feat: add linter workflow job that applies linter for the languages that are used in the repo

feat: add linter configuration and 2 test files to test the linter action

fix: remove error in python linter test file

ci: remove format checker from python

ci: add missing lowercase r extension check

fix: remove error from the R code to fix pipeline

ci: report only serious issues at R linter

refactor: remove test files

Author: Vlad-Andres

.github/workflows/lint.yml

@@ -0,0 +1,71 @@
+name: Lint
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  # detect which languages are present
+  detect:
+    runs-on: ubuntu-latest
+    outputs:
+      has-python: ${{ steps.check.outputs.has-python }}
+      has-r: ${{ steps.check.outputs.has-r }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Detect languages
+        id: check
+        run: |
+          if find . -name "*.py" ! -path "./.git/*" | grep -q .; then
+            echo "has-python=true" >> $GITHUB_OUTPUT
+          else
+            echo "has-python=false" >> $GITHUB_OUTPUT
+          fi
+
+          if find . \( -name "*.R" -o -name "*.Rmd" -o -name "*.r" -o -name "*.qmd" \) ! -path "./.git/*" | grep -q .; then
+            echo "has-r=true" >> $GITHUB_OUTPUT
+          else
+            echo "has-r=false" >> $GITHUB_OUTPUT
+          fi
+
+  lint-python:
+    needs: detect
+    if: needs.detect.outputs.has-python == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/ruff-action@v3
+        with:
+          args: "check ."
+
+  lint-r:
+    needs: detect
+    if: needs.detect.outputs.has-r == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          use-public-rspm: true
+
+      - name: Install lintr
+        run: Rscript -e "install.packages('lintr', repos = 'https://cloud.r-project.org')"
+
+      - name: Lint R files
+        run: |
+          Rscript -e "
+            issues <- lintr::lint_dir('.', linters = list(
+              lintr::object_usage_linter(),
+              lintr::assignment_linter()
+            ))
+            if (length(issues) > 0) {
+              print(issues)
+              quit(status = 1)
+            } else {
+              message('No linting issues found.')
+            }
+          "