feat(options): add optional Options arguments to New() function (#14)

Enables simpler creation of custom *Golden instances, as you can just pass in the custom values to New(), rather than modifying fields after increating the Golden instance.

golden.go

@@ -257,14 +257,21 @@ type Golden struct {
 }
 
 // New returns a new *Golden instance with default values correctly populated.
-func New() *Golden {
-	return &Golden{
+// It accepts zero or more Option functions that can modify the default values.
+func New(opts ...Option) *Golden {
+	g := &Golden{
 		DirMode:    DefaultDirMode,
 		FileMode:   DefaultFileMode,
 		Suffix:     DefaultSuffix,
 		Dirname:    DefaultDirname,
 		UpdateFunc: DefaultUpdateFunc,
 	}
+
+	for _, opt := range opts {
+		opt(g)
+	}
+
+	return g
 }
 
 // Do is a convenience function for calling Update(), Set(), and Get() in a

golden_test.go

@@ -11,6 +11,37 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+// assertSameFunc asserts that two functions are the same by comparing their
+// function names via reflection.
+func assertSameFunc(t *testing.T, want, got interface{}) {
+	t.Helper()
+
+	// Verify both arguments are functions
+	wantType := reflect.TypeOf(want)
+	gotType := reflect.TypeOf(got)
+
+	if wantType.Kind() != reflect.Func {
+		t.Fatalf(
+			"assertSameFunc: 'want' argument is not a function, got %s",
+			wantType.Kind(),
+		)
+	}
+
+	if gotType.Kind() != reflect.Func {
+		t.Fatalf(
+			"assertSameFunc: 'got' argument is not a function, got %s",
+			gotType.Kind(),
+		)
+	}
+
+	gotFP := reflect.ValueOf(got).Pointer()
+	gotFuncName := runtime.FuncForPC(gotFP).Name()
+	wantFP := reflect.ValueOf(want).Pointer()
+	wantFuncName := runtime.FuncForPC(wantFP).Name()
+
+	assert.Equal(t, wantFuncName, gotFuncName)
+}
+
 func TestDefaults(t *testing.T) {
 	t.Run("Default", func(t *testing.T) {
 		assert.IsType(t, &Golden{}, Default)
@@ -19,15 +50,7 @@ func TestDefaults(t *testing.T) {
 		assert.Equal(t, DefaultFileMode, Default.FileMode)
 		assert.Equal(t, DefaultSuffix, Default.Suffix)
 		assert.Equal(t, DefaultDirname, Default.Dirname)
-
-		// Use runtime.FuncForPC() to verify the UpdateFunc value is set to
-		// the EnvUpdateFunc function by default.
-		gotFP := reflect.ValueOf(Default.UpdateFunc).Pointer()
-		gotFuncName := runtime.FuncForPC(gotFP).Name()
-		wantFP := reflect.ValueOf(EnvUpdateFunc).Pointer()
-		wantFuncName := runtime.FuncForPC(wantFP).Name()
-
-		assert.Equal(t, wantFuncName, gotFuncName)
+		assertSameFunc(t, EnvUpdateFunc, Default.UpdateFunc)
 	})
 
 	t.Run("DefaultDirMode", func(t *testing.T) {
@@ -47,17 +70,10 @@ func TestDefaults(t *testing.T) {
 	})
 
 	t.Run("DefaultUpdateFunc", func(t *testing.T) {
-		gotFP := reflect.ValueOf(DefaultUpdateFunc).Pointer()
-		gotFuncName := runtime.FuncForPC(gotFP).Name()
-		wantFP := reflect.ValueOf(EnvUpdateFunc).Pointer()
-		wantFuncName := runtime.FuncForPC(wantFP).Name()
-		assert.Equal(t, wantFuncName, gotFuncName)
+		assertSameFunc(t, EnvUpdateFunc, DefaultUpdateFunc)
 	})
-}
 
