feat(ruby): add Ruby on Rails support (rspec, rubocop, rake, bundle)

Unifies 5 competing PRs (rtk-ai#198, rtk-ai#292, rtk-ai#379, rtk-ai#534, rtk-ai#643) into a single
coherent implementation.

New commands:
- rtk rspec: JSON parsing with text fallback (60%+ savings)
- rtk rubocop: JSON parsing, group by cop/severity (60%+ savings)
- rtk rake test: Minitest state machine parser (85-90% savings)
- rtk bundle install: TOML filter, strip Using lines (90%+ savings)

Shared infrastructure: ruby_exec(), fallback_tail(),
exit_code_from_output(), count_tokens() in utils.rs.

Discover/rewrite rules for rspec, rubocop, rake, rails, bundle
including bundle exec and bin/ variants.

56 new unit tests + 4 inline TOML tests. All 1035 tests passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: navidemad

PULL_REQUEST_DESCRIPTION.md

@@ -0,0 +1,118 @@
+![Ruby](https://img.shields.io/badge/Ruby-CC342D?logo=ruby&logoColor=white) ![Rails](https://img.shields.io/badge/Rails-D30001?logo=rubyonrails&logoColor=white)
+
+# Summary
+
+Unifies **5 competing PRs** (#198, #292, #379, #534, #643) into a single coherent Ruby on Rails implementation for RTK.
+
+Adds **RSpec**, **RuboCop**, **Minitest** (via rake/rails test), and **Bundler** support with 3 new Rust command modules, 1 TOML filter, shared Ruby infrastructure, and automatic discover/rewrite rules.
+
+Includes **56 unit tests** across the 3 modules and 4 inline TOML tests — all 1035 tests passing.
+
+# New Commands
+
+| Command | Supported Formats | Token Savings | Notes |
+| :--- | :--- | :--- | :--- |
+| **`rtk rspec`** | JSON, Text fallback | ![60%+ JSON](https://img.shields.io/badge/-60%25%2B_JSON-85E89D) ![30%+ text](https://img.shields.io/badge/-30%25%2B_text-FFD33D) | Injects `--format json` automatically. Falls back to text parsing when user specifies a custom format. |
+| **`rtk rubocop`** | JSON, Autocorrect | ![60%+](https://img.shields.io/badge/-60%25%2B-85E89D) | Injects `--format json`, groups offenses by cop name and severity. Skips JSON in autocorrect mode (`-a`, `-A`). |
+| **`rtk rake test`** | Text (state machine) | ![85-90%](https://img.shields.io/badge/-85--90%25-85E89D) | Parses Minitest output. Handles both standard and minitest-reporters formats. |
+| **`rtk bundle install`** | TOML filter | ![90%+](https://img.shields.io/badge/-90%25%2B-85E89D) | Strips `Using` lines, short-circuits to `ok bundle: complete` on success. |
+
+<details>
+<summary><b>Key Design Decisions</b> (click to expand)</summary>
+
+1. **JSON injection for rspec/rubocop** — Injects `--format json` unless user specified `-f`/`--format`/`-fj`/`--format=...`. Detects autocorrect mode (`-a`, `-A`) in rubocop to skip JSON.
+2. **Noise stripping in rspec** — Strips Spring preloader, SimpleCov coverage reports, DEPRECATION warnings, `Finished in` timing, and Capybara screenshot details (keeps only path).
+3. **3-tier JSON fallback in rspec** — Strip noise, parse JSON, try original, text parser, `fallback_tail()`. Logs serde error on final fallback for debugging.
+4. **Safe JSON fallback in rubocop** — JSON parse failure uses `fallback_tail()` instead of feeding JSON through the text parser.
+5. **State machine parsers** — Both rspec (text fallback) and minitest use state-machine text parsers for structured extraction.
+6. **TOML for bundle** — `bundle install/update` has simple output with a `match_output` short-circuit (90%+ savings on success), making it a natural fit for the TOML DSL rather than a full Rust module.
+7. **Defensive arithmetic** — `saturating_sub` throughout, graceful degradation on parse failure.
+8. **Signal-aware exit codes** — `exit_code_from_output` returns `128 + signal` on Unix per convention.
+
+</details>
+
+<details>
+<summary><b>Shared Infrastructure & Registry</b> (click to expand)</summary>
+
+### Shared Infrastructure (`utils.rs`)
+- **`ruby_exec(tool)`** — Auto-detects `bundle exec` when `Gemfile` exists in working directory. Transitive deps like `rake` (pulled in via `rails`) still go through bundler for version isolation.
