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Sep 27, 2020
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Improve docs about plugin discovery/loading at startup #7748

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Improve docs about plugin discovery/loading at startup
nicoddemus Sep 12, 2020
7324e90
Update doc/en/writing_plugins.rst
nicoddemus Sep 19, 2020
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36 changes: 22 additions & 14 deletions doc/en/writing_plugins.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -33,26 +33,34 @@ Plugin discovery order at tool startup

``pytest`` loads plugin modules at tool startup in the following way:

* by loading all builtin plugins
1. by scanning the command line for the ``-p no:name`` option
and *blocking* that plugin from being loaded (even builtin plugins can
be blocked this way). This happens before normal command-line parsing.

* by loading all plugins registered through `setuptools entry points`_.
2. by loading all builtin plugins.

* by pre-scanning the command line for the ``-p name`` option
and loading the specified plugin before actual command line parsing.
3. by scanning the command line for the ``-p name`` option
and loading the specified plugin. This happens before normal command-line parsing.

* by loading all :file:`conftest.py` files as inferred by the command line
invocation:
4. by loading all plugins registered through `setuptools entry points`_.

- if no test paths are specified use current dir as a test path
- if exists, load ``conftest.py`` and ``test*/conftest.py`` relative
to the directory part of the first test path.
5. by loading all plugins specified through the :envvar:`PYTEST_PLUGINS` environment variable.

Note that pytest does not find ``conftest.py`` files in deeper nested
sub directories at tool startup. It is usually a good idea to keep
your ``conftest.py`` file in the top level test or project root directory.
6. by loading all :file:`conftest.py` files as inferred by the command line
invocation:

* by recursively loading all plugins specified by the
:globalvar:`pytest_plugins` variable in ``conftest.py`` files
- if no test paths are specified use current dir as a test path
- if exists, load ``conftest.py`` and ``test*/conftest.py`` relative
to the directory part of the first test path. After the ``conftest.py``
Comment on lines +53 to +54
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Is this really how it works?? (The test*/conftest.py part, and the "first test path" part)

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Good catch, this was copied from the previous text.

No I don't think that's how it works, I will double check and update the text accordingly.

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Oh wow, it actually works this way:

pytest/src/_pytest/config/__init__.py

Lines 505 to 513 in d3f47bf

def _try_load_conftest(
self, anchor: py.path.local, importmode: Union[str, ImportMode]
) -> None:
self._getconftestmodules(anchor, importmode)
# let's also consider test* subdirs
if anchor.check(dir=1):
for x in anchor.listdir("test*"):
if x.check(dir=1):
self._getconftestmodules(x, importmode)

So that's correct.

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Eeek

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I concur... 😬

file is loaded, load all plugins specified in its
:globalvar:`pytest_plugins` variable if present.

Note that pytest does not find ``conftest.py`` files in deeper nested
sub directories at tool startup. It is usually a good idea to keep
your ``conftest.py`` file in the top level test or project root directory.

7. by recursively loading all plugins specified by the
:globalvar:`pytest_plugins` variable in ``conftest.py`` files.


.. _`pytest/plugin`: http://bitbucket.org/pytest-dev/pytest/src/tip/pytest/plugin/
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