[ctxloop]

resolver.Memory.Tag overwrites a reference's forward entry but leaves the reference in the reverse tag set of the descriptor it previously pointed to. oci.Store.isTagged reads that tag set, so Delete with AutoGC keeps a manifest whose tag has moved to another manifest, along with the blobs only it references, until an explicit GC(). Details and reproduction are in #1468.

The fix removes the reference from its previous descriptor's tag set before adding it to the new one, and drops that set once it is empty, as Untag does. It runs under the same lock as the rest of Tag, so a concurrent Resolve sees the reference pointing to either the old or the new descriptor, never to neither.

Tests

Both tests fail on main @ a0f6556 without the fix and pass with it.

• TestTagSetRetag (internal/resolver) moves latest from one descriptor to another and checks both tag sets:

  memory_test.go:140: TagSet(oldDesc) = map[latest:{}], want no "latest" after it moved to newDesc
  

• TestStore_DeleteWithAutoGCAfterRetag (content/oci) pushes an index I referencing manifest A, moves latest from A to manifest B, and deletes I. Before the fix, A and its layer foo remain:

  oci_test.go:2494: {application/vnd.oci.image.layer.v1.tar sha256:2c26b46b... 3 [] map[] [] <nil> } should not exist in store
  oci_test.go:2494: {application/vnd.oci.image.manifest.v1+json sha256:da223c7d... 335 [] map[] [] <nil> } should not exist in store
  

  It also checks that B, its layer, the shared config and latest → B are left intact.

Dropping the emptied set is exercised by TestTagSetRetag but not asserted, since TagSet returns an empty set either way. It only keeps m.tags from accumulating empty entries.

make test passes, including -race.

v2

The reverse index dates from #680, so v2 has had the same bug since v2.4.0, and both tests fail the same way there. I can send a backport once this is merged.

Fixes #1468

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.12%. Comparing base (a0f6556) to head (6c800bf).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1469      +/-   ##
==========================================
- Coverage   91.13%   91.12%   -0.01%     
==========================================
  Files          98       98              
  Lines        7614     7619       +5     
==========================================
+ Hits         6939     6943       +4     
- Misses        664      665       +1     
  Partials       11       11              

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[TerryHowe]

/lgtm