Add Fortran source code linting to MPAS dynamical core CI workflows

.github/workflows/mpas_dynamical_core_ci.yml

@@ -131,6 +131,7 @@ jobs:
     runs-on: ubuntu-24.04
     needs:
       - conditional-check
+      - source-code-linting
       - unit-tests
     if: ${{ always() }}
     steps:
@@ -167,6 +168,18 @@ jobs:
               ;;
           esac
 
+          case "${{ needs.source-code-linting.result }}" in
+            skipped|success)
+              :
+              ;;
+            cancelled|failure)
+              write_result_and_exit false
+              ;;
+            *)
+              write_result_and_exit error
+              ;;
+          esac
+
           case "${{ needs.unit-tests.result }}" in
             skipped|success)
               :
@@ -180,6 +193,45 @@ jobs:
           esac
 
           write_result_and_exit true
+  source-code-linting:
+    name: Lint Fortran source code
+    timeout-minutes: 10
+    runs-on: ubuntu-24.04
+    needs: conditional-check
+    if: ${{ needs.conditional-check.outputs.should-run == 'true' }}
+    env:
+      FORTITUDE_VERSION: '0.7.*'
+      SOURCE_CODE_PATH: ${{ github.workspace }}/src/dynamics/mpas
+    steps:
+      - name: Checkout CAM-SIMA
+        uses: actions/checkout@v5
+
+      - name: Setup Python
+        uses: actions/setup-python@v6
+        with:
+          cache: pip
+          python-version: '3.12'
+
+      - name: Install Fortitude
+        run: |
+          python3 -m venv venv-fortitude
+          source venv-fortitude/bin/activate
+          python3 -m pip install "fortitude-lint==$FORTITUDE_VERSION"
+
+      - name: Lint Fortran source code
+        run: |
+          source venv-fortitude/bin/activate
+          fortitude --config-file "$SOURCE_CODE_PATH/assets/fortitude_config.toml" check --exit-zero --output-file "$SOURCE_CODE_PATH/source-code-linting.log" --preview "$SOURCE_CODE_PATH"
+          cat "$SOURCE_CODE_PATH/source-code-linting.log"
+
+      - name: Upload Fortran source code linting log
+        if: ${{ always() }}
+        uses: actions/upload-artifact@v4
+        with:
+          if-no-files-found: ignore
+          name: source-code-linting-log
+          path: ${{ env.SOURCE_CODE_PATH }}/source-code-linting.log
+          retention-days: 7
   unit-tests:
     name: Build and run unit tests (GCC ${{ matrix.gcc-version }})
     timeout-minutes: 10

src/dynamics/mpas/assets/fortitude_config.toml

@@ -0,0 +1,29 @@
+[check]
+exclude = [
+    'src/dynamics/mpas/dycore'
+]
+file-extensions = [
+    'F',
+    'f',
+    'F90',
+    'f90'
+]
+# When ignoring a linting rule, a reason should be provided.
+ignore = [
+    'C003', # Temporarily ignored due to lack of support for Fortran 2018 `implicit none (external)` statement
+            # in the NVIDIA HPC SDK as of version 25.9.
+    'C182', # Requiring separate allocations and deallocations for each variable is too restrictive.
+            # Related variables can be grouped together at the discretion of developers.
+    'S102'  # Prefer only one space instead of two.
+]
+line-length = 132
+output-format = 'grouped'
+select = [
+    'ALL'
+]
+
+[check.exit-unlabelled-loops]
+allow-unnested-loops = true
+
+[check.strings]
+quotes = 'single'

src/dynamics/mpas/dyn_comp.F90

@@ -41,24 +41,28 @@ module dyn_comp
 
     interface
         module subroutine dyn_readnl(namelist_path)
+            implicit none
             character(*), intent(in) :: namelist_path
         end subroutine dyn_readnl
 
         module subroutine dyn_init(cam_runtime_opts, dyn_in, dyn_out)
             use runtime_obj, only: runtime_options
-
+            implicit none
             type(runtime_options), intent(in) :: cam_runtime_opts
             type(dyn_import_t), intent(in) :: dyn_in
             type(dyn_export_t), intent(in) :: dyn_out
         end subroutine dyn_init
 
         module subroutine dyn_run()
+            implicit none
         end subroutine dyn_run
 
         module subroutine dyn_final()
+            implicit none
         end subroutine dyn_final
 
         module subroutine dyn_debug_print(level, message, printer)
+            implicit none
             integer, intent(in) :: level
             character(*), intent(in) :: message
             integer, optional, intent(in) :: printer