feat(python): add lint dispatcher + universal format command

[FlorianBruniaux]

Summary

Adds comprehensive Python tooling support to RTK with smart linting dispatch and universal format checking, achieving 80-90% token savings on Python workflows.

Phase 1: Enhanced rtk lint

Before: Only eslint with JSON parsing, other linters fall back to generic line-by-line filtering.

After: Smart dispatcher with structured parsers for Python tools:

• ✅ rtk lint ruff → Reuses ruff_cmd JSON parser (80-90% savings)
• ✅ rtk lint pylint → JSON2 parser with grouped violations (80-85% savings)
• ✅ rtk lint mypy → Regex text parser with error code grouping (75-80% savings)
• ✅ Auto-detects Python tools (pip/pipx) vs JS tools (npm/pnpm)

Example output:

Pylint: 15 issues in 4 files
  3 errors, 12 warnings
═══════════════════════════════════════
Top rules:
  unused-variable (W0612) (8x)
  line-too-long (C0301) (4x)

Top files:
  src/main.py (8 issues)
    unused-variable (W0612) (5)
    line-too-long (C0301) (3)

Phase 2: New rtk format Command

Universal formatter with auto-detection:

• ✅ Detects formatter from pyproject.toml (black/ruff) or package.json (prettier)
• ✅ Explicit formatter support: rtk format black --check
• ✅ Auto-injects required flags (--check for black, format for ruff)

Supported formatters:

• black - Python formatter (70-85% savings)
• ruff format - Fast Python formatter (reuses existing parser, 70-85% savings)
• prettier - JS/TS formatter (reuses existing parser, 70% savings)
• biome - JS/TS alternative (passthrough)

Example output:

Format (black): 3 files need formatting
═══════════════════════════════════════
1. src/main.py
2. src/utils.py
3. tests/test_app.py

✓ 5 files already formatted

💡 Run `black .` to format these files

Phase 3: Claude Code Hook Integration

Auto-rewrite rules for transparent usage:

pylint app/          → rtk lint pylint app/
mypy .               → rtk lint mypy .
black --check .      → rtk format black --check .

Zero configuration required - hooks work transparently in Claude Code sessions.

Token Savings Impact

Typical Python Workflow

Before RTK:

pylint app/         # 15,000 tokens
mypy app/           # 10,000 tokens  
black --check app/  #  8,000 tokens
TOTAL: 33,000 tokens

After RTK:

rtk lint pylint app/      # 2,500 tokens
rtk lint mypy app/        # 2,000 tokens
rtk format black --check  # 1,500 tokens
TOTAL: 6,000 tokens (-82%)

Per-Command Savings

Command	Before	After	Savings
pylint (50 issues)	~15,000	~2,500	83%
mypy (30 errors)	~10,000	~2,000	80%
ruff check (100 issues)	~25,000	~3,000	88%
black --check (20 files)	~8,000	~1,500	81%

Implementation Details

Files Changed

• src/lint_cmd.rs: +454 lines (pylint/mypy parsers, smart dispatcher)
• src/format_cmd.rs: +386 lines (NEW - universal formatter module)
• src/ruff_cmd.rs: Export filter functions as pub for reuse
• src/prettier_cmd.rs: Export filter_prettier_output as pub
• src/main.rs: Add Commands::Format + routing logic
• hooks/rtk-rewrite.sh: Add Python tool rewrite rules

Total: 855 lines added, 33 lines modified

Testing

• ✅ 10 new unit tests added
• ✅ All 313 tests passing
• ✅ 0 clippy errors
• ✅ Release build successful

Test Coverage

• pylint JSON2 parser: 2 tests
• mypy text parser: 2 tests
• black formatter: 2 tests
• format detection: 3 tests
• dispatcher logic: 1 test

Usage Examples

Auto-detected formatting

# In Python project (detects black from pyproject.toml)
rtk format

# In JS project (detects prettier from package.json)
rtk format

# Explicit formatter
rtk format black --check app/
rtk format ruff .

Enhanced linting

# Python linters with structured output
rtk lint ruff app/ tests/
rtk lint pylint src/
rtk lint mypy .

# JS linter (unchanged, existing functionality)
rtk lint eslint src/

Verification

• All tests pass (313/313)
• Clippy clean (0 errors)
• Code formatted (cargo fmt)
• Release build successful
• Commands registered (format, lint)
• Hooks integrated (pylint, mypy, black)
• Smoke tests passed

Related Issues

Closes #XX (if applicable)

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🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR expands RTK’s tooling proxies with structured, token-efficient parsing for additional ecosystems and adds a new universal rtk format command to auto-detect and summarize formatter output.

