drop black and flake8 dependencies

.cirrus.yml

@@ -37,7 +37,7 @@ env:
   # Increment the build number to force new pip cache upload.
   PIP_CACHE_BUILD: "0"
   # Pip packages to be upgraded/installed.
-  PIP_CACHE_PACKAGES: "pip setuptools wheel nox"
+  PIP_CACHE_PACKAGES: "nox pip setuptools wheel"
   # Conda packages to be installed.
   CONDA_CACHE_PACKAGES: "nox pip"
   # Git commit hash for iris test data.
@@ -116,7 +116,7 @@ lint_task:
     image: python:3.8
     cpu: 2
     memory: 4G
-  name: "${CIRRUS_OS}: black, flake8 and isort"
+  name: "${CIRRUS_OS}: linting"
   pip_cache:
     folder: ~/.cache/pip
     fingerprint_script:
@@ -126,9 +126,7 @@ lint_task:
     - pip list
     - python -m pip install --retries 3 --upgrade ${PIP_CACHE_PACKAGES}
     - pip list
-    - nox --session black
-    - nox --session flake8
-    - nox --session isort
+    - nox --session lint
 
 
 #

.pre-commit-config.yaml

@@ -2,7 +2,7 @@
 # See https://pre-commit.com/hooks.html for more hooks
 repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: 'v4.0.1'
+    rev: "v4.0.1"
     hooks:
         # Prevent giant files from being committed.
     -   id: check-added-large-files
@@ -17,24 +17,24 @@ repos:
         # Don't commit to main branch.
     -   id: no-commit-to-branch
 -   repo: https://github.com/psf/black
-    rev: '21.6b0'
+    rev: "21.6b0"
     hooks:
     -   id: black
-        # Force black to run on whole repo, using settings from pyproject.toml
         pass_filenames: false
-        args: [--config=./pyproject.toml, .]
+        args: ["--config=./pyproject.toml", "--check", "docs", "lib", "noxfile.py", "setup.py"]
 -   repo: https://github.com/PyCQA/flake8
-    rev: '3.9.2'
+    rev: "3.9.2"
     hooks:
-        # Run flake8.
     -   id: flake8
-        args: [--config=./setup.cfg]
+        args: ["--config=./setup.cfg", "docs", "lib", "noxfile.py", "setup.py"]
 -   repo: https://github.com/pycqa/isort
-    rev: 5.9.1
+    rev: "5.9.1"
     hooks:
     -   id: isort
+        # Align CLI usage with other hooks, rather than use isort "src_paths" option
+        # in the pyproject.toml configuration.
         name: isort
-        args: ["--filter-files"]
+        args: ["--filter-files", "--check", "docs", "lib", "noxfile.py", "setup.py"]
 -   repo: https://github.com/asottile/blacken-docs
     rev: v1.8.0
     hooks:

docs/src/whatsnew/latest.rst

@@ -86,7 +86,8 @@ This document explains the changes made to Iris for this release
 🔗 Dependencies
 ===============
 
-#. N/A
+#. `@bjlittle`_ dropped both `black`_ and `flake8`_ package dependencies
+   from our `conda`_ YAML and ``setup.cfg`` PyPI requirements. (:pull:`4181`)
 
 
 📚 Documentation
@@ -128,7 +129,6 @@ This document explains the changes made to Iris for this release
    they render better in the published documentation.  See :issue:`4085`.
    (:pull:`4100`)
 
-
 💼 Internal
 ===========
 
@@ -187,6 +187,9 @@ This document explains the changes made to Iris for this release
 #. `@bjlittle`_ added the `blacken-docs`_ ``pre-commit`` hook to automate
    ``black`` linting of documentation code blocks. (:pull:`4205`)
 
+#. `@bjlittle`_ consolidated `nox`_ ``black``, ``flake8`` and ``isort`` sessions
+   into one ``lint`` session using ``pre-commit``. (:pull:`4181`)
+
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
     core dev names are automatically included by the common_links.inc:

noxfile.py

@@ -15,12 +15,6 @@
 #: Default to reusing any pre-existing nox environments.
 nox.options.reuse_existing_virtualenvs = True
 
