feat(coding-agent/tools): added ast_grep empty-result hints and enriched AST descriptions#2665
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metaphorics wants to merge 1 commit into
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feat(coding-agent/tools): added ast_grep empty-result hints and enriched AST descriptions#2665metaphorics wants to merge 1 commit into
metaphorics wants to merge 1 commit into
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…hed AST descriptions - Added a pure ast-pattern-hints module (getPatternHint + regex-misuse and language-shape detectors + best-effort language inference) and wired it into ast_grep so a zero-match result appends a one-line hint naming the likely mistake and routing text/alternation/cross-language searches to the search tool. - Enriched the ast_grep description with an anti-regex routing block and per-language gotchas/examples (Python no-trailing-colon, Go/Rust/TS need params+body), and the ast_edit description with the dry-run to resolve apply flow and its stale-preview guard. - Added AST shape-routing and parallel-exploration guidance to the system prompt, and a focused regression test for the hint detectors and language inference.
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Pull request overview
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Adds user-facing guidance when ast_grep returns zero matches by detecting common “pattern is regex/text” mistakes and a few language-specific incomplete-declaration shapes, plus updates tool docs/prompts accordingly.
Changes:
- Added
ast-pattern-hintsutilities (language inference + hint detectors) and tests. - Integrated hints into
ast_grepzero-match output. - Expanded
ast_grep/ast_editdocs and system prompt routing guidance; updated changelog.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/coding-agent/src/tools/ast-pattern-hints.ts | Introduces hint detection + language inference for zero-match ast_grep patterns. |
| packages/coding-agent/src/tools/ast-pattern-hints.test.ts | Adds Bun tests to lock in hint behavior and inference rules. |
| packages/coding-agent/src/tools/ast-grep.ts | Appends one-line hint to zero-match output for faster user correction. |
| packages/coding-agent/src/prompts/tools/ast-grep.md | Documents anti-regex guidance and language-specific “shape” gotchas. |
| packages/coding-agent/src/prompts/tools/ast-edit.md | Clarifies that rewrite patterns/outputs are AST (not regex/text) and adds stale-preview note. |
| packages/coding-agent/src/prompts/system/system-prompt.md | Adds routing guidance between structural tools vs search/find and parallel exploration advice. |
| packages/coding-agent/CHANGELOG.md | Records the new hint behavior and documentation updates. |
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| if (!src.includes("$") && /\w\.[*+]/.test(src)) { | ||
| return 'Hint: ".*" and ".+" are regex wildcards. In ast_grep use $$$ for multiple AST nodes and $VAR for a single node; for text patterns use the `search` tool.'; | ||
| } |
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| if (lang === "javascript" || lang === "typescript" || lang === "tsx") { | ||
| if (/^(export\s+)?(async\s+)?function\s+\$[A-Z_]+\s*$/i.test(src)) { | ||
| return 'Hint: function patterns need params and a body. Try "function $NAME($$$) { $$$ }".'; | ||
| } | ||
| } | ||
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| if (lang === "go" && /^func\s+\$[A-Z_]+\s*$/i.test(src)) { | ||
| return 'Hint: Go function patterns need params and a body. Try "func $NAME($$$) { $$$ }".'; | ||
| } | ||
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| if (lang === "rust" && /^fn\s+\$[A-Z_]+\s*$/i.test(src)) { | ||
| return 'Hint: Rust fn patterns need params and a body. Try "fn $NAME($$$) { $$$ }".'; | ||
| } |
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| * The empty-match hints turn the two most common `ast_grep` mistakes — regex | ||
| * leaking into an AST pattern, and a structurally incomplete declaration — into | ||
| * a one-line nudge. These lock the detection contract: every regex construct is | ||
| * caught and routed to `search`, valid patterns stay silent (no false nudge), | ||
| * regex detection outranks the language check, and language inference only | ||
| * commits when the extensions agree. |
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| if (src.startsWith("class ") && src.endsWith(":")) { | ||
| return `Hint: drop the trailing colon — ast_grep patterns are not full statements. Try: "${src.slice(0, -1)}"`; | ||
| } | ||
| if ((src.startsWith("def ") || src.startsWith("async def ")) && src.endsWith(":")) { | ||
| return `Hint: drop the trailing colon — ast_grep patterns are not full statements. Try: "${src.slice(0, -1)}"`; | ||
| } |
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| <critical> | ||
| - Parse issues mean the rewrite is malformed or mis-scoped — fix the pattern before assuming a clean no-op | ||
| - For one-off local text edits, you SHOULD prefer the Edit tool | ||
| - The apply re-runs the rewrite against the files at apply time and is rejected as a **stale preview** if the match set drifted since the preview (e.g. the file was edited in between) — re-run `ast_edit` to refresh, then `resolve` |
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If a file changes between the ast_edit preview and resolve apply, this guidance says the apply is rejected as stale, but the apply handler actually reruns runAstEditOnce(... dryRun: false) before computing stalePreview, so a mismatched nonzero run can already have written partial or extra replacements before returning an error. The prompt should not tell the model that drift prevents mutation unless the apply path is changed to dry-run/check first or roll back.
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Summary
Adds a pure pattern-hints module wired into
ast_grep: a zero-match result appends a one-line hint naming the likely mistake (regex leaking into an AST pattern, or a structurally incomplete declaration) and routes text/alternation/cross-language searches tosearch. Also enriches theast_grep/ast_editdescriptions and adds AST shape-routing + parallel-exploration guidance to the system prompt.Tests
Pure hint-detector + language-inference regression test;
bun checkgreen.Note: touches
prompts/system/system-prompt.mdalongside #2658 and #2659 (distinct sections); rebase if flagged.Closes #2657