Example backend plugins

This directory contains backend plugins that demonstrate how those can be written and used with Catala. They probably don't provide much value otherwise.

Use make plugins from the root of the source tree to build them.

A plugin is created by writing an OCaml module that calls Driver.Plugin.register_lcalc or Driver.Plugin.register_scalc and that links against catala.driver. Here is an example dune stanza to compile it:

(executable
 (name my-plugin)
 (modes plugin)
 (modules my_plugin_main_module)
 (libraries catala.driver))

See the following module for the registration interface:

• Driver.Plugin

Using plugins

Plugins are dynamically loaded. The Catala compiler will be looking for them at startup within <prefix>/lib/catala/plugins (assuming that the compiler is installed into <prefix>/bin), or any other directory specified through the `--plugin-dir` command-line flag or by setting the CATALA_PLUGINS environment variable.

The plugin of your choice can then be called just like the built-in backends, using:

$ catala MyPlugin <file> [options]

Examples

python example

This trivial example registers a plugin that uses the scalc format as input. It simply calls the code of the built-in Python backend, and should be no different to using the normal Catala Python output mode.

js_of_ocaml wrapper generator example

This plugin generates a js_of_ocaml wrapper from the lcalc representation of a Catala program.

It start by generating the OCaml module before generating the _api_web.ml one, which contains all the class types and conversion functions between the OCaml types and their corresponding JS objects. At the end the module exposes all methods in a JS lib <module_name>Lib.

See law_source for examples of generated code.

JSON schema generator example

This plugin generates a JSON schema corresponding to a scope of a Catala program.

See json_schemas for examples of generated schemas.