Add a newScratch template func

Fixes #4685

5 files changed, 21 insertions, 209 deletions

diff --git a/tpl/collections/collections.go b/tpl/collections/collections.go
index dd418d7d2..51bc5c796 100644
--- a/tpl/collections/collections.go
+++ b/tpl/collections/collections.go
@@ -23,6 +23,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/gohugoio/hugo/common/maps"
 	"github.com/gohugoio/hugo/common/types"
 	"github.com/gohugoio/hugo/deps"
 	"github.com/gohugoio/hugo/helpers"
@@ -650,3 +651,9 @@ func (ns *Namespace) Uniq(l interface{}) (interface{}, error) {
 func (ns *Namespace) KeyVals(key interface{}, vals ...interface{}) (types.KeyValues, error) {
 	return types.KeyValues{Key: key, Values: vals}, nil
 }
+
+// NewScratch creates a new Scratch which can be used to store values in a
+// thread safe way.
+func (ns *Namespace) NewScratch() *maps.Scratch {
+	return maps.NewScratch()
+}
diff --git a/tpl/collections/init.go b/tpl/collections/init.go
index 91b0dea01..b986b3b42 100644
--- a/tpl/collections/init.go
+++ b/tpl/collections/init.go
@@ -144,6 +144,14 @@ func init() {
 				{`{{ seq 3 }}`, `[1 2 3]`},
 			},
 		)
+
+		ns.AddMethodMapping(ctx.NewScratch,
+			[]string{"newScratch"},
+			[][2]string{
+				{`{{ $scratch := newScratch }}{{ $scratch.Add "b" 2 }}{{ $scratch.Add "b" 2 }}{{ $scratch.Get "b" }}`, `4`},
+			},
+		)
+
 		ns.AddMethodMapping(ctx.Uniq,
 			[]string{"uniq"},
 			[][2]string{
diff --git a/tpl/math/math.go b/tpl/math/math.go
index 534f7f284..fcc6abc3d 100644
--- a/tpl/math/math.go
+++ b/tpl/math/math.go
@@ -16,7 +16,8 @@ package math
 import (
 	"errors"
 	"math"
-	"reflect"
+
+	_math "github.com/gohugoio/hugo/common/math"
 
 	"github.com/spf13/cast"
 )
@@ -31,7 +32,7 @@ type Namespace struct{}
 
 // Add adds two numbers.
 func (ns *Namespace) Add(a, b interface{}) (interface{}, error) {
-	return DoArithmetic(a, b, '+')
+	return _math.DoArithmetic(a, b, '+')
 }
 
 // Ceil returns the least integer value greater than or equal to x.
@@ -46,7 +47,7 @@ func (ns *Namespace) Ceil(x interface{}) (float64, error) {
 
 // Div divides two numbers.
 func (ns *Namespace) Div(a, b interface{}) (interface{}, error) {
-	return DoArithmetic(a, b, '/')
+	return _math.DoArithmetic(a, b, '/')
 }
 
 // Floor returns the greatest integer value less than or equal to x.
@@ -98,7 +99,7 @@ func (ns *Namespace) ModBool(a, b interface{}) (bool, error) {
 
 // Mul multiplies two numbers.
 func (ns *Namespace) Mul(a, b interface{}) (interface{}, error) {
-	return DoArithmetic(a, b, '*')
+	return _math.DoArithmetic(a, b, '*')
 }
 
 // Round returns the nearest integer, rounding half away from zero.
@@ -113,121 +114,5 @@ func (ns *Namespace) Round(x interface{}) (float64, error) {
 
