Templ

With ordinary templates, a mistake is invisible until somebody loads the page: rename a struct field and the template keeps referring to the old name, printing nothing where the value should be. Nothing fails, nothing is logged, and the page is just quietly wrong.

Templ fixes that by compiling your templates into Go code. A component becomes a Go function taking typed arguments, so a renamed field is a compile error in the same build as the rest of your application. The cost is a generation step: after editing a .templ file you run templ generate, or let lemmego dev watch and do it for you.

Setup

If you chose Templ when you ran lemmego new, everything here is already in place — the files, the configuration and the watcher. There is nothing for you to set up.

Rendering a Templ Component

import "github.com/lemmego/templ"

func MyHandler(c app.Context) error {
    return c.Templ(components.Hello("World"))
}

Or using the package-level helper:

return templ.Respond(c, components.Hello("World"))

TemplResponse

The TemplResponse type implements the Renderer interface, enabling it to be used with c.Render():

response := templ.New(c, components.Page(data))
return c.Render(response)

How It Works

1. templ.New(ctx, component) creates a TemplResponse wrapping a templ.Component
2. On render, it sets Content-Type: text/html, writes the HTTP status code, then calls component.Render(ctx.RequestContext(), w)

Template Sources

Templ source files are located in templates/:

templates/
├── base-layout.templ     # Base layout component
├── index.templ           # Index page component
├── method.templ          # Method override helper
└── csrf.templ            # CSRF token helper

The generated _templ.go files (compiled from .templ) should not be edited directly.

Development Workflow

During development, run Templ in watch mode:

lemmego dev

This starts templ generate --watch alongside air, so changes to .templ files are automatically recompiled and the server reloads.

Example Component

// templates/hello.templ
package components

templ Hello(name string) {
    <div class="greeting">
        <h1>Hello, { name }!</h1>
    </div>
}

Usage in a handler:

func HelloHandler(c app.Context) error {
    return c.Templ(components.Hello(c.Query("name")))
}

CSRF and Method Helpers

The generated project includes Templ helpers for CSRF tokens and method override:

templ CsrfField() {
    <input type="hidden" name="_token" value={ templ.Raw(csrf.Token) }/>
}

templ MethodField(method string) {
    <input type="hidden" name="_method" value={ method }/>
}

Usage in forms:

templ EditForm(task models.Task) {
    <form method="POST" action={ templ.URL("/tasks/" + strconv.Itoa(task.ID)) }>
        @MethodField("PUT")
        @CsrfField()
        <input type="text" name="title" value={ task.Title }/>
        <button type="submit">Update</button>
    </form>
}