Ensure XPPM/YPPM consistency on CI

.github/workflows/lint.yaml

@@ -17,7 +17,10 @@ jobs:
         - name: Install pre-commit
           run: |
             pip install pre-commit
-
         - name: Run lint via pre-commit
           run: |
             pre-commit run --all-files
+
+        - name: Check advection code consistency
+          run: |
+            ./.github/workflows/scripts/ensure_xppm_yppm_consistency.sh

convert_xppm_yppm.sh → .github/workflows/scripts/convert_xppm_yppm.sh

@@ -1,14 +1,19 @@
 #!/bin/bash
 #
-# Script to convert xppm.py/xtp_u.py into yppm/ytp_v.py. Can be deleted once we
-# have a way to use the same codebase for x-direction and y-direction advection.
+# Script to automatically convert `xppm.py` and `xtp_u.py` into `yppm.py` and
+# `ytp_v.py` respectively. We use it as part of the linting workflow in the CI
+# to ensure these files stay in sync.
 #
+# This script (and the corresponding linting workflow) can be deleted once we
+# have a way to use the same codebase for x-direction and y-direction advection.
 
-set -e -x
+set -e
 
+# Copy XPPM codes into YPPM files
 cp pyFV3/stencils/xppm.py pyFV3/stencils/yppm.py
 cp pyFV3/stencils/xtp_u.py pyFV3/stencils/ytp_v.py
 
+# Fixup YPPM code
 for fname in pyFV3/stencils/yppm.py pyFV3/stencils/ytp_v.py
 do
     sed -i 's/ub/vb/g' $fname

.github/workflows/scripts/ensure_xppm_yppm_consistency.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Call the automatic conversion
+./.github/workflows/scripts/convert_xppm_yppm.sh
+
+# Check for uncommitted changes in the working tree
+if [ -n "$(git status --porcelain)" ]; then
+    echo "It looks like x-direction and y-direction advection are out of sync. We found uncommitted"
+    echo "changes in working tree after YPPM was generated from XPPM sources. Please ensure to make"
+    echo "symmetrical changes to XPPM and YPPM codes."
+    echo ""
+    echo "If this is a false positive, please fix \".github/workflows/scripts/convert_xppm_yppm.sh\""
+    echo "or re-evaluate the need for this part of the linting workflow."
+    echo ""
+    echo "git status"
+    echo "----------"
+    git status
+    echo ""
+    echo "git diff"
+    echo "--------"
+    git --no-pager diff
+    echo ""
+
+    exit 1
+else
+    echo "XPPM and YPPM are in sync."
+fi