3 files changed, 102 insertions, 15 deletions

diff --git a/common/maps/cache.go b/common/maps/cache.go
new file mode 100644
index 000000000..7e23a2662
--- /dev/null
+++ b/common/maps/cache.go
@@ -0,0 +1,90 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package maps
+
+import "sync"
+
+// Cache is a simple thread safe cache backed by a map.
+type Cache[K comparable, T any] struct {
+	m map[K]T
+	sync.RWMutex
+}
+
+// NewCache creates a new Cache.
+func NewCache[K comparable, T any]() *Cache[K, T] {
+	return &Cache[K, T]{m: make(map[K]T)}
+}
+
+// Delete deletes the given key from the cache.
+func (c *Cache[K, T]) Get(key K) (T, bool) {
+	c.RLock()
+	v, found := c.m[key]
+	c.RUnlock()
+	return v, found
+}
+
+// GetOrCreate gets the value for the given key if it exists, or creates it if not.
+func (c *Cache[K, T]) GetOrCreate(key K, create func() T) T {
+	c.RLock()
+	v, found := c.m[key]
+	c.RUnlock()
+	if found {
+		return v
+	}
+	c.Lock()
+	defer c.Unlock()
+	v, found = c.m[key]
+	if found {
+		return v
+	}
+	v = create()
+	c.m[key] = v
+	return v
+}
+
+// Set sets the given key to the given value.
+func (c *Cache[K, T]) Set(key K, value T) {
+	c.Lock()
+	c.m[key] = value
+	c.Unlock()
+}
+
+// SliceCache is a simple thread safe cache backed by a map.
+type SliceCache[T any] struct {
+	m map[string][]T
+	sync.RWMutex
+}
+
+func NewSliceCache[T any]() *SliceCache[T] {
+	return &SliceCache[T]{m: make(map[string][]T)}
+}
+
+func (c *SliceCache[T]) Get(key string) ([]T, bool) {
+	c.RLock()
+	v, found := c.m[key]
+	c.RUnlock()
+	return v, found
+}
+
+func (c *SliceCache[T]) Append(key string, values ...T) {
+	c.Lock()
+	c.m[key] = append(c.m[key], values...)
+	c.Unlock()
+}
+
+func (c *SliceCache[T]) Reset() {
+	c.Lock()
+	c.m = make(map[string][]T)
+	c.Unlock()
+}
diff --git a/common/maps/maps.go b/common/maps/maps.go
index f0fd3d5ce..2686baad6 100644
--- a/common/maps/maps.go
+++ b/common/maps/maps.go
@@ -29,7 +29,7 @@ func ToStringMapE(in any) (map[string]any, error) {
 	case Params:
 		return vv, nil
 	case map[string]string:
-		var m = map[string]any{}
+		m := map[string]any{}
 		for k, v := range vv {
 			m[k] = v
 		}
@@ -192,21 +192,20 @@ func (KeyRenamer) keyPath(k1, k2 string) string {
 }
 
 func (r KeyRenamer) renamePath(parentKeyPath string, m map[string]any) {
-	for key, val := range m {
-		keyPath := r.keyPath(parentKeyPath, key)
-		switch val.(type) {
+	for k, v := range m {
+		keyPath := r.keyPath(parentKeyPath, k)
+		switch vv := v.(type) {
 		case map[any]any:
-			val = cast.ToStringMap(val)
-			r.renamePath(keyPath, val.(map[string]any))
+			r.renamePath(keyPath, cast.ToStringMap(vv))
 		case map[string]any:
-			r.renamePath(keyPath, val.(map[string]any))
+			r.renamePath(keyPath, vv)
 		}
 
 		newKey := r.getNewKey(keyPath)
 
 		if newKey != "" {
-			delete(m, key)
-			m[newKey] = val
+			delete(m, k)
+			m[newKey] = v
 		}
 	}
 }
diff --git a/common/maps/params.go b/common/maps/params.go
index d94d16f9d..a8cbba555 100644
--- a/common/maps/params.go
+++ b/common/maps/params.go
@@ -61,7 +61,7 @@ func SetParams(dst, src Params) {
 
 // IsZero returns true if p is considered empty.
 func (p Params) IsZero() bool {
-	if p == nil || len(p) == 0 {
+	if len(p) == 0 {
 		return true
 	}
 
@@ -74,7 +74,6 @@ func (p Params) IsZero() bool {
 	}
 
 	return false
-
 }
 
 // MergeParamsWithStrategy transfers values from src to dst for new keys using the merge strategy given.
@@ -93,7 +92,7 @@ func MergeParams(dst, src Params) {
 func (p Params) merge(ps ParamsMergeStrategy, pp Params) {
 	ns, found := p.GetMergeStrategy()
 
-	var ms = ns
+	ms := ns
 	if !found && ps != "" {
 		ms = ps
 	}
@@ -248,7 +247,7 @@ const (
 // CleanConfigStringMapString removes any processing instructions from m,
 // m will never be modified.
 func CleanConfigStringMapString(m map[string]string) map[string]string {
-	if m == nil || len(m) == 0 {
+	if len(m) == 0 {
 		return m
 	}
 	if _, found := m[MergeStrategyKey]; !found {
@@ -267,7 +266,7 @@ func CleanConfigStringMapString(m map[string]string) map[string]string {
 // CleanConfigStringMap is the same as CleanConfigStringMapString but for
 // map[string]any.
 func CleanConfigStringMap(m map[string]any) map[string]any {
-	if m == nil || len(m) == 0 {
+	if len(m) == 0 {
 		return m
 	}
 	if _, found := m[MergeStrategyKey]; !found {
@@ -291,7 +290,6 @@ func CleanConfigStringMap(m map[string]any) map[string]any {
 
 	}
 	return m2
-
 }
 
 func toMergeStrategy(v any) ParamsMergeStrategy {