Fix caching to respect .dockerignore

Previously kaniko would compute the cache key for any copy command by computing
the combined hash of all files in a directory, even if they were listed
as ignored.

With this change, the cache key creation was updated to be aware of ignored
files.

Related issues:
* https://github.com/GoogleContainerTools/kaniko/issues/594

pkg/executor/build.go

@@ -158,8 +158,10 @@ func (s *stageBuilder) populateCompositeKey(command fmt.Stringer, files []string
 		compositeKey = s.populateCopyCmdCompositeKey(command, v.From(), compositeKey)
 	}
 
+	srcCtx := s.opts.SrcContext
+
 	for _, f := range files {
-		if err := compositeKey.AddPath(f); err != nil {
+		if err := compositeKey.AddPath(f, srcCtx); err != nil {
 			return compositeKey, err
 		}
 	}

pkg/executor/composite_cache.go

@@ -54,14 +54,18 @@ func (s *CompositeCache) Hash() (string, error) {
 	return util.SHA256(strings.NewReader(s.Key()))
 }
 
-func (s *CompositeCache) AddPath(p string) error {
+func (s *CompositeCache) AddPath(p, context string) error {
 	sha := sha256.New()
 	fi, err := os.Lstat(p)
 	if err != nil {
 		return err
 	}
+	if util.ExcludeFile(p, context) {
+		return os.ErrNotExist
+	}
+
 	if fi.Mode().IsDir() {
-		k, err := HashDir(p)
+		k, err := HashDir(p, context)
 		if err != nil {
 			return err
 		}
@@ -81,12 +85,20 @@ func (s *CompositeCache) AddPath(p string) error {
 }
 
 // HashDir returns a hash of the directory.
-func HashDir(p string) (string, error) {
+func HashDir(p, context string) (string, error) {
 	sha := sha256.New()
 	if err := filepath.Walk(p, func(path string, fi os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
+		exclude := util.ExcludeFile(path, context)
+		if fi.IsDir() && exclude {
+			return filepath.SkipDir
+		}
+		if exclude {
+			return nil
+		}
+
 		fileHash, err := util.CacheHasher()(path)
 		if err != nil {
 			return err

pkg/util/command_util.go

@@ -213,7 +213,7 @@ func IsSrcsValid(srcsAndDest instructions.SourcesAndDest, resolvedSources []stri
 	if !ContainsWildcards(srcs) {
 		totalSrcs := 0
 		for _, src := range srcs {
-			if excludeFile(src, root) {
+			if ExcludeFile(src, root) {
 				continue
 			}
 			totalSrcs++
@@ -250,7 +250,7 @@ func IsSrcsValid(srcsAndDest instructions.SourcesAndDest, resolvedSources []stri
 			return errors.Wrap(err, "failed to get relative files")
 		}
 		for _, file := range files {
-			if excludeFile(file, root) {
+			if ExcludeFile(file, root) {
 				continue
 			}
 			totalFiles++

pkg/util/fs_util.go

@@ -561,7 +561,7 @@ func CopyDir(src, dest, buildcontext string) ([]string, error) {
 		if err != nil {
 			return nil, err
 		}
-		if excludeFile(fullPath, buildcontext) {
+		if ExcludeFile(fullPath, buildcontext) {
 			logrus.Debugf("%s found in .dockerignore, ignoring", src)
 			continue
 		}
@@ -594,7 +594,7 @@ func CopyDir(src, dest, buildcontext string) ([]string, error) {
 
 // CopySymlink copies the symlink at src to dest
 func CopySymlink(src, dest, buildcontext string) (bool, error) {
-	if excludeFile(src, buildcontext) {
+	if ExcludeFile(src, buildcontext) {
 		logrus.Debugf("%s found in .dockerignore, ignoring", src)
 		return true, nil
 	}
@@ -612,7 +612,7 @@ func CopySymlink(src, dest, buildcontext string) (bool, error) {
 
 // CopyFile copies the file at src to dest
 func CopyFile(src, dest, buildcontext string) (bool, error) {
-	if excludeFile(src, buildcontext) {
+	if ExcludeFile(src, buildcontext) {
 		logrus.Debugf("%s found in .dockerignore, ignoring", src)
 		return true, nil
 	}
@@ -656,8 +656,8 @@ func GetExcludedFiles(dockerfilepath string, buildcontext string) error {
 	return err
 }
 
-// excludeFile returns true if the .dockerignore specified this file should be ignored
+// ExcludeFile returns true if the .dockerignore specified this file should be ignored
-func excludeFile(path, buildcontext string) bool {
+func ExcludeFile(path, buildcontext string) bool {
 	if HasFilepathPrefix(path, buildcontext, false) {
 		var err error
 		path, err = filepath.Rel(buildcontext, path)

pkg/util/fs_util_test.go

@@ -919,14 +919,14 @@ func Test_correctDockerignoreFileIsUsed(t *testing.T) {
 		}
 		for _, excl := range tt.args.excluded {
 			t.Run(tt.name+" to exclude "+excl, func(t *testing.T) {
-				if !excludeFile(excl, tt.args.buildcontext) {
+				if !ExcludeFile(excl, tt.args.buildcontext) {
 					t.Errorf("'%v' not excluded", excl)
 				}
 			})
 		}
 		for _, incl := range tt.args.included {
 			t.Run(tt.name+" to include "+incl, func(t *testing.T) {
-				if excludeFile(incl, tt.args.buildcontext) {
+				if ExcludeFile(incl, tt.args.buildcontext) {
 					t.Errorf("'%v' not included", incl)
 				}
 			})