Add binding for nix_store_build_paths

[RossComputerGuy]

Summary by CodeRabbit

• New Features
  • Added support to build multiple store paths in a single operation.
  • Returns a mapping of each requested path to its build result/status.
  • Improves throughput for batch build workflows and simplifies collecting build results.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a new public method Store::build_paths(&mut self, paths: &[&StorePath]) -> Result<BTreeMap<String, String>> that uses an unsafe extern "C" callback and the raw FFI store_build_paths to collect path→result string mappings and return them.

Changes

Cohort / File(s)	Summary
Store FFI Binding nix-bindings-store/src/store.rs	Added pub fn build_paths(&mut self, paths: &[&StorePath]) -> Result<BTreeMap<String, String>> which constructs an outputs map, defines an unsafe extern "C" callback to accumulate results via a user_data pointer, converts &StorePath to raw pointers, and calls raw::store_build_paths. Gated with #[cfg(nix_at_least = "2.31")] and documented as requiring Determinate Nix 3.11+.

Sequence Diagram

sequenceDiagram
    participant Caller
    participant Store as Store::build_paths
    participant Callback as "extern \"C\" callback"
    participant FFI as raw::store_build_paths
    participant Native as NativeStore

    Caller->>Store: build_paths(&paths)
    activate Store
    Store->>Store: create BTreeMap outputs
    Store->>Callback: register extern "C" callback (user_data -> map)
    Store->>Store: convert &StorePath -> raw pointers
    Store->>FFI: call raw::store_build_paths(paths, callback, user_data)
    activate FFI
    FFI->>Native: perform builds
    activate Native
    Native->>Callback: invoke callback with (path, result, user_data)
    activate Callback
    Callback->>Store: append path->result into map via user_data
    deactivate Callback
    deactivate Native
    deactivate FFI
    Store->>Caller: return BTreeMap<String, String>
    deactivate Store

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• Set up bindings for use with Determinate Nix #1: Adds FFI callback-backed Store methods that collect path/output mappings using a similar unsafe callback pattern.
• Add store and util versions getter, add util init #12: Adds other public Store methods in the same nix-bindings-store/src/store.rs impl (e.g., get_version), indicating related surface changes to Store APIs.

Suggested reviewers

• cole-h

Poem

🐰 I hopped into Store with a curious wiggle,
Callback in paw, with a tiny giggle,
Paths and results I neatly compile,
Returned as a map with rabbitish style,
Build on, dear devs, I'll cheer from the thicket. 🎩

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a binding for the nix_store_build_paths function, which is directly reflected in the new Store::build_paths method addition.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/store-build-paths

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

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

Inline comments:
In `@nix-bindings-store/src/store.rs`:
- Around line 392-393: The build_paths method must be gated with the same
feature flag as the BTreeMap import to avoid compile errors on Nix 2.26–2.30;
add #[cfg(nix_at_least = "2.31")] above the pub fn build_paths(&mut self, paths:
&[&StorePath]) -> Result<BTreeMap<String, String>> definition so the method
(like realise) is only compiled when nix_at_least = "2.31" is enabled, ensuring
the BTreeMap type and related code are present when build_paths is compiled.

---

ℹ️ Review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 0b80fcf and 60ee025.

📒 Files selected for processing (1)

• nix-bindings-store/src/store.rs

[coderabbitai]

🧹 Nitpick comments (2)

nix-bindings-store/src/store.rs (2)

401-418: Inline callback is inconsistent with the rest of the file — consider extracting.

Every other callback in this file (callback_get_result_store_path_set, callback_get_result_derivation, callback_make_drv_outputs) is defined at module level with a companion *_data helper. The inline definition here works but breaks the established pattern.

🤖 Prompt for AI Agents

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

In `@nix-bindings-store/src/store.rs` around lines 401 - 418, Extract the inline
unsafe extern "C" fn callback into a module-level function following the
existing pattern (e.g., name it callback_get_result_map) and add a companion
helper (e.g., callback_get_result_map_data) to create/pack the userdata pointer
from &mut BTreeMap<String, String>; move the current body (converting
path/result CStrs and inserting into the map) verbatim into that new function
and replace the inline closure call site to pass callback_get_result_map as the
function pointer and callback_get_result_map_data(...) as userdata so it matches
callback_get_result_store_path_set / callback_get_result_derivation /
callback_make_drv_outputs conventions.

---

392-437: No test coverage for build_paths.

All other gated store methods (realise, derivation_from_json, add_derivation, get_fs_closure) have corresponding tests in this file. build_paths has none, making it difficult to verify correctness of the callback wiring and argument passing.

🤖 Prompt for AI Agents

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

In `@nix-bindings-store/src/store.rs` around lines 392 - 437, Add a test for
Store::build_paths that mirrors the existing tests for
realise/derivation_from_json/add_derivation/get_fs_closure: create a Store and
one or more StorePath fixtures used elsewhere in the test file, call
build_paths(&[&path1, &path2...]) under the same #[cfg(nix_at_least = "2.31")]
gate, and assert the returned BTreeMap contains expected keys and values (verify
the C callback wiring by checking that the inserted map entries match the
supplied StorePath strings and expected result strings). Ensure the test uses
the same setup/teardown helpers in this module (context/Store construction) and
exercises the path pointer conversion (StorePath::as_ptr()) path so the unsafe
callback path and check_call!(raw::store_build_paths(...)) invocation are
covered.

🤖 Prompt for all review comments with AI agents

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

Nitpick comments:
In `@nix-bindings-store/src/store.rs`:
- Around line 401-418: Extract the inline unsafe extern "C" fn callback into a
module-level function following the existing pattern (e.g., name it
callback_get_result_map) and add a companion helper (e.g.,
callback_get_result_map_data) to create/pack the userdata pointer from &mut
BTreeMap<String, String>; move the current body (converting path/result CStrs
and inserting into the map) verbatim into that new function and replace the
inline closure call site to pass callback_get_result_map as the function pointer
and callback_get_result_map_data(...) as userdata so it matches
callback_get_result_store_path_set / callback_get_result_derivation /
callback_make_drv_outputs conventions.
- Around line 392-437: Add a test for Store::build_paths that mirrors the
existing tests for realise/derivation_from_json/add_derivation/get_fs_closure:
create a Store and one or more StorePath fixtures used elsewhere in the test
file, call build_paths(&[&path1, &path2...]) under the same #[cfg(nix_at_least =
"2.31")] gate, and assert the returned BTreeMap contains expected keys and
values (verify the C callback wiring by checking that the inserted map entries
match the supplied StorePath strings and expected result strings). Ensure the
test uses the same setup/teardown helpers in this module (context/Store
construction) and exercises the path pointer conversion (StorePath::as_ptr())
path so the unsafe callback path and check_call!(raw::store_build_paths(...))
invocation are covered.

---

ℹ️ Review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 60ee025 and cd1ddad.

📒 Files selected for processing (1)

• nix-bindings-store/src/store.rs