Add a newScratch template func

Fixes #4685

2 files changed, 305 insertions, 0 deletions

diff --git a/common/maps/scratch.go b/common/maps/scratch.go
new file mode 100644
index 000000000..d00971435
--- /dev/null
+++ b/common/maps/scratch.go
@@ -0,0 +1,135 @@
+// Copyright 2018 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 (
+	"reflect"
+	"sort"
+	"sync"
+
+	"github.com/gohugoio/hugo/common/math"
+)
+
+// Scratch is a writable context used for stateful operations in Page/Node rendering.
+type Scratch struct {
+	values map[string]interface{}
+	mu     sync.RWMutex
+}
+
+// Add will, for single values, add (using the + operator) the addend to the existing addend (if found).
+// Supports numeric values and strings.
+//
+// If the first add for a key is an array or slice, then the next value(s) will be appended.
+func (c *Scratch) Add(key string, newAddend interface{}) (string, error) {
+
+	var newVal interface{}
+	c.mu.RLock()
+	existingAddend, found := c.values[key]
+	c.mu.RUnlock()
+	if found {
+		var err error
+
+		addendV := reflect.ValueOf(existingAddend)
+
+		if addendV.Kind() == reflect.Slice || addendV.Kind() == reflect.Array {
+			nav := reflect.ValueOf(newAddend)
+			if nav.Kind() == reflect.Slice || nav.Kind() == reflect.Array {
+				newVal = reflect.AppendSlice(addendV, nav).Interface()
+			} else {
+				newVal = reflect.Append(addendV, nav).Interface()
+			}
+		} else {
+			newVal, err = math.DoArithmetic(existingAddend, newAddend, '+')
+			if err != nil {
+				return "", err
+			}
+		}
+	} else {
+		newVal = newAddend
+	}
+	c.mu.Lock()
+	c.values[key] = newVal
+	c.mu.Unlock()
+	return "", nil // have to return something to make it work with the Go templates
+}
+
+// Set stores a value with the given key in the Node context.
+// This value can later be retrieved with Get.
+func (c *Scratch) Set(key string, value interface{}) string {
+	c.mu.Lock()
+	c.values[key] = value
+	c.mu.Unlock()
+	return ""
+}
+
+// Reset deletes the given key
+func (c *Scratch) Delete(key string) string {
+	c.mu.Lock()
+	delete(c.values, key)
+	c.mu.Unlock()
+	return ""
+}
+
+// Get returns a value previously set by Add or Set
+func (c *Scratch) Get(key string) interface{} {
+	c.mu.RLock()
+	val := c.values[key]
+	c.mu.RUnlock()
+
+	return val
+}
+
+// SetInMap stores a value to a map with the given key in the Node context.
+// This map can later be retrieved with GetSortedMapValues.
+func (c *Scratch) SetInMap(key string, mapKey string, value interface{}) string {
+	c.mu.Lock()
+	_, found := c.values[key]
+	if !found {
+		c.values[key] = make(map[string]interface{})
+	}
+
+	c.values[key].(map[string]interface{})[mapKey] = value
+	c.mu.Unlock()
+	return ""
+}
+
+// GetSortedMapValues returns a sorted map previously filled with SetInMap
+func (c *Scratch) GetSortedMapValues(key string) interface{} {
+	c.mu.RLock()
+
+	if c.values[key] == nil {
+		c.mu.RUnlock()
+		return nil
+	}
+
+	unsortedMap := c.values[key].(map[string]interface{})
+	c.mu.RUnlock()
+	var keys []string
+	for mapKey := range unsortedMap {
+		keys = append(keys, mapKey)
+	}
+
+	sort.Strings(keys)
+
+	sortedArray := make([]interface{}, len(unsortedMap))
+	for i, mapKey := range keys {
+		sortedArray[i] = unsortedMap[mapKey]
+	}
+
+	return sortedArray
+}
+
+func NewScratch() *Scratch {
+	return &Scratch{values: make(map[string]interface{})}
+}
diff --git a/common/maps/scratch_test.go b/common/maps/scratch_test.go
new file mode 100644
index 000000000..8397ba830
--- /dev/null
+++ b/common/maps/scratch_test.go
@@ -0,0 +1,170 @@
