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-rw-r--r--lib/spack/docs/tutorial_advanced_packaging.rst505
1 files changed, 227 insertions, 278 deletions
diff --git a/lib/spack/docs/tutorial_advanced_packaging.rst b/lib/spack/docs/tutorial_advanced_packaging.rst
index 901e75bfd7..23e04082af 100644
--- a/lib/spack/docs/tutorial_advanced_packaging.rst
+++ b/lib/spack/docs/tutorial_advanced_packaging.rst
@@ -4,18 +4,17 @@
Advanced Topics in Packaging
============================
-While you can quickly accomplish most common tasks with what
-was covered in :ref:`packaging-tutorial`, there are times when such
-knowledge won't suffice. Usually this happens for libraries that provide
-more than one API and need to let dependents decide which one to use
-or for packages that provide tools that are invoked at build-time,
-or in other similar situations.
-
-In the following we'll dig into some of the details of package
-implementation that help us deal with these rare, but important,
-occurrences. You can rest assured that in every case Spack remains faithful to
-its philosophy: keep simple things simple, but be flexible enough when
-complex requests arise!
+Spack tries to automatically configure packages with information from
+dependencies such that all you need to do is to list the dependencies
+(i.e. with the ``depends_on`` directive) and the build system (for example
+by deriving from :code:`CmakePackage`).
+
+However, there are many special cases. Often you need to retrieve details
+about dependencies to set package-specific configuration options, or to
+define package-specific environment variables used by the package's build
+system. This tutorial covers how to retrieve build information from
+dependencies, and how you can automatically provide important information to
+dependents in your package.
----------------------
Setup for the tutorial
@@ -37,7 +36,7 @@ which comes with Spack and various packages pre-installed:
If you already started the image, you can set the ``EDITOR`` environment
variable to your preferred editor (``vi``, ``emacs``, and ``nano`` are included in the image)
-and move directly to :ref:`specs_build_interface_tutorial`.
+and move directly to :ref:`adv_pkg_tutorial_start`.
If you choose not to use the Docker image, you can clone the Spack repository
and build the necessary bits yourself:
@@ -76,29 +75,44 @@ Now, you are ready to set your preferred ``EDITOR`` and continue with
the rest of the tutorial.
-.. _specs_build_interface_tutorial:
+.. _adv_pkg_tutorial_start:
-----------------------
-Spec's build interface
-----------------------
+------------------------------
+Retrieving library information
+------------------------------
-Spack is designed with an emphasis on assigning responsibilities
-to the appropriate entities, as this results in a clearer and more intuitive interface
-for the users.
-When it comes to packaging, one of the most fundamental guideline that
-emerged from this tenet is that:
+Although Spack attempts to help packages locate their dependency libraries
+automatically (e.g. by setting PKG_CONFIG_PATH and CMAKE_PREFIX_PATH), a
+package may have unique configuration options that are required to locate
+libraries. When a package needs information about dependency libraries, the
+general approach in Spack is to query the dependencies for the locations of
+their libraries and set configuration options accordingly. By default most
+Spack packages know how to automatically locate their libraries. This section
+covers how to retrieve library information from dependencies and how to locate
+libraries when the default logic doesn't work.
- *It is a package's responsibility to know
- every software it directly depends on and to expose to others how to
- use the services it provides*.
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Accessing dependency libraries
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Spec's build interface is a protocol-like implementation of this guideline
-that allows packages to easily query their dependencies,
-and prescribes how they should expose their own build information.
+If you need to access the libraries of a dependency, you can do so
+via the ``libs`` property of the spec, for example in the ``arpack-ng``
+package:
+
+.. code-block:: python
-^^^^^^^^^^^^^^^^^^^^
-A motivating example
-^^^^^^^^^^^^^^^^^^^^
+ def install(self, spec, prefix):
+ lapack_libs = spec['lapack'].libs.joined(';')
+ blas_libs = spec['blas'].libs.joined(';')
+
+ cmake(*[
+ '-DLAPACK_LIBRARIES={0}'.format(lapack_libs),
+ '-DBLAS_LIBRARIES={0}'.format(blas_libs)
+ ], '.')
