chore(rust): re-land DocumentCompactor walker (squash-merge lost it from main)#288
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chopratejas merged 1 commit intomainfrom Apr 28, 2026
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…rom main) Stage 3c.2 PR3a-redux. The original PR3a (#286) was merged on GitHub on 2026-04-27 but its content never reached main — its parent merge (#285 PR2) was squash-merged, which drops commits stacked on top of the source branch. The walker module disappeared along with the intermediate commits. This PR re-lands `walker.rs` and updates the `compaction/mod.rs` re-exports — same content as commit 4db4f46 from the lost branch. No new functionality, no behavior change for existing crusher paths. # What the walker does (recap) Recursive descent over any JSON value: match value { Object(m) => recurse into each field Array(xs) => recurse into items, then try TabularCompactor on the array String(s) => parse-as-JSON-and-recurse / CCR-substitute / leave scalar => unchanged } Compactable spots become inline strings holding the rendered bytes. The wrapping JSON structure is preserved. # Why chore, not feat This is a re-land of previously-merged-but-lost code. No new feature shipped — fixing a regression caused by the stacked-PR squash-merge accident. Using `chore` keeps the version from bumping for what is effectively a parity restoration. # Tests - 13 walker unit tests pass. - 462/462 headroom-core lib tests overall. - 17/17 SmartCrusher parity fixtures byte-equal (untouched). - 185/185 Python tests pass. - make ci-precheck green. Module: crates/headroom-core/src/transforms/smart_crusher/compaction/walker.rs
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Summary
Re-lands the walker module that was lost when PR #285 (PR2) was squash-merged. The original PR3a (#286) was merged on GitHub on 2026-04-27, but because it was stacked on top of PR2's branch and PR2 was squash-merged, the walker commit (`4db4f46`) disappeared along with the intermediate history. This PR brings back the same content unmodified.
Type: `chore` — no new functionality, just a regression fix for the squash-merge accident. Using `chore` instead of `feat` so it doesn't bump the package version.
What the walker does
Recursive descent over any JSON value, applying lossless compaction at every compactable spot:
```rust
match value {
Object(m) => recurse into each field's value,
Array(xs) => recurse into items, then try TabularCompactor on the array,
String(s) => parse-as-JSON-and-recurse / CCR-substitute / leave,
scalar => unchanged,
}
```
Output: same JSON shape with compactable spots replaced by inline strings holding the rendered bytes. Wrapping object/array structure is preserved — only bulky leaves get replaced.
What stacks next
With the walker back, PR3b (document-level token budget + selective lossy escalation) can now build on top of it cleanly. Without the walker, PR3b had no place to plug in.
Tests
Provenance