Custom Transpiler Stage Plugin (layout) not showing

[iyanmv]

Environment

• Qiskit version: 1.1.0
• Python version: 3.11.8

What is happening?

I tried to create a custom layout plugin following this documentation. My custom layout did not appear when executing list_stage_plugins("layout") so I tried to to use the exact same example provided in the documentation. I created a python package, a pyproject.toml, etc. I install the new package without issues, but the plugin is still not listed with list_stage_plugins("layout").

This is the structure of my package:

pyproject.toml
src/
   qiskit_custom_layout
      __init__.py
      custom_layout_plugin.py

In the module custom_layout_plugin.py I copy-paste the example from the docs. And this is my pyproject.toml:

[project]
name = "qiskit-custom-layout"
version = "0.1.0"
description = "A transpiler stage plugin that implements a custom layout"
authors = [
    {name = "Iyán Méndez Veiga", email = "me@iyanmv.com"},
]
dependencies = [
    "qiskit>=1.0.0",
    "gmpy2>=2.1.5",
]
requires-python = ">=3.8"
readme = "README.md"
license = {text = "MIT"}

[project.entry-points."qiskit.transpiler.layout"]
custom_layout = "custom_layout_plugin:VF2LayoutPlugin"

I tried both with custom_layout and "custom_layout" as in the Qiskit docs the entry point variable is done with quotes but in the setuptools docs is always without, but it doesn't make a difference.

Am I doing something wrong?

How can we reproduce the issue?

Try to create a custom plugin exactly as described in the documentation.

What should happen?

Custom layout plugin should appear.

Any suggestions?

No response

[jakelishman]

In your entry point, you've not included the name of your package in the lookup path for the object. Your Python package is saying it's installing something that's called qiskit_custom_layout, so the plugin object is (presumably) found at qiskit_custom_layout.custom_layout_plugin.VF2LayoutPlugin.

[iyanmv]

In your entry point, you've not included the name of your package in the lookup path for the object. Your Python package is saying it's installing something that's called qiskit_custom_layout, so the plugin object is (presumably) found at qiskit_custom_layout.custom_layout_plugin.VF2LayoutPlugin.

Thanks for the quick answer! I just tried but it still doesn't work.

Oh, and I forgot to share before the contents of the __init__.py. I simply added this for the test:

from .custom_layout_plugin import VF2LayoutPlugin

[jakelishman]

Did you pip install again after you'd changed it? If you're ever changing plugins / entry points, you'll need to do that quite a lot, because you have to get the Python virtual environment to rewrite the metadata.

If you've updated the __init__.py file to that, then the shortest way you could write the entry point would be to have it set to

custom_layout = "qiskit_custom_layout.VF2LayoutPlugin"

I think.

[iyanmv]

Did you pip install again after you'd changed it? If you're ever changing plugins / entry points, you'll need to do that quite a lot, because you have to get the Python virtual environment to rewrite the metadata.

Yes, I'm running pip install . after each change.

If you've updated the __init__.py file to that, then the shortest way you could write the entry point would be to have it set to

No, this is what I had from the beginning, I just forgot to include it in the issue.

custom_layout = "qiskit_custom_layout.VF2LayoutPlugin"

Okay, let me try this :crossed_fingers:

[iyanmv]

Nothing... but if I run this

from importlib.metadata import entry_points
display_eps = entry_points(group="qiskit.transpiler.layout")
print(display_eps)

I can correctly see my custom entry point.

[EntryPoint(name='custom_layout', value='qiskit_custom_layout.VF2LayoutPlugin', group='qiskit.transpiler.layout'), EntryPoint(name='default', value='qiskit.transpiler.preset_passmanagers.builtin_plugins:DefaultLayoutPassManager', group='qiskit.transpiler.layout'), EntryPoint(name='dense', value='qiskit.transpiler.preset_passmanagers.builtin_plugins:DenseLayoutPassManager', group='qiskit.transpiler.layout'), EntryPoint(name='sabre', value='qiskit.transpiler.preset_passmanagers.builtin_plugins:SabreLayoutPassManager', group='qiskit.transpiler.layout'), EntryPoint(name='trivial', value='qiskit.transpiler.preset_passmanagers.builtin_plugins:TrivialLayoutPassManager', group='qiskit.transpiler.layout')]

[iyanmv]

Oh, now it worked! I had to write this:

[project.entry-points."qiskit.transpiler.layout"]
custom_layout = "qiskit_custom_layout:VF2LayoutPlugin"

Note the : instead of . to select the class.

Thanks for the help! I never worked with entry points so I was a bit confused (I still am :sweat_smile: )

[jakelishman]

Ahh thanks yeah, I'd missed the colon vs dot too sorry.