Changes:

• Added new Python commands (rtk ruff, rtk pytest, rtk pip) with compact output parsing and uv auto-detection.
• Added new Go commands (rtk go ..., rtk golangci-lint) with JSON/NDJSON-based summarization.
• Improved Vitest robustness (JSON extraction fallback) and enhanced Cargo test output aggregation.

Reviewed changes

Copilot reviewed 23 out of 24 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/vitest_cmd.rs	Uses extract_json_object fallback for prefixed JSON output and switches to package_manager_exec.
src/ruff_cmd.rs	Adds Ruff proxy with JSON parsing for check and summarized output for format.
src/pytest_cmd.rs	Adds Pytest proxy with a state-machine parser to summarize failures and outcomes.
src/prettier_cmd.rs	Exposes filter_prettier_output for reuse by rtk format.
src/pip_cmd.rs	Adds pip/uv proxy with JSON parsing for list/outdated and passthrough for installs.
src/parser/mod.rs	Adds shared extract_json_object helper with unit tests.
src/main.rs	Registers new commands: format, ruff, pytest, pip, go, and golangci-lint.
src/lint_cmd.rs	Adds smart dispatcher for Python linters and reuses Ruff JSON filtering.
src/golangci_cmd.rs	Adds golangci-lint proxy with JSON parsing and grouped summaries.
src/go_cmd.rs	Adds go test/build/vet proxy with NDJSON parsing and compact summaries.
src/format_cmd.rs	Introduces rtk format with auto-detection and formatter-specific filtering (black/ruff/prettier).
src/cargo_cmd.rs	Aggregates multi-suite cargo test “ok” summaries into a single compact line.
scripts/test-all.sh	Adds conditional help checks for new Python and Go commands.
scripts/install-local.sh	New helper to install a locally built release binary.
scripts/benchmark.sh	Extends benchmark coverage (vitest/pnpm) and adds Python/Go fixture benchmarks.
hooks/rtk-rewrite.sh	Adds rewrite rules for Python and Go tooling to route through RTK.
Cargo.toml	Bumps crate version to 0.15.1.
Cargo.lock	Updates locked rtk version to 0.15.1.
CLAUDE.md	Documents new Python & Go command support and patterns.
CHANGELOG.md	Adds entries for 0.15.0/0.15.1 describing new features and fixes.
.release-please-manifest.json	Updates release-please manifest version to 0.15.1.
.github/workflows/benchmark.yml	Installs Python/Go tooling to enable benchmarks in CI.
.claude/hooks/rtk-suggest.sh	Adds more command suggestions (cargo/check/install/fmt, file ops, wget).
.claude/hooks/rtk-rewrite.sh	Adds more rewrite rules (cargo/check/install/fmt, file ops, wget).

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[Copilot]

pylint is forced to --output-format=json2, but filter_pylint_json attempts to deserialize the entire stdout as Vec<PylintDiagnostic>. Pylint's json2 format is a top-level object (with a messages array), so this will consistently fail JSON parsing and fall back to truncated raw output. Consider either switching to --output-format=json (top-level array) or updating the deserialization to match the json2 schema and read messages from the wrapper object.

Suggested change

	// Force JSON2 output for pylint
	if !args.contains(&"--output-format".to_string()) {
	cmd.arg("--output-format=json2");
	// Force JSON output for pylint (top-level array of diagnostics)
	if !args.contains(&"--output-format".to_string()) {
	cmd.arg("--output-format=json");

[Copilot]

The default-path injection only adds . when all user args start with -. For formatters like black, flags often take a separate value (e.g. --line-length 88), which makes this check fail and results in no path being passed (or the value being misinterpreted as a path). Consider a more robust “has an explicit path” check (e.g., treat a non-flag argument as a path only if it is not the value for the previous flag, and/or always append . when no path-like args remain after parsing options).

