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Golang load HTML templates
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| // | |
| // Copyright (c) 2025 Konstantin Ivanov <[email protected]>. | |
| // All rights reserved. This program is free software. It comes without | |
| // any warranty, to the extent permitted by applicable law. You can | |
| // redistribute it and/or modify it under the terms of the Unlicense. | |
| // See LICENSE file for more details or see below. | |
| // | |
| // | |
| // This is free and unencumbered software released into the public domain. | |
| // | |
| // Anyone is free to copy, modify, publish, use, compile, sell, or | |
| // distribute this software, either in source code form or as a compiled | |
| // binary, for any purpose, commercial or non-commercial, and by any | |
| // means. | |
| // | |
| // In jurisdictions that recognize copyright laws, the author or authors | |
| // of this software dedicate any and all copyright interest in the | |
| // software to the public domain. We make this dedication for the benefit | |
| // of the public at large and to the detriment of our heirs and | |
| // successors. We intend this dedication to be an overt act of | |
| // relinquishment in perpetuity of all present and future rights to this | |
| // software under copyright law. | |
| // | |
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |
| // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |
| // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. | |
| // IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR | |
| // OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, | |
| // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR | |
| // OTHER DEALINGS IN THE SOFTWARE. | |
| // | |
| // For more information, please refer to <http://unlicense.org/> | |
| // | |
| package templates | |
| import ( | |
| "fmt" | |
| "html/template" | |
| "io/fs" | |
| "os" | |
| "path/filepath" | |
| "strings" | |
| ) | |
| type Option func(t *Tree) error | |
| func FollowSymlinks() Option { | |
| return func(t *Tree) (_ error) { | |
| t.followSymlinks = true | |
| return | |
| } | |
| } | |
| func WithFuncs(funcsMap template.FuncMap) Option { | |
| return func(t *Tree) (_ error) { | |
| t.funcsMap = funcsMap | |
| return | |
| } | |
| } | |
| func WithExt(ext string) Option { | |
| return func(t *Tree) (_ error) { | |
| t.ext = ext | |
| return | |
| } | |
| } | |
| // A Tree implements keeper and loader for HTML templates based on directory | |
| // tree. | |
| type Tree struct { | |
| *template.Template // root template | |
| // configurations | |
| ext string // only files with this extension | |
| followSymlinks bool // | |
| funcsMap template.FuncMap // | |
| } | |
| // New creates new Tree parsing given file system. | |
| // For example: | |
| // | |
| // var t, err = templates.New(os.DirFS("./templates/"), | |
| // templates.WithExt(".html"), | |
| // templates.FollowSymlinks(), | |
| // templates.WithFuncs(customFuncsMap)) | |
| func New(dir fs.FS, opts ...Option) (t *Tree, err error) { | |
| t = new(Tree) | |
| t.Template = template.New("") // unnamed root template | |
| for _, o := range opts { | |
| if err = o(t); err != nil { | |
| return | |
| } | |
| } | |
| t.Funcs(t.funcsMap) | |
| if err = t.load(dir, t.ext); err != nil { | |
| return nil, err | |
| } | |
| return | |
| } | |
| // Load templates. The dir argument is a directory to load templates from. | |
| // The ext argument is extension of tempaltes. | |
| func (t *Tree) load(dir fs.FS, ext string) (err error) { | |
| var walkFunc = func(path string, info fs.DirEntry, err error) (_ error) { | |
| // handle walking error if any | |
| if err != nil { | |
| return fmt.Errorf("walking file system: %w", err) | |
| } | |
| // skip all except regular files | |
| var realPath = path | |
| if !info.Type().IsRegular() { | |
| if info.Type()&os.ModeSymlink == 0 { | |
| return // skip, not a regular file, nor a symbolic link | |
| } | |
| if t.followSymlinks { | |
| return // skip, don't follow symbolic links | |
| } | |
| if realPath, err = filepath.EvalSymlinks(path); err != nil { | |
| return fmt.Errorf("resolving symbolic link %q: %w", path, | |
| err) | |
| } | |
| } | |
| // filter by extension | |
| if ext != "" { | |
| if filepath.Ext(path) != ext { | |
| return // skip | |
| } | |
| } | |
| // name of a template is its relative path | |
| // without extension | |
| if ext != "" { | |
| path = strings.TrimSuffix(path, ext) | |
| } | |
