fixup! repl: show reference errors during preview

This adds support for `--use-strict`.

Signed-off-by: Ruben Bridgewater <[email protected]>

Author: BridgeAR

lib/internal/repl/utils.js

@@ -271,6 +271,12 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
     });
   }
 
+  function isInStrictMode(repl) {
+    return repl.replMode === REPL_MODE_STRICT || process.execArgv
+      .map((e) => e.toLowerCase().replace(/_/g, '-'))
+      .includes('--use-strict');
+  }
+
   // This returns a code preview for arbitrary input code.
   function getInputPreview(input, callback) {
     // For similar reasons as `defaultEval`, wrap expressions starting with a
@@ -302,7 +308,7 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
                     // Report ReferenceError in case the strict mode is active
                     // for input that has no completions.
                     (result.className === 'ReferenceError' &&
-                     (hasCompletions || repl.replMode !== REPL_MODE_STRICT)))) {
+                     (hasCompletions || !isInStrictMode(repl))))) {
           callback(null, null);
         } else if (result.objectId) {
           // The writer options might change and have influence on the inspect

lib/repl.js

@@ -366,8 +366,7 @@ function REPLServer(prompt,
     }
     while (true) {
       try {
-        if (!/^\s*$/.test(code) &&
-            self.replMode === exports.REPL_MODE_STRICT) {
+        if (self.replMode === exports.REPL_MODE_STRICT && !/^\s*$/.test(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}`;

test/parallel/test-repl-strict-mode-previews.js

@@ -0,0 +1,44 @@
+// Previews in strict mode should indicate ReferenceErrors.
+
+'use strict';
+
+require('../common');
+
+if (process.argv[2] === 'child') {
+  const stream = require('stream');
+  const repl = require('repl');
+  class ActionStream extends stream.Stream {
+    readable = true;
+    run(data) {
+      this.emit('data', `${data}`);
+      this.emit('keypress', '', { ctrl: true, name: 'd' });
+    }
+    resume() {}
+    pause() {}
+  }
+
+  repl.start({
+    input: new ActionStream(),
+    output: new stream.Writable({
+      write(chunk, _, next) {
+        console.log(chunk.toString());
+        next();
+      }
+    }),
+    useColors: false,
+    terminal: true
+  }).inputStream.run('xyz');
+} else {
+  const assert = require('assert');
+  const { spawnSync } = require('child_process');
+
+  const result = spawnSync(
+    process.execPath,
+    ['--use-strict', `${__filename}`, 'child']
+  );
+
+  assert.match(
+    result.stdout.toString(),
+    /\/\/ ReferenceError: xyz is not defined/
+  );
+}