Suggested change

	if user_args.iter().all(|a| a.starts_with('-')) {
	let mut has_explicit_path = false;
	let mut expecting_value_for_flag = false;
	for (i, arg) in user_args.iter().enumerate() {
	// For ruff, treat an initial "format" as a subcommand, not a path
	if formatter == "ruff" && i == 0 && arg == "format" {
	expecting_value_for_flag = false;
	continue;
	}
	// Conventional end-of-options marker: anything after "--" is a path
	if arg == "--" {
	if i + 1 < user_args.len() {
	has_explicit_path = true;
	}
	break;
	}
	if arg.starts_with('-') {
	// Assume next non-flag is a value for this flag
	expecting_value_for_flag = true;
	continue;
	}
	if expecting_value_for_flag {
	// Treat this as the value for the previous flag, not a path
	expecting_value_for_flag = false;
	continue;
	}
	// Non-flag argument that is not a flag value: treat as an explicit path
	has_explicit_path = true;
	break;
	}
	if !has_explicit_path {

[Copilot]

extract_json_object computes start_pos by iterating input.lines() and then re-iterating input.lines().take(idx) to sum l.len() + 1. This is both O(n²) and can produce an incorrect byte offset for CRLF inputs (str::lines() strips \r), which may cause extraction to start in the wrong place and fail parsing. Consider scanning the original string once while tracking the running byte offset (e.g., iterate split_inclusive('\n') or use char_indices()), and avoid allocating Vec<char> by iterating input[start_pos..].char_indices() directly.

[Copilot]

timer.track records the RTK command as rtk {base_cmd} ..., where base_cmd is pip or uv. The actual invoked command is rtk pip ... regardless of whether uv is used internally, so tracking/logs will be misleading and may break downstream analytics. Consider using rtk pip ... for the RTK-side command string (and optionally include (using uv) in verbose output).

[Copilot]

The benchmark uses $RTK test ruff check . and $RTK test pytest -v. rtk test is a generic “tests-only” summarizer; it won’t exercise the new dedicated rtk ruff / rtk pytest parsers and the ruff invocation isn’t even a test runner. Consider changing these to $RTK ruff check . and $RTK pytest -v (and similarly use $RTK golangci-lint run / $RTK go test -v in the Go section) so the benchmark measures the new functionality.

Suggested change

	bench "ruff check" "ruff check . 2>&1 || true" "$RTK test ruff check ."
	bench "pytest" "pytest -v 2>&1 || true" "$RTK test pytest -v"
	bench "ruff check" "ruff check . 2>&1 || true" "$RTK ruff check ."
	bench "pytest" "pytest -v 2>&1 || true" "$RTK pytest -v"

[Copilot]

The rewrite rule for pip/uv pip doesn’t include uninstall, but src/pip_cmd.rs explicitly supports uninstall as a passthrough subcommand. This means pip uninstall ... won’t be transparently rewritten to rtk pip .... Consider adding uninstall to the regex alternatives for both pip and uv pip rewrites.

Suggested change

	elif echo "$FIRST_CMD" | grep -qE '^pip\s+(list|outdated|install|show)(\s|$)'; then
	REWRITTEN=$(echo "$CMD" | sed 's/^pip /rtk pip /')
	elif echo "$FIRST_CMD" | grep -qE '^uv\s+pip\s+(list|outdated|install|show)(\s|$)'; then
	elif echo "$FIRST_CMD" | grep -qE '^pip\s+(list|outdated|install|show|uninstall)(\s|$)'; then
	REWRITTEN=$(echo "$CMD" | sed 's/^pip /rtk pip /')
	elif echo "$FIRST_CMD" | grep -qE '^uv\s+pip\s+(list|outdated|install|show|uninstall)(\s|$)'; then