Merge branch 'fix-color-output'

.github/workflows/ci.yaml

@@ -40,7 +40,7 @@ jobs:
           CGO_ENABLED: 0
       - run: go test -v -race -coverprofile coverage.txt -covermode=atomic
       # Dog fooding 🐶
-      - run: ./actionlint
+      - run: ./actionlint -color
       - uses: codecov/codecov-action@v1
   lint:
     name: Lint

README.md

@@ -114,7 +114,7 @@ jobs:
         run: bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
         shell: bash
       - name: Check workflow files
-        run: ${{ steps.get_actionlint.outputs.executable }}
+        run: ${{ steps.get_actionlint.outputs.executable }} -color
         shell: bash
 ```
 

cmd/actionlint/main.go

@@ -107,14 +107,17 @@ func main() {
 	var opts actionlint.LinterOptions
 	var ignorePats ignorePatterns
 	var initConfig bool
+	var noColor bool
+	var color bool
 
 	flag.Var(&ignorePats, "ignore", "Regular expression matching to error messages you want to ignore. This flag can be specified multiple times")
 	flag.StringVar(&opts.Shellcheck, "shellcheck", "shellcheck", "Command name or file path of \"shellcheck\" external command")
 	flag.StringVar(&opts.Pyflakes, "pyflakes", "pyflakes", "Command name or file path of \"pyflakes\" external command")
 	flag.BoolVar(&opts.Oneline, "oneline", false, "Use one line per one error. Useful for reading error messages from programs")
 	flag.StringVar(&opts.ConfigFile, "config-file", "", "File path to config file")
 	flag.BoolVar(&initConfig, "init-config", false, "Generate default config file at .github/actionlint.yaml in current project")
-	flag.BoolVar(&opts.NoColor, "no-color", false, "Disable colorful output")
+	flag.BoolVar(&noColor, "no-color", false, "Disable colorful output")
+	flag.BoolVar(&color, "color", false, "Always enable colorful output. This is useful to force colorful outputs")
 	flag.BoolVar(&opts.Verbose, "verbose", false, "Enable verbose output")
 	flag.BoolVar(&opts.Debug, "debug", false, "Enable debug output (for development)")
 	flag.BoolVar(&ver, "version", false, "Show version and how this binary was installed")
@@ -128,6 +131,13 @@ func main() {
 
 	opts.IgnorePatterns = ignorePats
 
+	if color {
+		opts.Color = actionlint.ColorOptionKindAlways
+	}
+	if noColor {
+		opts.Color = actionlint.ColorOptionKindNever
+	}
+
 	errs, err := run(flag.Args(), &opts, initConfig)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err.Error())

linter.go

@@ -30,6 +30,20 @@ const (
 	LogLevelDebug = 2
 )
 
+// ColorOptionKind is kind of colorful output behavior.
+type ColorOptionKind int
+
+const (
+	// ColorOptionKindAuto is kind to determine to colorize errors output automatically. It is
+	// determined based on pty and $NO_COLOR environment variable. See document of fatih/color
+	// for more details.
+	ColorOptionKindAuto ColorOptionKind = iota
+	// ColorOptionKindAlways is kind to always colorize errors output.
+	ColorOptionKindAlways
+	// ColorOptionKindNever is kind never to colorize errors output.
+	ColorOptionKindNever
+)
+
 // LinterOptions is set of options for Linter instance. This struct should be created by user and
 // given to NewLinter factory function.
 type LinterOptions struct {
@@ -40,8 +54,8 @@ type LinterOptions struct {
 	// LogWriter is io.Writer object to use to print log outputs. Note that error outputs detected
 	// by the linter are not included in the log outputs.
 	LogWriter io.Writer
-	// NoColor is flag if colorful output is enabled.
-	NoColor bool
+	// Color is option for colorizing error outputs. See ColorOptionKind document for each enum values.
+	Color ColorOptionKind
 	// Oneline is flag if one line output is enabled. When enabling it, one error is output per one
 	// line. It is useful when reading outputs from programs.
 	Oneline bool
@@ -68,7 +82,6 @@ type Linter struct {
 	out           io.Writer
 	logOut        io.Writer
 	logLevel      LogLevel
-	noColor       bool
 	oneline       bool
 	shellcheck    string
 	pyflakes      string
@@ -87,15 +100,21 @@ func NewLinter(out io.Writer, opts *LinterOptions) (*Linter, error) {
 	} else if opts.Debug {
 		l = LogLevelDebug
 	}
-	if opts.NoColor {
+	if opts.Color == ColorOptionKindNever {
 		color.NoColor = true
+	} else {
+		if opts.Color == ColorOptionKindAlways {
+			color.NoColor = false
+		}
+		// Allow colorful output on Windows
+		if f, ok := out.(*os.File); ok {
+			out = colorable.NewColorable(f)
+		}
 	}
 
 	var lout io.Writer = os.Stderr
 	if opts.LogWriter != nil {
 		lout = opts.LogWriter
-	} else if !opts.NoColor {
-		lout = colorable.NewColorable(os.Stderr)
 	}
 
 	var cfg *Config
@@ -121,7 +140,6 @@ func NewLinter(out io.Writer, opts *LinterOptions) (*Linter, error) {
 		out,
 		lout,
 		l,
-		opts.NoColor,
 		opts.Oneline,
 		opts.Shellcheck,
 		opts.Pyflakes,