fix: preserve BOM in text tool round-trips#23797
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Hona merged 6 commits intoanomalyco:devfrom Apr 22, 2026
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Pull request overview
This PR introduces BOM-aware read/write helpers and applies them across the write, edit, and apply_patch tools to preserve UTF-8 BOMs on disk while keeping BOMs out of visible diffs/patch previews, along with regression tests.
Changes:
- Add
util/bom.tsto split/join BOMs, read files while preserving BOM state, and re-sync BOM after formatting. - Update
write,edit, andapply_patchflows to compute diffs on BOM-stripped text and to restore BOMs after formatter runs. - Add regression tests covering overwrite/edit/apply-patch scenarios involving BOM-prefixed files.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/opencode/src/util/bom.ts | New shared BOM utilities (split/join/read/sync). |
| packages/opencode/src/tool/write.ts | Preserve BOMs during write + after formatting, and keep BOM out of diff. |
| packages/opencode/src/tool/edit.ts | Preserve BOMs for in-place edits and after formatting (with a couple of ordering/overwrite concerns). |
| packages/opencode/src/tool/apply_patch.ts | Track BOM per file change and restore BOM after formatting so patches don’t invent first-line diffs. |
| packages/opencode/src/patch/index.ts | Carry BOM state through patch-derived updates (but BOM detection depends on read semantics). |
| packages/opencode/test/tool/write.test.ts | Regression test: overwriting existing BOM file preserves BOM. |
| packages/opencode/test/tool/edit.test.ts | Regression test: first visible line edit in BOM file works and diff omits BOM. |
| packages/opencode/test/tool/apply_patch.test.ts | Regression test: patch preview doesn’t show invented first-line diff; BOM preserved after apply. |
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Pull request overview
Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.
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erfianugrah
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fixes THIS:
after
no weird BOM rendering! :)
Summary
write,edit, andapply_patchwithout leaking the BOM into visible diff or edit textTesting