Can I use regex groups in the fix?

[Lodin]

I'm trying to replace a part of the variable name, like __PART_TO_REPLACE__OtherPart -> replacedOtherPart. Is it possible to do? I tried the following YAML, but it does not seem to work.

rule:
  pattern: $A
  regex: __PART_TO_REPLACE__(.*)
  kind: identifier
fix:
  replaced$1

[HerringtonDarkholme]

Thanks for trying out ast-grep!

Using regex group directly in fix is not possible. Because we can have multiple regex sub-rules in one YAML. It is not clear which group $1 refers to.

But ast-grep does have a (experimental) workaround.

transform is used to manipulate string in a matched variable. Refer to #436 (comment) for more explanation.

rule:
  pattern: $A
  regex: __PART_TO_REPLACE__(.*)
  kind: identifier
transform:
  CHANGED:
    replace:
      source: $A
      replace: __PART_TO_REPLACE__(.*)
      by: 'replaced$1'
fix:
  $CHANGED

https://ast-grep.github.io/playground.html#eyJtb2RlIjoiQ29uZmlnIiwibGFuZyI6ImphdmFzY3JpcHQiLCJxdWVyeSI6ImNvbnNvbGUubG9nKCRNQVRDSCkiLCJyZXdyaXRlIjoibG9nZ2VyLmxvZygkTUFUQ0gpIiwiY29uZmlnIjoicnVsZTpcbiAgcGF0dGVybjogJEFcbiAgcmVnZXg6IF9fUEFSVF9UT19SRVBMQUNFX18oLiopXG4gIGtpbmQ6IGlkZW50aWZpZXJcbnRyYW5zZm9ybTpcbiAgQ0hBTkdFRDpcbiAgICByZXBsYWNlOlxuICAgICAgc291cmNlOiAkQVxuICAgICAgcmVwbGFjZTogX19QQVJUX1RPX1JFUExBQ0VfXyguKilcbiAgICAgIGJ5OiAncmVwbGFjZWQkMSdcbmZpeDpcbiAgJENIQU5HRUQiLCJzb3VyY2UiOiJ2YXIgX19QQVJUX1RPX1JFUExBQ0VfX2ZvbyA9IDEyMyJ9