The (Too bold?) new public domain web framework for Lua

What is Restia?

A framework that aims to make developing web-applications in Lua easier. It has been designed to be used as just a library to better fit into existing applications. Restia runs inside Openresty to achieve top performance, but can easily be adapted to use different host APIs.

What makes it different?

• Simplicity: Restia has a small codebase and clear structure.
• Modularity: You can use the whole thing—or just a single function.
• No Elves: Things don't "just happen" unless you tell them to.
• Performance: Low overhead means short code paths means fast code.

What makes it special?

Powerful Templating

The MoonXML templating engine, inspired by the Lapis web framework, takes away much of the complexity of writing HTML templates by hand.

Cosmo templates, on the other hand, are blazing fast.

You can even chain them as "multistage templates": Restia will load a MoonXML template once and interpret the result as a cosmo template that you can then render repeatedly. Convenient and performant!

For even more modularity, Skooma ditches the separation between code and templates entirely. A document tree is constructed through pure functions and later rendered into actual HTML text. This two-stage process allows building transformation pipelines (read: "middleware") without having to parse HTML.

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Flexible Configuration

In Lua, structured Data is represented in tables.

Restia extends this pattern to your configuration data: Bind a directory and get a table that abstracts your complex file hierarchy and many different file types into one uniform structure that you already know how to use.

Even templates can be accessed this way, and with only a few lines of code, custom config loaders can be added for new file formats.

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No magical state transfer

Restia doesn't take care of the plumbing behind the scenes. Data should be passed around explicitly as function arguments to avoid over-sharing—both for security and predictability.

It's up to the developer to selectively override this and introduce global state where necessary.

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Cool! How do I start?

Assuming you have openresty installed:

luarocks install restia --dev --lua-version 5.1
restia new app
restia run &

That's it. You can now open it in your browser at localhost:8080 or start hacking the code right away :)

Work in Progress

In its current state, it should be obvious to anyone that Restia is still in development and nowhere near production ready.

If you want to use Restia for your own project, be warned that API changes are likely to happen unannounced during the zero-versions (0.x.y).

How do I build cool stuff?

• Run your application in the background with restia run & as you code.
• Check out getting-started.md in this repo for a detailed explanation.
• Just inspect the source tree, specially controllers, views and config.
• Read the documentation for detailed descriptions of what everything does.
• Wear sunglasses. 😎

Some Examples

Hello, World!

For a simple hello-world page one would usually set up a plain nginx route that just prints a string.

location = /hello { content_by_lua_block { ngx.say "Hello, World!" } }

However, for the sake of making a better example, here's how this could be done using a few more Restia features:

In a controller at controllers/hello.lua

local views = require("views")

return function(req)
	return ngx.say(views.hello{ name = "World" })
end

This controller simply renders a template called hello with an additional argument.

Then, in a view at views/hello.cosmo.moonhtml

h1 "Hello, $name!"

This moonhtml will be rendered and turned into a cosmo template once when it is first accessed, that is, the config module runs the moonhtml-cosmo-loader. The resulting cosmo template will look like this:

<h1>Hello, $name!</h1>

When a user accesses the route, the cosmo template gets rendered and the variable $name is replaced with "World", giving us "Hello, World!".

This behavior is not mandatory: one can also write a hello.moonhtml template that will get rendered anew for every request. This will decrease performance though, since the MoonXML renderer is much more expensive.

Simple Content Negotiation

Say you have some data like { name = "bob", hobby = "web-dev" } and want to present that information in different content types depending on the clients accept header.

Assuming there's a "data" template in the vews directory, the controller could look this:

local views = require 'views'
local json = require 'cjson'

local data = { name = "bob", hobby = "web-dev" }

return function(req)
	req:offer {
		{"application/json", function(req)
			return json.encode(data)
		end};
		{"text/html", function(req)
			return views.data(data)
		end};
	}
end

Scaffolding / Generators

Restia has a simple scaffolding mechanism which essentially wraps the restia.utils.builddir function within the restia executable.

The concept is simple: A scaffold generator is a Lua module that returns a function. This function, when called, should return a table representing the changes to be applied to the current directory.

The restia scaffold command accepts a module name and a list of extra arguments to be passed to the generator script as a table, to be evaluated internally.

More advanced scaffolds may choose to provide their own help flag.

The restia new command is a shortcut to builtin Restia generators that internally calls restia scaffold prepending 'restia.scaffold.' to the module name.

Modules

These are the most important modules that get most of the work done:

Request

Restia provides some convenience for request-handling in the restia.request module. This module is passed automatically to every request handler wrapped in restia.controller.xpcall as its first argument.

It wraps openresty functions to access request data and adds functionality to many of them, allowing the user to e.g. easily read and set cookies or access request parameters in a variety of formats.

