[Infrastructure] O2 linter: Remove prefix exception for constexpr constants

.clang-tidy

@@ -4,10 +4,9 @@ CheckOptions:
   - { key: readability-identifier-naming.ClassMemberPrefix, value: m }
   - { key: readability-identifier-naming.ConceptCase, value: CamelCase }
   - { key: readability-identifier-naming.ConstexprVariableCase, value: CamelCase }
-  - { key: readability-identifier-naming.ConstexprVariableIgnoredRegexp, value: "^k[A-Z][a-zA-Z0-9]*$" }  # Allow "k" prefix.
   - { key: readability-identifier-naming.EnumCase, value: CamelCase }
   - { key: readability-identifier-naming.EnumConstantCase, value: CamelCase }
-  - { key: readability-identifier-naming.EnumConstantIgnoredRegexp, value: "^k?[A-Z][a-zA-Z0-9_]*$" }  # Allow "k" prefix and underscores.
+  - { key: readability-identifier-naming.EnumConstantIgnoredRegexp, value: "^k?[A-Z][a-zA-Z0-9_]*$" }  # Allow "k" prefix and non-trailing underscores in PDG names.
   - { key: readability-identifier-naming.FunctionCase, value: camelBack }
   - { key: readability-identifier-naming.MacroDefinitionCase, value: UPPER_CASE }
   - { key: readability-identifier-naming.MacroDefinitionIgnoredRegexp, value: "^[A-Z][A-Z0-9_]*_$" }  # Allow the trailing underscore in header guards.

Scripts/o2_linter.py

@@ -988,21 +988,19 @@ class TestNameConstant(TestSpec):
     """Test constexpr constant names."""
 
     name = "name/constexpr-constant"
-    message = (
-        'Use UpperCamelCase for names of constexpr constants. Names of special constants may be prefixed with "k".'
-    )
+    message = "Use UpperCamelCase for names of constexpr constants."
     rationale = rationale_names
     references = references_names
     suffixes = [".h", ".cxx", ".C"]
 
     def __init__(self) -> None:
         super().__init__()
         keyword = r"(.+ )"  # e.g. "static "
-        type_val = r"([\w:<>+\-*\/, ]+ )" # value type e.g. "std::array<Type, n + 1> "
+        type_val = r"([\w:<>+\-*\/, ]+ )"  # value type e.g. "std::array<Type, n + 1> "
         prefix = r"(\w+::)"  # prefix with namespace or class, e.g. "MyClass::"
         name_val = r"(\w+)"  # name of the constant
-        array = r"(\[.*\])" # array declaration: "[...]"
-        assignment = r"( =|\(\d|{)" # value assignment, e.g. " = 2", " = expression", "(2)", "{2}", "{{...}}"
+        array = r"(\[.*\])"  # array declaration: "[...]"
+        assignment = r"( =|\(\d|{)"  # value assignment, e.g. " = 2", " = expression", "(2)", "{2}", "{{...}}"
         self.pattern = re.compile(rf"{keyword}?constexpr {type_val}?{prefix}*{name_val}{array}?{assignment}")
 
     def test_line(self, line: str) -> bool:
@@ -1013,8 +1011,6 @@ def test_line(self, line: str) -> bool:
             return True
         constant_name = match.group(4)
         # The actual test comes here.
-        if constant_name.startswith("k") and len(constant_name) > 1:  # exception for special constants
-            constant_name = constant_name[1:]  # test the name without "k"
         return is_upper_camel_case(constant_name)
 
 
@@ -1785,7 +1781,9 @@ def main():
             print("Skipping writing in GITHUB_OUTPUT.")
 
     # Print tips.
-    print("\nTip: You can run the O2 linter locally from the O2Physics directory with: python3 Scripts/o2_linter.py <files>")
+    print(
+        "\nTip: You can run the O2 linter locally from the O2Physics directory with: python3 Scripts/o2_linter.py <files>"
+    )
 
     if not passed:
         sys.exit(1)