Recompute the size in the same places that we recompute the digest. (#…

…193)

Fixes: #192

v1/mutate/mutate.go

@@ -16,6 +16,7 @@ package mutate
 
 import (
 	"archive/tar"
+	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -110,10 +111,17 @@ func Append(base v1.Image, adds ...Addendum) (v1.Image, error) {
 	image.configFile.RootFS.DiffIDs = diffIDs
 	image.configFile.History = history
 	image.manifest.Layers = manifestLayers
-	image.manifest.Config.Digest, err = image.ConfigName()
+
+	rcfg, err := image.RawConfigFile()
+	if err != nil {
+		return nil, err
+	}
+	d, sz, err := v1.SHA256(bytes.NewBuffer(rcfg))
 	if err != nil {
 		return nil, err
 	}
+	image.manifest.Config.Digest = d
+	image.manifest.Config.Size = sz
 
 	return image, nil
 }
@@ -139,10 +147,16 @@ func Config(base v1.Image, cfg v1.Config) (v1.Image, error) {
 		digestMap:  make(map[v1.Hash]v1.Layer),
 	}
 
-	image.manifest.Config.Digest, err = image.ConfigName()
+	rcfg, err := image.RawConfigFile()
+	if err != nil {
+		return nil, err
+	}
+	d, sz, err := v1.SHA256(bytes.NewBuffer(rcfg))
 	if err != nil {
 		return nil, err
 	}
+	image.manifest.Config.Digest = d
+	image.manifest.Config.Size = sz
 	return image, nil
 }
 

v1/mutate/mutate_test.go

@@ -172,6 +172,10 @@ func TestAppendWithHistory(t *testing.T) {
 		t.Fatalf("correct layer was not appended (-got, +want) %v", diff)
 	}
 
+	if configSizesAreEqual(t, source, result) {
+		t.Fatal("adding a layer MUST change the config file size")
+	}
+
 	cf := getConfigFile(t, result)
 
 	if diff := cmp.Diff(cf.History[1], addendum.History); diff != "" {
@@ -194,6 +198,10 @@ func TestAppendLayers(t *testing.T) {
 		t.Fatal("appending a layer did not mutate the config file")
 	}
 
+	if configSizesAreEqual(t, source, result) {
+		t.Fatal("adding a layer MUST change the config file size")
+	}
+
 	layers := getLayers(t, result)
 
 	if got, want := len(layers), 2; got != want {
@@ -232,6 +240,10 @@ func TestMutateConfig(t *testing.T) {
 		t.Fatal("mutating the config did not mutate the config file")
 	}
 
+	if configSizesAreEqual(t, source, result) {
+		t.Fatal("adding an enviornment variable MUST change the config file size")
+	}
+
 	if !reflect.DeepEqual(cfg.Config.Env, newEnv) {
 		t.Fatalf("incorrect environment set %v!=%v", cfg.Config.Env, newEnv)
 	}
@@ -245,8 +257,8 @@ func TestMutateCreatedAt(t *testing.T) {
 		t.Fatalf("failed to mutate a config: %v", err)
 	}
 
-	if manifestDigestsAreEqual(t, source, result) {
-		t.Fatal("mutating the created time MUST mutate the manifest digest")
+	if configDigestsAreEqual(t, source, result) {
+		t.Fatal("mutating the created time MUST mutate the config digest")
 	}
 
 	got := getConfigFile(t, result).Created.Time
@@ -340,7 +352,7 @@ func configFilesAreEqual(t *testing.T, first, second v1.Image) bool {
 	return cmp.Equal(fc, sc)
 }
 
-func manifestDigestsAreEqual(t *testing.T, first, second v1.Image) bool {
+func configDigestsAreEqual(t *testing.T, first, second v1.Image) bool {
 	t.Helper()
 
 	fm := getManifest(t, first)
@@ -349,6 +361,15 @@ func manifestDigestsAreEqual(t *testing.T, first, second v1.Image) bool {
 	return fm.Config.Digest == sm.Config.Digest
 }
 
+func configSizesAreEqual(t *testing.T, first, second v1.Image) bool {
+	t.Helper()
+
+	fm := getManifest(t, first)
+	sm := getManifest(t, second)
+
+	return fm.Config.Size == sm.Config.Size
+}
+
 func manifestsAreEqual(t *testing.T, first, second v1.Image) bool {
 	t.Helper()