Add mutable accessors to MultiIndexed et al.

[JoeyBF]

Summary by CodeRabbit

• New Features

  • Added mutable getter functionality to enable in-place modification of stored values.

• Tests

  • Expanded test coverage to validate mutable access patterns and synchronization with reference data structures.

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[coderabbitai]

Walkthrough

Added mutable accessor methods to the KdTrie multi-indexed data structure, enabling in-place mutation of stored values. The changes introduce get_mut at the public API level (KdTrie and MultiIndexed), with underlying unsafe helper methods get_child_mut and get_value_mut in the node layer, plus expanded test coverage for mutable access patterns.

Changes

Cohort / File(s)	Summary
KdTrie mutable accessor ext/crates/once/src/multiindexed/kdtrie.rs	Added public method get_mut(&mut self, coords: &[i32]) -> Option<&mut V> that traverses the trie and returns a mutable reference to the value at the given coordinates
MultiIndexed API and tests ext/crates/once/src/multiindexed/mod.rs	Added public method get_mut(&mut self, coords: [i32; K]) -> Option<&mut V> delegating to the inner KdTrie; expanded tests with new GetMut and Modify operations to validate mutable access semantics against a reference HashMap
Node-level mutable getters ext/crates/once/src/multiindexed/node.rs	Added unsafe pub(super) methods get_child_mut(&mut self, idx: i32) -> Option<&mut Self> and get_value_mut(&mut self, idx: i32) -> Option<&mut V> to retrieve mutable references to child nodes and leaf values

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐰 A trie now bends to mutable paws,
Where values shift without pause,
No copy, just change in place—
A rabbit's efficient grace! 🌿✨

Pre-merge checks and finishing touches

✅ 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 directly and clearly summarizes the main change: adding mutable accessor methods (get_mut) to MultiIndexed, KdTrie, and Node types.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 42b92bf and c06975d.

📒 Files selected for processing (3)

• ext/crates/once/src/multiindexed/kdtrie.rs
• ext/crates/once/src/multiindexed/mod.rs
• ext/crates/once/src/multiindexed/node.rs

🧰 Additional context used

🧠 Learnings (2)

📚 Learning: 2025-12-11T08:35:31.031Z

Learnt from: JoeyBF
Repo: SpectralSequences/sseq PR: 205
File: ext/crates/fp/src/limb.rs:11-28
Timestamp: 2025-12-11T08:35:31.031Z
Learning: In Rust 2024 edition (Cargo.toml edition = 2024), the mem::size_of, size_of_val, align_of, and align_of_val functions from std::mem are in the prelude and do not require explicit imports. During reviews, these can be used unqualified when the project targets edition = 2024. Verify the crate's Cargo.toml edition setting before assuming unqualified use, and avoid adding extraneous imports for these helpers.

Applied to files:

• ext/crates/once/src/multiindexed/mod.rs
• ext/crates/once/src/multiindexed/kdtrie.rs
• ext/crates/once/src/multiindexed/node.rs

📚 Learning: 2025-12-14T08:23:53.399Z

Learnt from: JoeyBF
Repo: SpectralSequences/sseq PR: 207
File: ext/crates/fp/src/simd/x86_64/avx512.rs:367-379
Timestamp: 2025-12-14T08:23:53.399Z
Learning: In Rust 2024 edition, do not remove explicit unsafe blocks inside unsafe fn bodies. The lint unsafe_op_in_unsafe_fn is enabled by default, treating the body of an unsafe fn as safe and requiring each unsafe operation to be wrapped in an explicit unsafe { ... } block. Do not suggest removing these blocks in code using edition = "2024"; ensure unsafe operations are enclosed in explicit unsafe blocks and review for unnecessary nesting.

Applied to files:

• ext/crates/once/src/multiindexed/mod.rs
• ext/crates/once/src/multiindexed/kdtrie.rs
• ext/crates/once/src/multiindexed/node.rs

🧬 Code graph analysis (2)

ext/crates/once/src/multiindexed/mod.rs (1)

ext/crates/once/src/multiindexed/kdtrie.rs (2)

• get_mut (195-205)
• get (71-82)

ext/crates/once/src/multiindexed/kdtrie.rs (3)

ext/crates/once/src/multiindexed/mod.rs (1)

• get_mut (185-187)

ext/crates/once/src/grove/mod.rs (2)

• get_mut (229-232)
• get_mut (597-603)

ext/crates/once/src/once.rs (1)

• get_mut (208-210)

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🔇 Additional comments (7)

ext/crates/once/src/multiindexed/node.rs (2)

111-127: LGTM: Mutable accessor for inner nodes correctly implemented.

The get_child_mut method properly mirrors the existing get_child pattern, delegating to the underlying TwoEndedGrove::get_mut. The safety documentation is clear, and the explicit unsafe block is correctly used per Rust 2024 edition requirements.

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147-163: LGTM: Mutable accessor for leaf values correctly implemented.

The get_value_mut method properly mirrors the existing get_value pattern, delegating to the underlying TwoEndedGrove::get_mut. The implementation and documentation are consistent with the codebase conventions.

ext/crates/once/src/multiindexed/kdtrie.rs (1)

160-205: LGTM: get_mut implementation is correct and well-documented.

The method properly implements mutable traversal through the trie structure:

• Correctly validates coordinate length (line 196)
• Uses mutable rebinding pattern (let mut node = &mut self.root) without creating overlapping borrows
• Traversal logic exactly mirrors the immutable get method
• Documentation clearly explains the exclusive access requirement and includes helpful examples
• Properly uses explicit unsafe blocks per Rust 2024 edition requirements

The ? operator on line 201 correctly short-circuits if any intermediate node doesn't exist, maintaining consistency with the immutable version.

ext/crates/once/src/multiindexed/mod.rs (4)

153-187: LGTM: Public API for mutable access is well-designed.

The get_mut method correctly:

• Delegates to the underlying KdTrie::get_mut implementation
• Requires exclusive access via &mut self, preventing concurrent access
• Provides clear documentation with a practical example demonstrating in-place mutation of a Vec

The API design aligns well with Rust conventions and the existing immutable get method.

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364-390: LGTM: Basic mutable access test is comprehensive.

The test thoroughly exercises the get_mut functionality:

• Tests various mutation patterns (assignment, compound assignment, multiplication)
• Covers positive and negative coordinates
• Verifies that get_mut returns None for non-existent coordinates
• Validates that mutations are visible through subsequent get calls

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544-566: LGTM: Property test operations extended correctly.

The new operation variants are well-designed:

• GetMut: Tests read-only mutable access
• Modify: Tests in-place mutation by adding a delta value

The operation_strategy correctly generates all four operation types using prop_oneof!, with proper boxing for each variant.

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584-633: LGTM: Property test implementation handles mutable operations correctly.

The updated test logic properly validates the new mutable access patterns:

• Line 585: arr is correctly made mutable to support get_mut calls
• Lines 608-613: GetMut handler dereferences to compare values correctly (&*v)
• Lines 614-625: Modify handler updates both the array and reference HashMap, then verifies consistency
• Lines 617, 621: wrapping_add is appropriate to prevent overflow panics in fuzz testing
• Lines 629-633: Final verification ensures complete consistency between implementations

The test design effectively validates that mutable access maintains correctness and synchronization with the reference HashMap.

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