 additions & 2 deletions
packages/esbuild-plugin/src/index.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,10 +253,15 @@ export function sentryEsbuildPlugin(userOptions: Options = {}): any {
 return {
 loader: "js",
 pluginName,
 // We wrap the default export access in a function call to prevent esbuild's
 // static analysis from generating an "Import 'default' will always be undefined"
 // warning when the original module has no default export. The function wrapper
 // is transparent and correctly forwards the default export when it exists.
 contents: `
 import "_sentry-debug-id-injection-stub";
 import * as OriginalModule from ${JSON.stringify(originalPath)};
 export default OriginalModule.default;
 import * as _sentry_original_module from ${JSON.stringify(originalPath)};
 var _sentry_default_export = (function(m) { return m.default; })(_sentry_original_module);
 export { _sentry_default_export as default };
 export * from ${JSON.stringify(originalPath)};`,
 resolveDir: originalResolveDir,
 };
Expand Down

134 changes: 134 additions & 0 deletions
packages/esbuild-plugin/test/no-default-export-warning.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,134 @@
import { sentryEsbuildPlugin } from "../src";
import { describe, it, expect, beforeAll, afterAll } from "vitest";
import * as esbuild from "esbuild";
import * as path from "path";
import * as fs from "fs";
import * as os from "os";

describe("esbuild proxy module default export handling", () => {
 let tmpDir: string;

 beforeAll(() => {
 tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "sentry-esbuild-test-"));
 });

 afterAll(() => {
 fs.rmSync(tmpDir, { recursive: true, force: true });

Comment on lines

+9
 to 
+16

CopilotAIMar 25, 2026

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afterAll unconditionally calls fs.rmSync(tmpDir, ...) but tmpDir is only set in beforeAll. If beforeAll fails (or a test is skipped before initialization), the cleanup can throw and mask the original failure. Consider guarding the cleanup (e.g., only remove when tmpDir is set/existing).

Suggested change

lettmpDir: string;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
fs.rmSync(tmpDir,{recursive: true,force: true});
lettmpDir: string|undefined;
beforeAll(()=>{
tmpDir=fs.mkdtempSync(path.join(os.tmpdir(),"sentry-esbuild-test-"));
});
afterAll(()=>{
if(tmpDir){
fs.rmSync(tmpDir,{recursive: true,force: true});
}
Copilot uses AI. Check for mistakes.

 });

 it("should build successfully without warnings when entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "no-default.ts");
 fs.writeFileSync(
 inputFile,
 [
 'import * as path from "path";',
 'console.log("No default export here", path.sep);',
 "",
 ].join("\n")
 );

 const outDir = path.join(tmpDir, "out-no-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // If esbuild version is new enough, warnings about "Import 'default' will always be
 // undefined" will be captured in result.warnings. On older esbuild versions this array
 // may be empty regardless, so the test at least verifies no build errors occur.
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );

 expect(importUndefinedWarnings).toHaveLength(0);
 });

 it("should preserve default export when the entry point has one", async () => {
 const inputFile = path.join(tmpDir, "with-default.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export default function main() { return "hello"; }', ""].join(
 "\n"
 )
 );

 const outDir = path.join(tmpDir, "out-with-default");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the default export function
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("main");
 });

 it("should preserve named exports when the entry point has no default export", async () => {
 const inputFile = path.join(tmpDir, "named-only.ts");
 fs.writeFileSync(
 inputFile,
 ["export const foo = 42;", 'export const bar = "hello";', ""].join("\n")
 );

 const outDir = path.join(tmpDir, "out-named-only");
 const result = await esbuild.build({
 entryPoints: [inputFile],
 sourcemap: true,
 bundle: true,
 outdir: outDir,
 platform: "node",
 format: "esm",
 plugins: [
 sentryEsbuildPlugin({
 telemetry: false,
 release: { name: "test-release", create: false },
 }),
 ],
 write: true,
 });

 // Should produce no warnings
 const importUndefinedWarnings = (result.warnings || []).filter(
 (w) => w.text.includes("Import") && w.text.includes("default") && w.text.includes("undefined")
 );
 expect(importUndefinedWarnings).toHaveLength(0);

 // Verify the output contains the named exports
 const outputFiles = fs.readdirSync(outDir).filter((f) => f.endsWith(".js"));
 expect(outputFiles.length).toBeGreaterThan(0);

 const outputContent = fs.readFileSync(path.join(outDir, outputFiles[0] as string), "utf-8");
 expect(outputContent).toContain("foo");
 expect(outputContent).toContain("bar");
 });
});
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