Add SHELL support

builder.go

@@ -442,6 +442,7 @@ var evaluateTable = map[string]StepFunc{
 	command.StopSignal:  stopSignal,
 	command.Arg:         arg,
 	command.Healthcheck: healthcheck,
+	command.Shell:       shell,
 }
 
 // builtinAllowedBuildArgs is list of built-in allowed build args

builder_test.go

@@ -207,7 +207,6 @@ func TestBuilder(t *testing.T) {
 			From:       "busybox",
 			Unrecognized: []Step{
 				Step{Command: "health", Message: "HEALTH ", Original: "HEALTH NONE", Args: []string{""}, Flags: []string{}, Env: []string{}},
-				Step{Command: "shell", Message: "SHELL /bin/sh -c", Original: "SHELL [\"/bin/sh\", \"-c\"]", Args: []string{"/bin/sh", "-c"}, Flags: []string{}, Env: []string{}, Attrs: map[string]bool{"json": true}},
 				Step{Command: "unrecognized", Message: "UNRECOGNIZED ", Original: "UNRECOGNIZED", Args: []string{""}, Env: []string{}},
 			},
 			Config: docker.Config{
@@ -350,6 +349,20 @@ func TestBuilder(t *testing.T) {
 				{Src: []string{"file4"}, Dest: "/var/www/", Download: true},
 			},
 		},
+		{
+			Dockerfile: "dockerclient/testdata/Dockerfile.shell",
+			From:       "centos:7",
+			Config: docker.Config{
+				Image: "centos:7",
+				Shell: []string{"/bin/bash", "-xc"},
+			},
+			ErrFn: func(err error) bool {
+				return err != nil && strings.Contains(err.Error(), "multiple FROM statements are not supported")
+			},
+			Runs: []Run{
+				{Shell: true, Args: []string{"env"}},
+			},
+		},
 	}
 	for i, test := range testCases {
 		t.Run(fmt.Sprintf("%s %d", test.Dockerfile, i), func(t *testing.T) {

dispatchers.go

@@ -533,6 +533,26 @@ func arg(b *Builder, args []string, attributes map[string]bool, flagArgs []strin
 	return nil
 }
 
+// SHELL powershell -command
+//
+// Set the non-default shell to use.
+func shell(b *Builder, args []string, attributes map[string]bool, flagArgs []string, original string) error {
+	shellSlice := handleJSONArgs(args, attributes)
+	switch {
+	case len(shellSlice) == 0:
+		// SHELL []
+		return errAtLeastOneArgument("SHELL")
+	case attributes["json"]:
+		// SHELL ["powershell", "-command"]
+		b.RunConfig.Shell = strslice.StrSlice(shellSlice)
+		// b.RunConfig.Shell = strslice.StrSlice(shellSlice)
+	default:
+		// SHELL powershell -command - not JSON
+		return errNotJSON("SHELL")
+	}
+	return nil
+}
+
 func errAtLeastOneArgument(command string) error {
 	return fmt.Errorf("%s requires at least one argument", command)
 }
@@ -544,3 +564,7 @@ func errExactlyOneArgument(command string) error {
 func errTooManyArguments(command string) error {
 	return fmt.Errorf("Bad input to %s, too many arguments", command)
 }
+
+func errNotJSON(command string) error {
+	return fmt.Errorf("%s requires the arguments to be in JSON form", command)
+}

dockerclient/client.go

@@ -225,6 +225,11 @@ func (e *ClientExecutor) Prepare(b *imagebuilder.Builder, node *parser.Node, fro
 
 	var sharedMount string
 
+	defaultShell := b.RunConfig.Shell
+	if len(defaultShell) == 0 {
+		defaultShell = []string{"/bin/sh", "-c"}
+	}
+
 	// create a container to execute in, if necessary
 	mustStart := b.RequiresStart(node)
 	if e.Container == nil {
@@ -264,12 +269,12 @@ func (e *ClientExecutor) Prepare(b *imagebuilder.Builder, node *parser.Node, fro
 			} else {
 				// TODO; replace me with a better default command
 				opts.Config.Cmd = []string{"sleep 86400"}
-				opts.Config.Entrypoint = []string{"/bin/sh", "-c"}
+				opts.Config.Entrypoint = append([]string{}, defaultShell...)
 			}
 		}
 
 		if len(opts.Config.Cmd) == 0 {
-			opts.Config.Entrypoint = []string{"/bin/sh", "-c", "# NOP"}
+			opts.Config.Entrypoint = append(append([]string{}, defaultShell...), "# NOP")
 		}
 