+- **`fallback_tail(output, label, n)`** — Last-resort filter fallback showing final N lines with diagnostic logging.
+- **`exit_code_from_output(output, label)`** — Signal-aware exit code extraction: returns `128 + signal` on Unix per convention.
+- **`count_tokens(text)`** — Shared test helper for token savings assertions.
+
+### Discover Registry
+- Detection patterns for `rspec`, `rubocop`, `rake test`, `rails test`, `bundle install/update` (with `bundle exec` and `bin/` variants)
+- Rewrite prefixes cover all common invocation patterns including `bin/rspec`, `bin/rails test`, `bundle exec rake test`
+
+</details>
+
+# Hook Integration
+
+The discover registry now correctly rewrites the following commands:
+
+| Rewritten to | From input |
+| :--- | :--- |
+| `rtk rspec` | `rspec`, `bundle exec rspec`, `bin/rspec` |
+| `rtk rubocop` | `rubocop`, `bundle exec rubocop` |
+| `rtk rake test` | `rake test`, `rails test`, `bundle exec rake test`, `bundle exec rails test`, `bin/rails test` |
+| `rtk bundle ...` | `bundle install`, `bundle update` |
+
+# How to Test
+
+```bash
+# 1. Run unit tests (no Ruby required)
+cargo test --all
+
+# 2. Run Ruby-specific tests only
+cargo test rspec_cmd    # 28 tests
+cargo test rubocop_cmd  # 18 tests
+cargo test rake_cmd     # 10 tests
+
+# 3. Build and install locally
+cargo install --path .
+
+# 4. Manual testing (requires Ruby/Rails project)
+rtk rspec spec/models/
+rtk rubocop
+rtk rake test
+rtk bundle install
+```
+
+# Attribution
+
+> [!NOTE]
+> This PR unifies 5 competing implementations. Below is what was taken from each and why.
+
+### PR #198 (by @deril) — RSpec only
+- **Incorporated**: `#[serde(default)]` on `backtrace` field — reviewer-requested fix for RSpec versions that omit backtrace from JSON
+- **Not taken**: Simpler rspec implementation — superseded by #292/#643's more robust version with noise stripping and state-machine text parser
+
+### PR #292 (by @navidemad) — RSpec + RuboCop
+- **Incorporated**: **Primary source** for `rspec_cmd.rs`, `rubocop_cmd.rs`, and shared utils (`ruby_exec`, `fallback_tail`, `exit_code_from_output`, `count_tokens`) — the most mature implementations with noise-stripping regex, 3-tier JSON fallback, state-machine text parser, and signal-aware exit codes
+- **Not taken**: E2E smoke test script (`test-ruby.sh`) — requires Rails installed on CI
+
+### PR #379 (by @navidemad) — Bundle + Rails (TOML DSL hybrid)
+- **Incorporated**: The **TOML filter concept** for `bundle install/update` — simpler than a full Rust module for low-savings commands
+- **Not taken**: The 7 Rails TOML filters (db:migrate, generate, etc.) — lower savings (10-40%) and tightly coupled to TOML DSL internals. Also `rails_cmd.rs` routes/other routing — too complex for initial merge
+
+### PR #534 (by @cosgroveb) — RSpec with parser trait
+- **Incorporated**: **Improved format flag detection** — handles `-fj`, `-fjson`, `-fdocumentation`, `--format=...` patterns that the other PRs missed, plus 4 dedicated tests
+- **Not taken**: `parser` module trait-based architecture (adds indirection without benefit for standalone modules), tempfile `--out` approach (adds complexity and temp file cleanup), `Gemfile.lock` detection (the `Gemfile` check is simpler and covers the same cases)
+
+### PR #643 (by @Maimer) — Most Complete
+- **Incorporated**: `rake_cmd.rs` (**unique** to this PR — only implementation of Minitest parsing), discover rules structure (most comprehensive), `bundle-install.toml`. **Preferred as base** when approaches conflicted.
+
+### Summary
+
+| Module | Source PRs | Tests |
+| :--- | :--- | :--- |
+| `rspec_cmd.rs` | #292/#643 + #534 format detection + #198 serde fix | 28 |
+| `rubocop_cmd.rs` | #292/#643 | 18 |
+| `rake_cmd.rs` | #643 (unique) | 10 |
+| `bundle-install.toml` | #643 + #379 (concept) | 4 |
+| `utils.rs` additions | #292/#643 | — |
+| `discover/rules.rs` | #643 (most complete) | — |
+
+Closes #292, #379
+
+Based on work by @deril (#198), @cosgroveb (#534), and @Maimer (#643) — thank you for your contributions.

