pre-commit isort and black --check only for cirrus-ci (#4235)

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

* run discovered hooks, with exclusion

* review actions

* match on pre-commit hook id

* add clarifying comment to nox

* support pre-commit excluded hooks

* rebrand lint to precommit

.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.
@@ -105,25 +105,25 @@ iris_test_data_template: &IRIS_TEST_DATA_TEMPLATE
 #
 # Linting
 #
-lint_task:
+precommit_task:
   only_if: ${SKIP_LINT_TASK} == ""
   << : *CREDITS_TEMPLATE
   auto_cancellation: true
   container:
     image: python:3.8
     cpu: 2
     memory: 4G
-  name: "${CIRRUS_OS}: linting"
+  name: "${CIRRUS_OS}: pre-commit hooks"
   pip_cache:
     folder: ~/.cache/pip
     fingerprint_script:
       - echo "${CIRRUS_TASK_NAME} py${PYTHON_VERSION}"
       - echo "$(date +%Y).$(expr $(date +%U) / ${CACHE_PERIOD}):${PIP_CACHE_BUILD} ${PIP_CACHE_PACKAGES}"
-  lint_script:
+  precommit_script:
     - pip list
     - python -m pip install --retries 3 --upgrade ${PIP_CACHE_PACKAGES}
     - pip list
-    - nox --session lint
+    - nox --session precommit
 
 
 #

.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

@@ -163,23 +163,38 @@ def prepare_venv(session: nox.sessions.Session) -> None:
 
 
 @nox.session
-def lint(session: nox.sessions.Session):
+def precommit(session: nox.sessions.Session):
     """
-    Perform pre-commit linting of iris codebase.
+    Perform pre-commit hooks of iris codebase.
 
     Parameters
     ----------
     session: object
         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"]
-    for hook in hooks:
-        session.run(*cmd, hook)
+
+    # Load the pre-commit configuration YAML file.
+    with open(".pre-commit-config.yaml", "r") as fi:
+        config = yaml.load(fi, Loader=yaml.FullLoader)
+
+    # List of pre-commit hook ids that we don't want to run.
+    excluded = ["no-commit-to-branch"]
+
+    # Enumerate the ids of pre-commit hooks we do want to run.
+    ids = [
+        hook["id"]
+        for entry in config["repos"]
+        for hook in entry["hooks"]
+        if hook["id"] not in excluded
+    ]
+
+    # Execute the pre-commit hooks.
+    [session.run("pre-commit", "run", "--all-files", id) for id in ids]
 
 
 @nox.session(python=PY_VER, venv_backend="conda")