imagebuildah.executor.getCreatedBy(): use digests for previous stages

imagebuildah/executor.go

@@ -121,7 +121,8 @@ type executor struct {
 	useCache                                bool
 	removeIntermediateCtrs                  bool
 	forceRmIntermediateCtrs                 bool
-	imageMap                                map[string]string           // Used to map images that we create to handle the AS construct.
+	imageMap                                map[string]string           // Used to map images that we create to handle the AS construct (stage name to image ID).
+	imageDigestMap                          map[string]string           // Used to map images that we create to handle the AS construct (stage name to image (manifest) digest).
 	containerMap                            map[string]*buildah.Builder // Used to map from image names to only-created-for-the-rootfs containers.
 	baseMap                                 map[string]struct{}         // Holds the names of every base image, as given.
 	rootfsMap                               map[string]struct{}         // Holds the names of every stage whose rootfs is referenced in a COPY or ADD instruction.
@@ -325,6 +326,7 @@ func newExecutor(logger *logrus.Logger, logPrefix string, store storage.Store, o
 		removeIntermediateCtrs:                  options.RemoveIntermediateCtrs,
 		forceRmIntermediateCtrs:                 options.ForceRmIntermediateCtrs,
 		imageMap:                                make(map[string]string),
+		imageDigestMap:                          make(map[string]string),
 		containerMap:                            make(map[string]*buildah.Builder),
 		baseMap:                                 make(map[string]struct{}),
 		rootfsMap:                               make(map[string]struct{}),
@@ -1162,6 +1164,7 @@ func (b *executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 		// that we can look it up later.
 		if r.Index < len(stages)-1 && r.ImageID != "" {
 			b.imageMap[stage.Name] = r.ImageID
+			b.imageDigestMap[stage.Name] = r.CommitResults.Digest.String()
 			// We're not populating the cache with intermediate
 			// images, so add this one to the list of images that
 			// we'll remove later.

imagebuildah/stage_executor.go

@@ -2055,7 +2055,7 @@ func (s *stageExecutor) getCreatedBy(node *parser.Node, addedContentSummary stri
 			if mountOptionFrom != "" {
 				if stage, ok := s.executor.stages[mountOptionFrom]; ok {
 					// If source is a previous stage then checksum is image digest for that stage
-					if image, isPreviousStage := s.executor.imageMap[stage.name]; isPreviousStage {
+					if image, isPreviousStage := s.executor.imageDigestMap[stage.name]; isPreviousStage {
 						mountCheckSum = image
 					}
 				} else {

tests/bud.bats

@@ -753,6 +753,31 @@ _EOF
   expect_output --substring "anotherfile"
 }
 
+@test "bud --layers with --mount type bind should burst cache if content is changed - source is previous stage" {
+  _prefetch busybox
+  local contextdir=${TEST_SCRATCH_DIR}/cache
+  mkdir -p $contextdir
+
+  for iteration in 1 2 ; do
+    for content in 1 2 ; do
+      # based on reproducer from #6845
+      cat > $contextdir/Containerfile <<-_EOF
+      FROM busybox AS base
+
+      FROM base AS builder
+      RUN mkdir /build && echo "$content" > /build/foo.txt
+
+      FROM base AS prod
+      RUN --mount=type=bind,source=/build,from=builder,target=/build cp /build/foo.txt bar.txt
+_EOF
+      run_buildah build $WITH_POLICY_JSON --layers --iidfile ${TEST_SCRATCH_DIR}/$content.$iteration.txt $contextdir
+    done
+  done
+  assert $(< ${TEST_SCRATCH_DIR}/1.1.txt) == $(< ${TEST_SCRATCH_DIR}/1.2.txt)
+  assert $(< ${TEST_SCRATCH_DIR}/2.1.txt) == $(< ${TEST_SCRATCH_DIR}/2.2.txt)
+  assert $(< ${TEST_SCRATCH_DIR}/1.1.txt) != $(< ${TEST_SCRATCH_DIR}/2.1.txt)
+}
+
 @test "bud --layers should not hit cache if heredoc is changed" {
   _prefetch alpine
   local contextdir=${TEST_SCRATCH_DIR}/bud/platform