src/discover/rules.rs

@@ -44,6 +44,11 @@ pub const PATTERNS: &[&str] = &[
     // Go tooling
     r"^go\s+(test|build|vet)",
     r"^golangci-lint(\s|$)",
+    // Ruby tooling
+    r"^bundle\s+(install|update)\b",
+    r"^(?:bundle\s+exec\s+)?(?:bin/)?(?:rake|rails)\s+test",
+    r"^(?:bundle\s+exec\s+)?rspec(?:\s|$)",
+    r"^(?:bundle\s+exec\s+)?rubocop(?:\s|$)",
     // AWS CLI
     r"^aws\s+",
     // PostgreSQL
@@ -332,6 +337,45 @@ pub const RULES: &[RtkRule] = &[
         subcmd_savings: &[],
         subcmd_status: &[],
     },
+    // Ruby tooling
+    RtkRule {
+        rtk_cmd: "rtk bundle",
+        rewrite_prefixes: &["bundle"],
+        category: "Ruby",
+        savings_pct: 70.0,
+        subcmd_savings: &[],
+        subcmd_status: &[],
+    },
+    RtkRule {
+        rtk_cmd: "rtk rake",
+        rewrite_prefixes: &[
+            "bundle exec rails",
+            "bundle exec rake",
+            "bin/rails",
+            "rails",
+            "rake",
+        ],
+        category: "Ruby",
+        savings_pct: 85.0,
+        subcmd_savings: &[("test", 90.0)],
+        subcmd_status: &[],
+    },
+    RtkRule {
+        rtk_cmd: "rtk rspec",
+        rewrite_prefixes: &["bundle exec rspec", "bin/rspec", "rspec"],
+        category: "Tests",
+        savings_pct: 65.0,
+        subcmd_savings: &[],
+        subcmd_status: &[],
+    },
+    RtkRule {
+        rtk_cmd: "rtk rubocop",
+        rewrite_prefixes: &["bundle exec rubocop", "rubocop"],
+        category: "Build",
+        savings_pct: 65.0,
+        subcmd_savings: &[],
+        subcmd_status: &[],
+    },
     // AWS CLI
     RtkRule {
         rtk_cmd: "rtk aws",

