# final-fix2-bincraft-report

## Summary

Critical correctness fix for the `bincraftr` package-patching feature.
Without `Built:` in the PACKAGES index, pak recompiles from the source tarball, silently discarding build-time fixes baked in at patch time (e.g. `RCPP_PARALLEL_USE_TBB=0`).

---

## Fix 1 — production code (`R/patches.R`)

One-line change in `prepare_patched_repo()`:

```r
# BEFORE (broken)
tools::write_PACKAGES(contrib, type = "source")

# AFTER (fixed)
tools::write_PACKAGES(contrib, type = "source", fields = "Built")
```

`tools::write_PACKAGES` only emits extra fields when explicitly requested via the `fields` argument.
Without it, the `Built:` line present in the tarball's DESCRIPTION is silently dropped from the PACKAGES index.

---

## Fix 2 — regression test (`tests/testthat/test-patches.R`)

Test: `"prepare_patched_repo src/contrib layout is resolvable by available.packages"`

Two additions:

1. The minimal `pkgfoo` DESCRIPTION written into the tarball now includes a `Built:` line:
   ```
   Built: R 4.5.3; x86_64-pc-linux-gnu; 2026-06-30 00:00:00 UTC; unix
   ```
   This makes the tarball look like a real prebuilt binary package.

2. After `prepare_patched_repo(...)`, a new assertion checks the index:
   ```r
   pkgs <- readLines(file.path(out, "src", "contrib", "PACKAGES"))
   expect_true(any(grepl("^Built:", pkgs)))
   ```

The real `tools::write_PACKAGES` is used (not mocked) so the assertion is meaningful.
The older "serves a cached binary and writes an index" test continues to mock `tools::write_PACKAGES` — that is intentional (it tests orchestration only).

---

## RED / GREEN evidence

Verified with a standalone script calling the real `tools::write_PACKAGES` on an identical tarball:

```
RED  (old, type="source", no fields)  — Built in PACKAGES: FALSE
GREEN (new, type="source", fields="Built") — Built in PACKAGES: TRUE
```

---

## Test run (post-fix)

```
[ FAIL 0 | WARN 0 | SKIP 1 | PASS 42 ]
```

SKIP: e2e test (`BINCRAFT_PATCH_E2E` not set) — expected.
All 42 unit/integration tests pass.

---

## Commit

```
10e610f fix(patches): preserve Built field so pak installs patched binary without recompiling
```

Branch: `feat/package-patching`
Repo: `/Users/pjs/git/codefloe.com/rpkgs/bincraftr`