prefixed output option --prefix (#120)

Author: notnmeyer

cmd/tsk/tsk.go

@@ -26,6 +26,7 @@ type Options struct {
 	init           bool
 	listTasks      bool
 	output         string
+	prefix         bool
 	pure           bool
 	taskFile       string
 	tasks          []string
@@ -46,6 +47,7 @@ func main() {
 	flag.BoolVar(&opts.init, "init", false, "create a tasks.toml file in $PWD")
 	flag.BoolVarP(&opts.listTasks, "list", "l", false, "list tasks")
 	flag.StringVarP(&opts.output, "output", "o", "text", fmt.Sprintf("output format (applies only to --list) (one of: %s)", output.String()))
+	flag.BoolVar(&opts.prefix, "prefix", false, "prefix task output with the task name")
 	flag.BoolVarP(&opts.pure, "pure", "", false, "don't inherit the parent env")
 	flag.StringVarP(&opts.taskFile, "file", "f", "", "taskfile to use")
 	flag.BoolVar(&opts.which, "which", false, "print the path to the found tasks.toml, or an error")
@@ -91,6 +93,7 @@ func main() {
 		Stdin:  os.Stdin,
 		Stderr: os.Stderr,
 		Config: cfg,
+		Prefix: opts.prefix,
 	}
 
 	if opts.listTasks {

internal/task/task.go

@@ -43,10 +43,13 @@ type Task struct {
 }
 
 type Executor struct {
-	Stdout io.Writer
-	Stdin  io.Reader
-	Stderr io.Writer
-	Config *Config
+	Stdout      io.Writer
+	Stdin       io.Reader
+	Stderr      io.Writer
+	Config      *Config
+	Prefix      bool
+	colorIndex  int
+	taskColors  map[string]string
 }
 
 // sets the top-level env
@@ -90,6 +93,26 @@ func (t *Task) CompileEnv(env []string) ([]string, error) {
 	return env, nil
 }
 
+func (exec *Executor) colorForTask(task string) string {
+	if exec.taskColors == nil {
+		exec.taskColors = make(map[string]string)
+	}
+	if color, ok := exec.taskColors[task]; ok {
+		return color
+	}
+	color := prefixColors[exec.colorIndex%len(prefixColors)]
+	exec.colorIndex++
+	exec.taskColors[task] = color
+	return color
+}
+
+func (exec *Executor) prefixedWriter(w io.Writer, prefix string, task string) io.Writer {
+	if exec.Prefix {
+		return newPrefixWriter(w, prefix, exec.colorForTask(task))
+	}
+	return w
+}
+
 func (exec *Executor) RunTasks(config *Config, tasks *[]string) error {
 	// top-level env
 	env, err := config.CompileEnv()
@@ -133,10 +156,18 @@ func (exec *Executor) RunTasks(config *Config, tasks *[]string) error {
 			return err
 		}
 
+		taskExec := &Executor{
+			Stdout: exec.prefixedWriter(exec.Stdout, "::"+task+":: ", task),
+			Stderr: exec.prefixedWriter(exec.Stderr, "::"+task+":: ", task),
+			Stdin:  exec.Stdin,
+			Config: exec.Config,
+			Prefix: exec.Prefix,
+		}
+
 		// if a task contains cmds, run them
 		if len(taskConfig.Cmds) > 0 {
 			for _, cmd := range taskConfig.Cmds {
-				err := exec.runCommand(cmd, taskConfig.Dir, env)
+				err := taskExec.runCommand(cmd, taskConfig.Dir, env)
 				if err != nil {
 					fmt.Println(err.Error())
 					// if the cmd exited with an error, bail immediately
@@ -146,7 +177,7 @@ func (exec *Executor) RunTasks(config *Config, tasks *[]string) error {
 		} else {
 			// if there are no cmds then we intend to run a script with the name name as the task
 			script := fmt.Sprintf("%s/%s", exec.Config.ScriptDir, task)
-			err := exec.runCommand(script, taskConfig.Dir, env)
+			err := taskExec.runCommand(script, taskConfig.Dir, env)
 			if err != nil {
 				fmt.Println(err.Error())
 				// if the cmd exited with an error, bail immediately

internal/task/util.go

@@ -3,12 +3,58 @@ package task
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"sort"
 	"text/template"
 
 	"github.com/joho/godotenv"
 )
 
+// ANSI color codes for prefix coloring. These are chosen for visual distinction.
+var prefixColors = []string{
+	"\033[36m",  // cyan
+	"\033[33m",  // yellow
+	"\033[35m",  // magenta
+	"\033[32m",  // green
+	"\033[34m",  // blue
+	"\033[31m",  // red
+	"\033[96m",  // bright cyan
+	"\033[93m",  // bright yellow
+	"\033[95m",  // bright magenta
+	"\033[92m",  // bright green
+	"\033[94m",  // bright blue
+	"\033[91m",  // bright red
+}
+
+const colorReset = "\033[0m"
+
+type prefixWriter struct {
+	writer io.Writer
+	prefix string
+	buf    []byte
+}
+
+func newPrefixWriter(w io.Writer, prefix string, color string) *prefixWriter {
+	coloredPrefix := color + prefix + colorReset
+	return &prefixWriter{writer: w, prefix: coloredPrefix}
+}
+
+func (p *prefixWriter) Write(b []byte) (int, error) {
+	p.buf = append(p.buf, b...)
+	for {
+		idx := bytes.IndexByte(p.buf, '\n')
+		if idx < 0 {
+			break
+		}
+		line := p.buf[:idx+1]
+		if _, err := fmt.Fprintf(p.writer, "%s%s", p.prefix, line); err != nil {
+			return 0, err
+		}
+		p.buf = p.buf[idx+1:]
+	}
+	return len(b), nil
+}
+
 type Vals struct {
 	CLI_ARGS string
 }