-#: Root directory.
-ROOT_DIR = Path(__file__).resolve().parent
-
-#: Name of the package to test.
-PACKAGE = str(ROOT_DIR / "lib" / "iris")
-
 #: Cirrus-CI environment variable hook.
 PY_VER = os.environ.get("PY_VER", ["3.7", "3.8"])
 
@@ -162,49 +156,9 @@ def prepare_venv(session: nox.sessions.Session) -> None:
 
 
 @nox.session
-def flake8(session: nox.sessions.Session):
-    """
-    Perform flake8 linting of iris.
-
-    Parameters
-    ----------
-    session: object
-        A `nox.sessions.Session` object.
-
-    """
-    # Pip install the session requirements.
-    session.install("flake8")
-    # Execute the flake8 linter on the package.
-    session.run("flake8", PACKAGE)
-    # Execute the flake8 linter on root Python files.
-    for fname in ROOT_DIR.glob("*.py"):
-        session.run("flake8", str(fname))
-
-
-@nox.session
-def black(session: nox.sessions.Session):
-    """
-    Perform black format checking of iris.
-
-    Parameters
-    ----------
-    session: object
-        A `nox.sessions.Session` object.
-
-    """
-    # Pip install the session requirements.
-    session.install("black==21.5b2")
-    # Execute the black format checker on the package.
-    session.run("black", "--check", PACKAGE)
-    # Execute the black format checker on root Python files.
-    for fname in ROOT_DIR.glob("*.py"):
-        session.run("black", "--check", str(fname))
-
-
-@nox.session
-def isort(session: nox.sessions.Session):
+def lint(session: nox.sessions.Session):
     """
-    Perform isort import checking of iris codebase.
+    Perform pre-commit linting of iris codebase.
 
     Parameters
     ----------
@@ -213,14 +167,12 @@ def isort(session: nox.sessions.Session):
 
     """
     # Pip install the session requirements.
-    session.install("isort")
-    # Execute the isort import checker on the package.
-    session.run("isort", "--check", str(PACKAGE))
-    # Execute the isort import checker on the documentation.
-    session.run("isort", "--check", str(ROOT_DIR / "docs"))
-    # Execute the isort import checker on the root Python files.
-    for fname in ROOT_DIR.glob("*.py"):
-        session.run("isort", "--check", str(fname))
+    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)
 
 
 @nox.session(python=PY_VER, venv_backend="conda")

pyproject.toml

@@ -1,3 +1,14 @@
+[build-system]
+# Defined by PEP 518
+requires = [
+  "scitools-pyke",
+  "setuptools>=40.8.0",
+  "wheel",
+]
+# Defined by PEP 517
+build-backend = "setuptools.build_meta"
+
+
 [tool.black]
 line-length = 79
 target-version = ['py37', 'py38']
@@ -29,15 +40,6 @@ exclude = '''
 )
 '''
 
-[build-system]
-# Defined by PEP 518
-requires = [
-  "scitools-pyke",
-  "setuptools>=40.8.0",
-  "wheel",
-]
-# Defined by PEP 517
-build-backend = "setuptools.build_meta"
 
 [tool.isort]
 force_sort_within_sections = "True"
@@ -53,4 +55,10 @@ extend_skip = [
   "tools",
 ]
 skip_gitignore = "True"
+src_paths = [
+  "docs",
+  "lib",
+  "noxfile.py",
+  "setup.py",
+]
 verbose = "False"

requirements/ci/py37.yml

@@ -34,9 +34,7 @@ dependencies:
 
 # Test dependencies.
   - asv
-  - black=21.5b2
   - filelock
-  - flake8
   - imagehash>=4.0
   - nose
   - pillow<7

requirements/ci/py38.yml

@@ -34,9 +34,7 @@ dependencies:
 
 # Test dependencies.
   - asv
-  - black=21.5b2
   - filelock
-  - flake8
   - imagehash>=4.0
   - nose
   - pillow<7

setup.cfg

@@ -77,9 +77,7 @@ docs =
     sphinx-panels
 test =
     asv
-    black==21.5b2
     filelock
-    flake8
     imagehash>=4.0
     nose
     pillow<7