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Diffstat (limited to 'src/text/template/examplefiles_test.go')
-rw-r--r-- | src/text/template/examplefiles_test.go | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/src/text/template/examplefiles_test.go b/src/text/template/examplefiles_test.go new file mode 100644 index 0000000..6534ee3 --- /dev/null +++ b/src/text/template/examplefiles_test.go @@ -0,0 +1,181 @@ +// 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)) +} |