fix(theme): validate and merge user theme files instead of blind override

theme/load_test.go

@@ -8,8 +8,7 @@ import (
 )
 
 func TestLoadAllIncludesBuiltinThemes(t *testing.T) {
-	// Point HOME somewhere empty so only embedded themes load.
-	t.Setenv("HOME", t.TempDir())
+	t.Setenv("CLIAMP_CONFIG_DIR", filepath.Join(t.TempDir(), "empty"))
 
 	themes := LoadAll()
 	if len(themes) == 0 {
@@ -33,7 +32,7 @@ func TestLoadAllIncludesBuiltinThemes(t *testing.T) {
 }
 
 func TestLoadAllSortedCaseInsensitive(t *testing.T) {
-	t.Setenv("HOME", t.TempDir())
+	t.Setenv("CLIAMP_CONFIG_DIR", filepath.Join(t.TempDir(), "empty"))
 
 	themes := LoadAll()
 	for i := 1; i < len(themes); i++ {
@@ -45,74 +44,126 @@ func TestLoadAllSortedCaseInsensitive(t *testing.T) {
 	}
 }
 
-func TestLoadAllUserThemeOverridesBuiltin(t *testing.T) {
-	home := t.TempDir()
-	t.Setenv("HOME", home)
-
-	// Put a user override file named "dracula.toml" with a distinctive accent color.
-	userDir := filepath.Join(home, ".config", "cliamp", "themes")
-	if err := os.MkdirAll(userDir, 0o755); err != nil {
-		t.Fatalf("MkdirAll: %v", err)
-	}
-	overridden := `accent = "#ff00ff"
-fg = "#123456"
-`
-	if err := os.WriteFile(filepath.Join(userDir, "dracula.toml"), []byte(overridden), 0o644); err != nil {
-		t.Fatalf("WriteFile: %v", err)
-	}
-
-	themes := LoadAll()
-	var got Theme
-	for _, th := range themes {
-		if strings.EqualFold(th.Name, "dracula") {
-			got = th
-			break
-		}
-	}
-	if got.Name == "" {
-		t.Fatal("dracula theme not present after override")
-	}
-	if got.Accent != "#ff00ff" {
-		t.Errorf("Accent = %q, want #ff00ff (user override)", got.Accent)
-	}
-	if got.FG != "#123456" {
-		t.Errorf("FG = %q, want #123456 (user override)", got.FG)
-	}
-}
-
-func TestLoadAllAddsUserOnlyTheme(t *testing.T) {
-	home := t.TempDir()
-	t.Setenv("HOME", home)
-
-	userDir := filepath.Join(home, ".config", "cliamp", "themes")
-	if err := os.MkdirAll(userDir, 0o755); err != nil {
-		t.Fatalf("MkdirAll: %v", err)
-	}
-	custom := `accent = "#abcdef"`
-	if err := os.WriteFile(filepath.Join(userDir, "mytheme.toml"), []byte(custom), 0o644); err != nil {
-		t.Fatalf("WriteFile: %v", err)
-	}
-
-	themes := LoadAll()
-	var found bool
-	for _, th := range themes {
-		if th.Name == "mytheme" {
-			found = true
-			if th.Accent != "#abcdef" {
-				t.Errorf("Accent = %q, want #abcdef", th.Accent)
+func TestLoadAllUserThemeScenarios(t *testing.T) {
+	tests := []struct {
+		name     string
+		fileName string
+		fileBody string
+		check    func(t *testing.T, themes []Theme)
+	}{
+		{
+			name:     "partial merge onto builtin",
+			fileName: "dracula.toml",
+			fileBody: "accent = \"#ff00ff\"\nfg = \"#123456\"\n",
+			check: func(t *testing.T, themes []Theme) {
+				var got Theme
+				for _, th := range themes {
+					if strings.EqualFold(th.Name, "dracula") {
+						got = th
+						break
+					}
+				}
+				if got.Name == "" {
+					t.Fatal("dracula theme not present after merge")
+				}
+				if got.Accent != "#ff00ff" {
+					t.Errorf("Accent = %q, want #ff00ff", got.Accent)
+				}
+				if got.FG != "#123456" {
+					t.Errorf("FG = %q, want #123456", got.FG)
+				}
+				if got.BrightFG != "#f8f8f2" {
+					t.Errorf("built-in BrightFG should survive: got %q, want #f8f8f2", got.BrightFG)
+				}
+			},