-// TestNew is a horribly hack to test that the New() function uses the
-// package-level Default* variables.
-func TestNew(t *testing.T) {
+	t.Run("customized Default* variables", func(t *testing.T) {
 		// Capture the default values before we change them.
 		defaultDirMode := DefaultDirMode
 		defaultFileMode := DefaultFileMode
@@ -90,14 +106,93 @@ func TestNew(t *testing.T) {
 		assert.Equal(t, DefaultFileMode, got.FileMode)
 		assert.Equal(t, DefaultSuffix, got.Suffix)
 		assert.Equal(t, DefaultDirname, got.Dirname)
+		assertSameFunc(t, updateFunc, got.UpdateFunc)
+	})
+}
 
-	// Verify the UpdateFunc value is set to the new value.
-	gotFP := reflect.ValueOf(got.UpdateFunc).Pointer()
-	gotFuncName := runtime.FuncForPC(gotFP).Name()
-	wantFP := reflect.ValueOf(updateFunc).Pointer()
-	wantFuncName := runtime.FuncForPC(wantFP).Name()
+func TestNew(t *testing.T) {
+	t.Run("defaults (no options)", func(t *testing.T) {
+		g := New()
+		assert.Equal(t, DefaultDirMode, g.DirMode)
+		assert.Equal(t, DefaultFileMode, g.FileMode)
+		assert.Equal(t, DefaultSuffix, g.Suffix)
+		assert.Equal(t, DefaultDirname, g.Dirname)
+		assertSameFunc(t, EnvUpdateFunc, g.UpdateFunc)
+	})
 
-	assert.Equal(t, wantFuncName, gotFuncName)
+	// Test each option individually
+	t.Run("WithDirMode", func(t *testing.T) {
+		customMode := os.FileMode(0o700)
+		g := New(WithDirMode(customMode))
+		assert.Equal(t, customMode, g.DirMode)
+		assert.Equal(t, DefaultFileMode, g.FileMode)
+		assert.Equal(t, DefaultSuffix, g.Suffix)
+		assert.Equal(t, DefaultDirname, g.Dirname)
+		assertSameFunc(t, EnvUpdateFunc, g.UpdateFunc)
+	})
+
+	t.Run("WithFileMode", func(t *testing.T) {
+		customMode := os.FileMode(0o600)
+		g := New(WithFileMode(customMode))
+		assert.Equal(t, DefaultDirMode, g.DirMode)
+		assert.Equal(t, customMode, g.FileMode)
+		assert.Equal(t, DefaultSuffix, g.Suffix)
+		assert.Equal(t, DefaultDirname, g.Dirname)
+		assertSameFunc(t, EnvUpdateFunc, g.UpdateFunc)
+	})
+
+	t.Run("WithSuffix", func(t *testing.T) {
+		customSuffix := ".my-suffix"
+		g := New(WithSuffix(customSuffix))
+		assert.Equal(t, DefaultDirMode, g.DirMode)
+		assert.Equal(t, DefaultFileMode, g.FileMode)
+		assert.Equal(t, customSuffix, g.Suffix)
+		assert.Equal(t, DefaultDirname, g.Dirname)
+		assertSameFunc(t, EnvUpdateFunc, g.UpdateFunc)
+	})
+
+	t.Run("WithDirname", func(t *testing.T) {
+		customDirname := "fixtures/generated"
+		g := New(WithDirname(customDirname))
+		assert.Equal(t, DefaultDirMode, g.DirMode)
+		assert.Equal(t, DefaultFileMode, g.FileMode)
+		assert.Equal(t, DefaultSuffix, g.Suffix)
+		assert.Equal(t, customDirname, g.Dirname)
+		assertSameFunc(t, EnvUpdateFunc, g.UpdateFunc)
+	})
+
+	t.Run("WithUpdateFunc", func(t *testing.T) {
+		customUpdateFunc := func() bool { return true }
+		g := New(WithUpdateFunc(customUpdateFunc))
+		assert.Equal(t, DefaultDirMode, g.DirMode)
+		assert.Equal(t, DefaultFileMode, g.FileMode)
+		assert.Equal(t, DefaultSuffix, g.Suffix)
+		assert.Equal(t, DefaultDirname, g.Dirname)
+		assertSameFunc(t, customUpdateFunc, g.UpdateFunc)
+	})
+
+	// Test multiple options at once
+	t.Run("MultipleOptions", func(t *testing.T) {
+		customDirMode := os.FileMode(0o700)
+		customFileMode := os.FileMode(0o600)
+		customSuffix := ".fixture"
+		customDirname := "fixtures"
+		customUpdateFunc := func() bool { return true }
+
+		g := New(
+			WithDirMode(customDirMode),
+			WithFileMode(customFileMode),
+			WithSuffix(customSuffix),
+			WithDirname(customDirname),
+			WithUpdateFunc(customUpdateFunc),
+		)
+
+		assert.Equal(t, customDirMode, g.DirMode)
+		assert.Equal(t, customFileMode, g.FileMode)
+		assert.Equal(t, customSuffix, g.Suffix)
+		assert.Equal(t, customDirname, g.Dirname)
+		assertSameFunc(t, customUpdateFunc, g.UpdateFunc)
+	})
 }
 
