module: exports not exported for null resolutions

PR-URL: #32838
Reviewed-By: Jan Krems <jan.krems@gmail.com>

Author: guybedford

doc/api/esm.md

@@ -1661,13 +1661,15 @@ The resolver can throw the following errors:
 > loop on any _Package Path Not Exported_ error.
 > 1. Throw a _Package Path Not Exported_ error.
 > 1. Otherwise, if _target_ is an Array, then
-> 1. If _target.length is zero, throw an _Invalid Package Target_ error.
+> 1. If _target.length is zero, throw a _Package Path Not Exported_ error.
 > 1. For each item _targetValue_ in _target_, do
 > 1. If _targetValue_ is an Array, continue the loop.
 > 1. Return the result of **PACKAGE_EXPORTS_TARGET_RESOLVE**(_packageURL_,
 > _targetValue_, _subpath_, _env_), continuing the loop on any
 > _Package Path Not Exported_ or _Invalid Package Target_ error.
 > 1. Throw the last fallback resolution error.
+> 1. Otherwise, if _target_ is _null_, throw a _Package Path Not Exported_
+> error.
 > 1. Otherwise throw an _Invalid Package Target_ error.
 
 **ESM_FORMAT**(_url_)

lib/internal/modules/cjs/loader.js

@@ -552,21 +552,22 @@ function resolveExportsTarget(baseUrl, target, subpath, mappingKey) {
 ,0,-1),mappingKey);
 }elseif(ArrayIsArray(target)){
 if(target.length===0)
-thrownewERR_INVALID_PACKAGE_TARGET(StringPrototypeSlice(baseUrl.pathname
-,0,-1),mappingKey,subpath,target);
+thrownewERR_PACKAGE_PATH_NOT_EXPORTED(
+StringPrototypeSlice(baseUrl.pathname,0,-1),mappingKey+subpath);
+letlastException;
 for(consttargetValueoftarget){
 try{
 returnresolveExportsTarget(baseUrl,targetValue,subpath,mappingKey);
 }catch(e){
+lastException=e;
 if(e.code!=='ERR_PACKAGE_PATH_NOT_EXPORTED'&&
 e.code!=='ERR_INVALID_PACKAGE_TARGET')
 throwe;
 }
 }
 // Throw last fallback error
-resolveExportsTarget(baseUrl,target[target.length-1],subpath,
-mappingKey);
-assert(false);
+assert(lastException!==undefined);
+throwlastException;
 }elseif(typeoftarget==='object'&&target!==null){
 constkeys=ObjectKeys(target);
 if(keys.some(isArrayIndex)){
@@ -595,6 +596,9 @@ function resolveExportsTarget(baseUrl, target, subpath, mappingKey) {
 }
 thrownewERR_PACKAGE_PATH_NOT_EXPORTED(
 StringPrototypeSlice(baseUrl.pathname,0,-1),mappingKey+subpath);
+}elseif(target===null){
+thrownewERR_PACKAGE_PATH_NOT_EXPORTED(
+StringPrototypeSlice(baseUrl.pathname,0,-1),mappingKey+subpath);
 }
 thrownewERR_INVALID_PACKAGE_TARGET(
 StringPrototypeSlice(baseUrl.pathname,0,-1),mappingKey,subpath,target);

lib/internal/modules/esm/resolve.js

@@ -16,7 +16,7 @@ const {
  StringPrototypeStartsWith,
  StringPrototypeSubstr,
 }=primordials;
-
+constassert=require('internal/assert');
 constinternalFS=require('internal/fs/utils');
 const{ NativeModule }=require('internal/bootstrap/loaders');
 const{
@@ -345,7 +345,7 @@ function resolveExportsTarget(
 returnfinalizeResolution(resolved,base);
 }elseif(ArrayIsArray(target)){
 if(target.length===0)
-throwExportsInvalid(packageSubpath,target,packageJSONUrl,base);
+throwExportsNotFound(packageSubpath,packageJSONUrl,base);
 
 letlastException;
 for(leti=0;i<target.length;i++){
@@ -366,6 +366,7 @@ function resolveExportsTarget(
 
 returnfinalizeResolution(resolved,base);
 }
+assert(lastException!==undefined);
 throwlastException;
 }elseif(typeoftarget==='object'&&target!==null){
 constkeys=ObjectGetOwnPropertyNames(target);
@@ -392,6 +393,8 @@ function resolveExportsTarget(
 }
 }
 throwExportsNotFound(packageSubpath,packageJSONUrl,base);
+}elseif(target===null){
+throwExportsNotFound(packageSubpath,packageJSONUrl,base);
 }
 throwExportsInvalid(packageSubpath,target,packageJSONUrl,base);
 }

test/es-module/test-esm-exports.mjs

@@ -64,6 +64,11 @@ import fromInside from '../fixtures/node_modules/pkgexports/lib/hole.js';
 // Conditional exports with no match are "not exported" errors
 ['pkgexports/invalid1','./invalid1'],
 ['pkgexports/invalid4','./invalid4'],
+// Null mapping
+['pkgexports/null','./null'],
+['pkgexports/null/subpath','./null/subpath'],
+// Empty fallback
+['pkgexports/nofallback1','./nofallback1'],
 ]);
 
 constinvalidExports=newMap([
@@ -74,13 +79,11 @@ import fromInside from '../fixtures/node_modules/pkgexports/lib/hole.js';
 ['pkgexports/belowdir/pkgexports/asdf.js','./belowdir/'],
 // This target file steps below the package
 ['pkgexports/belowfile','./belowfile'],
-// Invalid target handling
-['pkgexports/null','./null'],
+// Invalid targets
 ['pkgexports/invalid2','./invalid2'],
 ['pkgexports/invalid3','./invalid3'],
 ['pkgexports/invalid5','invalid5'],
 // Missing / invalid fallbacks
-['pkgexports/nofallback1','./nofallback1'],
 ['pkgexports/nofallback2','./nofallback2'],
 // Reaching into nested node_modules
 ['pkgexports/nodemodules','./nodemodules'],