fix: allow multiple levels of extends (#755)

* fix: allow recursive extends
* chore: add integrity test
* fix: detect recursion

internal/config/load.go

@@ -63,21 +63,27 @@ func Load(fs afero.Fs, repo *git.Repository) (*Config, error) {
 }
 
 func read(fs afero.Fs, path string, name string) (*viper.Viper, error) {
+	v := newViper(fs, path)
+	v.SetConfigName(name)
+
+	if err := v.ReadInConfig(); err != nil {
+		return nil, err
+	}
+
+	return v, nil
+}
+
+func newViper(fs afero.Fs, path string) *viper.Viper {
 	v := viper.New()
 	v.SetFs(fs)
 	v.AddConfigPath(path)
-	v.SetConfigName(name)
 
 	// Allow overwriting settings with ENV variables
 	v.SetEnvPrefix("LEFTHOOK")
 	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
 	v.AutomaticEnv()
 
-	if err := v.ReadInConfig(); err != nil {
-		return nil, err
-	}
-
-	return v, nil
+	return v
 }
 
 func readOne(fs afero.Fs, path string, names []string) (*viper.Viper, error) {
@@ -109,7 +115,7 @@ func mergeAll(fs afero.Fs, repo *git.Repository) (*viper.Viper, error) {
 		return nil, err
 	}
 
-	if err := extend(extends, repo.RootPath); err != nil {
+	if err := extend(fs, extends, repo.RootPath); err != nil {
 		return nil, err
 	}
 
@@ -125,7 +131,7 @@ func mergeAll(fs afero.Fs, repo *git.Repository) (*viper.Viper, error) {
 		// Local extends need to be re-applied only if they have different settings
 		localExtends := extends.GetStringSlice("extends")
 		if !slices.Equal(globalExtends, localExtends) {
-			if err = extend(extends, repo.RootPath); err != nil {
+			if err = extend(fs, extends, repo.RootPath); err != nil {
 				return nil, err
 			}
 		}
@@ -190,7 +196,7 @@ func mergeRemotes(fs afero.Fs, repo *git.Repository, v *viper.Viper) error {
 				return err
 			}
 
-			if err = extend(v, filepath.Dir(configPath)); err != nil {
+			if err = extend(fs, v, filepath.Dir(configPath)); err != nil {
 				return err
 			}
 		}
@@ -206,12 +212,34 @@ func mergeRemotes(fs afero.Fs, repo *git.Repository, v *viper.Viper) error {
 }
 
 // extend merges all files listed in 'extends' option into the config.
-func extend(v *viper.Viper, root string) error {
-	for i, path := range v.GetStringSlice("extends") {
+func extend(fs afero.Fs, v *viper.Viper, root string) error {
+	return extendRecursive(fs, v, root, make(map[string]struct{}))
+}
+
+// extendRecursive merges extends.
+// If extends contain other extends they get merged too.
+func extendRecursive(fs afero.Fs, v *viper.Viper, root string, extends map[string]struct{}) error {
+	for _, path := range v.GetStringSlice("extends") {
+		if _, contains := extends[path]; contains {
+			return fmt.Errorf("possible recursion in extends: path %s is specified multiple times", path)
+		}
+		extends[path] = struct{}{}
+
 		if !filepath.IsAbs(path) {
 			path = filepath.Join(root, path)
 		}
-		if err := merge(fmt.Sprintf("extend_%d", i), path, v); err != nil {
+
+		extendV := newViper(fs, root)
+		extendV.SetConfigFile(path)
+		if err := extendV.ReadInConfig(); err != nil {
+			return err
+		}
+
+		if err := extendRecursive(fs, extendV, root, extends); err != nil {
+			return err
+		}
+
+		if err := v.MergeConfigMap(extendV.AllSettings()); err != nil {
 			return err
 		}
 	}
@@ -222,9 +250,7 @@ func extend(v *viper.Viper, root string) error {
 // merge merges the configuration using viper builtin MergeInConfig.
 func merge(name, path string, v *viper.Viper) error {
 	v.SetConfigName(name)
-	if len(path) > 0 {
-		v.SetConfigFile(path)
-	}
+	v.SetConfigFile(path)
 	return v.MergeInConfig()
 }
 

testdata/many_extends_levels.txt

@@ -0,0 +1,80 @@
+[windows] skip
+
+exec git init
+exec lefthook dump
+cmp stdout dump.yml
+! stderr .
+
+-- lefthook.yml --
+extends:
+  - extends/e1.yml
+
+pre-commit:
+  commands:
+    echo:
+      run: echo 0
+
+-- extends/e1.yml --
+extends:
+  - extends/e2.yml
+
+pre-commit:
+  commands:
+    echo:
+      run: echo 1
+      skip: true
+
+e1:
+  commands:
+    echo:
+      run: e1
+
+-- extends/e2.yml --
+extends:
+  - extends/e3.yml
+
+pre-commit:
+  commands:
+    echo:
+      run: echo 2
+      tags: ["backend"]
+
+e2:
+  commands:
+    echo:
+      run: e2
+
+-- extends/e3.yml --
+pre-commit:
+  commands:
+    echo:
+      glob: 3
+
+e3:
+  commands:
+    echo:
+      run: e3
+
+-- dump.yml --
+e1:
+  commands:
+    echo:
+      run: e1
+e2:
+  commands:
+    echo:
+      run: e2
+e3:
+  commands:
+    echo:
+      run: e3
+extends:
+  - extends/e3.yml
+pre-commit:
+  commands:
+    echo:
+      run: echo 2
+      skip: true
+      tags:
+        - backend
+      glob: "3"