 // Sub subtracts two numbers.
 func (ns *Namespace) Sub(a, b interface{}) (interface{}, error) {
-	return DoArithmetic(a, b, '-')
-}
-
-// DoArithmetic performs arithmetic operations (+,-,*,/) using reflection to
-// determine the type of the two terms.
-func DoArithmetic(a, b interface{}, op rune) (interface{}, error) {
-	av := reflect.ValueOf(a)
-	bv := reflect.ValueOf(b)
-	var ai, bi int64
-	var af, bf float64
-	var au, bu uint64
-	switch av.Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		ai = av.Int()
-		switch bv.Kind() {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			bi = bv.Int()
-		case reflect.Float32, reflect.Float64:
-			af = float64(ai) // may overflow
-			ai = 0
-			bf = bv.Float()
-		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-			bu = bv.Uint()
-			if ai >= 0 {
-				au = uint64(ai)
-				ai = 0
-			} else {
-				bi = int64(bu) // may overflow
-				bu = 0
-			}
-		default:
-			return nil, errors.New("Can't apply the operator to the values")
-		}
-	case reflect.Float32, reflect.Float64:
-		af = av.Float()
-		switch bv.Kind() {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			bf = float64(bv.Int()) // may overflow
-		case reflect.Float32, reflect.Float64:
-			bf = bv.Float()
-		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-			bf = float64(bv.Uint()) // may overflow
-		default:
-			return nil, errors.New("Can't apply the operator to the values")
-		}
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-		au = av.Uint()
-		switch bv.Kind() {
-		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			bi = bv.Int()
-			if bi >= 0 {
-				bu = uint64(bi)
-				bi = 0
-			} else {
-				ai = int64(au) // may overflow
-				au = 0
-			}
-		case reflect.Float32, reflect.Float64:
-			af = float64(au) // may overflow
-			au = 0
-			bf = bv.Float()
-		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-			bu = bv.Uint()
-		default:
-			return nil, errors.New("Can't apply the operator to the values")
-		}
-	case reflect.String:
-		as := av.String()
-		if bv.Kind() == reflect.String && op == '+' {
-			bs := bv.String()
-			return as + bs, nil
-		}
-		return nil, errors.New("Can't apply the operator to the values")
-	default:
-		return nil, errors.New("Can't apply the operator to the values")
-	}
-
-	switch op {
-	case '+':
-		if ai != 0 || bi != 0 {
-			return ai + bi, nil
-		} else if af != 0 || bf != 0 {
-			return af + bf, nil
-		} else if au != 0 || bu != 0 {
-			return au + bu, nil
-		}
-		return 0, nil
-	case '-':
-		if ai != 0 || bi != 0 {
-			return ai - bi, nil
-		} else if af != 0 || bf != 0 {
-			return af - bf, nil
-		} else if au != 0 || bu != 0 {
-			return au - bu, nil
-		}
-		return 0, nil
-	case '*':
-		if ai != 0 || bi != 0 {
-			return ai * bi, nil
-		} else if af != 0 || bf != 0 {
-			return af * bf, nil
-		} else if au != 0 || bu != 0 {
-			return au * bu, nil
-		}
-		return 0, nil
-	case '/':
-		if bi != 0 {
-			return ai / bi, nil
-		} else if bf != 0 {
-			return af / bf, nil
-		} else if bu != 0 {
-			return au / bu, nil
-		}
-		return nil, errors.New("Can't divide the value by 0")
-	default:
-		return nil, errors.New("There is no such an operation")
-	}
+	return _math.DoArithmetic(a, b, '-')
 }
diff --git a/tpl/math/math_test.go b/tpl/math/math_test.go
index 97acfaeba..f2e6236af 100644
--- a/tpl/math/math_test.go
+++ b/tpl/math/math_test.go
@@ -56,93 +56,6 @@ func TestBasicNSArithmetic(t *testing.T) {
 	}
 }
 
