feat: Adds ANSI color support for Windows terminals (#39)

* feat: Adds ANSI color support for Windows terminals and prevents color output
when stdout is not a TTY

* fix: CI

* refactor: streamline ANSI support initialization for Windows terminals

* refactor: unify windowsansi into ansi

Co-authored-by: ccoVeille <3875889+ccoVeille@users.noreply.github.com>

* chore: add simple benchmark

---------

Co-authored-by: ccoVeille <3875889+ccoVeille@users.noreply.github.com>
Co-authored-by: Chris Miles <chris.miles.e@gmail.com>

Author: 3 people

ansi_windows.go

@@ -0,0 +1,19 @@
+//go:build windows
+
+package godump
+
+import (
+	"log"
+
+	"github.com/goforj/godump/internal/ansi"
+)
+
+// init activates ANSI support on Windows terminals by calling the Enable
+// function from the internal ansi package.
+// If enabling ANSI fails (e.g., not running in a real console), it logs
+// the error but continues execution, as colors are optional.
+func init() {
+	if err := ansi.Enable(); err != nil {
+		log.Printf("godump: failed to enable ANSI (likely due to output redirection): %v\n", err)
+	}
+}

go.mod

@@ -4,8 +4,11 @@ go 1.18
 
 require github.com/stretchr/testify v1.10.0
 
+require golang.org/x/sys v0.30.0 // indirect
+
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/term v0.29.0
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -4,6 +4,10 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.29.0 h1:L6pJp37ocefwRRtYPKSWOWzOtWSxVajvz2ldH/xi3iU=
+golang.org/x/term v0.29.0/go.mod h1:6bl4lRlvVuDgSf3179VpIxBF0o10JUpXWOnI7nErv7s=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

godump.go

@@ -698,7 +698,8 @@ func detectColor() bool {
 	if os.Getenv("FORCE_COLOR") != "" {
 		return true
 	}
-	return true
+
+	return isTerminal(os.Stdout)
 }
 
 func newColorizer() Colorizer {

godump_benchmark_test.go

@@ -0,0 +1,30 @@
+package godump
+
+import (
+	"io"
+	"testing"
+)
+
+func BenchmarkDumpStruct(b *testing.B) {
+	type Sample struct {
+		ID    int
+		Name  string
+		Email string
+		Meta  map[string]any
+	}
+
+	s := Sample{
+		ID:    1,
+		Name:  "Test User",
+		Email: "",
+		Meta:  map[string]any{"active": true, "roles": []string{"admin", "user"}},
+	}
+
+	d := NewDumper(WithWriter(io.Discard)) // no console output
+
+	b.ReportAllocs() // capture memory allocations
+
+	for i := 0; i < b.N; i++ {
+		d.Dump(s)
+	}
+}

godump_integration_test.go

@@ -0,0 +1,93 @@
+package godump
+
+import (
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+// TestAnsiInNonTty verifies that no ANSI codes are produced when output is redirected.
+func TestAnsiInNonTty(t *testing.T) {
+	// ANSI escape character. We expect this to be ABSENT from the output.
+	const escape = "\x1b"
+
+	// The source code for the program we're going to run.
+	const sourceCode = `
+package main
+import "github.com/goforj/godump"
+func main() {
+    s := struct{ Name string }{"test"}
+    godump.Dump(s)
+}
+`
+
+	// Create a temporary directory to avoid package main collision.
+	tempDir := t.TempDir()
+	tempFile, err := os.CreateTemp(tempDir, "test_*.go")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+
+	_, err = tempFile.WriteString(sourceCode)
+	if err != nil {
+		t.Fatalf("failed to write temp file: %v", err)
+	}
+	tempFile.Close()
+
+	// Run the program using `go run`. By capturing the output, we ensure
+	// that the program's stdout is not a TTY.
+	//nolint:gosec // tempFile.Name() is a controlled temporary file created by this test
+	cmd := exec.Command("go", "run", tempFile.Name())
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to run test program: %v\nOutput:\n%s", err, string(output))
+	}
+
+	if strings.Contains(string(output), escape) {
+		t.Errorf("expected output to NOT contain ANSI escape codes when not in a TTY, but it did. Output:\n%s", string(output))
+	}
+}
+
+// TestAnsiInTty verifies that ANSI codes are produced when FORCE_COLOR is set.
+func TestAnsiInTty(t *testing.T) {
+	// ANSI escape character. We expect this to be PRESENT in the output.
+	const escape = "\x1b"
+
+	// The source code for the program we're going to run.
+	const sourceCode = `
+package main
+import "github.com/goforj/godump"
+func main() {
+    s := struct{ Name string }{"test"}
+    godump.Dump(s)
+}
+`
+	// Create a temporary directory to avoid package main collision.
+	tempDir := t.TempDir()
+	tempFile, err := os.CreateTemp(tempDir, "test_*.go")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+
+	_, err = tempFile.WriteString(sourceCode)
+	if err != nil {
+		t.Fatalf("failed to write temp file: %v", err)
+	}
+	tempFile.Close()
+
+	// Run the program using `go run`. By capturing the output, we ensure
+	// that the program's stdout is not a TTY.
+	//nolint:gosec // tempFile.Name() is a controlled temporary file created by this test
+	cmd := exec.Command("go", "run", tempFile.Name())
+
+	cmd.Env = append(os.Environ(), "FORCE_COLOR=1")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to run test program: %v\nOutput:\n%s", err, string(output))
+	}
+
+	if !strings.Contains(string(output), escape) {
+		t.Errorf("expected output to contain ANSI escape codes when FORCE_COLOR is set, but it didn't. Output:\n%s", string(output))
+	}
+}