+// Copyright 2018 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 (
+	"reflect"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestScratchAdd(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	scratch.Add("int1", 10)
+	scratch.Add("int1", 20)
+	scratch.Add("int2", 20)
+
+	assert.Equal(t, int64(30), scratch.Get("int1"))
+	assert.Equal(t, 20, scratch.Get("int2"))
+
+	scratch.Add("float1", float64(10.5))
+	scratch.Add("float1", float64(20.1))
+
+	assert.Equal(t, float64(30.6), scratch.Get("float1"))
+
+	scratch.Add("string1", "Hello ")
+	scratch.Add("string1", "big ")
+	scratch.Add("string1", "World!")
+
+	assert.Equal(t, "Hello big World!", scratch.Get("string1"))
+
+	scratch.Add("scratch", scratch)
+	_, err := scratch.Add("scratch", scratch)
+
+	if err == nil {
+		t.Errorf("Expected error from invalid arithmetic")
+	}
+
+}
+
+func TestScratchAddSlice(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+
+	_, err := scratch.Add("intSlice", []int{1, 2})
+	assert.Nil(t, err)
+	_, err = scratch.Add("intSlice", 3)
+	assert.Nil(t, err)
+
+	sl := scratch.Get("intSlice")
+	expected := []int{1, 2, 3}
+
+	if !reflect.DeepEqual(expected, sl) {
+		t.Errorf("Slice difference, go %q expected %q", sl, expected)
+	}
+
+	_, err = scratch.Add("intSlice", []int{4, 5})
+
+	assert.Nil(t, err)
+
+	sl = scratch.Get("intSlice")
+	expected = []int{1, 2, 3, 4, 5}
+
+	if !reflect.DeepEqual(expected, sl) {
+		t.Errorf("Slice difference, go %q expected %q", sl, expected)
+	}
+
+}
+
+func TestScratchSet(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	scratch.Set("key", "val")
+	assert.Equal(t, "val", scratch.Get("key"))
+}
+
+func TestScratchDelete(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	scratch.Set("key", "val")
+	scratch.Delete("key")
+	scratch.Add("key", "Lucy Parsons")
+	assert.Equal(t, "Lucy Parsons", scratch.Get("key"))
+}
+
+// Issue #2005
+func TestScratchInParallel(t *testing.T) {
+	var wg sync.WaitGroup
+	scratch := NewScratch()
+	key := "counter"
+	scratch.Set(key, int64(1))
+	for i := 1; i <= 10; i++ {
+		wg.Add(1)
+		go func(j int) {
+			for k := 0; k < 10; k++ {
+				newVal := int64(k + j)
+
+				_, err := scratch.Add(key, newVal)
+				if err != nil {
+					t.Errorf("Got err %s", err)
+				}
+
+				scratch.Set(key, newVal)
+
+				val := scratch.Get(key)
+
+				if counter, ok := val.(int64); ok {
+					if counter < 1 {
+						t.Errorf("Got %d", counter)
+					}
+				} else {
+					t.Errorf("Got %T", val)
+				}
+			}
+			wg.Done()
+		}(i)
+	}
+	wg.Wait()
+}
+
+func TestScratchGet(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	nothing := scratch.Get("nothing")
+	if nothing != nil {
+		t.Errorf("Should not return anything, but got %v", nothing)
+	}
+}
+
+func TestScratchSetInMap(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	scratch.SetInMap("key", "lux", "Lux")
+	scratch.SetInMap("key", "abc", "Abc")
+	scratch.SetInMap("key", "zyx", "Zyx")
+	scratch.SetInMap("key", "abc", "Abc (updated)")
+	scratch.SetInMap("key", "def", "Def")
+	assert.Equal(t, []interface{}{0: "Abc (updated)", 1: "Def", 2: "Lux", 3: "Zyx"}, scratch.GetSortedMapValues("key"))
+}
+
+func TestScratchGetSortedMapValues(t *testing.T) {
+	t.Parallel()
+	scratch := NewScratch()
+	nothing := scratch.GetSortedMapValues("nothing")
+	if nothing != nil {
+		t.Errorf("Should not return anything, but got %v", nothing)
+	}
+}
+
+func BenchmarkScratchGet(b *testing.B) {
+	scratch := NewScratch()
+	scratch.Add("A", 1)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		scratch.Get("A")
+	}
+}