+
+Note that ``arpack-ng`` is querying virtual dependencies, which Spack
+automatically resolves to the installed implementation (e.g. ``openblas``
+for ``blas``).
We've started work on a package for ``armadillo``. You should open it,
read through the comment that starts with ``# TUTORIAL:`` and complete
@@ -160,8 +174,32 @@ Hopefully the installation went fine and the code we added expanded to the right
of semicolon separated libraries (you are encouraged to open ``armadillo``'s
build logs to double check).
-If we try to build another version tied to ``netlib-lapack`` we'll
-notice that this time the installation won't complete:
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Providing libraries to dependents
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Spack provides a default implementation for ``libs`` which often works
+out of the box. A user can write a package definition without having to
+implement a ``libs`` property and dependents can retrieve its libraries
+as shown in the above section. However, the default implementation assumes that
+libraries follow the naming scheme ``lib<package name>.so`` (or e.g.
+``lib<package name>.a`` for static libraries). Packages which don't
+follow this naming scheme must implement this function themselves, e.g.
+``opencv``:
+
+.. code-block:: python
+
+ @property
+ def libs(self):
+ shared = "+shared" in self.spec
+ return find_libraries(
+ "libopencv_*", root=self.prefix, shared=shared, recurse=True
+ )
+
+This issue is common for packages which implement an interface (i.e.
+virtual package providers in Spack). If we try to build another version of
+``armadillo`` tied to ``netlib-lapack`` we'll notice that this time the
+installation won't complete:
.. code-block:: console
@@ -190,8 +228,9 @@ notice that this time the installation won't complete:
See build log for details:
/usr/local/var/spack/stage/arpack-ng-3.5.0-bloz7cqirpdxj33pg7uj32zs5likz2un/arpack-ng-3.5.0/spack-build.out
-This is because ``netlib-lapack`` requires extra work, compared to ``openblas``,
-to expose its build information to other packages. Let's edit it:
+Unlike ``openblas`` which provides a library named ``libopenblas.so``,
+``netlib-lapack`` provides ``liblapack.so``, so it needs to implement
+customized library search logic. Let's edit it:
.. code-block:: console
@@ -210,7 +249,13 @@ What we need to implement is:
)
i.e. a property that returns the correct list of libraries for the LAPACK interface.
-Now we can finally install ``armadillo ^netlib-lapack``:
+
+We use the name ``lapack_libs`` rather than ``libs`` because
+``netlib-lapack`` can also provide ``blas``, and when it does it is provided
+as a separate library file. Using this name ensures that when
+dependents ask for ``lapack`` libraries, ``netlib-lapack`` will retrieve only
+the libraries associated with the ``lapack`` interface. Now we can finally
+install ``armadillo ^netlib-lapack``:
.. code-block:: console
@@ -225,62 +270,170 @@ Now we can finally install ``armadillo ^netlib-lapack``:
Fetch: 0.01s. Build: 3.75s. Total: 3.76s.
[+] /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/armadillo-8.100.1-sxmpu5an4dshnhickh6ykchyfda7jpyn
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-What happens at subscript time?
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Since each implementation of a virtual package is responsible for locating the
+libraries associated with the interfaces it provides, dependents do not need
+to include special-case logic for different implementations and for example
+need only ask for :code:`spec['blas'].libs`.
+
+---------------------------------------
+Modifying a package's build environment
+---------------------------------------
+
+Spack sets up several environment variables like PATH by default to aid in
+building a package, but many packages make use of environment variables which
+convey specific information about their dependencies, for example MPICC. This
+section covers how update your Spack packages so that package-specific
+environment variables are defined at build-time.
