@@ -6408,3 +6408,30 @@ func (s *DockerSuite) TestBuildSymlinkBasename(c *check.C) {

 	c.Assert(out, checker.Matches, "bar")

 }

+

+// #17827

+func (s *DockerSuite) TestBuildCacheRootSource(c *check.C) {

+	testRequires(c, DaemonIsLinux)

+	name := "testbuildrootsource"

+	ctx, err := fakeContext(`

+	FROM busybox

+	COPY / /data`,

+		map[string]string{

+			"foo": "bar",

+		})

+	c.Assert(err, checker.IsNil)

+	defer ctx.Close()

+

+	// warm up cache

+	_, err = buildImageFromContext(name, ctx, true)

+	c.Assert(err, checker.IsNil)

+

+	// change file, should invalidate cache

+	err = ioutil.WriteFile(filepath.Join(ctx.Dir, "foo"), []byte("baz"), 0644)

+	c.Assert(err, checker.IsNil)

+

+	_, out, err := buildImageFromContextWithOut(name, ctx, true)

+	c.Assert(err, checker.IsNil)

+

+	c.Assert(out, checker.Not(checker.Contains), "Using cache")

+}