Python Flake8 linter workflow to replace stickler-ci (#1786)

* adding flake8 linter workflow

* lint only changed files

* move changed files to env variable

* remove filename flag

* remove trailing dot

* rename job

* pass filenames as positional arguments

* pipe filenames to xargs

* change to check pvlib repo

* only lint python files

* missing parenthesis

* skip linting if no Python files edited

* try env instead of output

* reformatting

* create lint issues to try out the new linter

* Revert "create lint issues to try out the new linter"

This reverts commit 31cbb3b.

* create a lint issue in a file with other lint issues

* use flake8 --diff with flake8 5.0.4

* call to git fetch

* use GITHUB_TOKEN for fetching

* set repository read permission

* try using https link to repo instead of ssh

* test if GITHUB_TOKEN permissions are not needed

* add temporary example of linting annotations

* breaking workflow command into more steps

* use base ref variable instead of hard-coding main branch

* update whatsnew and remove lint error example

---------

Co-authored-by: Kevin Anderson <[email protected]>

Author: reepoi

.github/workflows/flake8-linter-matcher.json

@@ -0,0 +1,17 @@
+{
+    "problemMatcher": [
+        {
+            "owner": "flake8-linter-error",
+            "severity": "error",
+            "pattern": [
+                {
+                    "regexp": "^([^:]+):(\\d+):(\\d+):\\s+([EWCNF]\\d+\\s+.+)$",
+                    "file": 1,
+                    "line": 2,
+                    "column": 3,
+                    "message": 4
+                }
+            ]
+        }
+    ]
+}

.github/workflows/flake8.yml

@@ -0,0 +1,27 @@
+name: Python Flake8 Linter
+on:
+  pull_request:
+jobs:
+  flake8-linter:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v3
+      - name: Install Python 3.11
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+      - name: Install Flake8 5.0.4 linter
+        run: pip install flake8==5.0.4  # use this version for --diff option
+      - name: Setup Flake8 output matcher for PR annotations
+        run: echo '::add-matcher::.github/workflows/flake8-linter-matcher.json'
+      - name: Fetch pull request target branch
+        run: |
+          git remote add upstream https://github.com/pvlib/pvlib-python.git
+          git fetch upstream $GITHUB_BASE_REF
+      - name: Run Flake8 linter
+        run: git diff upstream/$GITHUB_BASE_REF HEAD | flake8
+          --exclude pvlib/version.py
+          --ignore E201,E241,E226,W503,W504
+          --max-line-length 79
+          --diff

docs/sphinx/source/whatsnew/v0.10.2.rst

@@ -23,7 +23,8 @@ Bug fixes
 
 Testing
 ~~~~~~~
-
+* Added GitHub action to lint file changes with Flake8, replacing Stickler-CI.
+  (:issue:`776`, :issue:`1722`, :pull:`1786`)
 
 Documentation
 ~~~~~~~~~~~~~
@@ -37,3 +38,4 @@ Requirements
 Contributors
 ~~~~~~~~~~~~
 * Adam R. Jensen (:ghuser:`AdamRJensen`)
+* Taos Transue (:ghuser:`reepoi`)