add a CI test to check submodule commit hash consistency

.github/workflows/general-ci-tests.yml

@@ -86,6 +86,19 @@ jobs:
       - name: Run the check_default_params script
         run: python tests/check_default_params.py
 
+  # Check that MOM6 submodule commit hashes are consistent
+  check_commit_hashes:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      # Checkout the repo
+      - uses: actions/checkout@v4
+
+      # Run the test
+      - name: Run the check_commit_hashes script
+        run: python tests/check_commit_hashes.py
+
   # Job to run check_input_data_list script
   check_input_data_list:
 

tests/check_commit_hashes.py

@@ -0,0 +1,78 @@
+# check that the MOM6 submodule commit is the same as what's specificed in .gitmodules:
+
+import sys
+import subprocess
+import re
+from pathlib import Path
+
+# path to this file:
+this_file = Path(__file__).resolve()
+mom_interface_root = this_file.parent.parent
+
+def get_mom6_gitmodules_commit():
+    """Get the commit hash of the MOM6 submodule from .gitmodules"""
+
+    with open(mom_interface_root / ".gitmodules") as f:
+        fxtag = None
+        url = None
+        in_MOM6_block = False
+        for line in f:
+            line = line.strip('[ ]\n').split()
+            if not line:
+                continue # skip empty lines
+            if len(line) == 2 and line[0] == "submodule":
+                in_MOM6_block = line[1] == '"MOM6"'
+            if in_MOM6_block:
+                if line[0] == "fxtag":
+                    fxtag = line[2]
+                elif line[0] == "url":
+                    url = line[2]
+
+    # get commit hash corresponding to fxtag
+    if fxtag is None:
+        raise Exception("Could not get MOM6 commit from .gitmodules")
+    elif url is None:
+        raise Exception("Could not get MOM6 url from .gitmodules")
+
+    # check if fxtag is a commit hash and not a tag
+    if re.match(r"^[0-9a-f]{40}$", fxtag) or re.match(r"^[0-9a-f]{7}$", fxtag):
+        return fxtag
+
+    # get commit hash from tag
+    p = subprocess.Popen(
+        ["git", "ls-remote", url, fxtag],
+        stdout=subprocess.PIPE,
+    )
+    out, _ = p.communicate()
+    if p.returncode != 0:
+        raise Exception("Could not get MOM6 commit from .gitmodules")
+    return out.decode().split()[0][:40] # first 40 characters are the commit hash
+
+
+def get_mom6_submodule_commit():
+    """Get the commit hash of the MOM6 submodule from the src/MOM6 directory"""
+
+    p = subprocess.Popen(
+        ["git", "submodule", "status", mom_interface_root / "MOM6"],
+        stdout=subprocess.PIPE,
+    )
+    out, _ = p.communicate()
+    if p.returncode != 0:
+        raise Exception("Could not get MOM6 submodule commit")
+    return out.decode().split()[0]
+
+
+def main():
+    """Check that the MOM6 submodule commit is the same as what's specificed in .gitmodules"""
+
+    mom6_commit = get_mom6_gitmodules_commit()
+    mom6_submodule_commit = get_mom6_submodule_commit()
+    if mom6_commit[:7] != mom6_submodule_commit[:7]:
+        print("ERROR: MOM6 commit in .gitmodules does not match the commit in src/MOM6")
+        print("MOM6 commit in .gitmodules: {}".format(mom6_commit))
+        print("MOM6 commit in src/MOM6: {}".format(mom6_submodule_commit))
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()