Route Rust toolchain trampolines through soldr

[zackees]

Summary

Replaces fbuild's hand-rolled PATH-munging trampolines with calls to soldr v0.7.0. soldr resolves each toolchain binary via `rustup which`, so the rustup-managed toolchain is always used without any per-call environment shaping. Closes #53.

Behavior-preserving — all the same commands work the same way. The implementation is just thinner underneath.

Changes

• `ci/trampoline.py`: `cargo` / `rustc` / `rustfmt` / `clippy_driver` now exec `soldr [--no-cache] ` instead of discovering `.cargo/bin` and prepending it to PATH. `cargo` passes `--no-cache` so soldr's own RUSTC_WRAPPER / managed-zccache path is not inserted — previous bare-cargo semantics are preserved. `_run_cargo_bin` (backing `run_fbuild` / `run_fbuild_daemon`) also routes through soldr.
• `_cargo` / `_rustc` / `_rustfmt` shell shims: one-liners that `exec uv run soldr ...`. Same user-facing behavior as before.
• `ci/dev-tools/pyproject.toml`: pulls `soldr>=0.7.0` as a Python dep so the `soldr` binary is available in the venv that the uv-run trampolines execute under.
• `ci/hooks/tool_guard.py`: accepts `soldr ...` as a valid prefix alongside `uv run` and the `_cargo` trampolines. New test case covers `soldr cargo`, `soldr --no-cache cargo`, `soldr rustc`, `soldr rustfmt`.
• Docs: `CLAUDE.md`, `CODEX.md`, `ci/dev-tools/README.md`, `ci/hooks/README.md` list `soldr ...` as an approved form.

Why soldr

soldr solves the exact problem this repo's trampolines were handling: finding the right rustup-managed toolchain binary on systems with polluted PATH (chocolatey cargo on Windows, stale system rust on Linux, etc.). Using soldr means:

• `ci/trampoline.py` drops ~60 lines of `.cargo/bin` discovery logic.
• Future fbuild contributors don't have to learn yet another trampoline system — soldr is a separate, documented tool.
• Downstream users who pin `fbuild` get a deterministic toolchain resolution story out of the box.

Verification

• `uv run cargo check --workspace --all-targets` — full workspace passes (46s, 11 crates)
• `uv run cargo clippy -p fbuild-cli --all-targets` — passes
• `uv run soldr --version` → `soldr 0.7.0`
• `uv run rustc --version` → `rustc 1.94.1` (correct rustup toolchain)
• `./_rustc --version` → `rustc 1.94.1` (shell trampoline)
• `python -m unittest test_tool_guard` — 6 tests pass including new `test_allows_soldr_wrapped_cargo`

Risk / rollback

Minimal. soldr's rustup resolver mirrors what fbuild's trampolines already do. If CI flags anything, revert is a single-commit rollback.

Closes #53

Summary by CodeRabbit

• Chores
  • Added soldr>=0.7.0 as a project dependency for improved Rust toolchain management.
  • Updated shell scripts and CI validation to route Rust tool invocations through soldr for consistent toolchain selection.
  • Updated documentation and test coverage to reflect new toolchain routing.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR replaces fbuild's hand-rolled Rust toolchain trampolines (_cargo, _rustc, _rustfmt, and ci/trampoline.py functions) with calls to the soldr tool (v0.7.0+), which resolves toolchain binaries via rustup which without PATH-munging. Dependencies, tool guards, and documentation are updated accordingly.

Changes

Cohort / File(s)	Summary
Shell Trampolines _cargo, _rustc, _rustfmt	Replaced PATH-prepending logic with direct soldr invocation via uv run. _cargo adds --no-cache flag to preserve prior bare-cargo semantics; _rustc and _rustfmt invoke soldr directly without the flag.
Documentation Updates CLAUDE.md, CODEX.md, ci/dev-tools/README.md, ci/hooks/README.md	Revised "Essential Rules" and command guidance to document soldr as approved method alongside uv run and repo trampolines. Clarified that toolchain selection uses rustup which and cargo passes --no-cache to preserve prior behavior.
Tool Guard Validation ci/hooks/tool_guard.py, ci/hooks/test_tool_guard.py	Extended ALLOWED_PREFIXES to accept soldr commands. Updated denial messages to include soldr {tool} as allowed alternative. Added test test_allows_soldr_wrapped_cargo validating soldr-wrapped invocations.
Dependency & Trampoline Logic ci/dev-tools/pyproject.toml, ci/trampoline.py	Added soldr>=0.7.0 dependency. Replaced cargo(), rustc(), rustfmt(), clippy_driver(), and _run_cargo_bin() implementations with soldr-based routing; removed PATH-mutation and rustup discovery logic (~24 net lines removed).

