21ce84653d
This leaves an unimplemented "langkit.lkt_lowering.create_nodes" function and a "nodes_from_lkt" switch that tests can use to enable the import of node definitions (nodes, fields, env specs, properties) from Lkt files rather than from the Python DSL. Once the transition to Lkt is over, this switch will disappear. TN: RA22-015
Langkit
Langkit (nickname for language kit) is a tool whose purpose is to make it easy to create syntactic and semantic analysis engines. Write a language specification in our Python DSL and Langkit will generate for you an Ada library with bindings for the C and Python programming languages.
The generated library is meant to provide a basis to write tooling, including tools working on potentially changing and incorrect code, such as IDEs.
The currently main Langkit user is Libadalang, a high performance semantic engine for the Ada programming language.
Dependencies
To use Langkit, you will need:
- A Python 3.7+ interpreter. Python2 is no longer supported.
- Some python libraries, including the mako template system for Python (see
REQUIREMENTS.devfor the full list). - A recent version of the GNAT Ada compiler, either from your OS's packages, or from here.
- The gnatcoll-core library.
- Ada bindings for GMP and Libiconv, from gnatcoll-bindings.
- Clang-format, optionally, if you want C/C++ files to be formated.
Install
There is no proper distribution for the langkit Python package, so just add the
top-level langkit directory to your PYTHONPATH in order to use it. Note that
this directory is self-contained, so you can copy it somewhere else.
Build
Langkit requires a build step: run ./manage.py make. If you installed all the
necessary dependencies, the build should succeed.
Testing
First, make sure the langkit package is available from the Python interpreter (see Install). Then, in order to run the testsuite, launch the following command from the top-level directory:
$ ./manage.py test
This is just a wrapper passing convenient options to the real testsuite
driver that is in testsuite/testsuite.py.
If you want to learn more about this test driver's options (for instance to run
tests under Valgrind), add a -h flag.
Documentation
The developer and user's documentation for Langkit is in langkit/doc. You can
consult it as a text files or you can build it. For instance, to generate HTML
documents, run from the top directory:
$ make -C langkit/doc html
And then open the following file in your favorite browser:
langkit/doc/_build/html/index.html
Bootstrapping a new language engine
Nothing is more simple than getting an initial project skeleton to work on a new language engine. Imagine you want to create an engine for the Foo language, run from the top-level directory:
$ python langkit/create-project.py Foo
And then have a look at the created foo directory: you have minimal lexers
and parsers and a manage.py script you can use to build this new engine:
$ python foo/manage.py make
Here you are!
Developer tools
Langkit uses mako templates generating Ada, C and Python code. This can be hard
to read. To ease development, Vim syntax files are available under the utils
directory (see makoada.vim, makocpp.vim). Install them in your
$HOME/.vim/syntax directory to get automatic highlighting of the template
files.