#285 add color output for mage list (#301)

* #285 add color output for mage list

* added color configuration via MAGEFILE_ENABLE_COLOR and MAGEFILE_TARGET_COLOR env vars
* use a list of specific terminals which don't support color

mage/main_test.go

@@ -57,9 +57,31 @@ func testmain(m *testing.M) int {
 	if err := os.Unsetenv(mg.IgnoreDefaultEnv); err != nil {
 		log.Fatal(err)
 	}
+	if err := os.Setenv(mg.CacheEnv, dir); err != nil {
+		log.Fatal(err)
+	}
+	if err := os.Unsetenv(mg.EnableColorEnv); err != nil {
+		log.Fatal(err)
+	}
+	if err := os.Unsetenv(mg.TargetColorEnv); err != nil {
+		log.Fatal(err)
+	}
+	resetTerm()
 	return m.Run()
 }
 
+func resetTerm() {
+	if term, exists := os.LookupEnv("TERM"); exists {
+		log.Printf("Current terminal: %s", term)
+		// unset TERM env var in order to disable color output to make the tests simpler
+		// there is a specific test for colorized output, so all the other tests can use non-colorized one
+		if err := os.Unsetenv("TERM"); err != nil {
+			log.Fatal(err)
+		}
+	}
+	os.Setenv(mg.EnableColorEnv, "false")
+}
+
 func TestTransitiveDepCache(t *testing.T) {
 	cache, err := internal.OutputDebug("go", "env", "GOCACHE")
 	if err != nil {
@@ -292,6 +314,7 @@ func TestListMagefilesLib(t *testing.T) {
 }
 
 func TestMixedMageImports(t *testing.T) {
+	resetTerm()
 	stderr := &bytes.Buffer{}
 	stdout := &bytes.Buffer{}
 	inv := Invocation{
@@ -420,7 +443,82 @@ Targets:
 	}
 }
 
+var terminals = []struct {
+	code          string
+	supportsColor bool
+}{
+	{"", true},
+	{"vt100", false},
+	{"cygwin", false},
+	{"xterm-mono", false},
+	{"xterm", true},
+	{"xterm-vt220", true},
+	{"xterm-16color", true},
+	{"xterm-256color", true},
+	{"screen-256color", true},
+}
+
+func TestListWithColor(t *testing.T) {
+	os.Setenv(mg.EnableColorEnv, "true")
+	os.Setenv(mg.TargetColorEnv, mg.Cyan.String())
+
+	expectedPlainText := `
+This is a comment on the package which should get turned into output with the list of targets.
+
+Targets:
+  somePig*       This is the synopsis for SomePig.
+  testVerbose    
+
+* default target
+`[1:]
+
+	// NOTE: using the literal string would be complicated because I would need to break it
+	// in the middle and join with a normal string for the target names,
+	// otherwise the single backslash would be taken literally and encoded as \\
+	expectedColorizedText := "" +
+		"This is a comment on the package which should get turned into output with the list of targets.\n" +
+		"\n" +
+		"Targets:\n" +
+		"  \x1b[36msomePig*\x1b[0m       This is the synopsis for SomePig.\n" +
+		"  \x1b[36mtestVerbose\x1b[0m    \n" +
+		"\n" +
+		"* default target\n"
+
+	for _, terminal := range terminals {
+		t.Run(terminal.code, func(t *testing.T) {
+			os.Setenv("TERM", terminal.code)
+
+			stdout := &bytes.Buffer{}
+			inv := Invocation{
+				Dir:    "./testdata/list",
+				Stdout: stdout,
+				Stderr: ioutil.Discard,
+				List:   true,
+			}
+
+			code := Invoke(inv)
+			if code != 0 {
+				t.Errorf("expected to exit with code 0, but got %v", code)
+			}
+			actual := stdout.String()
+			var expected string
+			if terminal.supportsColor {
+				expected = expectedColorizedText
+			} else {
+				expected = expectedPlainText
+			}
+
+			if actual != expected {
+				t.Logf("expected: %q", expected)
+				t.Logf("  actual: %q", actual)
+				t.Fatalf("expected:\n%v\n\ngot:\n%v", expected, actual)
+			}
+		})
+	}
+}
+
 func TestNoArgNoDefaultList(t *testing.T) {
+	resetTerm()
 	stdout := &bytes.Buffer{}
 	stderr := &bytes.Buffer{}
 	inv := Invocation{
@@ -458,6 +556,7 @@ func TestIgnoreDefault(t *testing.T) {
 	if err := os.Setenv(mg.IgnoreDefaultEnv, "1"); err != nil {
 		t.Fatal(err)
 	}
+	resetTerm()
 
