Use casesData and engineering

Large-scale codemods and migrations

Deterministic output, real pattern matching, and py() when you need an existing Python library.

The problem

Framework upgrades touch thousands of files. AST-aware tools exist in every ecosystem but rarely share one runtime with the AI step that handles the odd files regex cannot. Teams run a codemod, then a separate ChatGPT pass, and hope the outputs merge.

Why Ecko

Pattern matching
Match syntax shapes deterministically for the 95% case. Commit the transform; review the diff in git.
AI for the long tail
Send only unmatched files to ai with typed output, still in the same program.
py() bridge
Call lib2to3, libcst, or a vendor parser through py() when rewriting someone else's language syntax.

In practice

codemod.ecko
fn migrate(src: str) -> str {
  match parse(src) {
    OldCall(args) => rewrite(args)
    _ => ai "Modernise this syntax" from src
  }
}

Further reading

Related cases

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