 		// copy any source content into the temporary mount path
@@ -581,20 +586,28 @@ func (e *ClientExecutor) Run(run imagebuilder.Run, config docker.Config) error {
 	args := make([]string, len(run.Args))
 	copy(args, run.Args)
 
+	defaultShell := config.Shell
+	if len(defaultShell) == 0 {
+		if runtime.GOOS == "windows" {
+			defaultShell = []string{"cmd", "/S", "/C"}
+		} else {
+			defaultShell = []string{"/bin/sh", "-c"}
+		}
+	}
 	if runtime.GOOS == "windows" {
 		if len(config.WorkingDir) > 0 {
 			args[0] = fmt.Sprintf("cd %s && %s", imagebuilder.BashQuote(config.WorkingDir), args[0])
 		}
 		// TODO: implement windows ENV
-		args = append([]string{"cmd", "/S", "/C"}, args...)
+		args = append(defaultShell, args...)
 	} else {
 		if len(config.WorkingDir) > 0 {
 			args[0] = fmt.Sprintf("cd %s && %s", imagebuilder.BashQuote(config.WorkingDir), args[0])
 		}
 		if len(config.Env) > 0 {
 			args[0] = imagebuilder.ExportEnv(config.Env) + args[0]
 		}
-		args = append([]string{"/bin/sh", "-c"}, args...)
+		args = append(defaultShell, args...)
 	}
 
 	if e.StrictVolumeOwnership && !e.Volumes.Empty() {

dockerclient/conformance_test.go

@@ -84,6 +84,42 @@ func TestMount(t *testing.T) {
 	}
 }
 
+func TestShell(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "dockerbuild-conformance-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	c, err := docker.NewClientFromEnv()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	e := NewClientExecutor(c)
+	defer e.Release()
+
+	out := &bytes.Buffer{}
+	e.Out, e.ErrOut = out, out
+	e.Directory = tmpDir
+	e.Tag = filepath.Base(tmpDir)
+	b := imagebuilder.NewBuilder(nil)
+	node, err := imagebuilder.ParseFile("testdata/Dockerfile.shell")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := e.Prepare(b, node, ""); err != nil {
+		t.Fatal(err)
+	}
+	if err := e.Execute(b, node); err != nil {
+		t.Fatal(err)
+	}
+
+	if !strings.Contains(out.String(), "+ env\n") {
+		t.Errorf("Unexpected build output:\n%s", out.String())
+	}
+}
+
 // TestConformance* compares the result of running the direct build against a
 // sequential docker build. A dockerfile and git repo is loaded, then each step
 // in the file is run sequentially, committing after each step. The generated
@@ -135,6 +171,10 @@ func TestConformanceInternal(t *testing.T) {
 			Name:       "add",
 			Dockerfile: "testdata/Dockerfile.add",
 		},
+		{
+			Name:       "shell",
+			Dockerfile: "testdata/Dockerfile.shell",
+		},
 		{
 			Name:       "args",
 			Dockerfile: "testdata/Dockerfile.args",

dockerclient/testdata/Dockerfile.shell

@@ -0,0 +1,3 @@
+FROM centos:7
+SHELL ["/bin/bash", "-xc"]
+RUN env

dockerclient/testdata/Dockerfile.unknown

@@ -1,4 +1,3 @@
 FROM busybox
 HEALTH NONE
-SHELL ["/bin/sh", "-c"]
 UNRECOGNIZED