Add Rush reporter frontend controls

[Sean Larkin (TheLarkInn)]

Summary

• create the authoritative ReporterHost/ReporterManager in apps/rush before Rush version selection and pass selected rush-lib only an IReporterEventSink
• register and parse global --reporter, --output, --log-level, --quiet, --verbose, and --debug controls while preserving command-specific --json
• keep the pre-major default on the legacy path; explicit non-legacy --reporter or the repository useRushReporter experiment enables reporters, agent auto-selection remains disabled, and RUSH_REPORTER=legacy strips reporter-only controls before legacy-engine handoff
• retain existing -v meanings for rush list, rush change, and phased build commands

Stack

• parent: Add Rush reporter repository configuration #5987 (copilot/reporter-r2a-experiment-config)
• grandparent: [rush reporter][R1B] Generate install-run-rush bootstrap protocol #5986 (copilot/reporter-r1b-bootstrap-generation)
• great-grandparent: Wire rush-reporter package dependencies #5985 (copilot/reporter-r1a-package-wiring)

This is the R2B child of #5987. Keep auto-merge disabled while any ancestor is open. Merge and retarget #5985, #5986, and #5987 in order; only after #5987 merges should this PR be retargeted to main and considered for auto-merge.

Validation

• rush build --to @microsoft/rush --verbose
• rush test --only @microsoft/rush --only @microsoft/rush-lib --only @rushstack/rush-reporter --verbose
• node libraries/reporter/scripts/generateBootstrapProtocol.js --check
• rush check
• rush change --verify --no-fetch
• gh pr diff 5989 contains only the 18-file R2B frontend/control slice

Legacy safety

• frontend-owned --reporter, --output, and --log-level controls are removed before every Rush engine handoff, including repository-pinned older engines
• no opt-in registers a visible reporter, including TTY, non-TTY, CI, and agent environments
• RUSH_REPORTER=legacy remains the emergency override even when non-legacy or contradictory reporter controls are present
• legacy combinations such as --quiet --debug remain valid when the reporter path is disabled
• rush-pnpm --reporter and rushx arguments remain outside Rush reporter parsing

Repository opt-in

• useRushReporter is read before version selection
• TTY selects the interactive reporter; CI and generic non-TTY select plaintext
• agent detection is deliberately excluded from repository opt-in selection until R8

Non-goals

• no bootstrap handoff replay or prelude work (R6)
• no operation stream rendering or StreamCollator replacement (R5)

Part of #5975

[Sean Larkin (TheLarkInn)]

Stack integration review found and fixed three actionable issues in 42b0fae: frontend-only value flags no longer leak to repository-pinned engines; legacy verbosity combinations remain compatible, including under RUSH_REPORTER=legacy; and the repository useRushReporter opt-in is consumed before version selection with deterministic TTY/CI/non-TTY behavior while agent auto-selection stays disabled. Ordering gate: after #5985 merges and both PRs move to main, #5987 must merge before #5989 because #5987 owns the schema/API for the experiment that #5989 consumes.

[Sean Larkin (TheLarkInn)]

Linearized stack update: rebased the two R2B-only commits onto fresh origin/copilot/reporter-r2a-experiment-config and force-pushed with lease. New head is c54a29b; base is now copilot/reporter-r2a-experiment-config. The GitHub diff exactly matches the local R2A-to-R2B file list, with no R2A schema/API files included. Combined targeted tests, rush check, and changefile verification pass. Auto-merge remains disabled while #5985 and #5987 are open.

[Sean Larkin (TheLarkInn)]

Linear stack update: R2B is now head 732e704 based on #5987. Its GitHub diff is exactly the 18-file frontend/control slice. Final-tip build/tests, generation check, rush check, and change verification pass; auto-merge remains disabled while ancestors are open.

[Sean Larkin (TheLarkInn)]

Combined deep review of current head 732e7048f7.

1. HIGH RushReporterHost.ts:184-244 parses and strips reporter-shaped arguments after the -- separator. Pass-through tool arguments can be consumed or rejected. Stop both scans at --.
2. MEDIUM RushFrontend.ts:37-66 initializes frontend-owned reporters without an exactly-once success close path. Files, descriptors, and latest.log can remain incomplete until process exit. Add an awaitable close contract for success, failure, parser rejection, and termination.

[Sean Larkin (TheLarkInn)]

Fixed both deep-review findings in 709357f. Reporter control scans and stripping now stop at the first standalone --, preserving all pass-through arguments. Frontend-owned reporters now use one awaitable close promise across normal success, engine and parser failures, selector failures, explicit exits, older-engine beforeExit, and bounded signal termination. Tests passed: reporter 295, rush-lib 752, apps/rush 27, rush check, and stacked-base change verification.

