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