Sequence Diagram(s)

sequenceDiagram
    participant User as Build Command
    participant UV as uv run
    participant Soldr as soldr
    participant Rustup as rustup which
    participant Tool as Rust Tool<br/>(cargo/rustc)
    
    User->>UV: uv run cargo check
    UV->>Soldr: soldr --no-cache cargo check
    Soldr->>Rustup: rustup which cargo
    Rustup-->>Soldr: path to toolchain cargo
    Soldr->>Tool: Execute cargo check
    Tool-->>User: Build result

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 Hopping past the PATH, a soldr now leads,
No more cargo-bin munging for the deeds,
Rustup whispers which binary to run,
Trampolines rest—soldr gets the job done! 🎯

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 36.36% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Route Rust toolchain trampolines through soldr' clearly and specifically summarizes the main change: migrating from PATH-based trampolines to soldr-based routing for Rust tools.
Linked Issues check	✅ Passed	The PR comprehensively addresses all in-scope requirements from issue #53: shell trampolines routed through soldr with --no-cache for cargo [_cargo, _rustc, _rustfmt], ci/trampoline.py functions updated, tool_guard.py accepts soldr prefix, soldr>=0.7.0 added to dependencies, and all documentation updated.
Out of Scope Changes check	✅ Passed	All changes are directly aligned with the stated PR scope and linked issue #53 requirements. No extraneous modifications to zccache, legacy env helpers, or ecosystem tools were introduced.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/soldr-trampoline-migration

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

CLAUDE.md (1)

69-69: ⚠️ Potential issue | 🟡 Minor

Hook description is out of sync with the updated allow-list.

Line 7 (and ci/hooks/README.md, and the tool_guard.py denial message) now list soldr alongside uv run and the _cargo/_rustc/_rustfmt trampolines, but this line still mentions only uv run and the trampolines. Worth syncing to avoid confusing users who read the hooks section.

📝 Proposed doc fix

-- **PreToolUse**: `ci/hooks/tool_guard.py` blocks bare Rust commands (must use `uv run` or `_cargo`/`_rustc`/`_rustfmt` trampolines) and bare `python`/`pip` (must use `uv`) across supported shell tools, not just Bash
+- **PreToolUse**: `ci/hooks/tool_guard.py` blocks bare Rust commands (must use `uv run`, `soldr`, or `_cargo`/`_rustc`/`_rustfmt` trampolines) and bare `python`/`pip` (must use `uv`) across supported shell tools, not just Bash

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@CLAUDE.md` at line 69, Update the PreToolUse bullet so it matches the
allow-list by adding "soldr" alongside "uv run" and the
`_cargo`/`_rustc`/`_rustfmt` trampolines (i.e., change the text in the
PreToolUse line to list `soldr`, `uv run`, and the trampolines as allowed
patterns), and ensure the same wording is reflected in the tool_guard.py
messages and ci/hooks/README.md denial/help text to keep all descriptions
consistent (search for the PreToolUse string, the denial message in
tool_guard.py, and the corresponding README entry to update).

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Outside diff comments:
In `@CLAUDE.md`:
- Line 69: Update the PreToolUse bullet so it matches the allow-list by adding
"soldr" alongside "uv run" and the `_cargo`/`_rustc`/`_rustfmt` trampolines
(i.e., change the text in the PreToolUse line to list `soldr`, `uv run`, and the
trampolines as allowed patterns), and ensure the same wording is reflected in
the tool_guard.py messages and ci/hooks/README.md denial/help text to keep all
descriptions consistent (search for the PreToolUse string, the denial message in
tool_guard.py, and the corresponding README entry to update).

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 9a0a3386-c33b-4e77-bfa1-4a74948b732b

📥 Commits

Reviewing files that changed from the base of the PR and between 564a3e9 and dd0bbe2.

⛔ Files ignored due to path filters (2)

• Cargo.lock is excluded by !**/*.lock
• uv.lock is excluded by !**/*.lock

📒 Files selected for processing (11)

• CLAUDE.md
• CODEX.md
• _cargo
• _rustc
• _rustfmt
• ci/dev-tools/README.md
• ci/dev-tools/pyproject.toml
• ci/hooks/README.md
• ci/hooks/test_tool_guard.py
• ci/hooks/tool_guard.py
• ci/trampoline.py