repl: fix overzealous top-level await

Fixes: #43777
PR-URL: #43827
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: tniessen

lib/internal/repl/await.js

@@ -237,8 +237,16 @@ function processTopLevelAwait(src) {
 // semicolon. Since there can only be more right parentheses between
 // node.expression.end and the semicolon, appending one more to
 // node.expression should be fine.
-state.prepend(node,'return (');
-state.append(node.expression,')');
+//
+// We also create a wrapper object around the result of the expression.
+// Consider an expression of the form `(await x).y`. If we just return
+// this expression from an async function, the caller will await `y`, too,
+// if it evaluates to a Promise. Instead, we return
+// `{ value: ((await x).y) }`, which allows the caller to retrieve the
+// awaited value correctly.
+state.prepend(node.expression,'{ value: (');
+state.prepend(node,'return ');
+state.append(node.expression,') }');
 }
 break;
 }

lib/repl.js

@@ -616,7 +616,7 @@ function REPLServer(prompt,
 
 (async()=>{
 try{
-constresult=awaitpromise;
+constresult=(awaitpromise)?.value;
 finishExecution(null,result);
 }catch(err){
 if(err&&process.domain){

test/parallel/test-repl-preprocess-top-level-await.js

@@ -17,25 +17,25 @@ const testCases = [
 ['0',
 null],
 ['await 0',
-'(async () => { return (await 0) })()'],
+'(async () => { return { value: (await 0) } })()'],
 [`await ${surrogate}`,
-`(async () => { return (await ${surrogate}) })()`],
+`(async () => { return { value: (await ${surrogate}) } })()`],
 ['await 0;',
-'(async () => { return (await 0); })()'],
+'(async () => { return { value: (await 0) }; })()'],
 ['await 0;;;',
-'(async () => { return (await 0);;; })()'],
+'(async () => { return { value: (await 0) };;; })()'],
 [`await ${surrogate};`,
-`(async () => { return (await ${surrogate}); })()`],
+`(async () => { return { value: (await ${surrogate}) }; })()`],
 [`await ${surrogate};`,
-`(async () => { return (await ${surrogate}); })()`],
+`(async () => { return { value: (await ${surrogate}) }; })()`],
 ['(await 0)',
-'(async () => { return ((await 0)) })()'],
+'(async () => { return ({ value: (await 0) }) })()'],
 [`(await ${surrogate})`,
-`(async () => { return ((await ${surrogate})) })()`],
+`(async () => { return ({ value: (await ${surrogate}) }) })()`],
 ['(await 0);',
-'(async () => { return ((await 0)); })()'],
+'(async () => { return ({ value: (await 0) }); })()'],
 [`(await ${surrogate});`,
-`(async () => { return ((await ${surrogate})); })()`],
+`(async () => { return ({ value: (await ${surrogate}) }); })()`],
 ['async function foo() { await 0; }',
 null],
 ['async () => await 0',
@@ -45,7 +45,7 @@ const testCases = [
 ['await 0; return 0;',
 null],
 [`await ${surrogate}; await ${surrogate};`,
-`(async () => { await ${surrogate}; return (await ${surrogate}); })()`],
+`(async () => { await ${surrogate}; return { value: (await ${surrogate}) }; })()`],
 ['var a = await 1',
 'var a; (async () => { void (a = await 1) })()'],
 [`var a = await ${surrogate}`,
@@ -71,7 +71,7 @@ const testCases = [
 ' ([{d}] = [{d: 3}])) })()'],
 /* eslint-disable no-template-curly-in-string */
 ['console.log(`${(await { a: 1 }).a}`)',
-'(async () => { return (console.log(`${(await { a: 1 }).a}`)) })()'],
+'(async () => { return { value: (console.log(`${(await { a: 1 }).a}`)) } })()'],
 /* eslint-enable no-template-curly-in-string */
 ['await 0; function foo() {}',
 'var foo; (async () => { await 0; this.foo = foo; function foo() {} })()'],
@@ -92,15 +92,15 @@ const testCases = [
 ['let o = await 1, p',
 'let o, p; (async () => { void ( (o = await 1), (p=undefined)) })()'],
 ['await (async () => { let p = await 1; return p; })()',
-'(async () => { return (await (async () => '+
-'{ let p = await 1; return p; })()) })()'],
+'(async () => { return { value: (await (async () => '+
+'{ let p = await 1; return p; })()) } })()'],
 ['{ let p = await 1; }',
 '(async () => { { let p = await 1; } })()'],
 ['var p = await 1',
 'var p; (async () => { void (p = await 1) })()'],
 ['await (async () => { var p = await 1; return p; })()',
-'(async () => { return (await (async () => '+
-'{ var p = await 1; return p; })()) })()'],
+'(async () => { return { value: (await (async () => '+
+'{ var p = await 1; return p; })()) } })()'],
 ['{ var p = await 1; }',
 'var p; (async () => { { void (p = await 1); } })()'],
 ['for await (var i of asyncIterable) { i; }',
@@ -140,6 +140,10 @@ const testCases = [
 ['var x = await foo(); async function foo() { return Promise.resolve(1);}',
 'var x; var foo; (async () => { void (x = await foo()); this.foo = foo; '+
 'async function foo() { return Promise.resolve(1);} })()'],
+['(await x).y',
+'(async () => { return { value: ((await x).y) } })()'],
+['await (await x).y',
+'(async () => { return { value: (await (await x).y) } })()'],
 ];
 
 for(const[input,expected]oftestCases){

test/parallel/test-repl-top-level-await.js

@@ -182,6 +182,10 @@ async function ordinaryTests() {
 '3',
 'undefined',
 ]],
+// Regression test for https://github.com/nodejs/node/issues/43777.
+['await Promise.resolve(123), Promise.resolve(456)','Promise {',{line: 0}],
+['await Promise.resolve(123), await Promise.resolve(456)','456'],
+['await (Promise.resolve(123), Promise.resolve(456))','456'],
 ];
 
 for(const[input,expected=[`${input}\r`],options={}]oftestCases){