Add context to errors.

file_test.go

@@ -187,7 +187,7 @@ func TestSelectFileMutiple_script(t *testing.T) {
 		if skip, err := skip(err); skip {
 			t.Skip("skipping:", err)
 		}
-		if err == zenity.ErrUnsupported {
+		if errors.Is(err, zenity.ErrUnsupported) {
 			t.Skip("was not unsupported:", err)
 		}
 		if lst == nil || err != nil {

file_windows.go

@@ -1,6 +1,7 @@
 package zenity
 
 import (
+	"fmt"
 	"path/filepath"
 	"reflect"
 	"syscall"
@@ -199,7 +200,7 @@ func pickFolders(opts options, multi bool) (str string, lst []string, err error)
 		_IID_IFileOpenDialog, uintptr(unsafe.Pointer(&dialog)))
 	if int32(hr) < 0 {
 		if multi {
-			return "", nil, ErrUnsupported
+			return "", nil, fmt.Errorf("%w: multiple directory", ErrUnsupported)
 		}
 		return browseForFolder(opts)
 	}

list.go

@@ -12,7 +12,7 @@ func List(text string, items []string, options ...Option) (string, error) {
 
 // ListItems displays the list dialog.
 //
-// May return: ErrCanceled.
+// May return: ErrCanceled, ErrUnsupported.
 func ListItems(text string, items ...string) (string, error) {
 	return List(text, items)
 }
@@ -29,7 +29,7 @@ func ListMultiple(text string, items []string, options ...Option) ([]string, err
 
 // ListMultipleItems displays the list dialog, allowing multiple items to be selected.
 //
-// May return: ErrCanceled.
+// May return: ErrCanceled, ErrUnsupported.
 func ListMultipleItems(text string, items ...string) ([]string, error) {
 	return ListMultiple(text, items)
 }

list_darwin.go

@@ -1,12 +1,17 @@
 package zenity
 
 import (
+	"fmt"
+
 	"github.com/ncruces/zenity/internal/zenutil"
 )
 
 func list(text string, items []string, opts options) (string, error) {
-	if len(items) == 0 || opts.extraButton != nil {
+	if len(items) == 0 {
-		return "", ErrUnsupported
+		return "", fmt.Errorf("%w: empty items list", ErrUnsupported)
+	}
+	if opts.extraButton != nil {
+		return "", fmt.Errorf("%w: extra button", ErrUnsupported)
 	}
 
 	var data zenutil.List
@@ -23,8 +28,11 @@ func list(text string, items []string, opts options) (string, error) {
 }
 
 func listMultiple(text string, items []string, opts options) ([]string, error) {
-	if len(items) == 0 || opts.extraButton != nil {
+	if len(items) == 0 {
-		return nil, ErrUnsupported
+		return nil, fmt.Errorf("%w: empty items list", ErrUnsupported)
+	}
+	if opts.extraButton != nil {
+		return nil, fmt.Errorf("%w: extra button", ErrUnsupported)
 	}
 
 	var data zenutil.List

progress_darwin.go

@@ -1,12 +1,14 @@
 package zenity
 
 import (
+	"fmt"
+
 	"github.com/ncruces/zenity/internal/zenutil"
 )
 
 func progress(opts options) (ProgressDialog, error) {
 	if opts.extraButton != nil {
-		return nil, ErrUnsupported
+		return nil, fmt.Errorf("%w: extra button", ErrUnsupported)
 	}
 
 	var data zenutil.Progress

pwd_stub.go

@@ -2,9 +2,11 @@
 
 package zenity
 
+import "fmt"
+
 func password(opts options) (string, string, error) {
 	if opts.username {
-		return "", "", ErrUnsupported
+		return "", "", fmt.Errorf("%w: username", ErrUnsupported)
 	}
 	opts.hideText = true
 	str, err := entry("Password:", opts)

pwd_test.go

@@ -61,7 +61,9 @@ func TestPassword_username(t *testing.T) {
 		t.Skip("skipping:", err)
 	}
 	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
-		if err != zenity.ErrUnsupported {
+		if errors.Is(err, zenity.ErrUnsupported) {
+			t.Skip("was not unsupported:", err)
+		} else {
 			t.Error("was not unsupported:", err)
 		}
 	} else {
@@ -92,7 +94,7 @@ func TestPassword_script(t *testing.T) {
 			if skip, err := skip(err); skip {
 				t.Skip("skipping:", err)
 			}
-			if err == zenity.ErrUnsupported {
+			if errors.Is(err, zenity.ErrUnsupported) {
 				t.Skip("was not unsupported:", err)
 			}
 			if usr != tt.usr || pwd != tt.pwd || err != tt.err {