1 files changed, 222 insertions, 0 deletions
diff --git a/common/hreflect/helpers.go b/common/hreflect/helpers.go
new file mode 100644
index 000000000..1b7e5acf7
--- /dev/null
+++ b/common/hreflect/helpers.go
@@ -0,0 +1,222 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+// Some functions in this file (see comments) is based on the Go source code,
+// copyright The Go Authors and  governed by a BSD-style license.
+//
+// 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 hreflect contains reflect helpers.
+package hreflect
+
+import (
+	"context"
+	"reflect"
+	"sync"
+	"time"
+
+	"github.com/gohugoio/hugo/common/htime"
+	"github.com/gohugoio/hugo/common/types"
+)
+
+// TODO(bep) replace the private versions in /tpl with these.
+// IsNumber returns whether the given kind is a number.
+func IsNumber(kind reflect.Kind) bool {
+	return IsInt(kind) || IsUint(kind) || IsFloat(kind)
+}
+
+// IsInt returns whether the given kind is an int.
+func IsInt(kind reflect.Kind) bool {
+	switch kind {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return true
+	default:
+		return false
+	}
+}
+
+// IsUint returns whether the given kind is an uint.
+func IsUint(kind reflect.Kind) bool {
+	switch kind {
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return true
+	default:
+		return false
+	}
+}
+
+// IsFloat returns whether the given kind is a float.
+func IsFloat(kind reflect.Kind) bool {
+	switch kind {
+	case reflect.Float32, reflect.Float64:
+		return true
+	default:
+		return false
+	}
+}
+
+// IsTruthful returns whether in represents a truthful value.
+// See IsTruthfulValue
+func IsTruthful(in any) bool {
+	switch v := in.(type) {
+	case reflect.Value:
+		return IsTruthfulValue(v)
+	default:
+		return IsTruthfulValue(reflect.ValueOf(in))
+	}
+}
+
+var zeroType = reflect.TypeOf((*types.Zeroer)(nil)).Elem()
+
+// IsTruthfulValue returns whether the given value has a meaningful truth value.
+// This is based on template.IsTrue in Go's stdlib, but also considers
+// IsZero and any interface value will be unwrapped before it's considered
+// for truthfulness.
+//
+// Based on:
+// https://github.com/golang/go/blob/178a2c42254166cffed1b25fb1d3c7a5727cada6/src/text/template/exec.go#L306
+func IsTruthfulValue(val reflect.Value) (truth bool) {
+	val = indirectInterface(val)
+
+	if !val.IsValid() {
+		// Something like var x interface{}, never set. It's a form of nil.
+		return
+	}
+
+	if val.Type().Implements(zeroType) {
+		return !val.Interface().(types.Zeroer).IsZero()
+	}
+
+	switch val.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		truth = val.Len() > 0
+	case reflect.Bool:
+		truth = val.Bool()
+	case reflect.Complex64, reflect.Complex128:
+		truth = val.Complex() != 0
+	case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
+		truth = !val.IsNil()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		truth = val.Int() != 0
+	case reflect.Float32, reflect.Float64:
+		truth = val.Float() != 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		truth = val.Uint() != 0
+	case reflect.Struct:
+		truth = true // Struct values are always true.
+	default:
+		return
+	}
+
+	return
+}
+
+type methodKey struct {
+	typ  reflect.Type
+	name string
+}
+
+type methods struct {
+	sync.RWMutex
+	cache map[methodKey]int
+}
+
+var methodCache = &methods{cache: make(map[methodKey]int)}
+
+// GetMethodByName is the same as reflect.Value.MethodByName, but it caches the
+// type lookup.
+func GetMethodByName(v reflect.Value, name string) reflect.Value {
+	index := GetMethodIndexByName(v.Type(), name)
+
+	if index == -1 {
+		return reflect.Value{}
+	}
+
+	return v.Method(index)
+}
+
+// GetMethodIndexByName returns the index of the method with the given name, or
+// -1 if no such method exists.
+func GetMethodIndexByName(tp reflect.Type, name string) int {
+	k := methodKey{tp, name}
+	methodCache.RLock()
+	index, found := methodCache.cache[k]
+	methodCache.RUnlock()
+	if found {
+		return index
+	}
+
+	methodCache.Lock()
+	defer methodCache.Unlock()
+
+	m, ok := tp.MethodByName(name)
+	index = m.Index
+	if !ok {
+		index = -1
+	}
+	methodCache.cache[k] = index
+
+	if !ok {
+		return -1
+	}
+
+	return m.Index
+}
+
+var (
+	timeType           = reflect.TypeOf((*time.Time)(nil)).Elem()
+	asTimeProviderType = reflect.TypeOf((*htime.AsTimeProvider)(nil)).Elem()
+)
+
+// IsTime returns whether tp is a time.Time type or if it can be converted into one
+// in ToTime.
+func IsTime(tp reflect.Type) bool {
+	if tp == timeType {
+		return true
+	}
+
+	if tp.Implements(asTimeProviderType) {
+		return true
+	}
+	return false
+}
+
+// AsTime returns v as a time.Time if possible.
+// The given location is only used if the value implements AsTimeProvider (e.g. go-toml local).
+// A zero Time and false is returned if this isn't possible.
+// Note that this function does not accept string dates.
+func AsTime(v reflect.Value, loc *time.Location) (time.Time, bool) {
+	if v.Kind() == reflect.Interface {
+		return AsTime(v.Elem(), loc)
+	}
+
+	if v.Type() == timeType {
+		return v.Interface().(time.Time), true
+	}
+
+	if v.Type().Implements(asTimeProviderType) {
+		return v.Interface().(htime.AsTimeProvider).AsTime(loc), true
+	}
+
+	return time.Time{}, false
+}
+
+// Based on: https://github.com/golang/go/blob/178a2c42254166cffed1b25fb1d3c7a5727cada6/src/text/template/exec.go#L931
+func indirectInterface(v reflect.Value) reflect.Value {
+	if v.Kind() != reflect.Interface {
+		return v
+	}
+	if v.IsNil() {
+		return reflect.Value{}
+	}
+	return v.Elem()
+}
+
+var ContextInterface = reflect.TypeOf((*context.Context)(nil)).Elem()