test: switch repl import-no-crash to in-process REPL

Replace the child_process.spawn-based regression test with the
in-process startNewREPLServer pattern (similar to test-repl-null.js).
This is faster, avoids subprocess flake, and lets the test assert on
the REPL output stream directly instead of bytes piped through stdio.

Verified to still catch the regression: the test exits with code 1
against unpatched v26.1.0 (acorn SyntaxError escapes) and exits 0
against the fix.

Author: awbx

test/parallel/test-repl-import-statement-no-crash.js

@@ -1,33 +1,31 @@
 'use strict';
-// Regression test for the REPL crashing when an incomplete `import` statement
-// is entered. Typing `import` alone used to trigger V8's "Cannot use import
-// statement outside a module" SyntaxError, which the REPL tried to enrich with
-// a dynamic-import suggestion. Building that suggestion called acorn to parse
-// the line; acorn threw on the incomplete input, and the exception escaped to
-// terminate the process.
-// Refs: https://github.com/nodejs/node/issues/63551
+// Regression test for https://github.com/nodejs/node/issues/63551:
+// Typing a bare `import` keyword in the REPL used to terminate the process.
+//
+// V8 throws SyntaxError("Cannot use import statement outside a module"),
+// which the REPL enriched with a dynamic-import suggestion via
+// `toDynamicImport`. That helper called acorn without a try/catch; on
+// incomplete input acorn threw, and the exception escaped the REPL's input
+// pipeline to crash the process.
+//
+// The fix wraps the acorn call in try/catch and falls back to a plain
+// error message when the line cannot be parsed as a complete import
+// statement. This test asserts that:
+//   1. Emitting an incomplete `import` line through the REPL does not
+//      throw out of the line-handler, and
+//   2. The REPL still surfaces a SyntaxError to the user.
 
 require('../common');
 const assert = require('assert');
-const child_process = require('child_process');
+const { startNewREPLServer } = require('../common/repl');
 
-const child = child_process.spawn(process.execPath, ['--interactive'], {
-  stdio: 'pipe',
-});
+const { replServer, output } = startNewREPLServer();
 
-let stdout = '';
-child.stdout.setEncoding('utf8');
-child.stdout.on('data', (chunk) => { stdout += chunk; });
+replServer.emit('line', 'import');
+replServer.emit('line', '.exit');
 
-child.stdin.write('import\n');
-child.stdin.write('.exit\n');
-
-child.on('exit', (code, signal) => {
-  assert.strictEqual(signal, null);
-  assert.strictEqual(code, 0,
-                     `REPL exited with code ${code} (expected 0). ` +
-                     `stdout was:\n${stdout}`);
-  // The REPL should still have printed a SyntaxError message describing the
-  // issue with the input, rather than crashing silently.
-  assert.match(stdout, /SyntaxError/);
-});
+assert.match(output.accumulator, /SyntaxError/);
+assert.match(
+  output.accumulator,
+  /Cannot use import statement inside the Node\.js REPL\b/,
+);