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.
To use Langkit, you will need:
- A Python 3.9 interpreter (or more recent). Python2 is no longer supported.
- Some Python libraries, including the Mako template system for Python (see
requirements-pypi.txtandrequirements-github.txtfor the full list). - A recent version of the GNAT Ada compiler, either from your OS's packages, or use Alire to get one.
- The gnatcoll-core library.
- Ada bindings for GMP and Libiconv, from gnatcoll-bindings.
- The VSS library.
- The Prettier-Ada library.
- The AdaSAT library.
For all Ada libraries (GNATcoll, VSS, Prettier-Ada, AdaSAT), make sure to
install the version that corresponds to the version of Langkit that is built.
For instance, build all 24.1 branches, or all master branches. Mixing
versions is not supported.
We assume below that all the Ada dependencies are installed under the
$PREFIX directory, and that the environment is properly set up to use it:
-
GPRbuild has access to project files (
$PREFIX/share/gpris inGPR_PROJECT_PATH, for example). -
The dynamic linker has access to shared libraries (
$PREFIX/libis inLD_LIBRARY_PATH, for exmaple).
First, clone the adasat repository in the langkit subdirectory of the
langkit repository:
$ (cd langkit; git clone https://github.com/AdaCore/adasat)
Then, install the Langkit Python package itself:
$ pip install .
Build the Libpythonlang and Liblktlang support libraries:
$ python manage.py make --no-mypy --library-types=static,static-pic,relocatable
Install the Langkit_Support library:
$ python manage.py install-langkit-support $PREFIX --library-types=static,static-pic,relocatable
Install the Libpythonlang and Liblktlang support libraries:
$ (cd contrib/python && ./manage.py install $PREFIX --library-types=static,static-pic,relocatable --disable-all-mains)
$ (cd contrib/lkt && ./manage.py install $PREFIX --library-types=static,static-pic,relocatable --disable-all-mains)
$ pip install contrib/python/build/python
$ pip install contrib/lkt/build/python
If you are interested in shared (relocatable) libraries only, you can omit
the --library-types arguments.
In order to run the testsuite, launch the following command from the top-level directory:
$ python manage.py test
This is just a wrapper passing convenient options to the real testsuite
driver that is in testsuite/testsuite.py.
Note that even though the testsuite framework requires Python 3.9, it is possible to run the tests themselves using a different Python interpreter. For instance, to run them using Python 3.7, run:
$ python manage.py test --with-python=python3.7
If you want to learn more about this test driver's options (for instance to run
tests under Valgrind), add a -h flag.
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 doc html
And then open the following file in your favorite browser:
doc/_build/html/index.html
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 scripts/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!
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.
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