Don't run duplicate linters

.github/workflows/bandit.yml

@@ -4,7 +4,7 @@ name: Security check - Bandit
 on: push  # yamllint disable-line rule:truthy
 
 jobs:
-  build:
+  bandit:
     runs-on: ubuntu-latest
 
     steps:

.github/workflows/codespell.yml

@@ -0,0 +1,12 @@
+---
+name: codespell
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  codespell:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: codespell-project/actions-codespell@master

.github/workflows/flake8.yml

@@ -0,0 +1,17 @@
+---
+name: Flake8
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  flake8:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: TrueBrain/actions-flake8@v2
+        with:
+          plugins: >
+            flake8-2020>=1.6.1
+            flake8-bugbear>=22.1.11
+            flake8-comprehensions>=3.7.0

.github/workflows/isort.yml

@@ -0,0 +1,18 @@
+---
+name: isort
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  isort:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - run: pip install 'isort>=5.0.1'
+      - uses: wearerequired/[email protected]
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          isort: true
+          continue_on_error: false

.github/workflows/mypy.yml

@@ -0,0 +1,19 @@
+---
+name: mypy
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - run: pip install -U isort mypy pytest types-toml
+      - uses: wearerequired/[email protected]
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          mypy: true
+          mypy_args: "src"
+          continue_on_error: false

.github/workflows/pylint.yml

@@ -0,0 +1,18 @@
+---
+name: pylint
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  pylint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - run: pip install pylint
+      - uses: wearerequired/[email protected]
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          pylint: true
+          continue_on_error: false

.github/workflows/python-package.yml

@@ -1,5 +1,5 @@
 ---
-name: build
+name: Build and test
 
 on:  # yamllint disable-line rule:truthy
   push:
@@ -12,6 +12,34 @@ on:  # yamllint disable-line rule:truthy
 
 jobs:
 
+  build-wheel:
+    runs-on: ubuntu-latest
+    outputs:
+      wheel-path: ${{ steps.get-darker-version.outputs.wheel-path }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - name: Install wheel
+        run: python -m pip install wheel
+      - name: Build wheel distribution
+        run: python setup.py bdist_wheel
+      - name: Upload wheel for other jobs
+        uses: actions/upload-artifact@v3
+        with:
+          name: dist
+          path: dist/
+          if-no-files-found: error
+      - name: Find out Darker version and output it for test jobs
+        id: get-darker-version
+        shell: python
+        run: |
+          from runpy import run_path
+          version = run_path("src/darker/version.py")["__version__"]
+          print(
+              "::set-output name=wheel-path::"
+              f"dist/darker-{version}-py3-none-any.whl"
+          )
+
   test-nixos:
     runs-on: ${{ matrix.os }}
     strategy:
@@ -23,13 +51,15 @@ jobs:
           - os: macos-latest
             python-version: python39
             # see https://github.com/cachix/install-nix-action/issues/135
+    needs:
+      - build-wheel
     steps:
       - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
       - uses: cachix/install-nix-action@v17
         with:
           nix_path: nixpkgs=channel:nixos-21.11
+      - name: Download wheel uploaded by the build-wheel job
+        uses: actions/download-artifact@v3
       - name: Run tests in nix-shell
         run: |
           nix-shell \
@@ -38,13 +68,12 @@ jobs:
             --run '
               python -m venv venv
               source venv/bin/activate
-              pip install -e '.[isort,test]'
+              pip install "${{needs.build-wheel.outputs.wheel-path}}[test]"
               pytest
             ' \
             ./default.nix
 
-  build:
-
+  test:
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
@@ -59,7 +88,6 @@ jobs:
           - '3.9'
           - '3.10'
         constraints: ['']
-        lint: ['--darker --flake8 --isort']
         include:
           - os: ubuntu-latest
             python-version: '3.7'
@@ -68,71 +96,40 @@ jobs:
             python-version: '3.10'
             constraints: '--constraint constraints-future.txt'
             upgrade: '--upgrade --upgrade-strategy=eager'
-    env:
-      RUN_MYPY_AND_PYLINT: >-
-        ${{ matrix.python-version == '3.9' || matrix.python-version == '3.10' }}
+    needs:
+      - build-wheel
     steps:
       - uses: actions/checkout@v3
         with:
           fetch-depth: 0
-
+          # need full history since Pytest runs Darker itself below
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v3
         with:
           python-version: ${{ matrix.python-version }}
-      - name: Upgrade pip, install wheel and twine
-        run: |
-          # strict dependency resolution added in pip 20.3
-          python -m pip install --upgrade 'pip>=20.3' wheel twine
-      - name: Build source distribution
-        run: python setup.py sdist
-      - name: Build wheel distribution
-        run: python setup.py bdist_wheel
-      - name: Validate distributions
-        run: twine check dist/*
-      - name: Get Darker version
-        shell: python
-        run: |
-          from os import environ
-          from pathlib import Path
-          from runpy import run_path
-          version = run_path("src/darker/version.py")["__version__"]
-          Path(environ["GITHUB_ENV"]).write_text(f"VERSION={version}\n")
-      - name: Install Darker and its dependencies
+      - name: Download wheel uploaded by the build-wheel job
+        uses: actions/download-artifact@v3
+      - name: Install Darker and its dependencies from the wheel build earlier
         env:
           pip_options: ${{ matrix.upgrade }} ${{ matrix.constraints }}
         run: pip install ${pip_options}
-                 "dist/darker-${{ env.VERSION }}-py3-none-any.whl[isort,test]"
-      - name: Run Pytest without Mypy and Pylint if Python < 3.9
-        if: env.RUN_MYPY_AND_PYLINT == 'false'
+                 "${{needs.build-wheel.outputs.wheel-path}}[test]"
+      - name: Run Pytest
         run: |
-          pytest ${{ matrix.lint }}
-      - name: Run Pytest with Mypy and Pylint if Python >= 3.9
-        if: env.RUN_MYPY_AND_PYLINT == 'true'
-        shell: python
-        run: |
-          import sys
-          from pathlib import Path
-          from subprocess import run
-          import toml
+          pytest --darker
 
