fix(definitions): count a match as a definition only when it starts at the declared name

[gustav-fff]

A match is a definition only when it starts at the declared name, so Value no longer returns ArgValueCompletion or FromValue. Leading underscores in the name are skipped, and fuzzy matching does not change. MCP definitions_only pages now default to 30 matches, because real declarations are rarer and each page reads more files.

---

Line	Query	Before	After
pub enum Value {	Value	definition	definition
pub enum ValueKind {	Value	definition	definition
pub struct ArgValueCompletion<'a> {	Value	definition	other match
function handle(ctrl: UserController) {	UserController	other match	other match
struct _xmlDict {	xmlDict	definition	definition
function M.setup(opts)	M.setup	definition	definition

59 "where is X defined" queries on nushell, ghostty, opencode, ffmpeg and Chromium, MCP definitions_only with default arguments:

	#932	This PR
Lines where the query sits inside a longer name	1,788	2
Real declaration is the first file	20/59	30/59
Body of the real declaration shown	33/59	48/59
Real declaration not on page 1	7	7
Median output	4.6 KB	2.2 KB
Median latency, 4 smaller repos	6 ms	6 ms
Median / max latency, Chromium	222 / 1,104 ms	213 / 938 ms

Note

The classifier is shared, so Neovim live grep, the definition_only grep mode and the SDK classifyDefinitions modes use the same rule. A typed name prefix still marks the declaration. Ordinary grep pages keep the same matches; fewer lines get the definition label.

Important

With 100-match pages, this rule made Chromium definitions_only 3–5x slower (median 0.9 s, max 2.5 s), because 100 real declarations take more files to collect. The 30-match default keeps today's latency with the same quality. An explicit maxResults still wins. multi_grep and Pi already default to 20.

Stacked on #932. #933 now stacks on this PR.

Stack merge order: #924, #925, #927, #928, #930, #931, #932, #940, #933, #934.

Summary by CodeRabbit

• New Features
  • Definition-only searches now return 30 matches by default. Other searches continue to return up to 100, with a maximum of 200.
  • Definition matching now requires the match to start at the declared name, ignoring leading underscores when determining the start. Fuzzy Rust matching remains available.
  • Explicit result limits continue to be honored.

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📒 Files selected for processing: 6

• README.md
• crates/fff-core/benches/definition_bench.rs
• crates/fff-core/src/definition/mod.rs
• crates/fff-core/src/definition/rules.rs
• crates/fff-mcp/src/instructions.md
• crates/fff-mcp/src/server.rs

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📝 Walkthrough

Definition matching now requires a match to start at the declared name, with leading underscores handled as a special case. Definition-only Grep searches use a default page size of 30; other searches retain the 100-result default.

Changes: Definition-aware Grep

Layer / File(s)	Summary
Declared-name matching crates/fff-core/src/definition/rules.rs, crates/fff-core/src/definition/mod.rs, README.md, crates/fff-core/benches/definition_bench.rs	Non-fuzzy matches must include the declared name’s first byte, skipping leading underscores unless the name contains only underscores. Tests and examples cover positive and negative cases. The benchmark now places user_file at the start of generated identifiers.
Definition-only page size crates/fff-mcp/src/server.rs, README.md, crates/fff-mcp/src/instructions.md	Definition-only searches default to 30 results; other searches default to 100. Explicit maxResults values remain in effect, subject to the existing 200-result cap. Documentation and tests reflect these defaults.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~15 minutes

Change: Bug fix

Suggested reviewers: dmtrkovalenko, dkovalenko-oai

Merge Risk: ⚪ Minimal · up to 730e8

No merge-blocking issue is identified; this change is ready for normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (2 skipped: 2…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and accurately states the main change: definition matches must start at the declared name.

Full details: Docstring Coverage

Explanation

Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (2 skipped: 2 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

✨ Finishing Touches: 💡 1

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