ast-grep
Default invocation:
ast-grep -l LANG -p 'PATTERN' # search
ast-grep -l LANG -p 'OLD' -r 'NEW' # preview rewrite
ast-grep -l LANG -p 'OLD' -r 'NEW' --update-all # apply
-l is required -- auto-detect is unreliable. Interactive mode (-i) does not work from this harness.
Metavariables
$VAR-- one AST node (an expression, an identifier, ...)$$$ARGS-- zero or more items in a list (function args, statement bodies)$$STMT-- multiple statements
Canonical patterns
# Rename a function across all call sites
ast-grep -l typescript -p 'oldFn($$$ARGS)' -r 'newFn($$$ARGS)'
# Rename a method on any receiver
ast-grep -l javascript -p '$OBJ.oldMethod($$$ARGS)' -r '$OBJ.newMethod($$$ARGS)'
# Rewrite imports
ast-grep -l typescript -p 'import $WHAT from "old-pkg"' -r 'import $WHAT from "new-pkg"'
Workflow: run without -r to see matches, run with -r to preview the diff, then add --update-all. For surgical per-site control, use ast-grep to find locations and Edit to apply.
To list a file's or package's structure (functions, types, imports/exports) rather than match a pattern, use the outline subcommand -- see the code-structure skill.
