add env auto-gen hook and associated files

.conda-extra-dependencies.yml

@@ -0,0 +1,3 @@
+- openblas
+- pip
+- spyder-kernels >= 1.10.0

.pre-commit-config.yaml

@@ -64,10 +64,18 @@ repos:
         files: pyproject.toml
 
   # dependencies
+  - repo: local
+    hooks:
+      - id: update-env-file
+        name: Copy dependency changes from pyproject.toml to environment.yml
+        language: python
+        entry: ./tools/hooks/update_environment_file.py
+        files: pyproject.toml
+        additional_dependencies: ["PyYAML"]
   - repo: local
     hooks:
       - id: dependency-sync
-        name: Sync dependency list between pyproject.toml and README.rst
+        name: Copy core dependencies from pyproject.toml to README.rst
         language: python
         entry: ./tools/hooks/sync_dependencies.py
         files: pyproject.toml

tools/hooks/update_environment_file.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+# Authors: The MNE-Python contributors.
+# License: BSD-3-Clause
+# Copyright the MNE-Python contributors.
+
+from pathlib import Path
+
+import tomllib
+import yaml
+
+repo_root = Path(__file__).resolve().parents[2]
+with open(repo_root / "pyproject.toml", "rb") as fid:
+    pyproj = tomllib.load(fid)
+
+# Get our "full" dependences from `pyproject.toml`, but actually ignore the
+# "full" section as it's just "full-noqt" plus PyQt6, and for conda we need PySide
+ignore = ("dev", "doc", "test", "test_extra", "full", "full-pyqt6")
+deps = set(pyproj["project"]["dependencies"])
+for section, section_deps in pyproj["project"]["optional-dependencies"].items():
+    if section not in ignore:
+        deps |= set(section_deps)
+recursive_deps = set(d for d in deps if d.startswith("mne["))
+deps -= recursive_deps
+
+# python version
+req_python = "".join(pyproj["project"]["requires-python"].split())
+py_spec = f"python {req_python}"
+
+# load extra packages that *can't* be in `pyproject.toml`
+with open(".conda-extra-dependencies.yml") as fid:
+    deps |= set(yaml.safe_load(fid))
+
+# handle package name differences, and split package name from version spec
+translations = dict(neo="python-neo")
+pip_deps = set()
+conda_deps = set()
+for dep in deps:
+    package_name, version_spec, *_ = [*dep.split(maxsplit=1), ""]
+    package_name = translations.get(package_name, package_name)
+    # collapse spaces in version spec (cf. https://docs.conda.io/projects/conda/en/latest/user-guide/concepts/pkg-specs.html#package-match-specifications)  # noqa E501
+    version_spec = "".join(version_spec.split())
+    line = f"  - {package_name} {version_spec}".rstrip()
+    # use pip for anything that needs e.g. `platform_system=='Darwin'` triaging
+    if "platform_system" in version_spec:
+        pip_deps.add(f"    {line}")
+    else:
+        conda_deps.add(line)
+
+# prepare the pip dependencies section
+pip_section = f"""\
+  - pip:
+{"\n".join(sorted(pip_deps, key=str.casefold))}
+"""
+pip_section = pip_section if len(pip_deps) else ""
+# prepare the env file
+env = f"""\
+name: mne
+channels:
+  - conda-forge
+dependencies:
+  - {py_spec}
+{"\n".join(sorted(conda_deps, key=str.casefold))}
+{pip_section}"""
+
+with open(repo_root / "environment.yml", "w") as fid:
+    fid.write(env)