repl: processTopLevelAwait fallback error handling

PR-URL: #39290
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: ejose19

lib/internal/repl/await.js

@@ -184,7 +184,10 @@ function processTopLevelAwait(src) {
         '^\n\n' + RegExpPrototypeSymbolReplace(/ \([^)]+\)/, e.message, '');
     // V8 unexpected token errors include the token string.
     if (StringPrototypeEndsWith(message, 'Unexpected token'))
-      message += " '" + src[e.pos - wrapPrefix.length] + "'";
+      message += " '" +
+        // Wrapper end may cause acorn to report error position after the source
+        (src[e.pos - wrapPrefix.length] ?? src[src.length - 1]) +
+        "'";
     // eslint-disable-next-line no-restricted-syntax
     throw new SyntaxError(message);
   }

lib/repl.js

@@ -78,6 +78,7 @@ const {
   ReflectApply,
   RegExp,
   RegExpPrototypeExec,
+  RegExpPrototypeSymbolReplace,
   RegExpPrototypeTest,
   SafeSet,
   SafeWeakSet,
@@ -434,8 +435,39 @@ function REPLServer(prompt,
           awaitPromise = true;
         }
       } catch (e) {
-        decorateErrorStack(e);
-        err = e;
+        let recoverableError = false;
+        if (e.name === 'SyntaxError') {
+          let parentURL;
+          try {
+            const { pathToFileURL } = require('url');
+            // Adding `/repl` prevents dynamic imports from loading relative
+            // to the parent of `process.cwd()`.
+            parentURL = pathToFileURL(path.join(process.cwd(), 'repl')).href;
+          } catch {
+          }
+
+          // Remove all "await"s and attempt running the script
+          // in order to detect if error is truly non recoverable
+          const fallbackCode = RegExpPrototypeSymbolReplace(/\bawait\b/g, code, '');
+          try {
+            vm.createScript(fallbackCode, {
+              filename: file,
+              displayErrors: true,
+              importModuleDynamically: async (specifier) => {
+                return asyncESM.ESMLoader.import(specifier, parentURL);
+              }
+            });
+          } catch (fallbackError) {
+            if (isRecoverableError(fallbackError, fallbackCode)) {
+              recoverableError = true;
+              err = new Recoverable(e);
+            }
+          }
+        }
+        if (!recoverableError) {
+          decorateErrorStack(e);
+          err = e;
+        }
       }
     }
 

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

@@ -152,6 +152,36 @@ async function ordinaryTests() {
        'Unexpected token \'.\'',
      ],
     ],
+    ['for (const x of [1,2,3]) {\nawait x\n}', [
+      'for (const x of [1,2,3]) {\r',
+      '... await x\r',
+      '... }\r',
+      'undefined',
+    ]],
+    ['for (const x of [1,2,3]) {\nawait x;\n}', [
+      'for (const x of [1,2,3]) {\r',
+      '... await x;\r',
+      '... }\r',
+      'undefined',
+    ]],
+    ['for await (const x of [1,2,3]) {\nconsole.log(x)\n}', [
+      'for await (const x of [1,2,3]) {\r',
+      '... console.log(x)\r',
+      '... }\r',
+      '1',
+      '2',
+      '3',
+      'undefined',
+    ]],
+    ['for await (const x of [1,2,3]) {\nconsole.log(x);\n}', [
+      'for await (const x of [1,2,3]) {\r',
+      '... console.log(x);\r',
+      '... }\r',
+      '1',
+      '2',
+      '3',
+      'undefined',
+    ]],
   ];
 
   for (const [input, expected = [`${input}\r`], options = {}] of testCases) {