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// Copyright 2017 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 partials provides template functions for working with reusable
// templates.
package partials
import (
"fmt"
"html/template"
"io"
"io/ioutil"
"strings"
"sync"
texttemplate "text/template"
"github.com/gohugoio/hugo/tpl"
bp "github.com/gohugoio/hugo/bufferpool"
"github.com/gohugoio/hugo/deps"
)
// TestTemplateProvider is global deps.ResourceProvider.
// NOTE: It's currently unused.
var TestTemplateProvider deps.ResourceProvider
// partialCache represents a cache of partials protected by a mutex.
type partialCache struct {
sync.RWMutex
p map[string]interface{}
}
func (p *partialCache) clear() {
p.Lock()
defer p.Unlock()
p.p = make(map[string]interface{})
}
// New returns a new instance of the templates-namespaced template functions.
func New(deps *deps.Deps) *Namespace {
cache := &partialCache{p: make(map[string]interface{})}
deps.BuildStartListeners.Add(
func() {
cache.clear()
})
return &Namespace{
deps: deps,
cachedPartials: cache,
}
}
// Namespace provides template functions for the "templates" namespace.
type Namespace struct {
deps *deps.Deps
cachedPartials *partialCache
}
// contextWrapper makes room for a return value in a partial invocation.
type contextWrapper struct {
Arg interface{}
Result interface{}
}
// Set sets the return value and returns an empty string.
func (c *contextWrapper) Set(in interface{}) string {
c.Result = in
return ""
}
// Include executes the named partial.
// If the partial contains a return statement, that value will be returned.
// Else, the rendered output will be returned:
// A string if the partial is a text/template, or template.HTML when html/template.
func (ns *Namespace) Include(name string, contextList ...interface{}) (interface{}, error) {
if strings.HasPrefix(name, "partials/") {
name = name[8:]
}
var context interface{}
if len(contextList) == 0 {
context = nil
} else {
context = contextList[0]
}
n := "partials/" + name
templ, found := ns.deps.Tmpl.Lookup(n)
if !found {
// For legacy reasons.
templ, found = ns.deps.Tmpl.Lookup(n + ".html")
}
if !found {
return "", fmt.Errorf("partial %q not found", name)
}
var info tpl.Info
if ip, ok := templ.(tpl.TemplateInfoProvider); ok {
info = ip.TemplateInfo()
}
var w io.Writer
if info.HasReturn {
// Wrap the context sent to the template to capture the return value.
// Note that the template is rewritten to make sure that the dot (".")
// and the $ variable points to Arg.
context = &contextWrapper{
Arg: context,
}
// We don't care about any template output.
w = ioutil.Discard
} else {
b := bp.GetBuffer()
defer bp.PutBuffer(b)
w = b
}
if err := templ.Execute(w, context); err != nil {
return "", err
}
var result interface{}
if ctx, ok := context.(*contextWrapper); ok {
result = ctx.Result
} else if _, ok := templ.(*texttemplate.Template); ok {
result = w.(fmt.Stringer).String()
} else {
result = template.HTML(w.(fmt.Stringer).String())
}
if ns.deps.Metrics != nil {
ns.deps.Metrics.TrackValue(n, result)
}
return result, nil
}
// IncludeCached executes and caches partial templates. An optional variant
// string parameter (a string slice actually, but be only use a variadic
// argument to make it optional) can be passed so that a given partial can have
// multiple uses. The cache is created with name+variant as the key.
func (ns *Namespace) IncludeCached(name string, context interface{}, variant ...string) (interface{}, error) {
key := name
if len(variant) > 0 {
for i := 0; i < len(variant); i++ {
key += variant[i]
}
}
return ns.getOrCreate(key, name, context)
}
func (ns *Namespace) getOrCreate(key, name string, context interface{}) (interface{}, error) {
ns.cachedPartials.RLock()
p, ok := ns.cachedPartials.p[key]
ns.cachedPartials.RUnlock()
if ok {
return p, nil
}
p, err := ns.Include(name, context)
if err != nil {
return nil, err
}
ns.cachedPartials.Lock()
defer ns.cachedPartials.Unlock()
// Double-check.
if p2, ok := ns.cachedPartials.p[key]; ok {
return p2, nil
}
ns.cachedPartials.p[key] = p
return p, nil
}
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