feat(theming): integrate NvChad chadrc rewrite into Apply

internal/modules/neovim/neovim.go

@@ -88,6 +88,44 @@ func (m Module) resolvedTheme() string {
 	return "gruvbox"
 }
 
+// WriteChadrc renders chadrc.lua for the given NvChad theme name and writes
+// it to ~/.config/nvim/lua/chadrc.lua. If the file does not already exist
+// and the surrounding nvim config dir does not exist, the function returns
+// nil without writing anything (the user hasn't installed neovim yet).
+//
+// Exported so the theming package can re-render chadrc on theme switches
+// without re-running the full Module pipeline.
+func WriteChadrc(nvChadThemeName string) error {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return err
+	}
+	cfg := filepath.Join(home, ".config", "nvim")
+	chadrcPath := filepath.Join(cfg, "lua", "chadrc.lua")
+
+	// If chadrc doesn't exist, only write when the parent dir exists. A
+	// fresh system where nvim was never installed should be a no-op.
+	if _, err := os.Stat(chadrcPath); err != nil {
+		if _, err := os.Stat(cfg); err != nil {
+			return nil
+		}
+	}
+
+	tmplBytes, err := assets.ReadFile("assets/chadrc.lua.tmpl")
+	if err != nil {
+		return err
+	}
+	tmpl, err := template.New("chadrc").Parse(string(tmplBytes))
+	if err != nil {
+		return err
+	}
+	var buf bytes.Buffer
+	if err := tmpl.Execute(&buf, struct{ NvChadTheme string }{NvChadTheme: nvChadThemeName}); err != nil {
+		return err
+	}
+	return platform.WriteUserFile(chadrcPath, buf.Bytes(), 0o644)
+}
+
 func (m Module) renderChadrc() ([]byte, error) {
 	tmplBytes, err := assets.ReadFile("assets/chadrc.lua.tmpl")
 	if err != nil {

internal/modules/neovim/neovim_test.go

@@ -177,4 +177,34 @@ func TestUnknownThemeFallsBackToFirst(t *testing.T) {
 	}
 }
 
+func TestWriteChadrcWritesFile(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	cfg := filepath.Join(home, ".config", "nvim")
+	if err := os.MkdirAll(cfg, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := WriteChadrc("dracula"); err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(filepath.Join(cfg, "lua", "chadrc.lua"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(data), `theme = "dracula"`) {
+		t.Fatalf("theme not applied: %s", data)
+	}
+}
+
+func TestWriteChadrcNoopWithoutConfigDir(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	if err := WriteChadrc("gruvbox"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(filepath.Join(home, ".config", "nvim", "lua", "chadrc.lua")); !os.IsNotExist(err) {
+		t.Fatal("chadrc should not be created on a bare system")
+	}
+}
+
 var _ module.Module = Module{}

internal/theming/theming.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 
 	"github.com/MDietermann/ArduinoArchSetup/internal/config"
+	"github.com/MDietermann/ArduinoArchSetup/internal/modules/neovim"
 	"github.com/MDietermann/ArduinoArchSetup/internal/platform"
 	"gopkg.in/yaml.v3"
 )
@@ -144,6 +145,15 @@ func Apply(cfg config.Config, themeID string) error {
 	if err := updateOverlayActive(th.ID); err != nil {
 		return fmt.Errorf("update overlay: %w", err)
 	}
+
+	if err := neovim.WriteChadrc(th.NvChadTheme); err != nil {
+		return fmt.Errorf("update chadrc: %w", err)
+	}
+
+	// Clear NvChad's base46 theme cache so the new theme activates on next
+	// nvim launch. Errors ignored — the cache may not exist.
+	_ = os.RemoveAll(filepath.Join(home, ".cache", "nvim", "base46"))
+	_ = os.RemoveAll(filepath.Join(home, ".local", "share", "nvim", "lazy", "base46", "lua", "base46", "themes"))
 	return nil
 }
 

internal/theming/theming_test.go

@@ -117,3 +117,34 @@ func TestApplyPreservesOtherOverlayKeys(t *testing.T) {
 		t.Fatalf("active theme missing after preserve: %s", data)
 	}
 }
+
+func TestApplyRewritesChadrcIfPresent(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	nvimCfg := filepath.Join(home, ".config", "nvim", "lua")
+	if err := os.MkdirAll(nvimCfg, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(nvimCfg, "chadrc.lua"),
+		[]byte(`M.base46 = { theme = "onedark" }`), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := Apply(config.Config{}, "gruvbox"); err != nil {
+		t.Fatal(err)
+	}
+	data, _ := os.ReadFile(filepath.Join(nvimCfg, "chadrc.lua"))
+	if !strings.Contains(string(data), `theme = "gruvbox"`) {
+		t.Fatalf("chadrc not rewritten: %s", data)
+	}
+	if strings.Contains(string(data), `theme = "onedark"`) {
+		t.Fatalf("old theme still present: %s", data)
+	}
+}
+
+func TestApplyNoChadrcIsFine(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	if err := Apply(config.Config{}, "gruvbox"); err != nil {
+		t.Fatal(err)
+	}
+}