repl: Mitigate vm #548 function redefinition issue

```js
node 🙈 ₹ git:(upstream ⚡ repl-tmp-548) ./node
> function name() { return "node"; };
undefined
> name()
'node'
> function name() { return "nodejs"; };
undefined
> name()
'nodejs'
>
```

PR-URL: #7794
Reviewed-By: Evan Lucas <[email protected]>

lib/repl.js

@@ -471,19 +471,7 @@ function REPLServer(prompt,
  }
 
  var evalCmd = self.bufferedCommand + cmd;
- if (/^\s*\{/.test(evalCmd) && /\}\s*$/.test(evalCmd)) {
- // It's confusing for `{ a : 1 }` to be interpreted as a block
- // statement rather than an object literal. So, we first try
- // to wrap it in parentheses, so that it will be interpreted as
- // an expression.
- evalCmd = '(' + evalCmd + ')\n';
- self.wrappedCmd = true;
- } else {
- // otherwise we just append a \n so that it will be either
- // terminated, or continued onto the next expression if it's an
- // unexpected end of input.
- evalCmd = evalCmd + '\n';
- }
+ evalCmd = preprocess(evalCmd);
 
  debug('eval %j', evalCmd);
  self.eval(evalCmd, self.context, 'repl', finish);
@@ -538,6 +526,26 @@ function REPLServer(prompt,
  // Display prompt again
  self.displayPrompt();
  }
+
+ function preprocess(code) {
+ let cmd = code;
+ if (/^\s*\{/.test(cmd) && /\}\s*$/.test(cmd)) {
+ // It's confusing for `{ a : 1 }` to be interpreted as a block
+ // statement rather than an object literal. So, we first try
+ // to wrap it in parentheses, so that it will be interpreted as
+ // an expression.
+ cmd = `(${cmd})`;
+ self.wrappedCmd = true;
+ } else {
+ // Mitigate https:/nodejs/node/issues/548
+ cmd = cmd.replace(/^\s*function\s+([^(]+)/,
+ (_, name) => `var ${name} = function ${name}`);
+ }
+ // Append a \n so that it will be either
+ // terminated, or continued onto the next expression if it's an
+ // unexpected end of input.
+ return `${cmd}\n`;
+ }
  });
 
  self.on('SIGCONT', function() {

test/known_issues/test-repl-function-redefinition-edge-case.js

@@ -0,0 +1,38 @@
+// Reference: https:/nodejs/node/pull/7624
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const repl = require('repl');
+const stream = require('stream');
+
+common.globalCheck = false;
+
+const r = initRepl();
+
+r.input.emit('data', 'function a() { return 42; } (1)\n');
+r.input.emit('data', 'a\n');
+r.input.emit('data', '.exit');
+
+const expected = '1\n[Function a]\n';
+const got = r.output.accumulator.join('');
+assert.strictEqual(got, expected);
+
+function initRepl() {
+ const input = new stream();
+ input.write = input.pause = input.resume = () => {};
+ input.readable = true;
+
+ const output = new stream();
+ output.writable = true;
+ output.accumulator = [];
+
+ output.write = (data) => output.accumulator.push(data);
+
+ return repl.start({
+ input,
+ output,
+ useColors: false,
+ terminal: false,
+ prompt: ''
+ });
+}

test/parallel/test-repl.js

@@ -328,6 +328,11 @@ function error_test() {
  // or block comment. https:/nodejs/node/issues/3611
  { client: client_unix, send: 'a = 3.5e',
  expect: /^SyntaxError: Unexpected token ILLEGAL/ },
+ // Mitigate https:/nodejs/node/issues/548
+ { client: client_unix, send: 'function name(){ return "node"; };name()',
+ expect: "'node'\n" + prompt_unix },
+ { client: client_unix, send: 'function name(){ return "nodejs"; };name()',
+ expect: "'nodejs'\n" + prompt_unix },
  ]);
 }