boilerplate

boilerplate is a statically-checked Rust template engine with no runtime dependencies. There are two ways to use boilerplate, boilerplate::Boilerplate, a derive macro, and boilerplate::boilerplate, a function-like macro.

Derive Macro

Derive Boilerplate on the type you want to use as a template context:

use boilerplate::Boilerplate;
#[derive(Boilerplate)] struct MyTemplateTxt {   foo: bool,   bar: Result<String, Box<dyn std::error::Error>>, }

boilerplate template code and interpolations are Rust, so errors are checked at compile time and the template language is easy to learn:

%% if self.foo {
Foo was true!
%% }
%% match &self.bar {
%%   Ok(ok) => {
Pretty good: {{ ok }}
%%   }
%%   Err(err) => {
Not so great: {{ err }}
%%   }
%% }

The Boilerplate macro provides a Display implementation, so you can instantiate a template context and convert it to a string:

let rendered = MyTemplateTxt { foo: true, bar: Ok("hello".into()) }.to_string();

Or use it in a format string:

println!("The output is: {}", MyTemplateTxt { foo: false, bar: Err("hello".into()) });

boilerplate's implementation is exceedingly simple. Try using cargo-expand to expand the Boilerplate macro, inspect derived Display implementations, and debug template issues.

Function-like Macro

use boilerplate::boilerplate;
let foo = true; let bar: Result<&str, &str> = Ok("yassss");
let output = boilerplate!( "%% if foo { Foo was true! %% } %% match bar { %%   Ok(ok) => { Pretty good: {{ ok }} %%   } %%   Err(err) => { Not so great: {{ err }} %%   } %% } ");
assert_eq!(output, "Foo was true!\nPretty good: yassss\n");

Quick Start

Add boilerplate to your project's Cargo.toml:

[dependencies]
boilerplate = "*"

Create a template in templates/my-template.txt:

Foo is {{self.n}}!

Define, instantiate, and render the template context:

use boilerplate::Boilerplate;
#[derive(Boilerplate)] struct MyTemplateTxt {   n: u32, }
asserteq!(MyTemplateTxt  { n: 10 }.tostring(), "Foo is 10!\n");

Examples

See the docs for more information and examples.

Syntax Highlighting

This repository contains a Vim plugin for boilerplate syntax highlighting, in the vim subdirectory.

To install it with vim-plug:

Plug 'casey/boilerplate', { 'rtp': 'vim' }

Highlighting is enabled with the :Boilerplate command, rather than automatically, since boilerplate templates do not have a unique extension.

See :help boilerplate for more information.