+
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Set environment variables in dependent packages at build-time
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Dependencies can set environment variables that are required when their
+dependents build. For example, when a package depends on a python extension
+like py-numpy, Spack's ``python`` package will add it to ``PYTHONPATH``
+so it is available at build time; this is required because the default setup
+that spack does is not sufficient for python to import modules.
+
+To provide environment setup for a dependent, a package can implement the
+:py:func:`setup_dependent_environment <spack.package.PackageBase.setup_dependent_environment>`
+function. This function takes as a parameter a :py:class:`EnvironmentModifications <spack.environment.EnvironmentModifications>`
+object which includes convenience methods to update the environment. For
+example an MPI implementation can set ``MPICC`` for packages that depend on it:
+
+.. code-block:: python
+
+ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
+ spack_env.set('MPICC', join_path(self.prefix.bin, 'mpicc'))
+
+In this case packages which depend on ``mpi`` will have ``MPICC`` defined in
+their environment when they build. This section is focused on modifying the
+build-time environment represented by ``spack_env``, but it's worth noting that
+modifications to ``run_env`` are included in Spack's automatically-generated
+module files.
+
+We can practice by editing the ``mpich`` package to set the ``MPICC``
+environment variable in the build-time environment of dependent packages.
+
+.. code-block:: console
+
+ root@advanced-packaging-tutorial:/# spack edit mpich
+
+Once you're finished the method should look like this:
+
+.. code-block:: python
+
+ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
+ spack_env.set('MPICC', join_path(self.prefix.bin, 'mpicc'))
+ spack_env.set('MPICXX', join_path(self.prefix.bin, 'mpic++'))
+ spack_env.set('MPIF77', join_path(self.prefix.bin, 'mpif77'))
+ spack_env.set('MPIF90', join_path(self.prefix.bin, 'mpif90'))
+
+ spack_env.set('MPICH_CC', spack_cc)
+ spack_env.set('MPICH_CXX', spack_cxx)
+ spack_env.set('MPICH_F77', spack_f77)
+ spack_env.set('MPICH_F90', spack_fc)
+ spack_env.set('MPICH_FC', spack_fc)
+
+At this point we can, for instance, install ``netlib-scalapack``:
+
+.. code-block:: console
+
+ root@advanced-packaging-tutorial:/# spack install netlib-scalapack ^mpich
+ ...
+ ==> Created stage in /usr/local/var/spack/stage/netlib-scalapack-2.0.2-km7tsbgoyyywonyejkjoojskhc5knz3z
+ ==> No patches needed for netlib-scalapack
+ ==> Building netlib-scalapack [CMakePackage]
+ ==> Executing phase: 'cmake'
+ ==> Executing phase: 'build'
+ ==> Executing phase: 'install'
+ ==> Successfully installed netlib-scalapack
+ Fetch: 0.01s. Build: 3m 59.86s. Total: 3m 59.87s.
+ [+] /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/netlib-scalapack-2.0.2-km7tsbgoyyywonyejkjoojskhc5knz3z
+
+
+and double check the environment logs to verify that every variable was
+set to the correct value.
+
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Set environment variables in your own package
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Packages can modify their own build-time environment by implementing the
+:py:func:`setup_environment <spack.package.PackageBase.setup_environment>` function.
+For ``qt`` this looks like:
+
+.. code-block:: python
+
+ def setup_environment(self, spack_env, run_env):
+ spack_env.set('MAKEFLAGS', '-j{0}'.format(make_jobs))
+ run_env.set('QTDIR', self.prefix)
+
+When ``qt`` builds, ``MAKEFLAGS`` will be defined in the environment.
-The example above leaves us with a few questions. How could it be that the
-attribute:
+To contrast with ``qt``'s :py:func:`setup_dependent_environment <spack.package.PackageBase.setup_dependent_environment>`
+function:
.. code-block:: python
- spec['lapack'].libs
+ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
+ spack_env.set('QTDIR', self.prefix)
-stems from a property of the ``netlib-lapack`` package that has a different name?
-How is it even computed for ``openblas``, given that in its package there's no code
-that deals with finding libraries?