Config

The restia.config module takes care of everything configuration-related. Its main function is bind, which binds a directory to a table. Indexing the returned table will iterate through a series of loader functions, which each attempt to load the config entry in a certain way, like loading a yaml file or binding a subdirectory.

See the documentation of the restia.config module for more information.

Template

The restia.template module wraps the moonxml templating library and adds a series of convenient functions for common HTML structures.

Controller

The restia.controller module provides helper functions to find and call request handlers. It supports both a one handler per file approach, where the controller module returns a function, or a more rails-like system where each controller has several actions (that is, the module returns a table).

The module also takes care of catching errors and running a handler that can take care of reporting the error in a suitable manner.

Secret

The restia.secret module is a config table bound to the .secret directory with some additional functions for encryption/decryption. It assumes a special key file to exist in .secret, which should contain the servers secret key.

Building the Documentation

Restia doesn't install its documentation with luarocks, so it has to be built manually or read online. To build it, simply install ldoc, clone the restia repository and run ldoc . in its top level directory. The docs will be generated in the doc folder by default.

Docker

The repository includes a dockerfile and a convenient script containerize that generates a docker image based on alpine linux.

A simple dockerfile to turn a restia application into a docker image could look like this:

# Build a minimal restia image
from alpine
# Necessary requirements
run apk add curl openssh git linux-headers perl pcre libgcc openssl yaml
# Pull openresty, luarocks, restia, etc. from the restia image
copy --from=restia /usr/local /usr/local
# Copy the restia application
copy application /etc/application
workdir /etc/application
cmd restia run

Assuming that the application is in the application folder.

Note that the containerize script uses podman instead of docker; but it should be possible to just replace it with docker and run the script.

Manpage

For Linux* users, there's a command to generate and install a manpage.

Simply run restia manpage as root to install system-wide or as another user to installit locally in $HOME/.local/share/man.

* Yes, Linux. There's also non-GNU linuxes out there using musl+busybox and other GNU-alternatives.

Known Issues

attempt to yield across C-call boundary

This error occurs under certain conditions:

1. The code being run is being (directly or indirectly) required
2. The code is running inside an openresty event that has replaced LuaJITs builtin coroutine module with openrestys custom versions of those functions.
3. Somewhere in the code a coroutine yields, no matter where it yields to (it doesn't have to yield outside the require call, which would understandably not work, but anywhere within the code being executed by require)

Note that this problem not only happens with require, but also custom message handlers passed to xpcall when an error happens, but this is less likely to happen, as error handlers usually shouldn't have any complex code that could lead to more errors and thus shouldn't be running coroutines in the first place.

This problem isn't a bug in restia; it can be reproduced in vanilla openresty.

Typical situations when this happens:

• Moonscripts compiler makes use of coroutines, thus compiling moonscript code (for example, precompiling a cosmo-moonhtml template) in a module that gets required.

Typical workarounds:

• Wrap code that uses coroutines in an init function and call require 'mymodule'.init() (Sadly, this unavoidably leads to very ugly APIs)
• Preload cosmo-moonhtml templates in init_by_lua, which runs before 2. happens
• Precompile cosmo-moonscript templates so they don't need to be compiled when requireing a module

OpenResty issue: openresty/lua-nginx-module#1292

Planned features

• More MoonXML utility methods (lists, tables, etc.)
• Some High-Level functionality (Security-related, etc.)
• Portability (Currently only nginx is supported)

Contributing

In general, all meaningful contributions are welcome under the following conditions:

• All commit messages MUST be meaningful and properlt formatted.
• Commits SHOULD NOT group unrelated features.
• Exported functions MUST be documented in LDoc style.
• Local functions SHOULD be documented as well.
• Contributors MUST appear in contributors.lua.
• Contributors MAY add custom fields to their contributors.lua entry.
• Commits modifying contributors.lua MUST be signed.

See RFC2119 if you're wondering about the weird capitalization.

Changelog

Development

Version 0.1.0

• Add 'static' scaffold
• Add 'blog' scaffold
• Add 'app' scaffold
• Add restia.controller class
• Add skooma loader for functional templating
• Add simple scaffolding/generators system
• Add restia.utils.tree submodule
• Add restia.request module
• Add restia.accessors module
• Add restia.callsign module (Name subject to future change)
• Add restia.negotiator module
• Add restia.template.require function
• Add restia.handler module (formerly restia.controller)
• Add restia.secret module
• Add support for moonhtml+cosmo multistage templates
• Add support for cosmo templates
• Integrate templates with config
• Add restia.config module
• Rewrite template loading to use a table and render on demand ;)
• Rewrite template loading to use buffer and render instantly
• Add executable for scaffolding, running tests, starting a server, etc.
• Switch to moonxml initializers
• Add restia.template module
  • Add ttable function for more complex tables
  • Add vtable function for vertical tables
  • Add olist function for ordered lists
  • Add ulist function for unordered lists
  • Add html5 function for html 5 doctype

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License: The Unlicense