Merge pull request #275 from majiayu000/fix-250-need-a-method-to-avoid-the-pan-0101-1659

fix: add nil check for os.Stdout to prevent panic on Windows services

Author: fatih

color.go

@@ -19,15 +19,15 @@ var (
 	// set (regardless of its value). This is a global option and affects all
 	// colors. For more control over each color block use the methods
 	// DisableColor() individually.
-	NoColor = noColorIsSet() || os.Getenv("TERM") == "dumb" ||
-		(!isatty.IsTerminal(os.Stdout.Fd()) && !isatty.IsCygwinTerminal(os.Stdout.Fd()))
+	NoColor = noColorIsSet() || os.Getenv("TERM") == "dumb" || !stdoutIsTerminal()
 
 	// Output defines the standard output of the print functions. By default,
-	// os.Stdout is used.
-	Output = colorable.NewColorableStdout()
+	// stdOut() is used.
+	Output = stdOut()
 
-	// Error defines a color supporting writer for os.Stderr.
-	Error = colorable.NewColorableStderr()
+	// Error defines the standard error of the print functions. By default,
+	// stdErr() is used.
+	Error = stdErr()
 
 	// colorsCache is used to reduce the count of created Color objects and
 	// allows to reuse already created objects with required Attribute.
@@ -40,6 +40,33 @@ func noColorIsSet() bool {
 	return os.Getenv("NO_COLOR") != ""
 }
 
+// stdoutIsTerminal returns true if os.Stdout is a terminal.
+// Returns false if os.Stdout is nil (e.g., when running as a Windows service).
+func stdoutIsTerminal() bool {
+	if os.Stdout == nil {
+		return false
+	}
+	return isatty.IsTerminal(os.Stdout.Fd()) || isatty.IsCygwinTerminal(os.Stdout.Fd())
+}
+
+// stdOut returns a writer for color output.
+// Returns io.Discard if os.Stdout is nil (e.g., when running as a Windows service).
+func stdOut() io.Writer {
+	if os.Stdout == nil {
+		return io.Discard
+	}
+	return colorable.NewColorableStdout()
+}
+
+// stdErr returns a writer for color error output.
+// Returns io.Discard if os.Stderr is nil (e.g., when running as a Windows service).
+func stdErr() io.Writer {
+	if os.Stderr == nil {
+		return io.Discard
+	}
+	return colorable.NewColorableStderr()
+}
+
 // Color defines a custom color object which is defined by SGR parameters.
 type Color struct {
 	params  []Attribute

color_test.go

@@ -236,6 +236,42 @@ func Test_noColorIsSet(t *testing.T) {
 	}
 }
 
+func TestStdoutIsTerminal_NilStdout(t *testing.T) {
+	stdout := os.Stdout
+	os.Stdout = nil
+	t.Cleanup(func() {
+		os.Stdout = stdout
+	})
+
+	if stdoutIsTerminal() {
+		t.Fatal("stdoutIsTerminal() = true, want false")
+	}
+}
+
+func TestStdOut_NilStdout(t *testing.T) {
+	stdout := os.Stdout
+	os.Stdout = nil
+	t.Cleanup(func() {
+		os.Stdout = stdout
+	})
+
+	if got := stdOut(); got != io.Discard {
+		t.Fatalf("stdOut() = %v, want %v", got, io.Discard)
+	}
+}
+
+func TestStdErr_NilStderr(t *testing.T) {
+	stderr := os.Stderr
+	os.Stderr = nil
+	t.Cleanup(func() {
+		os.Stderr = stderr
+	})
+
+	if got := stdErr(); got != io.Discard {
+		t.Fatalf("stdErr() = %v, want %v", got, io.Discard)
+	}
+}
+
 func TestColorVisual(t *testing.T) {
 	// First Visual Test
 	Output = colorable.NewColorableStdout()

color_windows.go

@@ -9,6 +9,9 @@ import (
 func init() {
 	// Opt-in for ansi color support for current process.
 	// https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#output-sequences
+	if os.Stdout == nil {
+		return
+	}
 	var outMode uint32
 	out := windows.Handle(os.Stdout.Fd())
 	if err := windows.GetConsoleMode(out, &outMode); err != nil {