-The answer is that ``libs`` is one of the few properties of specs that follow the
-*build-interface protocol*. The others are currently ``command`` and ``headers``.
-These properties exist only on concrete specs that have been retrieved via the
-subscript notation.
+Let's see how it works by completing the ``elpa`` package:
-What happens is that, whenever you retrieve a spec using subscripts:
+.. code-block:: console
+
+ root@advanced-packaging-tutorial:/# spack edit elpa
+
+In the end your method should look like:
.. code-block:: python
- lapack = spec['lapack']
+ def setup_environment(self, spack_env, run_env):
+ spec = self.spec
+
+ spack_env.set('CC', spec['mpi'].mpicc)
+ spack_env.set('FC', spec['mpi'].mpifc)
+ spack_env.set('CXX', spec['mpi'].mpicxx)
+ spack_env.set('SCALAPACK_LDFLAGS', spec['scalapack'].libs.joined())
+
+ spack_env.append_flags('LDFLAGS', spec['lapack'].libs.search_flags)
+ spack_env.append_flags('LIBS', spec['lapack'].libs.link_flags)
+
+At this point it's possible to proceed with the installation of ``elpa``.
-the key that appears in the query (in this case ``'lapack'``) is attached to the
-returned item. When, later on, you access any of the build-interface attributes, this
-key is used to compute the result according to the following algorithm:
+----------------------
+Other Packaging Topics
+----------------------
-.. code-block:: none
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Attach attributes to other packages
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Given any pair of <query-key> and <build-attribute>:
+Build tools usually also provide a set of executables that can be used
+when another package is being installed. Spack gives the opportunity
+to monkey-patch dependent modules and attach attributes to them. This
+helps make the packager experience as similar as possible to what would
+have been the manual installation of the same package.
- 1. If <query-key> is the name of a virtual spec and the package
- providing it has an attribute named '<query-key>_<build-attribute>'
- return it
+An example here is the ``automake`` package, which overrides
+:py:func:`setup_dependent_package <spack.package.PackageBase.setup_dependent_package>`:
- 2. Otherwise if the package has an attribute named '<build-attribute>'
- return that
+.. code-block:: python
- 3. Otherwise use the default handler for <build-attribute>
+ def setup_dependent_package(self, module, dependent_spec):
+ # Automake is very likely to be a build dependency,
+ # so we add the tools it provides to the dependent module
+ executables = ['aclocal', 'automake']
+ for name in executables:
+ setattr(module, name, self._make_executable(name))
-Going back to our concrete case this means that, if the spec providing LAPACK
-is ``netlib-lapack``, we are returning the value computed in the ``lapack_libs``
-property. If it is ``openblas``, we are instead resorting to the default handler
-for ``libs`` (which searches for the presence of ``libopenblas`` in the
-installation prefix).
+so that every other package that depends on it can use directly ``aclocal``
+and ``automake`` with the usual function call syntax of :py:class:`Executable <spack.util.executable.Executable>`:
-.. note::
+.. code-block:: python
- Types commonly returned by build-interface attributes
- Even though there's no enforcement on it, the type of the objects returned most often when
- asking for the ``libs`` attributes is :py:class:`LibraryList <llnl.util.filesystem.LibraryList>`.
- Similarly the usual type returned for ``headers`` is :py:class:`HeaderList <llnl.util.filesystem.HeaderList>`,
- while for ``command`` is :py:class:`Executable <spack.util.executable.Executable>`. You can refer to
- these objects' API documentation to discover more about them.
+ aclocal('--force')
^^^^^^^^^^^^^^^^^^^^^^^
Extra query parameters
@@ -357,207 +510,3 @@ complete the installation of ``netcdf``:
==> Successfully installed netcdf
Fetch: 0.01s. Build: 24.61s. Total: 24.62s.
