PY-79910 Variable incorrectly marked as unused or redeclared without usage in nested try/if blocks

When there is no `finally` in try-except statement, use transparent exit instruction to tie all normal exits from try-, else- and except- parts to the next instruction


Merge-request: IJ-MR-158265
Merged-by: Aleksandr Govenko <aleksandr.govenko@jetbrains.com>

GitOrigin-RevId: 734581b732a1a558b72811fdda977c470d045cc9

python/python-psi-impl/src/com/jetbrains/python/codeInsight/controlflow/PyControlFlowBuilder.java

@@ -751,21 +751,18 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
     final Instruction finallyFailInstruction;
 
     // Store pending normal exit instructions from try-except-else parts
-    if (finallyPart != null) {
-      myBuilder.processPending((pendingScope, instruction) -> {
-        final PsiElement pendingElement = instruction.getElement();
-        if (pendingElement != null) {
-          final boolean isPending = PsiTreeUtil.isAncestor(node, pendingElement, false) &&
-                                    !PsiTreeUtil.isAncestor(finallyPart, pendingElement, false);
-          if (isPending && pendingScope != null) {
-            pendingNormalExits.add(Pair.createNonNull(pendingScope, instruction));
-          }
-          else {
-            myBuilder.addPendingEdge(pendingScope, instruction);
-          }
-        }
-      });
-    }
+    myBuilder.processPending((pendingScope, instruction) -> {
+      final PsiElement pendingElement = instruction.getElement();
+      final boolean isPending = pendingElement == null || 
+                                PsiTreeUtil.isAncestor(node, pendingElement, false) &&
+                                !PsiTreeUtil.isAncestor(finallyPart, pendingElement, false);
+      if (isPending && pendingScope != null) {
+        pendingNormalExits.add(Pair.createNonNull(pendingScope, instruction));
+      }
+      else {
+        myBuilder.addPendingEdge(pendingScope, instruction);
+      }
+    });
 
     // Finally-fail part handling
     if (finallyPart != null) {
@@ -809,6 +806,7 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       }
     }
 
+    final Instruction exitInstruction;
     if (finallyPart != null) {
       myBuilder.processPending((pendingScope, instruction) -> {
         final PsiElement e = instruction.getElement();
@@ -829,7 +827,6 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
 
       // Duplicate CFG for finally (-fail and -success) only if there are some successful exits from the
       // try part. Otherwise, a single CFG for finally provides the correct control flow
-      final Instruction finallyInstruction;
       if (!pendingNormalExits.isEmpty()) {
         // Finally-success part handling
         pendingBackup = new ArrayList<>(myBuilder.pending);
@@ -840,24 +837,28 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
         for (Pair<PsiElement, Instruction> pair : pendingBackup) {
           myBuilder.addPendingEdge(pair.first, pair.second);
         }
-        finallyInstruction = finallySuccessInstruction;
+        exitInstruction = finallySuccessInstruction;
       }
       else {
-        finallyInstruction = finallyFailInstruction;
+        exitInstruction = finallyFailInstruction;
       }
+    }
+    else {
+      exitInstruction = addTransparentInstruction();    
+      myBuilder.prevInstruction = exitInstruction;
+    }
 
-      // Connect normal exits from try and else parts to the finally part
-      for (Pair<PsiElement, Instruction> pendingScopeAndInstruction : pendingNormalExits) {
-        final PsiElement pendingScope = pendingScopeAndInstruction.first;
-        final Instruction instruction = pendingScopeAndInstruction.second;
+    // Connect normal exits from try and else parts to the finally part or exit instruction
+    for (Pair<PsiElement, Instruction> pendingScopeAndInstruction : pendingNormalExits) {
+      final PsiElement pendingScope = pendingScopeAndInstruction.first;
+      final Instruction instruction = pendingScopeAndInstruction.second;
 
-        myBuilder.addEdge(instruction, finallyInstruction);
+      myBuilder.addEdge(instruction, exitInstruction);
 
-        // When instruction continues outside try-except statement scope
-        // the last instruction in finally-block is marked as pointing to that continuation
-        if (PsiTreeUtil.isAncestor(pendingScope, node, true)) {
-          myBuilder.addPendingEdge(pendingScope, myBuilder.prevInstruction);
-        }
+      // When instruction continues outside try-except statement scope
+      // the last instruction in finally-block is marked as pointing to that continuation
+      if (PsiTreeUtil.isAncestor(pendingScope, node, true)) {
+        myBuilder.addPendingEdge(pendingScope, myBuilder.prevInstruction);
       }
     }
   }

python/testData/codeInsight/controlflow/TryExceptNoFinally.py

@@ -0,0 +1,11 @@
+try:
+    value = 42
+except ValueError:
+    value = 13
+except SomethingElse:
+    value = 1342
+    raise
+else:
+    value = 0
+    
+print(value)

python/testData/codeInsight/controlflow/TryExceptNoFinally.txt

@@ -0,0 +1,20 @@
+0(1) element: null
+1(2) element: PyTryExceptStatement
+2(3,8,12) element: PyTryPart
+3(4,8,12) element: PyAssignmentStatement
+4(5,8,12) WRITE ACCESS: value
+5(6) element: PyElsePart
+6(7) element: PyAssignmentStatement
+7(17) WRITE ACCESS: value
+8(9) element: PyExceptPart
+9(10) READ ACCESS: ValueError
+10(11) element: PyAssignmentStatement
+11(17) WRITE ACCESS: value
+12(13) element: PyExceptPart
+13(14) READ ACCESS: SomethingElse
+14(15) element: PyAssignmentStatement
+15(16) WRITE ACCESS: value
+16(19) raise: PyRaiseStatement
+17(18) element: PyPrintStatement
+18(19) READ ACCESS: value
+19() element: null

python/testSrc/com/jetbrains/python/PyControlFlowBuilderTest.java

@@ -578,6 +578,11 @@ public class PyControlFlowBuilderTest extends LightMarkedTestCase {
     doTest();
   }
 
+  // PY-79910
+  public void testTryExceptNoFinally() {
+    doTest();
+  }
+
   private void doTestFirstStatement() {
     final String testName = getTestName(false);
     configureByFile(testName + ".py");

python/testSrc/com/jetbrains/python/inspections/PyUnusedLocalInspectionTest.java

@@ -126,6 +126,24 @@ public class PyUnusedLocalInspectionTest extends PyInspectionTestCase {
     inspection.ignoreTupleUnpacking = false;
     doTest(inspection);
   }
+  
+  // PY-79910
+  public void testTryExceptInsideIfInsideFunction() {
+    doTestByText("""
+def test():
+    num = 7
+    if num < 10:
+        try:
+            next_num = input() # used
+        except ValueError:
+            next_num = None
+    else:
+        next_num = 0
+
+    return next_num
+        """
+    );
+  }
 
   // PY-16419, PY-26417
   public void testPotentiallySuppressedExceptions() {