feat(yarn): add yarn command support with smart delegation

[jzambrano12]

Summary

• Add yarn_cmd.rs module following the npm_cmd.rs flat-args pattern with run injection logic and YARN_SUBCOMMANDS list (35 known subcommands)
• Smart routing: auto-detect known tools (vitest, tsc, eslint, biome, next, prettier, playwright) and delegate to existing specialized RTK filters for maximum savings (up to 99%)
• Generic filter strips Yarn Classic v1 boilerplate (yarn run vX.Y.Z, $ cmd, Done in Xs) and Berry v2+ info lines (YN0000:)
• Specialized install filter strips progress phases ([1/4]...), info/warning lines (75% reduction)
• Register Yarn variant in Commands enum, routing, and operational command list in main.rs
• Add discover/rewrite rules: yarn pattern + rule with per-subcommand savings estimates
• Add yarn\s+ prefix to 7 existing tool patterns (tsc, lint, prettier, next, vitest, playwright, prisma) so yarn tsc, yarn vitest, etc. are recognized by discover

Motivation

rtk discover on a real project (615 sessions, 30 days) shows 126+ unhandled yarn commands:

yarn build          58 uses
yarn lint           19 uses
yarn check          17 uses
yarn vitest         14 uses
yarn tsc             9 uses
yarn validate-translations  9 uses

Token Savings

Command	Strategy	Expected Savings
yarn vitest	Delegate to vitest_cmd	99%
yarn build	Delegate to next_cmd or generic filter	85%
yarn lint	Delegate to lint_cmd	84%
yarn tsc	Delegate to tsc_cmd	83%
yarn install	Specialized install filter	75%
yarn check	Generic filter	65%
Custom scripts	Generic boilerplate strip	10-40%

Test Plan

• 35 yarn-specific tests passing (cargo test yarn → 35 passed)
• Full suite: 1149 tests passing, 0 clippy errors, clean fmt
• Unit tests: filter output, edge cases (ANSI, unicode, errors, Berry format, malformed input)
• Token savings assertions (≥55% for install, ≥10% for generic)
• Subcommand routing: all 35 YARN_SUBCOMMANDS verified, discover commands verified
• Registry tests: rewrite/classify for yarn build, install, lint, tsc, vitest, check, add, compound, redirect
• Smoke tests: help, --help, --version (conditional), --skip-env
• cargo fmt --all --check && cargo clippy --all-targets && cargo test passes

Files Changed

File	Action	Lines
src/yarn_cmd.rs	NEW	+479 (module + 35 tests)
src/main.rs	EDIT	+13 (mod, enum, routing)
src/discover/rules.rs	EDIT	+41 (patterns, rules, prefixes)
src/discover/registry.rs	EDIT	+125 (12 rewrite/classify tests)
scripts/test-all.sh	EDIT	+12 (smoke tests)
CHANGELOG.md	EDIT	+5 (feature entries)
README.md	EDIT	+1 (command table)

[CLAassistant]

All committers have signed the CLA.

[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

[jzambrano12]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

Done!

[pszymkowiak]

@jzambrano12 — bench-tested this PR on a real Yarn 4 / Berry project
(babel/babel, 1487 packages, 148 MB). The architecture works well:
Berry YN0000: parsing kicks in, smart routing for tsc shows real
savings, exit codes preserved.

yarn lint           raw=1793B  rtk-#867=1790B  (~0%, exit 2 preserved)
yarn tsc            raw=18436B rtk-#867=11351B (38.4%, group-by-file + top codes)
yarn workspaces fe  raw=1675B  rtk-#867=1674B  (~0%, exit 0 preserved)

One blocking issue before merge: the install filter is too
aggressive.

Reproduced with yarn install on babel (exit code 1 — workspace build
failure):

raw output (7389 B, head):
  ➤ YN0000: · Yarn 4.14.1
  ➤ YN0060: │ @babel/core is listed by your project with version 8.0.0-rc.5 (p5fada6), which doesn't satisfy what @babel/eslint-parser ...
  ➤ YN0060: │ @babel/core is listed by your project with version 8.0.0-rc.6 (p07b993), ...
  [40+ YN0060 peer-dep warnings]
  ➤ YN0086: │ Some peer dependencies are incorrectly met; run yarn explain peer-requirements for details.
  ➤ YN0007: │ babel@workspace:. must be built because it never has been before or the last one failed
  ➤ YN0009: │ babel@workspace:. couldn't be built successfully (exit code 1, ...)
  ➤ YN0000: · Failed with errors in 31s 918ms

rtk-#867 output (2 B): `ok`

The filter collapses to literal "ok" even though the install
failed with YN0009 (workspace build failure) plus 40+ peer-dep
warnings. Exit code 1 is correctly preserved, but the diagnostic
context is gone — an agent or developer seeing ok + exit 1 has no
way to know what broke without re-running raw yarn install.

Suggested fix: keep the "ok" short-circuit only when the install
truly succeeds (no YN0009, no YN0086, exit 0). On failure or with
peer-dep warnings, emit the offending YN-coded lines (typically <2KB
even for large projects).

Once that lands, this looks ready to merge. #317 will be closed as
superseded by this PR.

[rtk-release-bot]

This pull request has been automatically marked as stale due to 90 days of inactivity. If this pull request is still relevant, please leave any comment (for example, "bump"), and we'll keep it open. Your contribution is very much appreciated — we're sorry we haven't been able to review it yet.