Rusty Handlebars Parser

A type-safe Handlebars template parser and compiler for Rust. This crate provides the core parsing and compilation functionality for the rusty-handlebars templating engine.

Features

• Type-safe template parsing and compilation
• HTML escaping and safety
• Optional HTML minification
• Block helper support
• Expression evaluation
• Variable resolution and scope management
• Compile-time template validation

Components

Expression Parser

The expression parser handles various types of Handlebars expressions:

• Variables: {{name}}
• HTML-escaped variables: {{{name}}}
• Block helpers: {{#helper}}...{{/helper}}
• Comments: {{! comment }}
• Escaped content: \{{name}}

Block Helpers

Built-in block helpers include:

• if/unless for conditional rendering
• if_some/if_some_ref for Option handling
• with/with_ref for context changes
• each/each_ref for collection iteration

Compiler

The compiler transforms Handlebars templates into Rust code:

• Resolves variables and scopes
• Compiles block helpers
• Handles HTML escaping
• Generates type-safe code

Usage

Basic Template Compilation

use rusty_handlebars_parser::{Compiler, Options};
use rusty_handlebars_parser::block::add_builtins;

let mut block_map = HashMap::new();
add_builtins(&mut block_map);

let options = Options {
    root_var_name: Some("data"),
    write_var_name: "write"
};

let compiler = Compiler::new(options, block_map);
let rust = compiler.compile("Hello {{name}}!")?;

Complex Template Example

let template = r#"
<div class="user-profile">
    {{#if user}}
        <h1>{{user.name}}</h1>
        {{#if user.bio}}
            <p class="bio">{{user.bio}}</p>
        {{else}}
            <p class="no-bio">No bio available</p>
        {{/if}}
        
        {{#if_some user.posts as post}}
            <div class="posts">
                <h2>Posts</h2>
                {{#each post as post}}
                    <article class="post">
                        <h3>{{post.title}}</h3>
                        <p>{{post.content}}</p>
                        <div class="meta">
                            <span>Posted on {{post.date}}</span>
                            {{#if post.tags}}
                                <div class="tags">
                                    {{#each post.tags as tag}}
                                        <span class="tag">{{tag}}</span>
                                    {{/each}}
                                </div>
                            {{/if}}
                        </div>
                    </article>
                {{/each}}
            </div>
        {{/if_some}}
    {{else}}
        <p>Please log in to view your profile</p>
    {{/if}}
</div>
"#;

let rust = compiler.compile(template)?;

HTML Minification

When the minify-html feature is enabled, the parser can optimize HTML output:

#[cfg(feature = "minify-html")]
use rusty_handlebars_parser::build_helper::COMPRESS_CONFIG;

The minification configuration:

• Preserves Handlebars template syntax
• Maintains HTML validity
• Optimizes JavaScript and CSS
• Keeps essential HTML structure

Error Handling

The parser provides detailed error information:

use rusty_handlebars_parser::error::{Result, ParseError};

fn compile_template(template: &str) -> Result<String> {
    let compiler = Compiler::new(options, block_map);
    compiler.compile(template)
}

Module Structure

• compiler.rs: Core compilation logic
• block.rs: Block helper implementations
• expression.rs: Expression parsing
• expression_tokenizer.rs: Tokenization of expressions
• error.rs: Error handling
• build_helper.rs: Build-time configuration

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.