src/filters/bundle-install.toml

@@ -0,0 +1,61 @@
+[filters.bundle-install]
+description = "Compact bundle install/update — strip 'Using' lines, keep installs and errors"
+match_command = "^bundle\\s+(install|update)\\b"
+strip_ansi = true
+strip_lines_matching = [
+  "^Using ",
+  "^\\s*$",
+  "^Fetching gem metadata",
+  "^Resolving dependencies",
+]
+match_output = [
+  { pattern = "Bundle complete!", message = "ok bundle: complete" },
+  { pattern = "Bundle updated!", message = "ok bundle: updated" },
+]
+max_lines = 30
+
+[[tests.bundle-install]]
+name = "all cached short-circuits"
+input = """
+Using bundler 2.5.6
+Using rake 13.1.0
+Using ast 2.4.2
+Using base64 0.2.0
+Using minitest 5.22.2
+Bundle complete! 85 Gemfile dependencies, 200 gems now installed.
+Use `bundle info [gemname]` to see where a bundled gem is installed.
+"""
+expected = "ok bundle: complete"
+
+[[tests.bundle-install]]
+name = "mixed install keeps Fetching and Installing lines"
+input = """
+Fetching gem metadata from https://rubygems.org/.........
+Resolving dependencies...
+Using rake 13.1.0
+Using ast 2.4.2
+Fetching rspec 3.13.0
+Installing rspec 3.13.0
+Using rubocop 1.62.0
+Fetching simplecov 0.22.0
+Installing simplecov 0.22.0
+Bundle complete! 85 Gemfile dependencies, 202 gems now installed.
+"""
+expected = "ok bundle: complete"
+
+[[tests.bundle-install]]
+name = "update output"
+input = """
+Fetching gem metadata from https://rubygems.org/.........
+Resolving dependencies...
+Using rake 13.1.0
+Fetching rspec 3.14.0 (was 3.13.0)
+Installing rspec 3.14.0 (was 3.13.0)
+Bundle updated!
+"""
+expected = "ok bundle: updated"
+
+[[tests.bundle-install]]
+name = "empty output"
+input = ""
+expected = ""

src/main.rs

@@ -46,8 +46,11 @@ mod prettier_cmd;
 mod prisma_cmd;
 mod psql_cmd;
 mod pytest_cmd;
+mod rake_cmd;
 mod read;
 mod rewrite_cmd;
+mod rspec_cmd;
+mod rubocop_cmd;
 mod ruff_cmd;
 mod runner;
 mod session_cmd;
@@ -641,6 +644,27 @@ enum Commands {
         args: Vec<String>,
     },
 
+    /// Rake/Rails test with compact Minitest output (Ruby)
+    Rake {
+        /// Rake arguments (e.g., test, test TEST=path/to/test.rb)
+        #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
+        args: Vec<String>,
+    },
+
+    /// RuboCop linter with compact output (Ruby)
+    Rubocop {
+        /// RuboCop arguments (e.g., --auto-correct, -A)
+        #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
+        args: Vec<String>,
+    },
+
+    /// RSpec test runner with compact output (Rails/Ruby)
+    Rspec {
+        /// RSpec arguments (e.g., spec/models, --tag focus)
+        #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
+        args: Vec<String>,
+    },
+
     /// Pip package manager with compact output (auto-detects uv)
     Pip {
         /// Pip arguments (e.g., list, outdated, install)
@@ -1986,6 +2010,18 @@ fn main() -> Result<()> {
             mypy_cmd::run(&args, cli.verbose)?;
         }
 
+        Commands::Rake { args } => {
+            rake_cmd::run(&args, cli.verbose)?;
+        }
+
+        Commands::Rubocop { args } => {
+            rubocop_cmd::run(&args, cli.verbose)?;
+        }
+
+        Commands::Rspec { args } => {
+            rspec_cmd::run(&args, cli.verbose)?;
+        }
+
         Commands::Pip { args } => {
             pip_cmd::run(&args, cli.verbose)?;
         }
@@ -2245,6 +2281,9 @@ fn is_operational_command(cmd: &Commands) -> bool {
             | Commands::Curl { .. }
             | Commands::Ruff { .. }
             | Commands::Pytest { .. }
+            | Commands::Rake { .. }
+            | Commands::Rubocop { .. }
+            | Commands::Rspec { .. }
             | Commands::Pip { .. }
             | Commands::Go { .. }
             | Commands::GolangciLint { .. }