Add default PATH to 'scratch' images

Closes #19012

Signed-off-by: Doug Davis <dug@us.ibm.com>

builder/dockerfile/dispatchers.go

@@ -193,6 +193,11 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 
 	name := args[0]
 
+	var (
+		image builder.Image
+		err   error
+	)
+
 	// Windows cannot support a container with no base image.
 	if name == api.NoBaseImageSpecifier {
 		if runtime.GOOS == "windows" {
@@ -200,13 +205,7 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 		}
 		b.image = ""
 		b.noBaseImage = true
-		return nil
+	} else {
-	}
-
-	var (
-		image builder.Image
-		err   error
-	)
 		// TODO: don't use `name`, instead resolve it to a digest
 		if !b.options.PullParent {
 			image, err = b.docker.GetImage(name)
@@ -218,6 +217,8 @@ func from(b *Builder, args []string, attributes map[string]bool, original string
 				return err
 			}
 		}
+	}
+
 	return b.processImageFrom(image)
 }
 

builder/dockerfile/internals.go

@@ -35,6 +35,7 @@ import (
 	"github.com/docker/docker/pkg/system"
 	"github.com/docker/docker/pkg/tarsum"
 	"github.com/docker/docker/pkg/urlutil"
+	"github.com/docker/docker/runconfig/opts"
 )
 
 func (b *Builder) commit(id string, autoCmd *strslice.StrSlice, comment string) error {
@@ -394,15 +395,30 @@ func containsWildcards(name string) bool {
 }
 
 func (b *Builder) processImageFrom(img builder.Image) error {
+	if img != nil {
 		b.image = img.ID()
 
 		if img.Config() != nil {
 			b.runConfig = img.Config()
 		}
+	}
 
-	// The default path will be blank on Windows (set by HCS)
+	// Check to see if we have a default PATH, note that windows won't
-	if len(b.runConfig.Env) == 0 && system.DefaultPathEnv != "" {
+	// have one as its set by HCS
-		b.runConfig.Env = append(b.runConfig.Env, "PATH="+system.DefaultPathEnv)
+	if system.DefaultPathEnv != "" {
+		// Convert the slice of strings that represent the current list
+		// of env vars into a map so we can see if PATH is already set.
+		// If its not set then go ahead and give it our default value
+		configEnv := opts.ConvertKVStringsToMap(b.runConfig.Env)
+		if _, ok := configEnv["PATH"]; !ok {
+			b.runConfig.Env = append(b.runConfig.Env,
+				"PATH="+system.DefaultPathEnv)
+		}
+	}
+
+	if img == nil {
+		// Typically this means they used "FROM scratch"
+		return nil
 	}
 
 	// Process ONBUILD triggers if they exist

integration-cli/docker_cli_build_test.go

@@ -2143,6 +2143,39 @@ func (s *DockerSuite) TestBuildEnv(c *check.C) {
 	}
 }
 
+func (s *DockerSuite) TestBuildPATH(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	defPath := "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+
+	fn := func(dockerfile string, exp string) {
+		_, err := buildImage("testbldpath", dockerfile, true)
+		c.Assert(err, check.IsNil)
+
+		res, err := inspectField("testbldpath", "Config.Env")
+		c.Assert(err, check.IsNil)
+
+		if res != exp {
+			c.Fatalf("Env %q, expected %q for dockerfile:%q", res, exp, dockerfile)
+		}
+	}
+
+	tests := []struct{ dockerfile, exp string }{
+		{"FROM scratch\nMAINTAINER me", "[PATH=" + defPath + "]"},
+		{"FROM busybox\nMAINTAINER me", "[PATH=" + defPath + "]"},
+		{"FROM scratch\nENV FOO=bar", "[PATH=" + defPath + " FOO=bar]"},
+		{"FROM busybox\nENV FOO=bar", "[PATH=" + defPath + " FOO=bar]"},
+		{"FROM scratch\nENV PATH=/test", "[PATH=/test]"},
+		{"FROM busybox\nENV PATH=/test", "[PATH=/test]"},
+		{"FROM scratch\nENV PATH=''", "[PATH=]"},
+		{"FROM busybox\nENV PATH=''", "[PATH=]"},
+	}
+
+	for _, test := range tests {
+		fn(test.dockerfile, test.exp)
+	}
+}
+
 func (s *DockerSuite) TestBuildContextCleanup(c *check.C) {
 	testRequires(c, DaemonIsLinux)
 	testRequires(c, SameHostDaemon)