Fix forked process console forwarding reporting shared references as circular

[Leo Camus (Dev-next-gen)]

While fixing safeStringify in #335589 I noticed that src/bootstrap-fork.ts has its own copy of the same replacer. safeToString, which forwards console.* calls from forked processes to the parent when VSCODE_VERBOSE_LOGGING is set (the pty host, the file watcher and the agent host starters all set it), pushes every object into a seen array and never removes anything. So an object that is logged twice, or referenced from two properties, reaches the parent as "[Circular]" after its first occurrence, even though there is no cycle.

With a forked fixture that runs

const shared = { value: 1 };
console.log(shared, { a: shared, b: shared }, circular); // circular.self = circular

the __$console message the parent receives is:

before: [{"value":1},{"a":"[Circular]","b":"[Circular]"},{"name":"circular","self":"[Circular]"}]
after:  [{"value":1},{"a":{"value":1},"b":{"value":1}},{"name":"circular","self":"[Circular]"}]

The fix is the same one as in #335589 and in stableStringify (#327398). The replacer only tracks the current ancestor path, and uses this (the holder) to pop subtrees that are finished. Real cycles are still replaced with "[Circular]". I removed the isObject helper because every object has to go on the stack for the holder check to work. Together with the Array.isArray check, the only objects it left out were RegExp and Date instances, and a Date has already been turned into a string by toJSON by the time the replacer sees it.

How I tested it: I added a case to processes.integrationTest.ts that forks bootstrap-fork with a new fork_console fixture and checks the forwarded arguments, including a genuine cycle. It fails against the current bootstrap-fork.ts with the "before" output above and passes with the fix, and the other tests in the file still pass. I ran it with test/unit/node/index.js --run src/vs/base/test/node/processes/processes.integrationTest.ts, with the Node version check commented out because the machine I used has Node 22. eslint is clean on the changed files and typecheck-client reports nothing in them.

There is no issue for this that I could find. This PR doesn't depend on #335589, they touch different files.

AI tools used

[Copilot]

🟢 Approval recommended

The implementation and focused integration test correctly cover the regression; the remaining comment-style feedback is non-blocking.

Pull request overview

Fixes console forwarding so shared object references are serialized normally while genuine cycles remain protected.

Changes:

• Tracks only the active ancestor path during serialization.
• Adds integration coverage for shared references and cycles.
• Adds a forked-process fixture producing representative console output.

File summaries

File	Description
src/bootstrap-fork.ts	Corrects circular-reference detection.
src/vs/base/test/node/processes/processes.integrationTest.ts	Verifies forwarded console arguments.
src/vs/base/test/node/processes/fixtures/fork_console.ts	Provides shared and circular test values.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Balanced

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.