pre-commit isort and black --check only for cirrus-ci

.cirrus.yml

@@ -34,7 +34,7 @@ env:
   # Increment the build number to force new pip cache upload.
   PIP_CACHE_BUILD: "0"
   # Pip packages to be upgraded/installed.
-  PIP_CACHE_PACKAGES: "nox pip setuptools wheel"
+  PIP_CACHE_PACKAGES: "nox pip pyyaml setuptools wheel"
   # Conda packages to be installed.
   CONDA_CACHE_PACKAGES: "nox pip"
   # Git commit hash for iris test data.

.pre-commit-config.yaml

@@ -32,7 +32,7 @@ repos:
     hooks:
     -   id: black
         pass_filenames: false
-        args: [--config=./pyproject.toml, --check, .]
+        args: [--config=./pyproject.toml, .]
 
 -   repo: https://github.com/PyCQA/flake8
     rev: 3.9.2
@@ -46,7 +46,7 @@ repos:
     hooks:
     -   id: isort
         types: [file, python]
-        args: [--filter-files, --check]
+        args: [--filter-files]
 
 -   repo: https://github.com/asottile/blacken-docs
     rev: v1.10.0

noxfile.py

@@ -8,6 +8,8 @@
 import hashlib
 import os
 from pathlib import Path
+from tempfile import NamedTemporaryFile
+from urllib.parse import unquote, urlsplit
 
 import nox
 from nox.logger import logger
@@ -173,13 +175,34 @@ def lint(session: nox.sessions.Session):
         A `nox.sessions.Session` object.
 
     """
+    import yaml
+
     # Pip install the session requirements.
     session.install("pre-commit")
-    # Execute the pre-commit linting tasks.
-    cmd = ["pre-commit", "run", "--all-files"]
-    hooks = ["black", "blacken-docs", "flake8", "isort"]
+
+    # Load the pre-commit configuration YAML file.
+    with open(".pre-commit-config.yaml", "r") as fi:
+        config = yaml.load(fi, Loader=yaml.FullLoader)
+
+    # Ensure black and isort only perform a status check
+    # with a custom pre-commit configuration.
+    hooks = []
+    for entry in config["repos"]:
+        hook = Path(urlsplit(unquote(entry["repo"])).path).name
+        hooks.append(hook)
+        if hook in ["black", "isort"]:
+            # Enforce a "--check" for the hook.
+            entry["hooks"][0]["args"].insert(0, "--check")
+
+    with NamedTemporaryFile(mode="w+t", delete=False) as temp:
+        yaml.dump(config, temp)
+
+    # Execute the pre-commit linting tasks with the custom
+    # pre-commit configuration.
+    cmd = ["pre-commit", "run", "--all-files", f"--config={temp.name}"]
     for hook in hooks:
-        session.run(*cmd, hook)
+        if hook != "pre-commit-hooks":
+            session.run(*cmd, hook)
 
 
 @nox.session(python=PY_VER, venv_backend="conda")