@ossl-dev/differens-correlate

Finds the code that moved between files.

Part of differens. A per-file diff cannot see this: extracting a function into a new module looks like a deletion in one file and an unrelated addition in another, and no amount of looking at either file alone will connect them.

npm install @ossl-dev/differens-correlate

Use

Run your per-file diffs first, then hand the whole set over at once.

import { correlate } from "@ossl-dev/differens-correlate";

const { moves } = correlate([
  { filePath: "src/utils.ts", actions: utilsActions },
  { filePath: "src/validators.ts", actions: validatorsActions },
]);

moves[0];
// { node:       { kind: "Function", label: "validate", ... },
//   fromFile:   "src/utils.ts",
//   toFile:     "src/validators.ts",
//   modified:   false,
//   similarity: 1 }

modified says whether the code changed on the way. A clean relocation is false with similarity: 1; something that was moved and edited comes back true with a score below it, which is the difference between "this moved" and "this moved and you should read it again".

correlate(fileChanges, { renameSimilarityThreshold: 0.75 }); // default 0.6

How it decides

Deleted and inserted nodes are bucketed by structure hash, so only things shaped alike are ever compared. Within a bucket, an identical content hash or an identical value is an unambiguous move. Anything short of that is scored, and only clears the bar above the threshold.

Only named nodes are considered. Correlating anonymous ones produced confident nonsense: two unrelated files that happened to share a directory name in their paths would report their contents as having moved between them.

Related

• @ossl-dev/differens-core -- produces the per-file actions this reads
• @ossl-dev/differens-narrate -- turns a move into "moved function validate from utils.ts to validators.ts"
• differens -- the CLI, which runs this across a whole changeset

MIT. Source.