-func TestDoArithmetic(t *testing.T) {
-	t.Parallel()
-
-	for i, test := range []struct {
-		a      interface{}
-		b      interface{}
-		op     rune
-		expect interface{}
-	}{
-		{3, 2, '+', int64(5)},
-		{3, 2, '-', int64(1)},
-		{3, 2, '*', int64(6)},
-		{3, 2, '/', int64(1)},
-		{3.0, 2, '+', float64(5)},
-		{3.0, 2, '-', float64(1)},
-		{3.0, 2, '*', float64(6)},
-		{3.0, 2, '/', float64(1.5)},
-		{3, 2.0, '+', float64(5)},
-		{3, 2.0, '-', float64(1)},
-		{3, 2.0, '*', float64(6)},
-		{3, 2.0, '/', float64(1.5)},
-		{3.0, 2.0, '+', float64(5)},
-		{3.0, 2.0, '-', float64(1)},
-		{3.0, 2.0, '*', float64(6)},
-		{3.0, 2.0, '/', float64(1.5)},
-		{uint(3), uint(2), '+', uint64(5)},
-		{uint(3), uint(2), '-', uint64(1)},
-		{uint(3), uint(2), '*', uint64(6)},
-		{uint(3), uint(2), '/', uint64(1)},
-		{uint(3), 2, '+', uint64(5)},
-		{uint(3), 2, '-', uint64(1)},
-		{uint(3), 2, '*', uint64(6)},
-		{uint(3), 2, '/', uint64(1)},
-		{3, uint(2), '+', uint64(5)},
-		{3, uint(2), '-', uint64(1)},
-		{3, uint(2), '*', uint64(6)},
-		{3, uint(2), '/', uint64(1)},
-		{uint(3), -2, '+', int64(1)},
-		{uint(3), -2, '-', int64(5)},
-		{uint(3), -2, '*', int64(-6)},
-		{uint(3), -2, '/', int64(-1)},
-		{-3, uint(2), '+', int64(-1)},
-		{-3, uint(2), '-', int64(-5)},
-		{-3, uint(2), '*', int64(-6)},
-		{-3, uint(2), '/', int64(-1)},
-		{uint(3), 2.0, '+', float64(5)},
-		{uint(3), 2.0, '-', float64(1)},
-		{uint(3), 2.0, '*', float64(6)},
-		{uint(3), 2.0, '/', float64(1.5)},
-		{3.0, uint(2), '+', float64(5)},
-		{3.0, uint(2), '-', float64(1)},
-		{3.0, uint(2), '*', float64(6)},
-		{3.0, uint(2), '/', float64(1.5)},
-		{0, 0, '+', 0},
-		{0, 0, '-', 0},
-		{0, 0, '*', 0},
-		{"foo", "bar", '+', "foobar"},
-		{3, 0, '/', false},
-		{3.0, 0, '/', false},
-		{3, 0.0, '/', false},
-		{uint(3), uint(0), '/', false},
-		{3, uint(0), '/', false},
-		{-3, uint(0), '/', false},
-		{uint(3), 0, '/', false},
-		{3.0, uint(0), '/', false},
-		{uint(3), 0.0, '/', false},
-		{3, "foo", '+', false},
-		{3.0, "foo", '+', false},
-		{uint(3), "foo", '+', false},
-		{"foo", 3, '+', false},
-		{"foo", "bar", '-', false},
-		{3, 2, '%', false},
-	} {
-		errMsg := fmt.Sprintf("[%d] %v", i, test)
-
-		result, err := DoArithmetic(test.a, test.b, test.op)
-
-		if b, ok := test.expect.(bool); ok && !b {
-			require.Error(t, err, errMsg)
-			continue
-		}
-
-		require.NoError(t, err, errMsg)
-		assert.Equal(t, test.expect, result, errMsg)
-	}
-}
-
 func TestCeil(t *testing.T) {
 	t.Parallel()
 
diff --git a/tpl/tplimpl/template_funcs_test.go b/tpl/tplimpl/template_funcs_test.go
index 341be805a..8594c67a4 100644
--- a/tpl/tplimpl/template_funcs_test.go
+++ b/tpl/tplimpl/template_funcs_test.go
@@ -125,7 +125,6 @@ func TestTemplateFuncsExamples(t *testing.T) {
 			}
 		}
 	}
-
 }
 
 // TODO(bep) it would be dandy to put this one into the partials package, but