forgejo-federation/modules/templates/htmlrenderer.go
wxiaoguang 722dab5286
Make HTML template functions support context (#24056)
# Background

Golang template is not friendly for large projects, and Golang template
team is quite slow, related:
* `https://github.com/golang/go/issues/54450`

Without upstream support, we can also have our solution to make HTML
template functions support context.

It helps a lot, the above Golang template issue `#54450` explains a lot:

1. It makes `{{Locale.Tr}}` could be used in any template, without
passing unclear `(dict "root" . )` anymore.
2. More and more functions need `context`, like `avatar`, etc, we do not
need to do `(dict "Context" $.Context)` anymore.
3. Many request-related functions could be shared by parent&children
templates, like "user setting" / "system setting"

See the test `TestScopedTemplateSetFuncMap`, one template set, two
`Execute` calls with different `CtxFunc`.

# The Solution

Instead of waiting for upstream, this PR re-uses the escaped HTML
template trees, use `AddParseTree` to add related templates/trees to a
new template instance, then the new template instance can have its own
FuncMap , the function calls in the template trees will always use the
new template's FuncMap.

`template.New` / `template.AddParseTree` / `adding-FuncMap` are all
quite fast, so the performance is not affected.

The details:

1. Make a new `html/template/Template` for `all` templates
2. Add template code to the `all` template
3. Freeze the `all` template, reset its exec func map, it shouldn't
execute any template.
4. When a router wants to render a template by its `name`
    1. Find the `name` in `all`
    2. Find all its related sub templates
3. Escape all related templates (just like what the html template
package does)
4. Add the escaped parse-trees of related templates into a new (scoped)
`text/template/Template`
    5. Add context-related func map into the new (scoped) text template
    6. Execute the new (scoped) text template
7. To improve performance, the escaped templates are cached to `template
sets`

# FAQ

## There is a `unsafe` call, is this PR unsafe?

This PR is safe. Golang has strict language definition, it's safe to do
so: https://pkg.go.dev/unsafe#Pointer (1) Conversion of a *T1 to Pointer
to *T2


## What if Golang template supports such feature in the future?

The public structs/interfaces/functions introduced by this PR is quite
simple, the code of `HTMLRender` is not changed too much. It's very easy
to switch to the official mechanism if there would be one.

## Does this PR change the template execution behavior?

No, see the tests (welcome to design more tests if it's necessary)

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: Giteabot <teabot@gitea.io>
2023-04-20 04:08:58 -04:00

