gh-105658: fix excess trace events for except block ending with a conditional block (#109384)

Author: iritkatriel

Lib/test/test_dis.py

@@ -642,7 +642,8 @@ def _tryfinallyconst(b):
             CALL                     0
             POP_TOP
             RERAISE                  0
-         >> COPY                     3
+
+None     >> COPY                     3
             POP_EXCEPT
             RERAISE                  1
 ExceptionTable:
@@ -674,7 +675,8 @@ def _tryfinallyconst(b):
             CALL                     0
             POP_TOP
             RERAISE                  0
-         >> COPY                     3
+
+None     >> COPY                     3
             POP_EXCEPT
             RERAISE                  1
 ExceptionTable:
@@ -1822,9 +1824,9 @@ def _prepare_test_cases():
   Instruction(opname='CALL', opcode=53, arg=1, argval=1, argrepr='', offset=414, start_offset=414, starts_line=False, line_number=28, is_jump_target=False, positions=None),
   Instruction(opname='POP_TOP', opcode=32, arg=None, argval=None, argrepr='', offset=422, start_offset=422, starts_line=False, line_number=28, is_jump_target=False, positions=None),
   Instruction(opname='RERAISE', opcode=102, arg=0, argval=0, argrepr='', offset=424, start_offset=424, starts_line=False, line_number=28, is_jump_target=False, positions=None),
-  Instruction(opname='COPY', opcode=61, arg=3, argval=3, argrepr='', offset=426, start_offset=426, starts_line=False, line_number=28, is_jump_target=False, positions=None),
-  Instruction(opname='POP_EXCEPT', opcode=31, arg=None, argval=None, argrepr='', offset=428, start_offset=428, starts_line=False, line_number=28, is_jump_target=False, positions=None),
-  Instruction(opname='RERAISE', opcode=102, arg=1, argval=1, argrepr='', offset=430, start_offset=430, starts_line=False, line_number=28, is_jump_target=False, positions=None),
+  Instruction(opname='COPY', opcode=61, arg=3, argval=3, argrepr='', offset=426, start_offset=426, starts_line=True, line_number=None, is_jump_target=False, positions=None),
+  Instruction(opname='POP_EXCEPT', opcode=31, arg=None, argval=None, argrepr='', offset=428, start_offset=428, starts_line=False, line_number=None, is_jump_target=False, positions=None),
+  Instruction(opname='RERAISE', opcode=102, arg=1, argval=1, argrepr='', offset=430, start_offset=430, starts_line=False, line_number=None, is_jump_target=False, positions=None),
 ]
 
 # One last piece of inspect fodder to check the default line number handling

Lib/test/test_sys_settrace.py

@@ -929,6 +929,35 @@ def func():
              (6, 'line'),
              (6, 'return')])
 
+    def test_finally_with_conditional(self):
+
+        # See gh-105658
+        condition = True
+        def func():
+            try:
+                try:
+                    raise Exception
+                finally:
+                    if condition:
+                        result = 1
+                result = 2
+            except:
+                result = 3
+            return result
+
+        self.run_and_compare(func,
+            [(0, 'call'),
+             (1, 'line'),
+             (2, 'line'),
+             (3, 'line'),
+             (3, 'exception'),
+             (5, 'line'),
+             (6, 'line'),
+             (8, 'line'),
+             (9, 'line'),
+             (10, 'line'),
+             (10, 'return')])
+
     def test_break_to_continue1(self):
 
         def func():
@@ -2123,7 +2152,7 @@ def test_jump_in_nested_finally_3(output):
             output.append(11)
         output.append(12)
 
-    @jump_test(5, 11, [2, 4], (ValueError, 'exception'))
+    @jump_test(5, 11, [2, 4], (ValueError, 'comes after the current code block'))
     def test_no_jump_over_return_try_finally_in_finally_block(output):
         try:
             output.append(2)

Misc/NEWS.d/next/Core and Builtins/2023-09-13-19-16-51.gh-issue-105658.z2nR2u.rst

@@ -0,0 +1,2 @@
+Fix bug where the line trace of an except block ending with a conditional
+includes an excess event with the line of the conditional expression.

Python/compile.c

@@ -3261,18 +3261,6 @@ compiler_continue(struct compiler *c, location loc)
 }
 
 
-static location
-location_of_last_executing_statement(asdl_stmt_seq *stmts)
-{
-    for (Py_ssize_t i = asdl_seq_LEN(stmts) - 1; i >= 0; i++) {
-        location loc = LOC((stmt_ty)asdl_seq_GET(stmts, i));
-        if (loc.lineno > 0) {
-            return loc;
-        }
-    }
-    return NO_LOCATION;
-}
-
 /* Code generated for "try: <body> finally: <finalbody>" is as follows:
 
         SETUP_FINALLY           L
@@ -3341,9 +3329,9 @@ compiler_try_finally(struct compiler *c, stmt_ty s)
     RETURN_IF_ERROR(
         compiler_push_fblock(c, loc, FINALLY_END, end, NO_LABEL, NULL));
     VISIT_SEQ(c, stmt, s->v.Try.finalbody);
-    loc = location_of_last_executing_statement(s->v.Try.finalbody);
     compiler_pop_fblock(c, FINALLY_END, end);
 
+    loc = NO_LOCATION;
     ADDOP_I(c, loc, RERAISE, 0);
 
     USE_LABEL(c, cleanup);
@@ -3392,9 +3380,9 @@ compiler_try_star_finally(struct compiler *c, stmt_ty s)
         compiler_push_fblock(c, loc, FINALLY_END, end, NO_LABEL, NULL));
 
     VISIT_SEQ(c, stmt, s->v.TryStar.finalbody);
-    loc = location_of_last_executing_statement(s->v.Try.finalbody);
 
     compiler_pop_fblock(c, FINALLY_END, end);
+    loc = NO_LOCATION;
     ADDOP_I(c, loc, RERAISE, 0);
 
     USE_LABEL(c, cleanup);