 	code := Invoke(inv)
 	if code != 0 {
@@ -1286,6 +1385,7 @@ func TestGoCmd(t *testing.T) {
 var runtimeVer = regexp.MustCompile(`go1\.([0-9]+)`)
 
 func TestGoModules(t *testing.T) {
+	resetTerm()
 	matches := runtimeVer.FindStringSubmatch(runtime.Version())
 	if len(matches) < 2 || minorVer(t, matches[1]) < 11 {
 		t.Skipf("Skipping Go modules test because go version %q is less than go1.11", runtime.Version())

mage/template.go

@@ -92,7 +92,135 @@ Options:
 		fs.Usage()
 		return
 	}
-	  
+
+		
+	// color is ANSI color type
+	type color int
+
+	// If you add/change/remove any items in this constant,
+	// you will need to run "stringer -type=color" in this directory again.
+	// NOTE: Please keep the list in an alphabetical order.
+	const (
+		black color = iota
+		red
+		green
+		yellow
+		blue
+		magenta
+		cyan
+		white
+		brightblack
+		brightred
+		brightgreen
+		brightyellow
+		brightblue
+		brightmagenta
+		brightcyan
+		brightwhite
+	)
+
+	// AnsiColor are ANSI color codes for supported terminal colors.
+	var ansiColor = map[color]string{
+		black:         "\u001b[30m",
+		red:           "\u001b[31m",
+		green:         "\u001b[32m",
+		yellow:        "\u001b[33m",
+		blue:          "\u001b[34m",
+		magenta:       "\u001b[35m",
+		cyan:          "\u001b[36m",
+		white:         "\u001b[37m",
+		brightblack:   "\u001b[30;1m",
+		brightred:     "\u001b[31;1m",
+		brightgreen:   "\u001b[32;1m",
+		brightyellow:  "\u001b[33;1m",
+		brightblue:    "\u001b[34;1m",
+		brightmagenta: "\u001b[35;1m",
+		brightcyan:    "\u001b[36;1m",
+		brightwhite:   "\u001b[37;1m",
+	}
+	
+	const _color_name = "blackredgreenyellowbluemagentacyanwhitebrightblackbrightredbrightgreenbrightyellowbrightbluebrightmagentabrightcyanbrightwhite"
+
+	var _color_index = [...]uint8{0, 5, 8, 13, 19, 23, 30, 34, 39, 50, 59, 70, 82, 92, 105, 115, 126}
+
+	colorToLowerString := func (i color) string {
+		if i < 0 || i >= color(len(_color_index)-1) {
+			return "color(" + strconv.FormatInt(int64(i), 10) + ")"
+		}
+		return _color_name[_color_index[i]:_color_index[i+1]]
+	}
+
+	// ansiColorReset is an ANSI color code to reset the terminal color.
+	const ansiColorReset = "\033[0m"
+
+	// defaultTargetAnsiColor is a default ANSI color for colorizing targets.
+	// It is set to Cyan as an arbitrary color, because it has a neutral meaning
+	var defaultTargetAnsiColor = ansiColor[cyan]
+
+	getAnsiColor := func(color string) (string, bool) {
+		colorLower := strings.ToLower(color)
+		for k, v := range ansiColor {
+			colorConstLower := colorToLowerString(k)
+			if colorConstLower == colorLower {
+				return v, true
+			}
+		}
+		return "", false
+	}
+
+	// Terminals which  don't support color:
+	// 	TERM=vt100
+	// 	TERM=cygwin
+	// 	TERM=xterm-mono
+    var noColorTerms = map[string]bool{
+		"vt100":      false,
+		"cygwin":     false,
+		"xterm-mono": false,
+	}
+
+	// terminalSupportsColor checks if the current console supports color output
+	//
+	// Supported:
+	// 	linux, mac, or windows's ConEmu, Cmder, putty, git-bash.exe, pwsh.exe
+	// Not supported:
+	// 	windows cmd.exe, powerShell.exe
+	terminalSupportsColor := func() bool {
+		envTerm := os.Getenv("TERM")
+		if _, ok := noColorTerms[envTerm]; ok {
+			return false
+		}
+		return true
+	}
+
+	// enableColor reports whether the user has requested to enable a color output.
+	enableColor := func() bool {
+		b, _ := strconv.ParseBool(os.Getenv("MAGEFILE_ENABLE_COLOR"))
+		return b
+	}
+
+	// targetColor returns the ANSI color which should be used to colorize targets.
+	targetColor := func() string {
+		s, exists := os.LookupEnv("MAGEFILE_TARGET_COLOR")
+		if exists == true {
+			if c, ok := getAnsiColor(s); ok == true {
+				return c
+			}
+		}
+		return defaultTargetAnsiColor
+	}
+
+	// store the color terminal variables, so that the detection isn't repeated for each target
+	var enableColorValue = enableColor() && terminalSupportsColor()
+	var targetColorValue = targetColor()
+
+	printName := func(str string) string {
+		if enableColorValue {
+			return fmt.Sprintf("%s%s%s", targetColorValue, str, ansiColorReset)
+		} else {
+			return str
+		}
+	}
+
 	list := func() error {
 		{{with .Description}}fmt.Println(` + "`{{.}}\n`" + `)
 		{{- end}}
@@ -117,7 +245,7 @@ Options:
 		fmt.Println("Targets:")
 		w := tabwriter.NewWriter(os.Stdout, 0, 4, 4, ' ', 0)
 		for _, name := range keys {
-			fmt.Fprintf(w, "  %v\t%v\n", name, targets[name])
+			fmt.Fprintf(w, "  %v\t%v\n", printName(name), targets[name])
 		}
 		err := w.Flush()
 		{{- if .DefaultFunc.Name}}