269 lines
8.3 KiB
Go

// Copyright 2022 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package templates
import (
"bufio"
"bytes"
"context"
"errors"
"fmt"
"io"
"net/http"
"path/filepath"
"regexp"
"strconv"
"strings"
"sync/atomic"
texttemplate "text/template"
"code.gitea.io/gitea/modules/assetfs"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/templates/scopedtmpl"
"code.gitea.io/gitea/modules/util"
)
var rendererKey interface{} = "templatesHtmlRenderer"
type TemplateExecutor scopedtmpl.TemplateExecutor
type HTMLRender struct {
templates atomic.Pointer[scopedtmpl.ScopedTemplate]
}
var ErrTemplateNotInitialized = errors.New("template system is not initialized, check your log for errors")
func (h *HTMLRender) HTML(w io.Writer, status int, name string, data interface{}) error {
if respWriter, ok := w.(http.ResponseWriter); ok {
if respWriter.Header().Get("Content-Type") == "" {
respWriter.Header().Set("Content-Type", "text/html; charset=utf-8")
}
respWriter.WriteHeader(status)
}
t, err := h.TemplateLookup(name)
if err != nil {
return texttemplate.ExecError{Name: name, Err: err}
}
return t.Execute(w, data)
}
func (h *HTMLRender) TemplateLookup(name string) (TemplateExecutor, error) {
tmpls := h.templates.Load()
if tmpls == nil {
return nil, ErrTemplateNotInitialized
}
return tmpls.Executor(name, NewFuncMap()[0])
}
func (h *HTMLRender) CompileTemplates() error {
assets := AssetFS()
extSuffix := ".tmpl"
tmpls := scopedtmpl.NewScopedTemplate()
tmpls.Funcs(NewFuncMap()[0])
files, err := ListWebTemplateAssetNames(assets)
if err != nil {
return nil
}
for _, file := range files {
if !strings.HasSuffix(file, extSuffix) {
continue
}
name := strings.TrimSuffix(file, extSuffix)
tmpl := tmpls.New(filepath.ToSlash(name))
buf, err := assets.ReadFile(file)
if err != nil {
return err
}
if _, err = tmpl.Parse(string(buf)); err != nil {
return err
}
}
tmpls.Freeze()
h.templates.Store(tmpls)
return nil
}
// HTMLRenderer returns the current html renderer for the context or creates and stores one within the context for future use
func HTMLRenderer(ctx context.Context) (context.Context, *HTMLRender) {
if renderer, ok := ctx.Value(rendererKey).(*HTMLRender); ok {
return ctx, renderer
}
rendererType := "static"
if !setting.IsProd {
rendererType = "auto-reloading"
}
log.Log(1, log.DEBUG, "Creating "+rendererType+" HTML Renderer")
renderer := &HTMLRender{}
if err := renderer.CompileTemplates(); err != nil {
p := &templateErrorPrettier{assets: AssetFS()}
wrapFatal(p.handleFuncNotDefinedError(err))
wrapFatal(p.handleUnexpectedOperandError(err))
wrapFatal(p.handleExpectedEndError(err))
wrapFatal(p.handleGenericTemplateError(err))
log.Fatal("HTMLRenderer CompileTemplates error: %v", err)
}
if !setting.IsProd {
go AssetFS().WatchLocalChanges(ctx, func() {
if err := renderer.CompileTemplates(); err != nil {
log.Error("Template error: %v\n%s", err, log.Stack(2))
}
})
}
return context.WithValue(ctx, rendererKey, renderer), renderer
}
func wrapFatal(msg string) {
if msg == "" {
return
}
log.FatalWithSkip(1, "Unable to compile templates, %s", msg)
}
type templateErrorPrettier struct {
assets *assetfs.LayeredFS
}
var reGenericTemplateError = regexp.MustCompile(`^template: (.*):([0-9]+): (.*)`)
func (p *templateErrorPrettier) handleGenericTemplateError(err error) string {
groups := reGenericTemplateError.FindStringSubmatch(err.Error())
if len(groups) != 4 {
return ""
}
tmplName, lineStr, message := groups[1], groups[2], groups[3]
return p.makeDetailedError(message, tmplName, lineStr, -1, "")
}
var reFuncNotDefinedError = regexp.MustCompile(`^template: (.*):([0-9]+): (function "(.*)" not defined)`)
func (p *templateErrorPrettier) handleFuncNotDefinedError(err error) string {
groups := reFuncNotDefinedError.FindStringSubmatch(err.Error())
if len(groups) != 5 {
return ""
}
tmplName, lineStr, message, funcName := groups[1], groups[2], groups[3], groups[4]
funcName, _ = strconv.Unquote(`"` + funcName + `"`)
return p.makeDetailedError(message, tmplName, lineStr, -1, funcName)
}
