fix: support Bun module accessor descriptors (fixes #386)

[RyanGarber]

just-bash currently is entirely unusable with Bun (see #386).

Bun exposes Module._resolveFilename as an accessor descriptor. Spreading that descriptor and adding value creates an invalid mixed descriptor. This means even new Bash(...).exec("echo hello") fails when running in Bun, with DefenseInDepthBox: critical patches failed: Module._resolveFilename.

This installs a valid data descriptor for accessor-backed module methods in both DefenseInDepthBox and WorkerDefenseInDepth. Preserves enumerability/configurability and derive writability from setter availability. Existing data descriptors, blocking proxies, installation verification, fail-closed behavior, and saved descriptors used for teardown remain intact. Nothing about the existing defense-in-depth behavior changes.

Also adds a patch changeset and subprocess regression tests for getter-only and getter/setter descriptors, both module methods, main/worker blocking, and exact descriptor restoration.

Validation:

• Accessor and lifecycle tests: 10 passed.
• Built CLI on Bun 1.3.14: echo bun returns exit 0 with empty stderr.
• Repository build/typecheck, lint:fix, and knip passed.
• New accessor regressions fail against the unmodified upstream source and pass with this fix; generated-worker sync also passes.
• Full pnpm test:run is not clean locally: 15,534 passed, 22 failed, 98 skipped, plus 7 runner errors. Failures include XZ tests after the optional node-liblzma install failed (node-gyp unavailable), timeout-sensitive tests under load, and process.env descriptor errors from the bundle/Vitest interaction. All unrelated to the changes in this PR.

[vercel]

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[auto-maintain]

🤖 auto-maintain review

Automated, advisory triage for @RyanGarber's PR. Facts below are read from the GitHub API.

Check	Result
Author's merged PRs (this repo)	0 — ⚠️ first-time contributor
Account established	✅ (age 5176d · 12 followers · 29 public repos)
Commits signed/verified	✅ 1/1
Changeset included	✅ (.changeset/bun-module-accessors.md)

Review panel: 🟡 medium highest severity

just-bash maintainer code review: 🟢 low

No actionable correctness or maintainability issues found in the complete diff.

General code review: 🟢 low

No actionable correctness or compatibility issues found in the complete diff.

Adversarial security: 🟢 low

No actionable adversarial security findings in the complete base-to-head diff.

Adversarial security (second opinion): 🟢 low

Accessor-descriptor handling for Bun's Module._load/_resolveFilename is additive and fail-closed: the Node data-descriptor path is unchanged, the new branch installs through the host setter with post-install verification, adds a write gate that closes a setter-swap hole, and registers rollback before invoking host code with correct teardown ordering. No backdoor, exfiltration, dependency, or CI changes found.

Standard Bash and host portability: 🟡 medium

The runtime fix is portable, but the new Bun regression tests use a non-portable filesystem path conversion.

• packages/just-bash/src/security/module-accessor-descriptors.bun.test.ts:32 — Using URL.pathname as `cwd` leaves percent-encoded characters (for example `%20`) and produces unsuitable Windows drive paths, so Bun tests fail in checkouts with spaces/non-ASCII names or on Windows. Convert the URL with `fileURLToPath()` instead.

_{Posted by auto-maintain. This automated code review is advisory; a human maintainer makes the call.}

[Copilot]

Copilot review overview

🟢 Approval recommended

The reviewed changes have no unresolved issues blocking approval.

Review effort: Lite
Findings: None

What changed in this PR

Fixes Bun compatibility by safely handling accessor descriptors for protected module methods.

Changes:

• Supports accessor-backed descriptors in main and worker protections.
• Adds regression tests for blocking and descriptor restoration.
• Adds a patch changeset.

File	Description
packages/​just-bash/​src/​security/​worker-defense-in-depth.ts	Handles accessor-backed module methods in worker protection.
packages/​just-bash/​src/​security/​module-accessor-descriptors.test.ts	Tests accessor variants, blocking, and restoration.
packages/​just-bash/​src/​security/​defense-in-depth-box.ts	Handles accessor-backed module methods in main protection.
.changeset/​bun-module-accessors.md	Documents the patch release.

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