Custom Extensions¶
Spack extensions permit you to extend Spack capabilities by deploying your own custom commands or logic in an arbitrary location on your filesystem. This might be extremely useful e.g. to develop and maintain a command whose purpose is too specific to be considered for reintegration into the mainline or to evolve a command through its early stages before starting a discussion to merge it upstream. From Spack’s point of view an extension is any path in your filesystem which respects a prescribed naming and layout for files:
spack-scripting/ # The top level directory must match the format 'spack-{extension_name}'
├── pytest.ini # Optional file if the extension ships its own tests
├── scripting # Folder that may contain modules that are needed for the extension commands
│ └── cmd # Folder containing extension commands
│ └── filter.py # A new command that will be available
├── tests # Tests for this extension
│ ├── conftest.py
│ └── test_filter.py
└── templates # Templates that may be needed by the extension
In the example above the extension named scripting adds an additional command (filter
)
and unit tests to verify its behavior. The code for this example can be
obtained by cloning the corresponding git repository:
$ cd ~/
$ mkdir tmp && cd tmp
$ git clone https://github.com/alalazo/spack-scripting.git
Cloning into 'spack-scripting'...
remote: Counting objects: 11, done.
remote: Compressing objects: 100% (7/7), done.
remote: Total 11 (delta 0), reused 11 (delta 0), pack-reused 0
Receiving objects: 100% (11/11), done.
As you can see by inspecting the sources, Python modules that are part of the extension can import any core Spack module.
Configure Spack to Use Extensions¶
To make your current Spack instance aware of extensions you should add their root
paths to config.yaml
. In the case of our example this means ensuring that:
config:
extensions:
- ~/tmp/spack-scripting
is part of your configuration file. Once this is setup any command that the extension provides will be available from the command line:
$ spack filter --help
usage: spack filter [-h] [--installed | --not-installed]
[--explicit | --implicit] [--output OUTPUT]
...
filter specs based on their properties
positional arguments:
specs specs to be filtered
optional arguments:
-h, --help show this help message and exit
--installed select installed specs
--not-installed select specs that are not yet installed
--explicit select specs that were installed explicitly
--implicit select specs that are not installed or were installed implicitly
--output OUTPUT where to dump the result
The corresponding unit tests can be run giving the appropriate options
to spack unit-test
:
$ spack unit-test --extension=scripting
============================================================== test session starts ===============================================================
platform linux2 -- Python 2.7.15rc1, pytest-3.2.5, py-1.4.34, pluggy-0.4.0
rootdir: /home/mculpo/tmp/spack-scripting, inifile: pytest.ini
collected 5 items
tests/test_filter.py ...XX
============================================================ short test summary info =============================================================
XPASS tests/test_filter.py::test_filtering_specs[flags3-specs3-expected3]
XPASS tests/test_filter.py::test_filtering_specs[flags4-specs4-expected4]
=========================================================== slowest 20 test durations ============================================================
3.74s setup tests/test_filter.py::test_filtering_specs[flags0-specs0-expected0]
0.17s call tests/test_filter.py::test_filtering_specs[flags3-specs3-expected3]
0.16s call tests/test_filter.py::test_filtering_specs[flags2-specs2-expected2]
0.15s call tests/test_filter.py::test_filtering_specs[flags1-specs1-expected1]
0.13s call tests/test_filter.py::test_filtering_specs[flags4-specs4-expected4]
0.08s call tests/test_filter.py::test_filtering_specs[flags0-specs0-expected0]
0.04s teardown tests/test_filter.py::test_filtering_specs[flags4-specs4-expected4]
0.00s setup tests/test_filter.py::test_filtering_specs[flags4-specs4-expected4]
0.00s setup tests/test_filter.py::test_filtering_specs[flags3-specs3-expected3]
0.00s setup tests/test_filter.py::test_filtering_specs[flags1-specs1-expected1]
0.00s setup tests/test_filter.py::test_filtering_specs[flags2-specs2-expected2]
0.00s teardown tests/test_filter.py::test_filtering_specs[flags2-specs2-expected2]
0.00s teardown tests/test_filter.py::test_filtering_specs[flags1-specs1-expected1]
0.00s teardown tests/test_filter.py::test_filtering_specs[flags0-specs0-expected0]
0.00s teardown tests/test_filter.py::test_filtering_specs[flags3-specs3-expected3]
====================================================== 3 passed, 2 xpassed in 4.51 seconds =======================================================