var reUnexpectedOperandError = regexp.MustCompile(`^template: (.*):([0-9]+): (unexpected "(.*)" in operand)`)
func (p *templateErrorPrettier) handleUnexpectedOperandError(err error) string {
groups := reUnexpectedOperandError.FindStringSubmatch(err.Error())
if len(groups) != 5 {
return ""
}
tmplName, lineStr, message, unexpected := groups[1], groups[2], groups[3], groups[4]
unexpected, _ = strconv.Unquote(`"` + unexpected + `"`)
return p.makeDetailedError(message, tmplName, lineStr, -1, unexpected)
}
var reExpectedEndError = regexp.MustCompile(`^template: (.*):([0-9]+): (expected end; found (.*))`)
func (p *templateErrorPrettier) handleExpectedEndError(err error) string {
groups := reExpectedEndError.FindStringSubmatch(err.Error())
if len(groups) != 5 {
return ""
}
tmplName, lineStr, message, unexpected := groups[1], groups[2], groups[3], groups[4]
return p.makeDetailedError(message, tmplName, lineStr, -1, unexpected)
}
var (
reTemplateExecutingError = regexp.MustCompile(`^template: (.*):([1-9][0-9]*):([1-9][0-9]*): (executing .*)`)
reTemplateExecutingErrorMsg = regexp.MustCompile(`^executing "(.*)" at <(.*)>: `)
)
func (p *templateErrorPrettier) handleTemplateRenderingError(err error) string {
if groups := reTemplateExecutingError.FindStringSubmatch(err.Error()); len(groups) > 0 {
tmplName, lineStr, posStr, msgPart := groups[1], groups[2], groups[3], groups[4]
target := ""
if groups = reTemplateExecutingErrorMsg.FindStringSubmatch(msgPart); len(groups) > 0 {
target = groups[2]
}
return p.makeDetailedError(msgPart, tmplName, lineStr, posStr, target)
} else if execErr, ok := err.(texttemplate.ExecError); ok {
layerName := p.assets.GetFileLayerName(execErr.Name + ".tmpl")
return fmt.Sprintf("asset from: %s, %s", layerName, err.Error())
} else {
return err.Error()
}
}
func HandleTemplateRenderingError(err error) string {
p := &templateErrorPrettier{assets: AssetFS()}
return p.handleTemplateRenderingError(err)
}
const dashSeparator = "----------------------------------------------------------------------"
func (p *templateErrorPrettier) makeDetailedError(errMsg, tmplName string, lineNum, posNum any, target string) string {
code, layer, err := p.assets.ReadLayeredFile(tmplName + ".tmpl")
if err != nil {
return fmt.Sprintf("template error: %s, and unable to find template file %q", errMsg, tmplName)
}
line, err := util.ToInt64(lineNum)
if err != nil {
return fmt.Sprintf("template error: %s, unable to parse template %q line number %q", errMsg, tmplName, lineNum)
}
pos, err := util.ToInt64(posNum)
if err != nil {
return fmt.Sprintf("template error: %s, unable to parse template %q pos number %q", errMsg, tmplName, posNum)
}
detail := extractErrorLine(code, int(line), int(pos), target)
var msg string
if pos >= 0 {
msg = fmt.Sprintf("template error: %s:%s:%d:%d : %s", layer, tmplName, line, pos, errMsg)
} else {
msg = fmt.Sprintf("template error: %s:%s:%d : %s", layer, tmplName, line, errMsg)
}
return msg + "\n" + dashSeparator + "\n" + detail + "\n" + dashSeparator
}
func extractErrorLine(code []byte, lineNum, posNum int, target string) string {
b := bufio.NewReader(bytes.NewReader(code))
var line []byte
var err error
for i := 0; i < lineNum; i++ {
if line, err = b.ReadBytes('\n'); err != nil {
if i == lineNum-1 && errors.Is(err, io.EOF) {
err = nil
}
break
}
}
if err != nil {
return fmt.Sprintf("unable to find target line %d", lineNum)
}
line = bytes.TrimRight(line, "\r\n")
var indicatorLine []byte
targetBytes := []byte(target)
targetLen := len(targetBytes)
for i := 0; i < len(line); {
if posNum == -1 && target != "" && bytes.HasPrefix(line[i:], targetBytes) {
for j := 0; j < targetLen && i < len(line); j++ {
indicatorLine = append(indicatorLine, '^')
i++
}
} else if i == posNum {
indicatorLine = append(indicatorLine, '^')
i++
} else {
if line[i] == '\t' {
indicatorLine = append(indicatorLine, '\t')
} else {
indicatorLine = append(indicatorLine, ' ')
}
i++
}
}
// if the indicatorLine only contains spaces, trim it together
return strings.TrimRight(string(line)+"\n"+string(indicatorLine), " \t\r\n")
}