lguohan
diff --git a/‎builder/dockerfile/builder.go‎
Lines changed: 16 additions & 12 deletions b/‎builder/dockerfile/builder.go‎
Lines changed: 16 additions & 12 deletions
diff --git a/‎image/fs.go‎
Lines changed: 10 additions & 5 deletions b/‎image/fs.go‎
Lines changed: 10 additions & 5 deletions
@@ -287,18 +287,7 @@ func (b *Builder) build(stdout io.Writer, stderr io.Writer, out io.Writer) (stri
 		}
 	}
 
-	// check if there are any leftover build-args that were passed but not
-	// consumed during build. Return a warning, if there are any.
-	leftoverArgs := []string{}
-	for arg := range b.options.BuildArgs {
-		if !b.isBuildArgAllowed(arg) {
-			leftoverArgs = append(leftoverArgs, arg)
-		}
-	}
-
-	if len(leftoverArgs) > 0 {
-		fmt.Fprintf(b.Stderr, "[Warning] One or more build-args %v were not consumed\n", leftoverArgs)
-	}
+	b.warnOnUnusedBuildArgs()
 
 	if b.image == "" {
 		return "", errors.New("No image was generated. Is your Dockerfile empty?")
@@ -326,6 +315,21 @@ func (b *Builder) build(stdout io.Writer, stderr io.Writer, out io.Writer) (stri
 	return b.image, nil
 }
 
+// check if there are any leftover build-args that were passed but not
+// consumed during build. Print a warning, if there are any.
+func (b *Builder) warnOnUnusedBuildArgs() {
+	leftoverArgs := []string{}
+	for arg := range b.options.BuildArgs {
+		if !b.isBuildArgAllowed(arg) {
+			leftoverArgs = append(leftoverArgs, arg)
+		}
+	}
+
+	if len(leftoverArgs) > 0 {
+		fmt.Fprintf(b.Stderr, "[Warning] One or more build-args %v were not consumed\n", leftoverArgs)
+	}
+}
+
 // Cancel cancels an ongoing Dockerfile build.
 func (b *Builder) Cancel() {
 	b.cancel()
 
@@ -10,6 +10,7 @@ import (
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/pkg/ioutils"
 	"github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
 )
 
 // DigestWalkFunc is function called by StoreBackend.Walk
@@ -47,10 +48,10 @@ func newFSStore(root string) (*fs, error) {
 		root: root,
 	}
 	if err := os.MkdirAll(filepath.Join(root, contentDirName, string(digest.Canonical)), 0700); err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "failed to create storage backend")
 	}
 	if err := os.MkdirAll(filepath.Join(root, metadataDirName, string(digest.Canonical)), 0700); err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "failed to create storage backend")
 	}
 	return s, nil
 }
@@ -96,7 +97,7 @@ func (s *fs) Get(dgst digest.Digest) ([]byte, error) {
 func (s *fs) get(dgst digest.Digest) ([]byte, error) {
 	content, err := ioutil.ReadFile(s.contentFile(dgst))
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "failed to get digest %s", dgst)
 	}
 
 	// todo: maybe optional
@@ -118,7 +119,7 @@ func (s *fs) Set(data []byte) (digest.Digest, error) {
 
 	dgst := digest.FromBytes(data)
 	if err := ioutils.AtomicWriteFile(s.contentFile(dgst), data, 0600); err != nil {
-		return "", err
+		return "", errors.Wrap(err, "failed to write digest data")
 	}
 
 	return dgst, nil
@@ -161,7 +162,11 @@ func (s *fs) GetMetadata(dgst digest.Digest, key string) ([]byte, error) {
 	if _, err := s.get(dgst); err != nil {
 		return nil, err
 	}
-	return ioutil.ReadFile(filepath.Join(s.metadataDir(dgst), key))
+	bytes, err := ioutil.ReadFile(filepath.Join(s.metadataDir(dgst), key))
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to read metadata")
+	}
+	return bytes, nil
 }
 
 // DeleteMetadata removes the metadata associated with a digest.
Original file line number	Diff line number	Diff line change
`@@ -10,6 +10,7 @@ import (`
`10`	`10`	`"github.com/Sirupsen/logrus"`
`11`	`11`	`"github.com/docker/docker/pkg/ioutils"`
`12`	`12`	`"github.com/opencontainers/go-digest"`
	`13`	`+ "github.com/pkg/errors"`
`13`	`14`	`)`
`14`	`15`
`15`	`16`	`// DigestWalkFunc is function called by StoreBackend.Walk`
`@@ -47,10 +48,10 @@ func newFSStore(root string) (*fs, error) {`
`47`	`48`	`root: root,`
`48`	`49`	`}`
`49`	`50`	`if err := os.MkdirAll(filepath.Join(root, contentDirName, string(digest.Canonical)), 0700); err != nil {`
`50`		`- return nil, err`
	`51`	`+ return nil, errors.Wrap(err, "failed to create storage backend")`
`51`	`52`	`}`
`52`	`53`	`if err := os.MkdirAll(filepath.Join(root, metadataDirName, string(digest.Canonical)), 0700); err != nil {`
`53`		`- return nil, err`
	`54`	`+ return nil, errors.Wrap(err, "failed to create storage backend")`
`54`	`55`	`}`
`55`	`56`	`return s, nil`
`56`	`57`	`}`
`@@ -96,7 +97,7 @@ func (s *fs) Get(dgst digest.Digest) ([]byte, error) {`
`96`	`97`	`func (s *fs) get(dgst digest.Digest) ([]byte, error) {`
`97`	`98`	`content, err := ioutil.ReadFile(s.contentFile(dgst))`
`98`	`99`	`if err != nil {`
`99`		`- return nil, err`
	`100`	`+ return nil, errors.Wrapf(err, "failed to get digest %s", dgst)`
`100`	`101`	`}`
`101`	`102`
`102`	`103`	`// todo: maybe optional`
`@@ -118,7 +119,7 @@ func (s *fs) Set(data []byte) (digest.Digest, error) {`
`118`	`119`
`119`	`120`	`dgst := digest.FromBytes(data)`
`120`	`121`	`if err := ioutils.AtomicWriteFile(s.contentFile(dgst), data, 0600); err != nil {`
`121`		`- return "", err`
	`122`	`+ return "", errors.Wrap(err, "failed to write digest data")`
`122`	`123`	`}`
`123`	`124`
`124`	`125`	`return dgst, nil`
`@@ -161,7 +162,11 @@ func (s *fs) GetMetadata(dgst digest.Digest, key string) ([]byte, error) {`
`161`	`162`	`if _, err := s.get(dgst); err != nil {`
`162`	`163`	`return nil, err`
`163`	`164`	`}`
`164`		`- return ioutil.ReadFile(filepath.Join(s.metadataDir(dgst), key))`
	`165`	`+ bytes, err := ioutil.ReadFile(filepath.Join(s.metadataDir(dgst), key))`
	`166`	`+ if err != nil {`
	`167`	`+ return nil, errors.Wrap(err, "failed to read metadata")`
	`168`	`+ }`
	`169`	`+ return bytes, nil`
`165`	`170`	`}`
`166`	`171`
`167`	`172`	`// DeleteMetadata removes the metadata associated with a digest.`