apitpl

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apisite/apitpl

golang template engine which renders templates by executing them 2 times, one for content and another one for layout

• Project status: MVP is ready
• Future plans: tests & docs

This package offers 2-step template processing, where page content template called first, so it can

1. change page layout (among them previous markup) and content type
2. abort processing and return error page (this will render layout with error and without content)
3. abort processing and return redirect

If page content template returns HTML, at step 2, layout template will be called for result page markup build.

Why do we need another template engine?

1. Adding template file without source recompiling
2. Support plain HTML body as template (adding layout without additional markup in content)
3. Attach all (pages,layouts,includes) templates at start (see lookupfs)
4. Auto create routes for all page templates allowing them get required data via api (see ginapitpl)

Request processing flow

Template structure

As shown in testdata, site templates tree might looks like:

tmpl
├── includes
│   ├── inc.html
│   └── subdir1
│       └── inc.html
├── layouts
│   ├── default.html
│   └── subdir2
│       └── lay.html
└── pages
    ├── page.html
    └── subdir3
        └── page.html

Usage

Template parsing

All templates from the Root directory tree are parsed in Parse() call and program should be aborted on error. Routes for all page URI should be set in Route() call after that.

You can enable per request templates parsing for debugging purposes via ParseAlways(true) but you still have to restart your program for adding or removing any template file.

See also

• Package examples
• ginapitpl - gin bindings for this package

Template methods

Get http.Request data

{{ request.Host }}{{ request.URL.String | HTML }}

Get query params

{{ $param := .Request.URL.Query.Get "param" -}}

Set page title

{{ .SetTitle "admin:index" -}}

Choose layout

{{ .SetLayout "wide" -}}

Stop template processing and raise error

{{ .Raise 403 true "Error description" }}

Stop template processing and return redirect

{{ .RedirectFound "/page" }}

Custom methods

in code

reqFuncs["data"] = func() interface{} {
    return data
}
p, err := mlt.RenderPage(uri, reqFuncs, r)

in templates

{{range data.Todos -}}
    <li>{{- .Title }}
{{end -}}

See also

• https://stackoverflow.com/questions/42747183/how-to-render-templates-to-multiple-layouts-in-go
• https://medium.com/@leeprovoost/dealing-with-go-template-errors-at-runtime-1b429e8b854a

License

The MIT License (MIT), see LICENSE.

Copyright (c) 2018 Aleksei Kovrizhkin lekovr+apisite@gmail.com

Documentation

Overview

Package apitpl implements template engine which renders templates by executing them 2 times, one for content and another one for layout.

Example (Execute)

Render template with layout

package main

import (
	"bytes"
	"embed"
	"html/template"
	"io/fs"
	"log"
	"os"

	"github.com/apisite/apitpl"
	"github.com/apisite/apitpl/lookupfs"

	"github.com/apisite/apitpl/samplemeta"
)

//go:embed testdata/*
var embedFS embed.FS

// Render template with layout
func main() {

	// BufferPool size for rendered templates
	const bufferSize int = 64

	cfg := lookupfs.Config{
		Includes:  "inc_minimal",
		Layouts:   "layouts",
		Pages:     "pages",
		Ext:       ".html",
		DefLayout: "default",
	}
	embedDirFS, _ := fs.Sub(embedFS, "testdata")
	tfs, err := apitpl.New(bufferSize).
		LookupFS(lookupfs.New(cfg).
			FileSystem(embedDirFS)).
		Parse()
	if err != nil {
		log.Fatal(err)
	}
	var b bytes.Buffer
	page := &samplemeta.Meta{}
	page.SetLayout("default")
	err = tfs.Execute(&b, "subdir3/page", template.FuncMap{}, page)
	if err != nil {
		log.Fatal(err)
	}
	_, err = b.WriteTo(os.Stdout)
	if err != nil {
		log.Fatal(err)
	}

}

Output:

<title>Template title</title>
==
page2 here (inc2 here)==inc1

Example (Http)

Handle set of templates via http

package main

import (
	"fmt"
	"html/template"
	"io/fs"
	"log"
	"net/http"
	"net/http/httptest"

	"github.com/apisite/apitpl"
	"github.com/apisite/apitpl/lookupfs"

	//	samplefs "github.com/apisite/apitpl/testdata"
	"github.com/apisite/apitpl/samplemeta"
)

