feat(extensions): run extensions

[scottlovegrove]

Slice 3 of 7, on top of slice 2.

The execution half of the contract: arguments reach the extension exactly as the user typed them, the three standard streams are the host's own, and the host exits with whatever the extension exited with.

Node-shebang scripts are launched with the host's own Node, which makes them work on Windows and pins them to the Node version the CLI already requires. Other scripts run directly on POSIX and through sh on Windows.

The environment adds the documented TD_* contract. No credential is ever injected: an extension that needs a token runs td auth token view. A token the user exported themselves is inherited like any other variable, which the spec records as a deliberate exception, and there is now a test pinning that behaviour so it cannot change by accident.

Stack: #521 core · #522 discovery · #523 dispatch · #524 tools · #525 install · #526 upgrade · #527 manager

[doistbot]

This slice wires up extension execution: arguments pass through verbatim, the host shares the child's stdio streams, exit codes propagate, and the environment gets the TD_* contract with no credentials injected. Security-wise this looks solid — argument-array spawning with no shell interpolation on POSIX, and the Windows sh -c fallback keeps user input as positional parameters, so nothing user-controlled can escape into a command.

Few things worth tightening:

• The Windows .cmd/.bat branch can't work: spawn() without shell: true can't launch these via CreateProcess, so valid extensions resolved by discovery will always fail with EXTENSION_NOT_EXECUTABLE. Run them through cmd.exe /d /s /c instead.
• buildExtensionEnv leaks an inherited TD_USER into nested td invocations when no --user is given — the existing test only passes because it stubs the variable to undefined. Delete ${prefix}_USER when no user is supplied, matching the extra loop's behavior.
• Node-shebang replacement drops the interpreter's options, so directives like #!/usr/bin/node --conditions=development break. Parse the Node directive (including env -S forms) and prepend its options before the script path.

I also included a few optional follow-up notes in the details below.

Optional follow-up notes (7)

• src/lib/extensions/dispatch.test.ts:136: expect(env.TD_EXTENSION).toBe(process.env.TD_EXTENSION) can never fail: buildExtensionEnv spreads process.env, so the two are identical by construction. If the intent is "the TDC prefix doesn't leak TD_* variables", assert expect(env.TD_EXTENSION).toBeUndefined().
• src/lib/extensions/dispatch.ts:91: ExtensionEnvOptions re-declares user and extra on top of the existing DispatchOptions in ./types.ts, which already defines user and env with the same "merged last" child-environment semantics. Compose DispatchOptions (or reuse its fields) and keep one name for the child env override — the current env/extra split is an easy way for the dispatch and manager layers to drift.
• src/lib/extensions/dispatch.test.ts:112: Hardcoded 'TODOIST_API_TOKEN' duplicates the canonical TOKEN_ENV_VAR from ../auth-store.js (also re-exported by ../auth.js). Import that constant so the pass-through test stays in sync if the token env var name changes.
• src/lib/extensions/dispatch.test.ts:41: This test asserts POSIX-only behavior but has no platform guard, so running npm test on Windows fails at expect(plan.command).toBe(join(dir, 'td-shell')) because the Windows branch routes through sh. Skip it on Windows (e.g., it.skipIf(process.platform === 'win32')) or branch the expectation.
• src/lib/extensions/dispatch.ts:49: buildSpawnPlan stats the executable here via isExecutable, then readShebang opens the same path again on line 66. Since readShebang already has a file handle, it can call handle.stat() there to answer both "is this a runnable file" and "what is its shebang" in a single open. That removes the duplicate I/O and closes the TOCTOU window where the file changes between the two checks.
• src/lib/extensions/dispatch.test.ts:22: buildSpawnPlan's Windows branches have no coverage: .exe/.cmd/.bat files that should run directly, and every other script that should become sh -c '"$0" "$@"'. That sh quoting is what preserves argument passthrough on Windows, and CI runs only on Linux, so a regression there would pass silently. Add a platform-forced test (e.g., temporarily redefine process.platform as win32 and restore it) covering both branches.
• src/lib/extensions/dispatch.test.ts:195: The signal branch in dispatchExtension is untested: a child killed by a signal must yield 128+signal (e.g. 130 for SIGINT), and a regression that resolves with code ?? 0 would make the host silently report success after an extension is killed. A fixture that runs process.kill(process.pid, 'SIGKILL') (POSIX) would pin this. The three --exit-code cases at lines 196-198 only cover the normal-close path.

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[craigcarlyle]

✅

[doist-release-bot]

🎉 This PR is included in version 5.4.0-next.1 🎉

The release is available on:

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