repl: fix overzealous top-level await

Fixes: nodejs#43777

PR-URL: nodejs#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>

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 {
-            const result = await promise;
+            const result = (await promise)?.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] of testCases) {

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 = {}] of testCases) {