feat: Support C23/C++23 style elifdef and elifndef

Author: ibbem

src/main/java/org/variantsync/diffdetective/feature/cpp/CPPDiffLineFormulaExtractor.java

@@ -27,7 +27,7 @@
  */
 public class CPPDiffLineFormulaExtractor implements DiffLineFormulaExtractor {
     // ^[+-]?\s*#\s*(if|ifdef|ifndef|elif)(\s+(.*)|\((.*)\))$
-    private static final String CPP_ANNOTATION_REGEX = "^[+-]?\\s*#\\s*(if|ifdef|ifndef|elif)([\\s(].*)$";
+    private static final String CPP_ANNOTATION_REGEX = "^[+-]?\\s*#\\s*(if|ifdef|ifndef|elif|elifdef|elifndef)([\\s(].*)$";
     private static final Pattern CPP_ANNOTATION_PATTERN = Pattern.compile(CPP_ANNOTATION_REGEX);
 
     /**
@@ -63,18 +63,18 @@ public Node extractFormula(final String line) throws UnparseableFormulaException
             throw new UnparseableFormulaException(e);
         }
 
-        // treat {@code #ifdef id} and {@code #ifndef id}
+        // treat {@code #ifdef id}, {@code #ifndef id}, {@code #elifdef id} and {@code #elifndef id}
         // like {@code defined(id)} and {@code !defined(id)}
-        if ("ifdef".equals(annotationType) || "ifndef".equals(annotationType)) {
+        if (annotationType.endsWith("def")) {
             if (parsedFormula instanceof Literal literal) {
                 literal.var = String.format("defined(%s)", literal.var);
 
                 // negate for ifndef
-                if ("ifndef".equals(annotationType)) {
+                if (annotationType.endsWith("ndef")) {
                     literal.positive = false;
                 }
             } else {
-                throw new UnparseableFormulaException("When using #ifdef or #ifndef, only literals are allowed. Hence, \"" + line + "\" is disallowed.");
+                throw new UnparseableFormulaException("When using #ifdef, #ifndef, #elifdef or #elifndef, only literals are allowed. Hence, \"" + line + "\" is disallowed.");
             }
         }
 

src/test/java/CPPParserTest.java

@@ -25,6 +25,8 @@ private static List<TestCase> testCases() {
                 new TestCase("#if A", var("A")),
                 new TestCase("#ifdef A", var("defined(A)")),
                 new TestCase("#ifndef A", negate(var("defined(A)"))),
+                new TestCase("#elifdef A", var("defined(A)")),
+                new TestCase("#elifndef A", negate(var("defined(A)"))),
                 new TestCase("#elif A", var("A")),
 
                 new TestCase("#if !A", negate(var("A"))),