repl: ensure correct syntax err for await parsing

PR-URL: #39154
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/internal/repl/await.js

@@ -7,10 +7,19 @@ const {
   ArrayPrototypePush,
   FunctionPrototype,
   ObjectKeys,
+  RegExpPrototypeSymbolReplace,
+  StringPrototypeEndsWith,
+  StringPrototypeIncludes,
+  StringPrototypeIndexOf,
+  StringPrototypeRepeat,
+  StringPrototypeSplit,
+  StringPrototypeStartsWith,
+  SyntaxError,
 } = primordials;
 
 const parser = require('internal/deps/acorn/acorn/dist/acorn').Parser;
 const walk = require('internal/deps/acorn/acorn-walk/dist/walk');
+const { Recoverable } = require('internal/repl');
 
 const noop = FunctionPrototype;
 const visitorsWithoutAncestors = {
@@ -79,13 +88,40 @@ for (const nodeType of ObjectKeys(walk.base)) {
 }
 
 function processTopLevelAwait(src) {
-  const wrapped = `(async () => { ${src} })()`;
+  const wrapPrefix = '(async () => { ';
+  const wrapped = `${wrapPrefix}${src} })()`;
   const wrappedArray = ArrayFrom(wrapped);
   let root;
   try {
     root = parser.parse(wrapped, { ecmaVersion: 'latest' });
-  } catch {
-    return null;
+  } catch (e) {
+    if (StringPrototypeStartsWith(e.message, 'Unterminated '))
+      throw new Recoverable(e);
+    // If the parse error is before the first "await", then use the execution
+    // error. Otherwise we must emit this parse error, making it look like a
+    // proper syntax error.
+    const awaitPos = StringPrototypeIndexOf(src, 'await');
+    const errPos = e.pos - wrapPrefix.length;
+    if (awaitPos > errPos)
+      return null;
+    // Convert keyword parse errors on await into their original errors when
+    // possible.
+    if (errPos === awaitPos + 6 &&
+        StringPrototypeIncludes(e.message, 'Expecting Unicode escape sequence'))
+      return null;
+    if (errPos === awaitPos + 7 &&
+        StringPrototypeIncludes(e.message, 'Unexpected token'))
+      return null;
+    const line = e.loc.line;
+    const column = line === 1 ? e.loc.column - wrapPrefix.length : e.loc.column;
+    let message = '\n' + StringPrototypeSplit(src, '\n')[line - 1] + '\n' +
+        StringPrototypeRepeat(' ', column) +
+        '^\n\n' + RegExpPrototypeSymbolReplace(/ \([^)]+\)/, e.message, '');
+    // V8 unexpected token errors include the token string.
+    if (StringPrototypeEndsWith(message, 'Unexpected token'))
+      message += " '" + src[e.pos - wrapPrefix.length] + "'";
+    // eslint-disable-next-line no-restricted-syntax
+    throw new SyntaxError(message);
   }
   const body = root.body[0].expression.callee.body;
   const state = {

lib/repl.js

@@ -431,59 +431,66 @@ function REPLServer(prompt,
         ({ processTopLevelAwait } = require('internal/repl/await'));
       }
 
-      const potentialWrappedCode = processTopLevelAwait(code);
-      if (potentialWrappedCode !== null) {
-        code = potentialWrappedCode;
-        wrappedCmd = true;
-        awaitPromise = true;
+      try {
+        const potentialWrappedCode = processTopLevelAwait(code);
+        if (potentialWrappedCode !== null) {
+          code = potentialWrappedCode;
+          wrappedCmd = true;
+          awaitPromise = true;
+        }
+      } catch (e) {
+        decorateErrorStack(e);
+        err = e;
       }
     }
 
     // First, create the Script object to check the syntax
     if (code === '\n')
       return cb(null);
 
-    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 {
-    }
-    while (true) {
+    if (err === null) {
+      let parentURL;
       try {
-        if (self.replMode === module.exports.REPL_MODE_STRICT &&
-            !RegExpPrototypeTest(/^\s*$/, code)) {
-          // "void 0" keeps the repl from returning "use strict" as the result
-          // value for statements and declarations that don't return a value.
-          code = `'use strict'; void 0;\n${code}`;
-        }
-        script = vm.createScript(code, {
-          filename: file,
-          displayErrors: true,
-          importModuleDynamically: async (specifier) => {
-            return asyncESM.ESMLoader.import(specifier, parentURL);
+        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 {
+      }
+      while (true) {
+        try {
+          if (self.replMode === module.exports.REPL_MODE_STRICT &&
+              !RegExpPrototypeTest(/^\s*$/, code)) {
+            // "void 0" keeps the repl from returning "use strict" as the result
+            // value for statements and declarations that don't return a value.
+            code = `'use strict'; void 0;\n${code}`;
           }
-        });
-      } catch (e) {
-        debug('parse error %j', code, e);
-        if (wrappedCmd) {
-          // Unwrap and try again
-          wrappedCmd = false;
-          awaitPromise = false;
-          code = input;
-          wrappedErr = e;
-          continue;
+          script = vm.createScript(code, {
+            filename: file,
+            displayErrors: true,
+            importModuleDynamically: async (specifier) => {
+              return asyncESM.ESMLoader.import(specifier, parentURL);
+            }
+          });
+        } catch (e) {
+          debug('parse error %j', code, e);
+          if (wrappedCmd) {
+            // Unwrap and try again
+            wrappedCmd = false;
+            awaitPromise = false;
+            code = input;
+            wrappedErr = e;
+            continue;
+          }
+          // Preserve original error for wrapped command
+          const error = wrappedErr || e;
+          if (isRecoverableError(error, code))
+            err = new Recoverable(error);
+          else
+            err = error;
         }
-        // Preserve original error for wrapped command
-        const error = wrappedErr || e;
-        if (isRecoverableError(error, code))
-          err = new Recoverable(error);
-        else
-          err = error;
+        break;
       }
-      break;
     }
 
     // This will set the values from `savedRegExMatches` to corresponding

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

@@ -142,6 +142,16 @@ async function ordinaryTests() {
        'undefined',
      ],
     ],
+    ['await Promise..resolve()',
+     [
+       'await Promise..resolve()\r',
+       'Uncaught SyntaxError: ',
+       'await Promise..resolve()',
+       '              ^',
+       '',
+       'Unexpected token \'.\'',
+     ],
+    ],
   ];
 
   for (const [input, expected = [`${input}\r`], options = {}] of testCases) {