| path = strings.Join(strings.Split(path, string(os.PathSeparator)), "/") | |
| // load or reload | |
| var ( | |
| nt = t.Template.New(path) | |
| b []byte | |
| ) | |
| if b, err = fs.ReadFile(dir, realPath); err != nil { | |
| return err | |
| } | |
| _, err = nt.Parse(string(b)) | |
| return err | |
| } | |
| if err = fs.WalkDir(dir, ".", walkFunc); err != nil { | |
| return | |
| } | |
| return | |
| } |
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| // | |
| // Copyright (c) 2025 Konstantin Ivanov <[email protected]>. | |
| // All rights reserved. This program is free software. It comes without | |
| // any warranty, to the extent permitted by applicable law. You can | |
| // redistribute it and/or modify it under the terms of the Unlicense. | |
| // See LICENSE file for more details or see below. | |
| // | |
| // | |
| // This is free and unencumbered software released into the public domain. | |
| // | |
| // Anyone is free to copy, modify, publish, use, compile, sell, or | |
| // distribute this software, either in source code form or as a compiled | |
| // binary, for any purpose, commercial or non-commercial, and by any | |
| // means. | |
| // | |
| // In jurisdictions that recognize copyright laws, the author or authors | |
| // of this software dedicate any and all copyright interest in the | |
| // software to the public domain. We make this dedication for the benefit | |
| // of the public at large and to the detriment of our heirs and | |
| // successors. We intend this dedication to be an overt act of | |
| // relinquishment in perpetuity of all present and future rights to this | |
| // software under copyright law. | |
| // | |
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |
| // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |
| // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. | |
| // IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR | |
| // OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, | |
| // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR | |
| // OTHER DEALINGS IN THE SOFTWARE. | |
| // | |
| // For more information, please refer to <http://unlicense.org/> | |
| // | |
| package templates | |
| import ( | |
| "html/template" | |
| "strings" | |
| "testing" | |
| "testing/fstest" | |
| "time" | |
| "github.com/stretchr/testify/assert" | |
| "github.com/stretchr/testify/require" | |
| ) | |
| // templates/ | |
| // layout/ | |
| // footer.html | |
| // header.html | |
| // main.html | |
| // users/ | |
| // entity.html | |
| // list.html | |
| // user.html | |
| // | |
| func TestTree(t *testing.T) { | |
| var ( | |
| mapfs = make(fstest.MapFS) | |
| now = time.Now() | |
| ) | |
| mapfs["templates/layout/header.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| HEADER | |
| TITILE: {{ .Title }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| mapfs["templates/layout/footer.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| FOOTER | |
| CONTACTS: {{ .Contacts }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| mapfs["templates/layout/main.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| {{ template "layout/header" . }} | |
| MAIN CONTENT | |
| {{ template "layout/footer" . }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| mapfs["templates/users/entity.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| - Name: {{ .Name }} | |
| Age: {{ .Age }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| mapfs["templates/users/list.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| {{ template "layout/header" . }} | |
| TOTAL {{ len .Users }} | |
| {{ range .Users }} | |
| {{ template "users/entity" . }} | |
| {{ end }} | |
| {{ template "layout/footer" . }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| mapfs["templates/users/user.html"] = &fstest.MapFile{ | |
| Data: []byte(` | |
| {{ template "layout/header" . }} | |
| {{ with .User }} | |
| {{ .Name }}, {{ .Age }} years old | |
| {{ end }} | |
| {{ fish }} | |
| {{ template "layout/footer" . }} | |
| `), | |
| Mode: 0644, | |
| ModTime: now, | |
| } | |
| type User struct { | |
| Name string | |
| Age int | |
| } | |
| type Data struct { | |
| Title string | |
| Contacts string | |
| Users []User | |
| User User | |
| } | |
| var data = Data{ | |
| Title: "Testing Templates", | |
| Contacts: "[email protected]", | |
| Users: []User{ | |
| {"Alex", 31}, | |
| {"Alic", 25}, | |
| {"Eva", 27}, | |
| }, | |
| User: User{"Abigail", 29}, | |
| } | |
| var sub, err = mapfs.Sub("templates") | |