+		},
+		{
+			name:     "full standalone theme accepted",
+			fileName: "mytheme.toml",
+			fileBody: `accent = "#abcdef"
+bright_fg = "#ffffff"
+fg = "#cccccc"
+green = "#00ff00"
+yellow = "#ffff00"
+red = "#ff0000"`,
+			check: func(t *testing.T, themes []Theme) {
+				var found bool
+				for _, th := range themes {
+					if th.Name == "mytheme" {
+						found = true
+						if th.Accent != "#abcdef" {
+							t.Errorf("Accent = %q, want #abcdef", th.Accent)
+						}
+					}
+				}
+				if !found {
+					t.Error("user theme mytheme not loaded")
+				}
+			},
+		},
+		{
+			name:     "partial without builtin match skipped",
+			fileName: "broken.toml",
+			fileBody: "accent = \"#ff0000\"",
+			check: func(t *testing.T, themes []Theme) {
+				for _, th := range themes {
+					if th.Name == "broken" {
+						t.Fatal("partial theme without built-in match should not be loaded")
+					}
+				}
+			},
+		},
+		{
+			name:     "invalid hex in merge ignored",
+			fileName: "dracula.toml",
+			fileBody: `accent = "#ff0000"
+bright_fg = "#f8f8f2"
+fg = "#6272a4"
+green = "#50fa7b"
+yellow = "#f1fa8c"
+red = "not-a-color"`,
+			check: func(t *testing.T, themes []Theme) {
+				var got Theme
+				for _, th := range themes {
+					if strings.EqualFold(th.Name, "dracula") {
+						got = th
+						break
+					}
+				}
+				if got.Name == "" {
+					t.Fatal("dracula theme not found after merge")
+				}
+				if got.Accent != "#ff0000" {
+					t.Errorf("valid Accent should merge: got %q, want #ff0000", got.Accent)
+				}
+				if got.Red != "#ff5555" {
+					t.Errorf("invalid Red should be ignored (built-in): got %q, want #ff5555", got.Red)
+				}
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			configDir := filepath.Join(t.TempDir(), ".config", "cliamp")
+			t.Setenv("CLIAMP_CONFIG_DIR", configDir)
+			userDir := filepath.Join(configDir, "themes")
+			if err := os.MkdirAll(userDir, 0o755); err != nil {
+				t.Fatalf("MkdirAll: %v", err)
 			}
-		}
-	}
-	if !found {
-		t.Error("user theme mytheme not loaded")
+			if err := os.WriteFile(filepath.Join(userDir, tt.fileName), []byte(tt.fileBody), 0o644); err != nil {
+				t.Fatalf("WriteFile: %v", err)
+			}
+
+			tt.check(t, LoadAll())
+		})
 	}
 }
 
 func TestLoadAllIgnoresNonTomlFiles(t *testing.T) {
-	home := t.TempDir()
-	t.Setenv("HOME", home)
-
-	userDir := filepath.Join(home, ".config", "cliamp", "themes")
+	configDir := filepath.Join(t.TempDir(), ".config", "cliamp")
+	t.Setenv("CLIAMP_CONFIG_DIR", configDir)
+	userDir := filepath.Join(configDir, "themes")
 	if err := os.MkdirAll(userDir, 0o755); err != nil {
 		t.Fatalf("MkdirAll: %v", err)
 	}
@@ -133,8 +184,7 @@ func TestLoadAllIgnoresNonTomlFiles(t *testing.T) {
 }
 
 func TestLoadAllMissingUserDir(t *testing.T) {
-	// HOME points at a dir where ~/.config/cliamp/themes doesn't exist.
-	t.Setenv("HOME", t.TempDir())
+	t.Setenv("CLIAMP_CONFIG_DIR", filepath.Join(t.TempDir(), "empty"))
 	themes := LoadAll()
 	if len(themes) == 0 {
 		t.Error("LoadAll() with missing user dir should still return built-in themes")

theme/theme.go

@@ -5,6 +5,7 @@ import (
 	"bufio"
 	"cmp"
 	"embed"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -36,6 +37,71 @@ func (t Theme) IsDefault() bool {
 	return t.Accent == "" && t.Green == "" && t.BrightFG == ""
 }
 