 func TestDo(t *testing.T) {

options.go

@@ -0,0 +1,43 @@
+package golden
+
+import (
+	"os"
+)
+
+// Option is a function that modifies a Golden instance.
+type Option func(*Golden)
+
+// WithDirMode sets the directory mode for a Golden instance.
+func WithDirMode(mode os.FileMode) Option {
+	return func(g *Golden) {
+		g.DirMode = mode
+	}
+}
+
+// WithFileMode sets the file mode for a Golden instance.
+func WithFileMode(mode os.FileMode) Option {
+	return func(g *Golden) {
+		g.FileMode = mode
+	}
+}
+
+// WithSuffix sets the file suffix for a Golden instance.
+func WithSuffix(suffix string) Option {
+	return func(g *Golden) {
+		g.Suffix = suffix
+	}
+}
+
+// WithDirname sets the directory name for a Golden instance.
+func WithDirname(dirname string) Option {
+	return func(g *Golden) {
+		g.Dirname = dirname
+	}
+}
+
+// WithUpdateFunc sets the update function for a Golden instance.
+func WithUpdateFunc(updateFunc UpdateFunc) Option {
+	return func(g *Golden) {
+		g.UpdateFunc = updateFunc
+	}
+}

options_test.go

@@ -0,0 +1,58 @@
+package golden
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWithDirMode(t *testing.T) {
+	customMode := os.FileMode(0o700)
+	g := &Golden{}
+
+	opt := WithDirMode(customMode)
+	opt(g)
+
+	assert.Equal(t, customMode, g.DirMode)
+}
+
+func TestWithFileMode(t *testing.T) {
+	customMode := os.FileMode(0o600)
+	g := &Golden{}
+
+	opt := WithFileMode(customMode)
+	opt(g)
+
+	assert.Equal(t, customMode, g.FileMode)
+}
+
+func TestWithSuffix(t *testing.T) {
+	customSuffix := ".custom"
+	g := &Golden{}
+
+	opt := WithSuffix(customSuffix)
+	opt(g)
+
+	assert.Equal(t, customSuffix, g.Suffix)
+}
+
+func TestWithDirname(t *testing.T) {
+	customDirname := "custom-testdata"
+	g := &Golden{}
+
+	opt := WithDirname(customDirname)
+	opt(g)
+
+	assert.Equal(t, customDirname, g.Dirname)
+}
+
+func TestWithUpdateFunc(t *testing.T) {
+	customUpdateFunc := func() bool { return true }
+	g := &Golden{}
+
+	opt := WithUpdateFunc(customUpdateFunc)
+	opt(g)
+
+	assertSameFunc(t, customUpdateFunc, g.UpdateFunc)
+}