invoke: load defaults from image config

If user does not specify image certain container parameters, we can load
them from the exporter metadata.

Additionally, we introduce a new "default" value for the --invoke flag,
that keeps all of the default parameters (since cobra does not have an
easy way of accepting an optional flag argument).

Signed-off-by: Justin Chadwell <me@jedevc.com>

build/build.go

@@ -640,14 +640,17 @@ func toSolveOpt(ctx context.Context, di DriverInfo, multiDriver bool, opt Option
 // ContainerConfig is configuration for a container to run.
 type ContainerConfig struct {
 	ResultCtx *ResultContext
-	Args      []string
+
-	Env       []string
-	User      string
-	Cwd       string
-	Tty       bool
 	Stdin  io.ReadCloser
 	Stdout io.WriteCloser
 	Stderr io.WriteCloser
+	Tty    bool
+
+	Entrypoint []string
+	Cmd        []string
+	Env        []string
+	User       *string
+	Cwd        *string
 }
 
 // ResultContext is a build result with the client that built it.
@@ -703,11 +706,53 @@ func Invoke(ctx context.Context, cfg ContainerConfig) error {
 		}
 		defer ctr.Release(context.TODO())
 
+		imgData := res.Metadata[exptypes.ExporterImageConfigKey]
+		var img *specs.Image
+		if len(imgData) > 0 {
+			img = &specs.Image{}
+			if err := json.Unmarshal(imgData, img); err != nil {
+				fmt.Println(err)
+				return nil, err
+			}
+		}
+
+		user := ""
+		if cfg.User != nil {
+			user = *cfg.User
+		} else if img != nil {
+			user = img.Config.User
+		}
+
+		cwd := ""
+		if cfg.Cwd != nil {
+			cwd = *cfg.Cwd
+		} else if img != nil {
+			cwd = img.Config.WorkingDir
+		}
+
+		env := []string{}
+		if img != nil {
+			env = append(env, img.Config.Env...)
+		}
+		env = append(env, cfg.Env...)
+
+		args := []string{}
+		if cfg.Entrypoint != nil {
+			args = append(args, cfg.Entrypoint...)
+		} else if img != nil {
+			args = append(args, img.Config.Entrypoint...)
+		}
+		if cfg.Cmd != nil {
+			args = append(args, cfg.Cmd...)
+		} else if img != nil {
+			args = append(args, img.Config.Cmd...)
+		}
+
 		proc, err := ctr.Start(ctx, gateway.StartRequest{
-			Args:   cfg.Args,
+			Args:   args,
-			Env:    cfg.Env,
+			Env:    env,
-			User:   cfg.User,
+			User:   user,
-			Cwd:    cfg.Cwd,
+			Cwd:    cwd,
 			Tty:    cfg.Tty,
 			Stdin:  cfg.Stdin,
 			Stdout: cfg.Stdout,

commands/build.go

@@ -326,18 +326,20 @@ func buildTargets(ctx context.Context, dockerCli command.Cli, opts map[string]bu
 }
 
 func parseInvokeConfig(invoke string) (cfg build.ContainerConfig, err error) {
+	cfg.Tty = true
+	if invoke == "default" {
+		return cfg, nil
+	}
+
 	csvReader := csv.NewReader(strings.NewReader(invoke))
 	fields, err := csvReader.Read()
 	if err != nil {
 		return cfg, err
 	}
-	cfg.Tty = true
 	if len(fields) == 1 && !strings.Contains(fields[0], "=") {
-		cfg.Args = []string{fields[0]}
+		cfg.Cmd = []string{fields[0]}
 		return cfg, nil
 	}
-	var entrypoint string
-	var args []string
 	for _, field := range fields {
 		parts := strings.SplitN(field, "=", 2)
 		if len(parts) != 2 {
@@ -347,15 +349,15 @@ func parseInvokeConfig(invoke string) (cfg build.ContainerConfig, err error) {
 		value := parts[1]
 		switch key {
 		case "args":
-			args = append(args, value) // TODO: support JSON
+			cfg.Cmd = append(cfg.Cmd, value) // TODO: support JSON
 		case "entrypoint":
-			entrypoint = value // TODO: support JSON
+			cfg.Entrypoint = append(cfg.Entrypoint, value) // TODO: support JSON
 		case "env":
 			cfg.Env = append(cfg.Env, value)
 		case "user":
-			cfg.User = value
+			cfg.User = &value
 		case "cwd":
-			cfg.Cwd = value
+			cfg.Cwd = &value
 		case "tty":
 			cfg.Tty, err = strconv.ParseBool(value)
 			if err != nil {
@@ -365,13 +367,6 @@ func parseInvokeConfig(invoke string) (cfg build.ContainerConfig, err error) {
 			return cfg, errors.Errorf("unknown key %q", key)
 		}
 	}
-	cfg.Args = args
-	if entrypoint != "" {
-		cfg.Args = append([]string{entrypoint}, cfg.Args...)
-	}
-	if len(cfg.Args) == 0 {
-		cfg.Args = []string{"sh"}
-	}
 	return cfg, nil
 }