Check C/C++ code formatting in CI. (#1732)

* Add C/C++ formatting check.

Fix [check-]clang-format targets in clean builds.

* Do not format nrnmpidec.h.

* clang-format-12.0.1: apply

.github/workflows/formatting.yml

@@ -33,7 +33,6 @@ jobs:
       - uses: actions/checkout@v3
 
       - name: Check Python formatting
-        shell: bash
         working-directory: ${{runner.workspace}}/nrn
         run: |
           git ls-tree -z -r HEAD --name-only \
@@ -63,14 +62,56 @@ jobs:
       - uses: actions/checkout@v3
 
       - name: Configure
-        shell: bash
         working-directory: ${{runner.workspace}}/nrn
         run: |
           mkdir build
           cd build/
-          # Need to configure the build to trigger the hpc-coding-conventions YAML magic
-          cmake -G Ninja .. -DNRN_CMAKE_FORMAT=ON -DNRN_ENABLE_RX3D=OFF -DNRN_ENABLE_PYTHON=OFF -DNRN_ENABLE_INTERVIEWS=OFF -DNRN_ENABLE_MPI=OFF
+          # Need to configure the build to trigger the hpc-coding-conventions
+          # YAML magic
+          cmake -G Ninja .. \
+            -DNRN_CMAKE_FORMAT=ON \
+            -DNRN_ENABLE_RX3D=OFF \
+            -DNRN_ENABLE_PYTHON=OFF \
+            -DNRN_ENABLE_INTERVIEWS=OFF \
+            -DNRN_ENABLE_MPI=OFF
 
       - name: Check CMake formatting
         working-directory: ${{runner.workspace}}/nrn/build
         run: ninja check-cmake-format
+
+  cpp:
+    name: C/C++
+    runs-on: ubuntu-20.04
+    timeout-minutes: 5
+    steps:
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install cython3 libopenmpi-dev ninja-build python3-dev \
+            python3-numpy python3-pytest python3-pytest-cov
+          # The last .1 refers to ssciwr/clang-format-wheel#23.
+          sudo pip install clang-format==12.0.1.1
+          command -v clang-format
+          clang-format --version
+
+      - uses: actions/checkout@v3
+
+      - name: Configure
+        working-directory: ${{runner.workspace}}/nrn
+        run: |
+          mkdir build
+          cd build/
+          # Need to configure the build to trigger the hpc-coding-conventions
+          # YAML magic. Unlike the CMake formatting check, the C/C++ formatting
+          # check is based on the compilation dictionary generated by CMake, so
+          # we need to configure the build to compile as many source files as
+          # possible.
+          cmake -G Ninja .. \
+            -DClangFormat_EXECUTABLE=$(command -v clang-format) \
+            -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
+            -DNRN_CLANG_FORMAT=ON \
+            -DNRN_ENABLE_INTERVIEWS=OFF
+
+      - name: Check C/C++ formatting
+        working-directory: ${{runner.workspace}}/nrn/build
+        run: ninja check-clang-format

CMakeLists.txt

@@ -618,6 +618,13 @@ endif()
 # =============================================================================
 set(CODING_CONV_PREFIX "NRN")
 set(${CODING_CONV_PREFIX}_3RDPARTY_DIR "external")
+set(${CODING_CONV_PREFIX}_ClangFormat_REQUIRED_VERSION 12.0.1)
+set(${CODING_CONV_PREFIX}_ClangFormat_EXCLUDES_RE
+    # Exclude translated MOD files that are put in the source tree. This can be
+    # dropped once https://github.com/neuronsimulator/nrn/pull/1673 is merged.
+    ".*?/src/nrnoc/\\(apcount\\|exp2syn\\|expsyn\\|feature\\|hh\\|intfire1\\|intfire2\\|intfire4\\|netstim\\|oclmp\\|passive\\|pattern\\|ppmark\\|stim\\|svclmp\\|syn\\|vclmp\\)\\.c$"
+    ".*?/src/nrnoc/nrnversion\\.h$"
+    CACHE STRING "")
 set(CODING_CONV_CMAKE "${PROJECT_SOURCE_DIR}/${NRN_3RDPARTY_DIR}/coding-conventions/cpp/cmake")
 if(NOT EXISTS "${CODING_CONV_CMAKE}/3rdparty.cmake")
   nrn_initialize_submodule(external/coding-conventions)
@@ -629,6 +636,13 @@ include("${CODING_CONV_CMAKE}/3rdparty.cmake")
 # =============================================================================
 if(NRN_CMAKE_FORMAT OR NRN_CLANG_FORMAT)
   add_subdirectory(external/coding-conventions/cpp)
+  if(NRN_CLANG_FORMAT)
+    # The clang-format and check-clang-format targets fail out of the box in clean builds because
+    # the headers generated by Bison and Flex are not available. The generated_source_files target
+    # makes sure all such files exist, without forcing a full build of NEURON.
+    add_dependencies(clang-format generated_source_files)
+    add_dependencies(check-clang-format generated_source_files)
+  endif()
 endif()
 
 # =============================================================================