Use pytest_collection_modifyitems in a plugin

[mdhaisne]

Hello everyone,
I'm trying to create a pytest plugin on my own but my hook pytest_collection_modifyitems is neved called (at least seems like).
Below a bit of code:

foo_plugin.py

class FooPlugin:
    def __init__(self, config: Config) -> None:
        self.config = config

    @hookimpl
    def pytest_collection_modifyitems(self, config: Config, items: List[Item]) -> None:
        for item in items:
            item.add_marker("foo")

    @hookimpl
    def pytest_configure(self, config: Config) -> None:
        line = f"foo(): Mark a test as a member of foo."
        config.addinivalue_line("markers", line)

plugin.py (entrypoint)

from foo_plugin import FooPlugin

def pytest_configure(config: Config) -> None:
    fp= FooPlugin(config)
    config.pluginmanager.register(fp, "FooPlugin")

I've a small test using pytester and added breakpoint in both pytest_configure and pytest_collection_modifyitems. pytest_configure is called without problem and does it job. But my breakpoints in pytest_collection_modifyitems are never triggered.
What am I missing here ?

Thanks for your help

[The-Compiler]

Works for me (with your plugin.py as conftest.py). Can you try inserting a 1/0 there to make sure it's really not triggered? With a pytest --debug you should get a pytestdebug.log which could tell you more.

[mdhaisne]

Okay that was a mistake on my side ups.

I had this code

def pytest_configure(config: Config) -> None:
    if config.getoption("foo"):
        fp= FooPlugin(config)
        config.pluginmanager.register(fp, "FooPlugin")

But I've oversimplified it because I thought that the if condition couldn't have been the cause of my issue. I should have shared the full code because the error wasn't in what I've shared.

My problem got fixed by removing the if statement. Sorry for the errors, the fault on me.

Thank you for your fast reply, appreciate it.