[+] /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/netcdf-4.4.1.1-gk2xxhbqijnrdwicawawcll4t3c7dvoj
-
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Single package providing multiple virtual specs
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-At the close of this tutorial's subsection, it may be useful to see where the
-build-interface protocol shines the most i.e. when it comes to manage packages
-that provide more than one virtual spec. An example of a package of this kind is
-``intel-parallel-studio``, and due to its complexity we'll limit our discussion
-here to just a few considerations (without any hands-on). You can open
-the related ``package.py`` in the usual way:
-
-.. code-block:: console
-
- root@advanced-packaging-tutorial:/# spack edit intel-parallel-studio
-
-As you can see this package provides a lot of virtual specs, and thus it has
-more than one function that enters into the build-interface protocol. These
-functions will be invoked for *exactly the same spec* according to the key used
-by its dependents in the subscript query.
-
-So, for instance, the ``blas_libs`` property will be returned when
-``intel-parallel-studio`` is the BLAS provider in the current DAG and
-is retrieved by a dependent with:
-
-.. code-block:: python
-
- blas = self.spec['blas']
- blas_libs = blas.libs
-
-Within the property we inspect various aspects of the current spec:
-
-.. code-block:: python
-
- @property
- def blas_libs(self):
- spec = self.spec
- prefix = self.prefix
- shared = '+shared' in spec
-
- if '+ilp64' in spec:
- mkl_integer = ['libmkl_intel_ilp64']
- else:
- mkl_integer = ['libmkl_intel_lp64']
- ...
-
-and construct the list of library we need to return accordingly.
-
-What we achieved is that the complexity of dealing with ``intel-parallel-studio``
-is now gathered in the package itself, instead of being spread
-all over its possible dependents.
-Thus, a package that uses MPI or LAPACK doesn't care which implementation it uses,
-as each virtual dependency has
-*a uniform interface* to ask for libraries or headers and manipulate them.
-The packages that provide this virtual spec, on the other hand, have a clear
-way to differentiate their answer to the query [#uniforminterface]_.
-
-.. [#uniforminterface] Before this interface was added, each package that
- depended on MPI or LAPACK had dozens of lines of code copied from other
- packages telling it where to find the libraries and what they are called.
- With the addition of this interface, the virtual dependency itself tells
- other packages that depend on it where it can find its libraries.
-
----------------------------
-Package's build environment
----------------------------
-
-Besides Spec's build interface, Spack provides means to set environment
-variables, either for yourself or for your dependent packages, and to
-attach attributes to your dependents. We'll see them next with the help
-of a few real use cases.
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Set variables at build-time for yourself
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Spack provides a way to manipulate a package's build time and
-run time environments using the
-:py:func:`setup_environment <spack.package.PackageBase.setup_environment>` function.
-Let's try to see how it works by completing the ``elpa`` package:
-
-.. code-block:: console
-
- root@advanced-packaging-tutorial:/# spack edit elpa
-
-In the end your method should look like:
-
-.. code-block:: python
-
- def setup_environment(self, spack_env, run_env):
- spec = self.spec
-
- spack_env.set('CC', spec['mpi'].mpicc)
- spack_env.set('FC', spec['mpi'].mpifc)
- spack_env.set('CXX', spec['mpi'].mpicxx)
- spack_env.set('SCALAPACK_LDFLAGS', spec['scalapack'].libs.joined())
-
- spack_env.append_flags('LDFLAGS', spec['lapack'].libs.search_flags)
- spack_env.append_flags('LIBS', spec['lapack'].libs.link_flags)
-
-The two arguments, ``spack_env`` and ``run_env``, are both instances of
-:py:class:`EnvironmentModifications <spack.environment.EnvironmentModifications>` and
-permit you to register modifications to either the build-time or the run-time
-environment of the package, respectively.
-At this point it's possible to proceed with the installation of ``elpa``:
-
-.. code-block:: console
-
- root@advanced-packaging-tutorial:/# spack install elpa
- ==> pkg-config is already installed in /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/pkg-config-0.29.2-ae2hwm7q57byfbxtymts55xppqwk7ecj
- ==> ncurses is already installed in /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/ncurses-6.0-ukq4tccptm2rxd56d2bumqthnpcjzlez
- ...