// Handle set of templates via http
func main() {

	// BufferPool size for rendered templates
	const bufferSize int = 64

	cfg := lookupfs.Config{
		Includes:  "includes",
		Layouts:   "layouts",
		Pages:     "pages",
		Ext:       ".html",
		DefLayout: "default",
	}

	funcs := template.FuncMap{
		"request": func() http.Request {
			return http.Request{}
		},
		"content": func() template.HTML { return template.HTML("") },
	}

	embedDirFS, _ := fs.Sub(embedFS, "testdata")
	tfs, err := apitpl.New(bufferSize).
		Funcs(funcs).
		LookupFS(
			lookupfs.New(cfg).
				FileSystem(embedDirFS)).
		ParseAlways(true).
		Parse()
	if err != nil {
		log.Fatal(err)
	}

	router := http.NewServeMux()
	for _, uri := range tfs.PageNames(false) {
		router.HandleFunc("/"+uri, handleHTML(tfs, uri))
	}

	resp := httptest.NewRecorder()
	req, err := http.NewRequest("GET", "/subdir3/page", nil)
	if err != nil {
		log.Fatal(err)
	}
	router.ServeHTTP(resp, req)

	fmt.Println(resp.Code)
	fmt.Println(resp.Header().Get("Content-Type"))
	fmt.Println(resp.Body.String())

}

// handleHTML returns page handler
func handleHTML(tfs *apitpl.TemplateService, uri string) func(w http.ResponseWriter, r *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		//		log.Debugf("Handling page (%s)", uri)

		page := samplemeta.NewMeta(http.StatusOK, "text/html; charset=utf-8")
		funcs := template.FuncMap{
			"request": func() http.Request {
				return *r
			},
		}
		content := tfs.RenderContent(uri, funcs, page)
		if page.Status() == http.StatusMovedPermanently || page.Status() == http.StatusFound {
			http.Redirect(w, r, page.Title, page.Status())
			return
		}
		header := w.Header()
		header["Content-Type"] = []string{page.ContentType()}
		w.WriteHeader(page.Status())
		funcs["content"] = func() template.HTML { return template.HTML(content.Bytes()) }

		err := tfs.Render(w, funcs, page, content)
		if err != nil {
			log.Fatal(err)
		}

	}
}

Output:

200
text/html; charset=utf-8
<title>Template title</title>
==
page2 here (inc2 here)==inc1 (URI: /subdir3/page)

Index

• type MetaData
• type TemplateService
  • func New(size int) (tfs *TemplateService)
  • func (tfs TemplateService) Execute(wr io.Writer, name string, funcs template.FuncMap, data MetaData) error
  • func (tfs *TemplateService) Funcs(funcMap template.FuncMap) *TemplateService
  • func (tfs *TemplateService) LookupFS(fs *lookupfs.LookupFileSystem) *TemplateService
  • func (tfs TemplateService) PageNames(hide bool) []string
  • func (tfs *TemplateService) Parse() (*TemplateService, error)
  • func (tfs *TemplateService) ParseAlways(flag bool) *TemplateService
  • func (tfs TemplateService) Render(w io.Writer, funcs template.FuncMap, data MetaData, content *bytes.Buffer) (err error)
  • func (tfs TemplateService) RenderContent(name string, funcs template.FuncMap, data MetaData) *bytes.Buffer

Examples

• Package (Execute)
• Package (Http)

Types

type MetaData

type MetaData interface {
	Error() error   // Template exec error
	SetError(error) // Store unhandler template error
	Layout() string // Return layout name
}

MetaData holds template metadata access methods

type TemplateService

type TemplateService struct {
	// contains filtered or unexported fields
}

TemplateService holds templates data & methods

func New

func New(size int) (tfs *TemplateService)

New creates TemplateService with BufferPool of given size

func (TemplateService) Execute

func (tfs TemplateService) Execute(wr io.Writer, name string, funcs template.FuncMap, data MetaData) error

Execute renders page content and layout

func (*TemplateService) Funcs

func (tfs *TemplateService) Funcs(funcMap template.FuncMap) *TemplateService

Funcs loads initial funcmap

func (*TemplateService) LookupFS

func (tfs *TemplateService) LookupFS(fs *lookupfs.LookupFileSystem) *TemplateService

LookupFS sets lookup filesystem

func (TemplateService) PageNames

func (tfs TemplateService) PageNames(hide bool) []string

PageNames returns page names for router setup

func (*TemplateService) Parse

func (tfs *TemplateService) Parse() (*TemplateService, error)

Parse parses all of service templates

func (*TemplateService) ParseAlways

func (tfs *TemplateService) ParseAlways(flag bool) *TemplateService

ParseAlways disables template caching

func (TemplateService) Render

func (tfs TemplateService) Render(w io.Writer, funcs template.FuncMap, data MetaData, content *bytes.Buffer) (err error)

Render renders layout with prepared content

func (TemplateService) RenderContent

func (tfs TemplateService) RenderContent(name string, funcs template.FuncMap, data MetaData) *bytes.Buffer

RenderContent renders page content