cuppa

Cuppa

A simple, extensible build system for use with Scons <http://www.scons.org/>__. Cuppa is designed to leverage the capabilities of Scons, while allowing developers to focus on the task of describing what needs to be built. In general cuppa supports make like usage on the command-line. That is developers can simply write:

.. code:: sh

scons -D

and have Scons "do the right thing"; building targets for any sconscript files found in the current directory.

Cuppa can be installed as a normal python package or installed locally into a site_scons directory allowing it to be effortlessly integrated into any Scons setup.

Note: ``-D`` tells ``scons`` to look for an ``sconstruct`` file in
the current or in parent directories and if it finds one execute the
``sconscript`` files as if called from that directory. This ensures
everything works as expected. For more details refer to the `Scons
documentation <http://www.scons.org/documentation.php>`__

Quick Intro

Get cuppa

The simpest way to get **cuppa** is to ``pip install`` it using:

::

    pip install cuppa


Sample ``sconstruct`` file

Let's look at a minimal sconstruct that makes use of cuppa. It could look like this:

.. code:: python

# Pull in all the Cuppa goodies..
import cuppa

# Call sconscripts to do the work
cuppa.run()

Calling the run method in the cuppa module starts the build process calling sconscript files.

Sample sconscript file

Here is an example ``sconscript`` file that builds all \*.cpp files in
the directory where it resides:

.. code:: python

    Import( 'env' )

    # Build all *.cpp source files as executables
    for Source in env.GlobFiles('*.cpp'):
        env.Build( Source[:-4], Source )

The ``env.Build()`` method is provided by **cuppa** and does essentially
what ``env.Program()`` does but in addition is both toolchain and
variant aware, and further can provide notifications on progress.

    Note: Source[:-4] simply strips off the file extension ``.cpp``,
    that is, the last 4 characters of the file name.

If our ``sconscript`` file was for a directory containing \*.cpp files
that are actually tests then we could instead write the ``sconscript``
file as:

.. code:: python

    Import( 'env' )

    # Build all *.cpp source files as executables to be run as tests
    for Source in env.GlobFiles('*.cpp'):
        env.BuildTest( Source[:-4], Source )

The ``env.BuildTest()`` method is provided by **cuppa** and builds the
sources specified as ``env.Build()`` does.

However, in addition, passing ``--test`` on the command-line will also
result in the executable produced being run by a **runner**. The default
test runner simply treats each executable as a test case and each
directory or executables as a test suite. If the process executes
cleanly the test passed, if not it failed.

To run this on the command-line we would write:

.. code:: sh

    scons -D --test

If we only want to build and test *debug* executables we can instead
write this:

.. code:: sh

    scons -D --dbg --test

Or for release only pass ``--rel``.

**cuppa** also makes it easy to work with dependencies. For example, if
`boost <http://www.boost.org/>`__ was a default dependency for all your
``sconscript`` files you could write your sconstruct file as follows:

.. code:: python

    import cuppa

    cuppa.run(
        default_options = {
             'boost-home': '<Location of Boost>'
        },
        default_dependencies = [
            'boost'
        ]
    )

This will automatically ensure that necessary includes and other compile
options are set for the boost version that is found at ``boost-home``.
If you need to link against specific boost libraries this can also be
done in the sconscript file as follows:

.. code:: python

    Import('env')

    Test = 'my_complex_test'

    Sources = [
        Test + '.cpp'
    ]

    env.AppendUnique( STATICLIBS = [
        env.BoostStaticLibrary( 'system' ),
        env.BoostStaticLibrary( 'log' ),
        env.BoostStaticLibrary( 'thread' ),
        env.BoostStaticLibrary( 'timer' ),
        env.BoostStaticLibrary( 'chrono' ),
        env.BoostStaticLibrary( 'filesystem' ),
    ] )

    env.BuildTest( Test, Sources )

The ``BoostStaticLibrary()`` method ensures that the library is built in
the correct build variant as required. If you preferred to use dynamic
linking then that can also be achieved using ``BoostSharedLibrary()``.

The point is the complexities of using `boost <http://www.boost.org/>`__
as a dependency are encapsulated and managed separately from the
scontruct and sconscript files allowing developers to focus on intent
not method.

Design Principles
-----------------

**cuppa** has been written primarily to provide a clean and structured
way to leverage the power of Scons without the usual problems of hugely
complex ``scontruct`` files that diverge between projects. Key goals of
**cuppa** are:

-  minimise the need for adding logic into ``sconscript`` files, keeping
   them as declarative as possible.
-  allow declarative ``sconscript``\ s that are both much clearer and
   significantly simpler than the equivalent ``make`` file, without the
   need to learn a whole new scripting language like ``make`` or
   ``cmake``.
-  provide a clear structure for extending the facilities offered by
   **cuppa**
-  provide a clear vocabulary for building projects
-  codify Scons best practices into **cuppa** itself so that users just
   need to call appropriate methods knowing that **cuppa** will do the
   right thing with their intent
-  provide a framework that allows experts to focus on providing
   facilities for others to use. Write once, use everywhere. For example
   one person who knows how best to make
   `boost <http://www.boost.org/>`__ available as a dependency can
   manage that dependency and allow others to use it seamlessly.

More Details
------------

For more details refer to the `project homepage <https://github.com/ja11sop/cuppa>`__.

Acknowledgements
----------------

This work is based on the build system used in
`clearpool.io <http://www.clearpool.io>`__ during development of its
next generation exchange platform.