- ==> Executing phase: 'build'
- ==> Executing phase: 'install'
- ==> Successfully installed elpa
- Fetch: 3.94s. Build: 41.93s. Total: 45.87s.
- [+] /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/elpa-2016.05.004-sdbfhwcexg7s2zqf52vssb762ocvklbu
-
-If you had modifications to ``run_env``, those would have appeared e.g. in the module files
-generated for the package.
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Set variables in dependencies at build-time
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Another common occurrence, particularly for packages like ``r`` and ``python``
-that support extensions and for packages that provide build tools,
-is to require *their dependents* to have some environment variables set.
-
-The mechanism is similar to what we just saw, except that we override the
-:py:func:`setup_dependent_environment <spack.package.PackageBase.setup_dependent_environment>`
-function, which takes one additional argument, i.e. the dependent spec that needs the modified
-environment. Let's practice completing the ``mpich`` package:
-
-.. code-block:: console
-
- root@advanced-packaging-tutorial:/# spack edit mpich
-
-Once you're finished the method should look like this:
-
-.. code-block:: python
-
- def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
- spack_env.set('MPICC', join_path(self.prefix.bin, 'mpicc'))
- spack_env.set('MPICXX', join_path(self.prefix.bin, 'mpic++'))
- spack_env.set('MPIF77', join_path(self.prefix.bin, 'mpif77'))
- spack_env.set('MPIF90', join_path(self.prefix.bin, 'mpif90'))
-
- spack_env.set('MPICH_CC', spack_cc)
- spack_env.set('MPICH_CXX', spack_cxx)
- spack_env.set('MPICH_F77', spack_f77)
- spack_env.set('MPICH_F90', spack_fc)
- spack_env.set('MPICH_FC', spack_fc)
-
-At this point we can, for instance, install ``netlib-scalapack``:
-
-.. code-block:: console
-
- root@advanced-packaging-tutorial:/# spack install netlib-scalapack ^mpich
- ...
- ==> Created stage in /usr/local/var/spack/stage/netlib-scalapack-2.0.2-km7tsbgoyyywonyejkjoojskhc5knz3z
- ==> No patches needed for netlib-scalapack
- ==> Building netlib-scalapack [CMakePackage]
- ==> Executing phase: 'cmake'
- ==> Executing phase: 'build'
- ==> Executing phase: 'install'
- ==> Successfully installed netlib-scalapack
- Fetch: 0.01s. Build: 3m 59.86s. Total: 3m 59.87s.
- [+] /usr/local/opt/spack/linux-ubuntu16.04-x86_64/gcc-5.4.0/netlib-scalapack-2.0.2-km7tsbgoyyywonyejkjoojskhc5knz3z
-
-
-and double check the environment logs to verify that every variable was
-set to the correct value. More complicated examples of the use of this function
-may be found in the ``r`` and ``python`` package.
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Attach attributes to other packages
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Build tools usually also provide a set of executables that can be used
-when another package is being installed. Spack gives the opportunity
-to monkey-patch dependent modules and attach attributes to them. This
-helps make the packager experience as similar as possible to what would
-have been the manual installation of the same package.
-
-An example here is the ``automake`` package, which overrides
-:py:func:`setup_dependent_package <spack.package.PackageBase.setup_dependent_package>`:
-
-.. code-block:: python
-
- def setup_dependent_package(self, module, dependent_spec):
- # Automake is very likely to be a build dependency,
- # so we add the tools it provides to the dependent module
- executables = ['aclocal', 'automake']
- for name in executables:
- setattr(module, name, self._make_executable(name))
-
-so that every other package that depends on it can use directly ``aclocal``
-and ``automake`` with the usual function call syntax of :py:class:`Executable <spack.util.executable.Executable>`:
-
-.. code-block:: python
-
- aclocal('--force') \ No newline at end of file