godump_test.go

@@ -186,10 +186,14 @@ func TestForceExported(t *testing.T) {
 
 func TestDetectColorVariants(t *testing.T) {
 	t.Run("no environment variables", func(t *testing.T) {
-		assert.True(t, detectColor())
-
-		out := NewDumper().colorize(colorYellow, "test")
-		assert.Equal(t, "\x1b[33mtest\x1b[0m", out)
+		// The result depends on whether stdout is a real terminal during tests
+		// On Windows with PowerShell, it's usually true; on Unix with redirected output, it's false
+		result := detectColor()
+		isTerminalResult := isTerminal(os.Stdout)
+		t.Logf("detectColor() returned: %v, isTerminal(os.Stdout): %v", result, isTerminalResult)
+		
+		// The result should match what isTerminal returns for os.Stdout
+		assert.Equal(t, isTerminalResult, result)
 	})
 
 	t.Run("forcing no color", func(t *testing.T) {

internal/ansi/ansi_windows.go

@@ -0,0 +1,48 @@
+//go:build windows
+
+package ansi
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	SYS_CALL_FAILURE                   = 0
+	enableVirtualTerminalProcessing     = 0x0004
+)
+
+// Enable activates ANSI support on Windows terminals by setting the
+// ENABLE_VIRTUAL_TERMINAL_PROCESSING flag.
+// Returns an error if the output is not a console or if setting the mode fails.
+func Enable() error {
+
+	// Load kernel32.dll and the necessary procedures dynamically.
+	// This avoids a hard dependency and allows the program to run on non-Windows
+	// systems, although this file is guarded by a build tag.
+	kernel32 := syscall.NewLazyDLL("kernel32.dll")
+	procGetConsoleMode := kernel32.NewProc("GetConsoleMode")
+	procSetConsoleMode := kernel32.NewProc("SetConsoleMode")
+
+	// Get the handle for standard output.
+	handle := syscall.Handle(os.Stdout.Fd())
+	var mode uint32
+
+	// GetConsoleMode fails if not in a real console.
+	ret, _, err := procGetConsoleMode.Call(uintptr(handle), uintptr(unsafe.Pointer(&mode)))
+	if ret == SYS_CALL_FAILURE {
+		return err
+	}
+
+	// Add the virtual terminal processing flag to the current mode.
+	newMode := mode | enableVirtualTerminalProcessing
+
+	// Try to set the new console mode.
+	ret, _, err = procSetConsoleMode.Call(uintptr(handle), uintptr(newMode))
+	if ret == SYS_CALL_FAILURE {
+		return err
+	}
+
+	return nil
+} 

internal/ansi/ansi_windows_test.go

@@ -0,0 +1,65 @@
+//go:build windows
+
+package ansi
+
+import (
+	"os"
+	"syscall"
+	"testing"
+	"unsafe"
+
+	"github.com/stretchr/testify/require"
+)
+
+// getConsoleMode is a helper to retrieve the current console mode for a given handle.
+func getConsoleMode(handle syscall.Handle) (uint32, error) {
+	var mode uint32
+	ret, _, err := syscall.NewLazyDLL("kernel32.dll").NewProc("GetConsoleMode").Call(uintptr(handle), uintptr(unsafe.Pointer(&mode)))
+	if ret == SYS_CALL_FAILURE {
+		// Note: err may be non-nil even on success, so we must check ret first.
+		return 0, err
+	}
+	return mode, nil
+}
+
+// setConsoleMode is a helper to set the console mode for a given handle.
+func setConsoleMode(handle syscall.Handle, mode uint32) error {
+	ret, _, err := syscall.NewLazyDLL("kernel32.dll").NewProc("SetConsoleMode").Call(uintptr(handle), uintptr(mode))
+	if ret == SYS_CALL_FAILURE {
+		return err
+	}
+	return nil
+}
+
+func TestEnable(t *testing.T) {
+	// This test requires a real Windows console. If stdout is redirected (e.g., in some CI/CD
+	// environments), GetConsoleMode will fail. In that case, we should skip the test.
+	handle := syscall.Handle(os.Stdout.Fd())
+	originalMode, err := getConsoleMode(handle)
+	if err != nil && err.Error() != "The handle is invalid." {
+		// "The handle is invalid." is the typical error when not in a console.
+		// We skip on this specific error.
+		t.Skipf("cannot get console mode, skipping test: %v", err)
+	}
+
+	// Defer the restoration of the original console mode.
+	// This ensures that we don't mess up the terminal for subsequent tests.
+	if err == nil { // Only restore if we successfully got the mode.
+		defer func() {
+			err := setConsoleMode(handle, originalMode)
+			require.NoError(t, err, "failed to restore original console mode")
+		}()
+	}
+
+	// Run the function we want to test.
+	err = Enable()
+	require.NoError(t, err, "Enable() should not return an error in a real console")
+
+	// After running Enable(), check the console mode again to see if the flag was set.
+	newMode, err := getConsoleMode(handle)
+	require.NoError(t, err, "failed to get new console mode after enabling ANSI")
+
+	// Assert that the flag for virtual terminal processing is now set.
+	flagIsSet := (newMode & enableVirtualTerminalProcessing) != 0
+	require.True(t, flagIsSet, "ENABLE_VIRTUAL_TERMINAL_PROCESSING flag should have been set")
+} 

terminal.go

@@ -0,0 +1,12 @@
+package godump
+
+import (
+	"os"
+
+	"golang.org/x/term"
+)
+
+// isTerminal checks if the given file is a terminal using the Go standard library.
+func isTerminal(f *os.File) bool {
+	return term.IsTerminal(int(f.Fd()))
+}