fix(cli): let theme show accept custom theme file paths again

cmd/theme.go

@@ -82,11 +82,18 @@ func newThemeShowCmd(load themeLoadFunc, list themeListFunc) *cobra.Command {
 			// a stale config value can't stop the TUI from launching. That is
 			// wrong for "show", where silently reporting the default theme
 			// hides the typo, so reject unknown names up front.
+			//
+			// Path forms are exempt: theme.Load reads those straight from disk
+			// and they never appear in ListThemes, so checking them against the
+			// built-in list would reject every custom theme file. Let Load
+			// handle them and surface its error.
 			name := args[0]
-			available := list()
-			if !slices.Contains(available, name) {
-				return fmt.Errorf("unknown theme %q (available: %s)",
-					name, strings.Join(available, ", "))
+			if !theme.LooksLikePath(name) {
+				available := list()
+				if !slices.Contains(available, name) {
+					return fmt.Errorf("unknown theme %q (available: %s)",
+						name, strings.Join(available, ", "))
+				}
 			}
 			resolved, err := load(name)
 			if err != nil {

cmd/theme_test.go

@@ -3,6 +3,7 @@ package cmd
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"testing"
 
 	"github.com/jongio/grut/internal/theme"
@@ -156,6 +157,58 @@ func TestThemeShowCommandUnknownThemeErrors(t *testing.T) {
 	assert.False(t, loadCalled, "load should not run for an unknown theme")
 }
 
+// Custom theme files are loaded by path and never appear in ListThemes, so
+// validating a path form against the built-in list would reject every custom
+// theme. Assert path arguments reach load instead of being rejected.
+func TestThemeShowCommandAllowsPathForms(t *testing.T) {
+	paths := []string{
+		"my-theme.toml",
+		"./themes/custom.toml",
+		"/etc/grut/theme.toml",
+		`C:\themes\custom.toml`,
+	}
+
+	for _, p := range paths {
+		t.Run(p, func(t *testing.T) {
+			var gotName string
+			cmd := newThemeShowCmd(func(name string) (*theme.Theme, error) {
+				gotName = name
+				return &theme.Theme{Name: "custom", Variant: "dark", Mode: theme.ModeColor}, nil
+			}, func() []string { return []string{"default", "gruvbox"} })
+			cmd.SetArgs([]string{p})
+			var out bytes.Buffer
+			cmd.SetOut(&out)
+			cmd.SetErr(&out)
+			cmd.SilenceUsage = true
+
+			err := cmd.Execute()
+
+			require.NoError(t, err, "path form must not be rejected as an unknown theme")
+			assert.Equal(t, p, gotName, "the path should be passed through to load unchanged")
+			assert.Contains(t, out.String(), "Name:    custom")
+		})
+	}
+}
+
+// A path that load rejects must surface load's error, not a misleading
+// "unknown theme" message listing the built-in names.
+func TestThemeShowCommandPropagatesPathLoadError(t *testing.T) {
+	cmd := newThemeShowCmd(func(string) (*theme.Theme, error) {
+		return nil, errors.New("open missing.toml: no such file or directory")
+	}, func() []string { return []string{"default", "gruvbox"} })
+	cmd.SetArgs([]string{"missing.toml"})
+	var out bytes.Buffer
+	cmd.SetOut(&out)
+	cmd.SetErr(&out)
+	cmd.SilenceUsage = true
+
+	err := cmd.Execute()
+
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "no such file or directory")
+	assert.NotContains(t, err.Error(), "unknown theme")
+}
+
 func TestRootRegistersThemeListCommand(t *testing.T) {
 	root, cleanup := newRootCommand()
 	defer cleanup()

internal/theme/load.go

@@ -226,7 +226,7 @@ func (tf *themeFile) toColors() Colors {
 // theme and logs a warning.
 func Load(name string) (*Theme, error) {
 	// File path — read directly from disk.
-	if looksLikePath(name) {
+	if LooksLikePath(name) {
 		// Defence-in-depth: clean the path and reject directory
 		// traversal so a malicious or misconfigured theme value
 		// cannot read arbitrary files outside intended directories.
@@ -464,10 +464,12 @@ func validateColors(c Colors) error {
 	return nil
 }
 
-// looksLikePath returns true if the name contains a path separator or
+// LooksLikePath returns true if the name contains a path separator or
 // common file extension, suggesting it is a file path rather than a
-// built-in theme name.
-func looksLikePath(name string) bool {
+// built-in theme name. Callers that validate a theme name against the
+// built-in list must use this to let path forms through, since those
+// will never appear in ListThemes.
+func LooksLikePath(name string) bool {
 	return strings.ContainsAny(name, `/\`) || strings.HasSuffix(name, ".toml")
 }
 

internal/theme/theme_test.go

@@ -267,7 +267,7 @@ func TestBuiltinNamesReturnsCopy(t *testing.T) {
 }
 
 // ---------------------------------------------------------------------------
-// looksLikePath
+// LooksLikePath
 // ---------------------------------------------------------------------------
 
 func TestLooksLikePath(t *testing.T) {
@@ -285,7 +285,7 @@ func TestLooksLikePath(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.input, func(t *testing.T) {
-			assert.Equal(t, tt.want, looksLikePath(tt.input))
+			assert.Equal(t, tt.want, LooksLikePath(tt.input))
 		})
 	}
 }