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text/template: add examples that use multiple templates
Fixes #2742. R=golang-dev, peterthrun, adg CC=golang-dev https://golang.org/cl/5699083
This commit is contained in:
Rob Pike
parent
f0886ab7e2
commit
dd001b5931
182
src/pkg/text/template/examplefiles_test.go
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182
src/pkg/text/template/examplefiles_test.go
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// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package template_test
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import (
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"io"
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"io/ioutil"
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"log"
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"os"
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"path/filepath"
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"text/template"
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)
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// templateFile defines the contents of a template to be stored in a file, for testing.
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type templateFile struct {
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name string
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contents string
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}
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func createTestDir(files []templateFile) string {
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dir, err := ioutil.TempDir("", "template")
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if err != nil {
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log.Fatal(err)
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}
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for _, file := range files {
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f, err := os.Create(filepath.Join(dir, file.name))
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if err != nil {
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log.Fatal(err)
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}
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defer f.Close()
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_, err = io.WriteString(f, file.contents)
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if err != nil {
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log.Fatal(err)
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}
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}
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return dir
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}
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// Here we demonstrate loading a set of templates from a directory.
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func ExampleTemplate_glob() {
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// Here we create a temporary directory and populate it with our sample
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// template definition files; usually the template files would already
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// exist in some location known to the program.
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dir := createTestDir([]templateFile{
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// T0.tmpl is a plain template file that just invokes T1.
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{"T0.tmpl", `T0 invokes T1: ({{template "T1"}})`},
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// T1.tmpl defines a template, T1 that invokes T2.
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{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
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// T2.tmpl defines a template T2.
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{"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
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})
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// Clean up after the test; another quirk of running as an example.
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defer os.RemoveAll(dir)
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// pattern is the glob pattern used to find all the template files.
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pattern := filepath.Join(dir, "*.tmpl")
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// Here starts the example proper.
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// T0.tmpl is the first name matched, so it becomes the starting template,
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// the value returned by ParseGlob.
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tmpl := template.Must(template.ParseGlob(pattern))
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err := tmpl.Execute(os.Stdout, nil)
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if err != nil {
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log.Fatalf("template execution: %s", err)
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}
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// Output:
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// T0 invokes T1: (T1 invokes T2: (This is T2))
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}
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// This example demonstrates one way to share some templates
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// and use them in different contexts. In this variant we add multiple driver
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// templates by hand to an existing bundle of templates.
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func ExampleTemplate_helpers() {
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// Here we create a temporary directory and populate it with our sample
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// template definition files; usually the template files would already
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// exist in some location known to the program.
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dir := createTestDir([]templateFile{
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// T1.tmpl defines a template, T1 that invokes T2.
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{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
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// T2.tmpl defines a template T2.
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{"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
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})
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// Clean up after the test; another quirk of running as an example.
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defer os.RemoveAll(dir)
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// pattern is the glob pattern used to find all the template files.
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pattern := filepath.Join(dir, "*.tmpl")
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// Here starts the example proper.
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// Load the helpers.
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templates := template.Must(template.ParseGlob(pattern))
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// Add one driver template to the bunch; we do this with an explicit template definition.
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_, err := templates.Parse("{{define `driver1`}}Driver 1 calls T1: ({{template `T1`}})\n{{end}}")
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if err != nil {
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log.Fatal("parsing driver1: ", err)
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}
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// Add another driver template.
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_, err = templates.Parse("{{define `driver2`}}Driver 2 calls T2: ({{template `T2`}})\n{{end}}")
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if err != nil {
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log.Fatal("parsing driver2: ", err)
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}
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// We load all the templates before execution. This package does not require
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// that behavior but html/template's escaping does, so it's a good habit.
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err = templates.ExecuteTemplate(os.Stdout, "driver1", nil)
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if err != nil {
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log.Fatalf("driver1 execution: %s", err)
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}
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err = templates.ExecuteTemplate(os.Stdout, "driver2", nil)
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if err != nil {
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log.Fatalf("driver2 execution: %s", err)
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}
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// Output:
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// Driver 1 calls T1: (T1 invokes T2: (This is T2))
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// Driver 2 calls T2: (This is T2)
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}
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// This example demonstrates how to use one group of driver
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// templates with distinct sets of helper templates.
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func ExampleTemplate_share() {
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// Here we create a temporary directory and populate it with our sample
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// template definition files; usually the template files would already
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// exist in some location known to the program.
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dir := createTestDir([]templateFile{
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// T0.tmpl is a plain template file that just invokes T1.
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{"T0.tmpl", "T0 ({{.}} version) invokes T1: ({{template `T1`}})\n"},
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// T1.tmpl defines a template, T1 that invokes T2. Note T2 is not defined
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{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
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})
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// Clean up after the test; another quirk of running as an example.
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defer os.RemoveAll(dir)
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// pattern is the glob pattern used to find all the template files.
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pattern := filepath.Join(dir, "*.tmpl")
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// Here starts the example proper.
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// Load the drivers.
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drivers := template.Must(template.ParseGlob(pattern))
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// We must define an implementation of the T2 template. First we clone
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// the drivers, then add a definition of T2 to the template name space.
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// 1. Clone the helper set to create a new name space from which to run them.
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first, err := drivers.Clone()
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if err != nil {
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log.Fatal("cloning helpers: ", err)
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}
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// 2. Define T2, version A, and parse it.
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_, err = first.Parse("{{define `T2`}}T2, version A{{end}}")
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if err != nil {
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log.Fatal("parsing T2: ", err)
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}
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// Now repeat the whole thing, using a different version of T2.
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// 1. Clone the drivers.
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second, err := drivers.Clone()
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if err != nil {
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log.Fatal("cloning drivers: ", err)
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}
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// 2. Define T2, version B, and parse it.
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_, err = second.Parse("{{define `T2`}}T2, version B{{end}}")
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if err != nil {
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log.Fatal("parsing T2: ", err)
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}
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// Execute the templates in the reverse order to verify the
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// first is unaffected by the second.
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err = second.ExecuteTemplate(os.Stdout, "T0.tmpl", "second")
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if err != nil {
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log.Fatalf("second execution: %s", err)
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}
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err = first.ExecuteTemplate(os.Stdout, "T0.tmpl", "first")
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if err != nil {
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log.Fatalf("first: execution: %s", err)
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}
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// Output:
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// T0 (second version) invokes T1: (T1 invokes T2: (T2, version B))
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// T0 (first version) invokes T1: (T1 invokes T2: (T2, version A))
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}
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