SONARPY-4544 Count terminal raises as exits

python-checks/src/main/java/org/sonar/python/checks/InvariantReturnCheck.java

@@ -80,17 +80,37 @@ public void initialize(Context context) {
 
   private static List<LatestExecutedBlock> collectLatestExecutedBlocks(ControlFlowGraph cfg) {
     List<LatestExecutedBlock> collectedBlocks = new ArrayList<>();
+    Set<CfgBlock> reachableBlocks = reachableBlocks(cfg.start());
     for (CfgBlock predecessor : cfg.end().predecessors()) {
+      if (!reachableBlocks.contains(predecessor)) {
+        continue;
+      }
       if (predecessor instanceof PythonCfgBranchingBlock pythonCfgBranchingBlock) {
-        collectBranchingBlock(collectedBlocks, pythonCfgBranchingBlock);
-      } else if (!endsWithElementKind(predecessor, Kind.RAISE_STMT)) {
+        collectBranchingBlock(collectedBlocks, pythonCfgBranchingBlock, reachableBlocks);
+      } else {
         collectedBlocks.add(new LatestExecutedBlock(predecessor));
       }
     }
     return collectedBlocks;
   }
 
-  private static void collectBranchingBlock(List<LatestExecutedBlock> collectedBlocks, PythonCfgBranchingBlock branchingBlock) {
+  private static Set<CfgBlock> reachableBlocks(CfgBlock start) {
+    Set<CfgBlock> reachable = new HashSet<>();
+    Deque<CfgBlock> blockToVisit = new ArrayDeque<>();
+    blockToVisit.push(start);
+    reachable.add(start);
+    while (!blockToVisit.isEmpty()) {
+      CfgBlock block = blockToVisit.pop();
+      for (CfgBlock successor : block.successors()) {
+        if (reachable.add(successor)) {
+          blockToVisit.push(successor);
+        }
+      }
+    }
+    return reachable;
+  }
+
+  private static void collectBranchingBlock(List<LatestExecutedBlock> collectedBlocks, PythonCfgBranchingBlock branchingBlock, Set<CfgBlock> reachableBlocks) {
     Tree branchingTree = branchingBlock.branchingTree();
     if (branchingTree.is(Kind.TRY_STMT)) {
       TryStatement tryStatement = (TryStatement) branchingTree;
@@ -100,16 +120,19 @@ private static void collectBranchingBlock(List<LatestExecutedBlock> collectedBlo
     } else if (branchingTree.is(Kind.IF_STMT) || branchingTree instanceof Pattern) {
       collectedBlocks.add(new LatestExecutedBlock(branchingBlock));
     } else {
-      collectBlocksHavingReturnBeforeExceptOrFinallyBlock(collectedBlocks, branchingBlock);
+      collectBlocksHavingReturnBeforeExceptOrFinallyBlock(collectedBlocks, branchingBlock, reachableBlocks);
     }
   }
 
-  private static void collectBlocksHavingReturnBeforeExceptOrFinallyBlock(List<LatestExecutedBlock> collectedBlocks, PythonCfgBranchingBlock branchingBlock) {
+  private static void collectBlocksHavingReturnBeforeExceptOrFinallyBlock(List<LatestExecutedBlock> collectedBlocks, PythonCfgBranchingBlock branchingBlock, Set<CfgBlock> reachableBlocks) {
     if (branchingBlock.branchingTree().is(Kind.EXCEPT_CLAUSE, Kind.FINALLY_CLAUSE)) {
       for (CfgBlock predecessor : branchingBlock.predecessors()) {
+        if (!reachableBlocks.contains(predecessor)) {
+          continue;
+        }
         if (predecessor instanceof PythonCfgBranchingBlock pythonCfgBranchingBlock) {
-          collectBlocksHavingReturnBeforeExceptOrFinallyBlock(collectedBlocks, pythonCfgBranchingBlock);
-        } else if (endsWithElementKind(predecessor, Kind.RETURN_STMT)) {
+          collectBlocksHavingReturnBeforeExceptOrFinallyBlock(collectedBlocks, pythonCfgBranchingBlock, reachableBlocks);
+        } else if (endsWithElementKind(predecessor, Kind.RETURN_STMT) || endsWithElementKind(predecessor, Kind.RAISE_STMT)) {
           collectedBlocks.add(new LatestExecutedBlock(predecessor));
         }
       }

python-checks/src/test/resources/checks/invariantReturn.py

@@ -433,15 +433,56 @@ def f_raise_is_not_a_return(a, b):
         raise b
     return b
 
-def f_function_exit_through_raise_should_be_ignored(a, b, c): # Noncompliant
-#   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+def f_function_exit_through_raise_prevents_reporting(a, b, c):
     if a:
         return b
-#       ^^^^^^^^<
     if c:
         raise
     return b
-#   ^^^^^^^^<
+
+def f_early_return_with_raise_guard(already_valid, invalid, obj):
+    if already_valid:
+        return obj
+    if invalid:
+        raise ValueError()
+    return obj
+
+def f_unreachable_raise_does_not_prevent_reporting(a, b): # Noncompliant
+    if a:
+        return b
+    return b
+    raise ValueError()
+
+def f_raise_in_try_with_finally(early, invalid, value):
+    if early:
+        return value
+    try:
+        if invalid:
+            raise ValueError()
+    finally:
+        pass
+    return value
+
+def f_raise_in_try_with_except(early, invalid, value):
+    if early:
+        return value
+    try:
+        if invalid:
+            raise ValueError()
+    except TypeError:
+        cleanup()
+    return value
+
+def f_unreachable_raise_before_finally_does_not_prevent_reporting(a, b): # Noncompliant
+    try:
+        if a:
+            return b
+        else:
+            return b
+        raise ValueError()
+    finally:
+        pass
+    return b
 
 def f_same_binding_through_multiple_paths(a): # Noncompliant
     d = 3