mg/color.go

@@ -0,0 +1,80 @@
+package mg
+
+// Color is ANSI color type
+type Color int
+
+// If you add/change/remove any items in this constant,
+// you will need to run "stringer -type=Color" in this directory again.
+// NOTE: Please keep the list in an alphabetical order.
+const (
+	Black Color = iota
+	Red
+	Green
+	Yellow
+	Blue
+	Magenta
+	Cyan
+	White
+	BrightBlack
+	BrightRed
+	BrightGreen
+	BrightYellow
+	BrightBlue
+	BrightMagenta
+	BrightCyan
+	BrightWhite
+)
+
+// AnsiColor are ANSI color codes for supported terminal colors.
+var ansiColor = map[Color]string{
+	Black:         "\u001b[30m",
+	Red:           "\u001b[31m",
+	Green:         "\u001b[32m",
+	Yellow:        "\u001b[33m",
+	Blue:          "\u001b[34m",
+	Magenta:       "\u001b[35m",
+	Cyan:          "\u001b[36m",
+	White:         "\u001b[37m",
+	BrightBlack:   "\u001b[30;1m",
+	BrightRed:     "\u001b[31;1m",
+	BrightGreen:   "\u001b[32;1m",
+	BrightYellow:  "\u001b[33;1m",
+	BrightBlue:    "\u001b[34;1m",
+	BrightMagenta: "\u001b[35;1m",
+	BrightCyan:    "\u001b[36;1m",
+	BrightWhite:   "\u001b[37;1m",
+}
+
+// AnsiColorReset is an ANSI color code to reset the terminal color.
+const AnsiColorReset = "\033[0m"
+
+// DefaultTargetAnsiColor is a default ANSI color for colorizing targets.
+// It is set to Cyan as an arbitrary color, because it has a neutral meaning
+var DefaultTargetAnsiColor = ansiColor[Cyan]
+
+func toLowerCase(s string) string {
+	// this is a naive implementation
+	// borrowed from https://golang.org/src/strings/strings.go
+	// and only considers alphabetical characters [a-zA-Z]
+	// so that we don't depend on the "strings" package
+	buf := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if 'A' <= c && c <= 'Z' {
+			c += 'a' - 'A'
+		}
+		buf[i] = c
+	}
+	return string(buf)
+}
+
+func getAnsiColor(color string) (string, bool) {
+	colorLower := toLowerCase(color)
+	for k, v := range ansiColor {
+		colorConstLower := toLowerCase(k.String())
+		if colorConstLower == colorLower {
+			return v, true
+		}
+	}
+	return "", false
+}