-          data = toml.load("pyproject.toml")
-          data["tool"]["darker"]["lint"] = ["pylint", "mypy"]
-          Path("pyproject.toml").write_text(toml.dumps(data))
-          pytest_cmd = ["pytest"] + "${{ matrix.lint }}".split()
-          retval = run(pytest_cmd).returncode
-          run(["git", "restore", "pyproject.toml"])
-          sys.exit(retval)
-      - name: Check English spelling in the code base using codespell
-        run: codespell
-      - name: Ensure modern Python style using pyupgrade
-        # This script is written in a Linux / macos / windows portable way
-        run: |
-          python -c "
-          from pyupgrade._main import main
-          from glob import glob
-          files = glob('**/*.py', recursive=True)
-          main(files + ['--py37-plus'])
-          "
-      - name: Check dependencies for known security vulterabilities using Safety
-        run: safety check
+  build-sdist-validate-dists:
+    runs-on: ubuntu-latest
+    needs:
+      - build-wheel
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - name: Install twine
+        run: python -m pip install twine
+      - name: Download wheel uploaded by the build-wheel job
+        uses: actions/download-artifact@v3
+      - name: Build source distribution
+        run: python setup.py sdist
+      - name: Validate distributions
+        run: twine check dist/*

.github/workflows/pyupgrade.yml

@@ -0,0 +1,23 @@
+---
+name: pyupgrade
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  pyupgrade:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - run: pip install pyupgrade
+      - name: Ensure modern Python style using pyupgrade
+        # This script is written in a Linux / macos / windows portable way
+        run: |
+          python -c "
+          import sys
+          from pyupgrade._main import main
+          from glob import glob
+          files = glob('**/*.py', recursive=True)
+          sys.exit(main(files + ['--py37-plus']))
+          " || ( git diff ; false )

.github/workflows/safety.yml

@@ -0,0 +1,15 @@
+---
+name: safety
+
+on: push  # yamllint disable-line rule:truthy
+
+jobs:
+  safety:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v3
+      - run: pip install -U safety
+      - name: Check dependencies for known security vulnerabilities using Safety
+        run: safety check

.github/workflows/test-future.yml

@@ -9,7 +9,7 @@ on:  # yamllint disable-line rule:truthy
     - cron: "05 20 * * 6"
 
 jobs:
-  build:
+  test-future:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
@@ -27,7 +27,7 @@ jobs:
             --constraint=constraints-future.txt \
             --upgrade \
             --upgrade-strategy=eager \
-            -e '.[isort,test]'
+            -e '.[test]'
       - name: Test with pytest
         run: |
           pytest

.github/workflows/yaml-lint.yml

@@ -6,7 +6,5 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
       - name: yaml-lint
         uses: ibiqlik/action-yamllint@v3

CHANGES.rst

@@ -7,6 +7,7 @@ Added
 -----
 - Add a CI workflow which verifies that the ``darker --help`` output in ``README.rst``
   is up to date.
+- Only run linters, security checks and package builds once in the CI build.
 
 Fixed
 -----

constraints-oldest.txt

@@ -4,25 +4,17 @@
 # interpreter and Python ependencies. Keep this up-to-date with minimum
 # versions in `setup.cfg`.
 airium==0.2.3
-bandit==1.7.1
 black==21.8b0
-codespell==2.1.0
 defusedxml==0.7.1
 flake8-2020==1.6.1
 flake8-bugbear==22.1.11
 flake8-comprehensions==3.7.0
-mypy==0.940
 Pygments==2.4.0
-pylint==2.13.0
 pytest==6.2.0
-pytest-flake8==1.0.6
-pytest-isort==1.1.0
 pytest-kwparametrize==0.0.3
-pyupgrade==2.31.0
 regex==2021.4.4
 requests_cache==0.7
 ruamel.yaml==0.17.21
-safety==1.10.3
 toml==0.10.0
 twine==2.0.0
 types-toml==0.10.4

pyproject.toml

@@ -15,6 +15,3 @@ src = [
     "src",
 ]
 revision = "origin/master..."
-# The empty linter list is here so `.github/workflows/python-package.yml` can
-# add Pylint in certain run configurations:
-lint = []