Pi Lens Ast Grep

What it does

When your agent uses it

• Replacing code patterns - use ast-grep instead of text search for semantic accuracy

Example prompts

• “/pi-lens-ast-grep”

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Be specific — fetchMetrics($ARGS) not fetchMetrics
2. 2Scope it — always specify paths to relevant files
3. 3Retry once on zero matches — simplify the pattern, same paths, then fall back to grep
4. 4Dry-run first — apply: false before apply: true
5. 5Valid code only — function $NAME($$$) { $$$ } not function $NAME(
6. 6Avoid selector unless expert — narrows to AST node kind; does not extract metavariables
7. 7Metavariables don't work inside strings — from "$PATH" matches literal "$PATH", not a wildcard

What it can do on your machine

Read from SKILL.md and the folder at commit db92612. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are yaml and bash).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • ast-grep.github.io

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Pi Lens Ast Grep loads about 2k tokens when it runs. Until then it costs about 31 tokens; SKILL.md has 745 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~31

When it runs · the whole SKILL.md, loaded when a task matches

~2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from apmantza/pi-lens at commit db92612, republished under its MIT licence (© apmantza). 745 words, ~1,987 tokens.

name

pi-lens-ast-grep

description

Use when searching or replacing code patterns - use ast-grep instead of text search for semantic accuracy

# search (≈ ast_grep_search)
ast-grep run -p 'fetchMetrics($$$ARGS)' -l ts src/

# rewrite (≈ ast_grep_replace; -U applies all)
ast-grep run -p 'var $X' -r 'let $X' -l js src/ -U

# full YAML rule (≈ the rule: parameter)
ast-grep scan --rule my-rule.yml src/

# console.log only inside functions
ast_grep_search pattern="console.log($MSG)" lang="typescript" insideKind="function_declaration"

# replace var with let, scoped to functions only
ast_grep_replace pattern="var $X" rewrite="let $X" lang="javascript" insideKind="function_declaration"

ast_grep_search rule="id: my-rule
language: TypeScript
rule:
  pattern: console.log($MSG)
  inside:
    kind: function_declaration
    stopBy: end" lang="typescript"

ast_grep_search dump=true pattern="function foo() { return 1; }" lang="typescript"

# console.log inside a class method
pattern: console.log($$$)
inside:
  kind: method_definition
  stopBy: end

# any arrow function
kind: arrow_function

❌ $VAR inside quotes — matches literal "$VAR", not a metavar
   from "$PATH"  →  use grep for wildcard path matching
   from "./utils"  →  ✅ exact string literal works fine

❌ Trailing comma in objects
   { type: $T, }  →  use { type: $T }

❌ Shorthand property mismatch
   { runnerId: $RID }  →  won't match { runnerId }
   use { runnerId } or { runnerId, $$$REST }

❌ Unnamed $$$ when you need the value
   foo($$$)  →  captures nothing; use foo($$$ARGS) to inspect matches

❌ Multiple top-level statements — triggers "Multiple AST nodes are detected"
   Two shapes, two fixes:

   1. Sequence inside a block — wrap in braces:
      foo(); bar();  →  { foo(); bar(); }

   2. Cross-context (module-level + block-level together, e.g. an import AND a call) —
      wrapping in {} makes the pattern invalid (imports can't live inside a block).
      Use two searches: find files containing the import, then scope the call search
      to those paths. Or use a YAML `inside:`/`has:` rule (see Composite section above).

src/foo.ts:1:1: const x = foo(a, b)
  $VAR=x  $$$ARGS=a,b

© apmantza, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/pi-lens-ast-grep of apmantza/pi-lens.

Open the folder on GitHubat commit db92612