| require.NoError(t, err) | |
| _, err = sub.Open("layout/footer.html") | |
| require.NoError(t, err) | |
| var customFuncsMap = template.FuncMap{ | |
| "fish": func() string { | |
| return "Lorem Ipsum Dolor Sit a met" | |
| }, | |
| } | |
| var tr *Tree | |
| tr, err = New(sub, | |
| WithExt(".html"), | |
| FollowSymlinks(), | |
| WithFuncs(customFuncsMap)) | |
| require.NoError(t, err) | |
| var defTempl = tr.DefinedTemplates() | |
| for _, dt := range []string{ | |
| "layout/footer", | |
| "layout/header", | |
| "layout/main", | |
| "users/entity", | |
| "users/list", | |
| "users/user", | |
| } { | |
| assert.True(t, strings.Contains(defTempl, dt)) | |
| } | |
| var out strings.Builder | |
| err = tr.ExecuteTemplate(&out, "layout/main", data) | |
| require.NoError(t, err) | |
| assert.Equal(t, ` | |
| HEADER | |
| TITILE: Testing Templates | |
| MAIN CONTENT | |
| FOOTER | |
| CONTACTS: [email protected] | |
| `, out.String()) | |
| out.Reset() | |
| err = tr.ExecuteTemplate(&out, "users/list", data) | |
| require.NoError(t, err) | |
| assert.Equal(t, ` | |
| HEADER | |
| TITILE: Testing Templates | |
| TOTAL 3 | |
| - Name: Alex | |
| Age: 31 | |
| - Name: Alic | |
| Age: 25 | |
| - Name: Eva | |
| Age: 27 | |
| FOOTER | |
| CONTACTS: [email protected] | |
| `, out.String()) | |
| out.Reset() | |
| } |
Can I ask you how to use it?
For a directory structure, for example,
templates/
one/
one-a.html
one-b.html
two/
two-a.html
two-b.html
Load templates
var templs, err = NeTempl("./templates/", ".html", false)
if err != nil {
// handle error
}Use the templates
// the w is a io.Writer, can be a http.ResponseWriter for example
err = templs.Render(w, "one/one-a", map[string]interface{
"key": "value, for example"
})
if err != nil {
// rendering or writing error
}Everything is described in the load.go header.
Thank you for your quick answer.
I'm using the precious code as you indicated but I have this error:
panic: NewTmpl: template: tests/templates/test.tmpl:1: function "title" not defined
I think the error is correct because if one of the templates contains the following code:
func {{title .EntityName}} ...
it doesn't know how to interpret "title" and I can't even use:
templs.Funcs(funcMap)after the NewTempl() because there is already the call to Load in it that uses nt.Parse(string(b)).
Do you think a change is needed?
Should we also pass funcs in NewTempl()?
panic: NewTmpl: template: tests/templates/test.tmpl:1: function "title" not defined
Do you think a change is needed?
Should we also pass funcs in NewTempl()?
Hm. May be. Pass funcs in the NewTempl or move the Load out of the NewTempl and load outside, when functions are set. Also, I would change Funcs to SetFuncs for a better naming. And I would get rid out of the development stuff (the .devel and all related).
@frederikhors , I've updated the load.go. And I've not tested it.
var templs = NeTempl()
// may be not 100% correct here
templs.SetFuncs(template.FuncMap{
"title": strings.Title,
})
var err = templs.Load("./templates/", ".html")
if err != nil {
// handle error
}Use the templates
// the w is a io.Writer, can be a http.ResponseWriter for example
err = templs.ExecuteTemplatte(w, "one/one-a", map[string]interface{
"key": "value, for example"
})
if err != nil {
// rendering or writing error
}
You forgot t.dir on line https://gist.github.com/logrusorgru/abd846adb521a6fb39c7405f32fec0cf#file-load-go-L136.
Why did you remove the develop part? Do you find it no longer useful?
Plus I'm having a problem because I'm on Windows I think.
All the templates it finds have the key like: templates\customDir\subdir\file.
And even if I use path.Join() everywhere it won't find them unless I point to them using \ instead of / (example "one\\one-a" instead of "one/one-a").
This is very strange. Do you understand why?
This is very strange. Do you understand why?
It uses relative filesystem path as a template name. You can add this line (below), to convert Windows-like paths to UNIX-like for a template name. The line is
rel = strings.TrimSuffix(rel, ext)
rel = strings.Join(strings.Split(rel, os.PathSeparator), "/") // additional lineThis way, all template names will be UNIX-like (e.g. /-separated). I've added this to the load.go.
Why did you remove the develop part? Do you find it no longer useful?
Yes, I think it useless.
The error with this new code now is:
Maybe we should use: string(os.PathSeparator).
Yep
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Can I ask you how to use it?