+// validHex reports whether s is a valid hex color like "#fff" or "#aabbcc".
+func validHex(s string) bool {
+	if len(s) < 4 || s[0] != '#' {
+		return false
+	}
+	for _, r := range s[1:] {
+		if !(r >= '0' && r <= '9') && !(r >= 'a' && r <= 'f') && !(r >= 'A' && r <= 'F') {
+			return false
+		}
+	}
+	n := len(s) - 1
+	return n == 3 || n == 6 || n == 8
+}
+
+// Validate checks that all six color fields are non-empty hex values.
+func (t Theme) Validate() error {
+	missing := make([]string, 0, 6)
+	if !validHex(t.Accent) {
+		missing = append(missing, "accent")
+	}
+	if !validHex(t.BrightFG) {
+		missing = append(missing, "bright_fg")
+	}
+	if !validHex(t.FG) {
+		missing = append(missing, "fg")
+	}
+	if !validHex(t.Green) {
+		missing = append(missing, "green")
+	}
+	if !validHex(t.Yellow) {
+		missing = append(missing, "yellow")
+	}
+	if !validHex(t.Red) {
+		missing = append(missing, "red")
+	}
+	if len(missing) > 0 {
+		return fmt.Errorf("missing or invalid hex fields: %s", strings.Join(missing, ", "))
+	}
+	return nil
+}
+
+// merge applies every non-empty valid-hex field from src onto dst.
+// Fields with invalid hex values are silently ignored so that a corrupt
+// or partial user file only changes the colours it explicitly sets.
+func merge(dst *Theme, src Theme) {
+	if validHex(src.Accent) {
+		dst.Accent = src.Accent
+	}
+	if validHex(src.BrightFG) {
+		dst.BrightFG = src.BrightFG
+	}
+	if validHex(src.FG) {
+		dst.FG = src.FG
+	}
+	if validHex(src.Green) {
+		dst.Green = src.Green
+	}
+	if validHex(src.Yellow) {
+		dst.Yellow = src.Yellow
+	}
+	if validHex(src.Red) {
+		dst.Red = src.Red
+	}
+}
+
 // Default returns a sentinel "Default" theme with empty hex values,
 // signaling that ANSI fallback colors should be used.
 func Default() Theme {
@@ -129,6 +195,12 @@ func loadBuiltin(themes map[string]Theme) {
 }
 
 // loadUserDir loads themes from ~/.config/cliamp/themes/*.toml.
+//
+// If a user file matches a built-in theme name its fields are merged onto
+// the built-in, so that a partial override (e.g. only "accent = ...")
+// changes only that colour.  Themes without a built-in match require all
+// six hex fields to pass validation.  Invalid hex values in either mode are
+// silently ignored — the corresponding built-in (or zero) value survives.
 func loadUserDir(dir string, themes map[string]Theme) {
 	entries, err := os.ReadDir(dir)
 	if err != nil {
@@ -149,6 +221,18 @@ func loadUserDir(dir string, themes map[string]Theme) {
 		if err != nil {
 			continue
 		}
-		themes[strings.ToLower(name)] = t
+		key := strings.ToLower(name)
+		if _, exists := themes[key]; exists {
+			// Merge onto the existing (built-in) theme.
+			existing := themes[key]
+			merge(&existing, t)
+			themes[key] = existing
+		} else {
+			// New theme (no built-in match): all six fields required.
+			if err := t.Validate(); err != nil {
+				continue
+			}
+			themes[key] = t
+		}
 	}
 }