Some very quick, superficial differences:

• ast-grep uses tree-sitter for understanding languages

• ast-grep is written in Rust

• ast-grep uses YAML for config

• ast-grep more normal --flags

• comby doesn’t use tree-sitter and does it’s own thing… not sure what to think of this approach

• comby is written in OCaml

• comby uses TOML for config

• comby uses -single-dash-flags

• both have online playgrounds for testing

I personally hate YAML, so it’s comby for me! (For now.)

Also, here’s what Comby says about its approach to matching: https://comby.dev/docs/faq

Underneath the hood, Comby uses no tree definition, but turns patterns into an executable routine (a language-aware parser) where the tree structure is implicit in this executable routine. In theory, the syntax matched by this routine could dump a serialized parse tree, but this isn’t implemented :-). With this design, Comby sacrifices this ability to recognize many predefined language constructs in order to support a more freeform pattern writing and matching process. This loses precision for deeply recognizing all of a program’s structures, and may fall short of your needs depending on your use case.

I found ast-grep inconvenient to match several consecutive lines of python whereas comby handles this reasonably fine.