imagebuildah,multi-stage: do not remove base-image when built without --layers

imagebuildah/executor.go

@@ -470,14 +470,14 @@ func (b *Executor) getImageTypeAndHistoryAndDiffIDs(ctx context.Context, imageID
 	return manifestFormat, oci.History, oci.RootFS.DiffIDs, nil
 }
 
-func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageExecutor, stages imagebuilder.Stages, stageIndex int) (imageID string, ref reference.Canonical, err error) {
+func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageExecutor, stages imagebuilder.Stages, stageIndex int) (imageID string, ref reference.Canonical, onlyBaseImage bool, err error) {
 	stage := stages[stageIndex]
 	ib := stage.Builder
 	node := stage.Node
 	base, err := ib.From(node)
 	if err != nil {
 		logrus.Debugf("buildStage(node.Children=%#v)", node.Children)
-		return "", nil, err
+		return "", nil, false, err
 	}
 
 	// If this is the last stage, then the image that we produce at
@@ -508,7 +508,7 @@ func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageE
 			if len(labelLine) > 0 {
 				additionalNode, err := imagebuilder.ParseDockerfile(strings.NewReader("LABEL" + labelLine + "\n"))
 				if err != nil {
-					return "", nil, fmt.Errorf("while adding additional LABEL step: %w", err)
+					return "", nil, false, fmt.Errorf("while adding additional LABEL step: %w", err)
 				}
 				stage.Node.Children = append(stage.Node.Children, additionalNode.Children...)
 			}
@@ -527,13 +527,13 @@ func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageE
 				value := env[1]
 				envLine += fmt.Sprintf(" %q=%q", key, value)
 			} else {
-				return "", nil, fmt.Errorf("BUG: unresolved environment variable: %q", key)
+				return "", nil, false, fmt.Errorf("BUG: unresolved environment variable: %q", key)
 			}
 		}
 		if len(envLine) > 0 {
 			additionalNode, err := imagebuilder.ParseDockerfile(strings.NewReader("ENV" + envLine + "\n"))
 			if err != nil {
-				return "", nil, fmt.Errorf("while adding additional ENV step: %w", err)
+				return "", nil, false, fmt.Errorf("while adding additional ENV step: %w", err)
 			}
 			// make this the first instruction in the stage after its FROM instruction
 			stage.Node.Children = append(additionalNode.Children, stage.Node.Children...)
@@ -574,8 +574,8 @@ func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageE
 	}
 
 	// Build this stage.
-	if imageID, ref, err = stageExecutor.Execute(ctx, base); err != nil {
-		return "", nil, err
+	if imageID, ref, onlyBaseImage, err = stageExecutor.Execute(ctx, base); err != nil {
+		return "", nil, onlyBaseImage, err
 	}
 
 	// The stage succeeded, so remove its build container if we're
@@ -588,7 +588,7 @@ func (b *Executor) buildStage(ctx context.Context, cleanupStages map[int]*StageE
 		b.stagesLock.Unlock()
 	}
 
-	return imageID, ref, nil
+	return imageID, ref, onlyBaseImage, nil
 }
 
 type stageDependencyInfo struct {
@@ -880,10 +880,11 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 	b.warnOnUnsetBuildArgs(stages, dependencyMap, b.args)
 
 	type Result struct {
-		Index   int
-		ImageID string
-		Ref     reference.Canonical
-		Error   error
+		Index         int
+		ImageID       string
+		OnlyBaseImage bool
+		Ref           reference.Canonical
+		Error         error
 	}
 
 	ch := make(chan Result, len(stages))
@@ -943,21 +944,23 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 						return
 					}
 				}
-				stageID, stageRef, stageErr := b.buildStage(ctx, cleanupStages, stages, index)
+				stageID, stageRef, stageOnlyBaseImage, stageErr := b.buildStage(ctx, cleanupStages, stages, index)
 				if stageErr != nil {
 					cancel = true
 					ch <- Result{
-						Index: index,
-						Error: stageErr,
+						Index:         index,
+						Error:         stageErr,
+						OnlyBaseImage: stageOnlyBaseImage,
 					}
 					return
 				}
 
 				ch <- Result{
-					Index:   index,
-					ImageID: stageID,
-					Ref:     stageRef,
-					Error:   nil,
+					Index:         index,
+					ImageID:       stageID,
+					Ref:           stageRef,
+					OnlyBaseImage: stageOnlyBaseImage,
+					Error:         nil,
 				}
 			}()
 		}
@@ -987,7 +990,9 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 			// We're not populating the cache with intermediate
 			// images, so add this one to the list of images that
 			// we'll remove later.
-			if !b.layers {
+			// Only remove intermediate image is `--layers` is not provided
+			// or following stage was not only a base image ( i.e a different image ).
+			if !b.layers && !r.OnlyBaseImage {
 				cleanupImages = append(cleanupImages, r.ImageID)
 			}
 		}