[Sean Larkin (TheLarkInn)]

Four-review rerun on 709357fced confirms the original separator and normal close fixes. Five actionable findings remain:

1. CRITICAL Global --verbose collides with existing action flags. rush build --verbose, rush rebuild --verbose, and rush check --verbose can fail as ambiguous. Preserve existing action syntax.
2. HIGH Global reporter parameter names can collide with repository custom command parameters. Detect conflicts early or avoid parser-level collisions.
3. HIGH An older selected engine can still initialize reporters, strip an explicit request, and never close on process.exit(). Reject unsupported explicit requests and keep old engines on a closed legacy path.
4. MEDIUM A signal can join an existing longer close and miss the advertised two-second wall-clock deadline.
5. MEDIUM Signal and beforeExit handlers are installed even when reporting is disabled, changing the no-opt-in legacy path.

Useful low follow-ons: close errors should not replace the command result, and current -- preservation is frontend-only because Rush actions do not yet consume a remainder. Descendant remediation stays paused.

[Sean Larkin (TheLarkInn)]

Round two fixed in 5f8ef5e. Reporter options are no longer ts-command-line globals, so existing build, rebuild, check, and repository custom parameters retain their action-owned behavior. Explicit non-legacy reporter requests reserve reporter value controls; implicit opt-in preserves custom output and log-level parameters. Incompatible engines now reject explicit reporters before initialization and otherwise stay on disabled legacy behavior. Lifecycle handlers are installed only when enabled, signals use one two-second wall-clock deadline, and close errors set failure state without replacing command errors. Tests passed: reporter 295, rush-lib 757, apps/rush 38, regenerated snapshots, rush check, and stacked-base change verification.

[Sean Larkin (TheLarkInn)]

Four-review rerun on 5f8ef5e948 confirms all prior compatibility and lifecycle fixes. Two related flag-ownership gaps remain:

1. HIGH An unsupported --reporter value is still claimed by the frontend, breaking custom commands that historically own --reporter, including common test reporter values. Preserve it unless the frontend has an explicit supported reporter request or repository opt-in ownership.
2. MEDIUM RUSH_REPORTER=legacy plus explicit --reporter=legacy can strip valid custom --output and --log-level parameters. Strip only the reporter selection flag in that case.

Auto-merge remains disabled. Descendant remediation stays paused.

[Sean Larkin (TheLarkInn)]

Final focused ownership fix is in c732e19. Unsupported custom --reporter values such as junit now pass through unchanged until repository opt-in, a supported reporter name, or a reporter-shaped output establishes frontend ownership. RUSH_REPORTER=legacy with explicit --reporter=legacy strips only the selection flag, preserving custom output, log-level, and verbose parameters. Incompatible engines retain the explicit failure and legacy-safe escape paths with clearer contract wording. Tests passed: reporter 295, rush-lib 757, apps/rush 44, parser snapshots, rush check, and stacked-base change verification.

[Sean Larkin (TheLarkInn)]

Four-review gate on c732e195b5 confirms the prior findings are fixed. One MEDIUM compatibility gap remains: a repository custom command that owns a value-less --reporter flag still fails during the frontend ownership probe before Rush loads the command definition.

Required fix: make the probe tolerant of missing values and raise requires a value only after frontend ownership is established. Add a custom flag fixture.

One dismissible low follow-on remains: repository opt-in currently rejects contradictory legacy verbosity aliases that the legacy path accepts.

[Sean Larkin (TheLarkInn)]

Final narrow fix is in 62d9e7a. The first reporter ownership probe now tolerates a value-less custom --reporter flag and only performs the strict missing-value check after opt-in, a supported reporter value, or reporter-shaped output establishes frontend ownership. A real custom flag fixture verifies end-to-end pass-through. Implicit repository opt-in now applies debug, verbose, then quiet alias precedence, while explicit log-level contradictions still fail. Tests passed: reporter 295, rush-lib 758, apps/rush 46, parser snapshots, rush check, and stacked-base change verification.

[Sean Larkin (TheLarkInn)]

Final combined review of 62d9e7af04 found no critical, high, medium, or useful low issues. All recorded findings have fixes and regression coverage.

The repeated command-name concern was dismissed because no failing invocation was reproduced and the full frontend path verification found no affected supported entry point. This head is review-clean. Auto-merge remains disabled while ancestors are open.