pythongh-139640: Fix swallowing syntax warnings in different modules

Revert pythonGH-131993. Explicitly silence the duplicated PEP 765 syntax warnings
in the REPL.

Fix swallowing some syntax warnings in different modules if they accidentally
have the same message and are emitted from the same line.

Co-authored-by: Tomas R. <[email protected]>

Author: serhiy-storchaka

Include/cpython/warnings.h

@@ -18,9 +18,3 @@ PyAPI_FUNC(int) PyErr_WarnExplicitFormat(
 
 // DEPRECATED: Use PyErr_WarnEx() instead.
 #define PyErr_Warn(category, msg) PyErr_WarnEx((category), (msg), 1)
-
-int _PyErr_WarnExplicitObjectWithContext(
-    PyObject *category,
-    PyObject *message,
-    PyObject *filename,
-    int lineno);

Lib/_pyrepl/console.py

@@ -217,8 +217,26 @@ def runsource(self, source, filename="<input>", symbol="single"):
             wrapper = ast.Interactive if stmt is last_stmt else ast.Module
             the_symbol = symbol if stmt is last_stmt else "exec"
             item = wrapper([stmt])
+            import warnings
             try:
-                code = self.compile.compiler(item, filename, the_symbol)
+                with warnings.catch_warnings(record=True) as caught_warnings:
+                    # Enable all warnings
+                    warnings.simplefilter("always")
+                    code = self.compile.compiler(item, filename, the_symbol)
+                for warning in caught_warnings:
+                    if issubclass(warning.category, SyntaxWarning) and "in a 'finally' block" in str(warning.message):
+                        # Ignore this warning as it would've alread been raised
+                        # when compiling the code above
+                        pass
+                    else:
+                        # Re-emit other warnings
+                        warnings.warn_explicit(
+                            message=warning.message,
+                            category=warning.category,
+                            filename=warning.filename,
+                            lineno=warning.lineno,
+                            source=warning.source
+                        )
                 linecache._register_code(code, source, filename)
             except SyntaxError as e:
                 if e.args[0] == "'await' outside function":

Lib/test/test_compile.py

@@ -1664,22 +1664,21 @@ class WeirdDict(dict):
         self.assertRaises(NameError, ns['foo'])
 
     def test_compile_warnings(self):
-        # See gh-131927
-        # Compile warnings originating from the same file and
-        # line are now only emitted once.
+        # Each invocation of compile() emits compiler warnings, even if they
+        # have the same message and line number.
+        source = textwrap.dedent(r"""
+            # tokenizer
+            1or 0  # line 3
+            # code generator
+            1 is 1  # line 5
+        """)
         with warnings.catch_warnings(record=True) as caught:
             warnings.simplefilter("default")
-            compile('1 is 1', '<stdin>', 'eval')
-            compile('1 is 1', '<stdin>', 'eval')
-
-        self.assertEqual(len(caught), 1)
+            for i in range(2):
+                # Even if compile() is at the same line.
+                compile(source, '<stdin>', 'exec')
 
-        with warnings.catch_warnings(record=True) as caught:
-            warnings.simplefilter("always")
-            compile('1 is 1', '<stdin>', 'eval')
-            compile('1 is 1', '<stdin>', 'eval')
-
-        self.assertEqual(len(caught), 2)
+        self.assertEqual([wm.lineno for wm in caught], [3, 5] * 2)
 
     def test_compile_warning_in_finally(self):
         # Ensure that warnings inside finally blocks are
@@ -1690,16 +1689,47 @@ def test_compile_warning_in_finally(self):
             try:
                 pass
             finally:
-                1 is 1
+                1 is 1  # line 5
+                try:
+                    pass
+                finally: # nested
+                    1 is 1  # line 9
         """)
 
         with warnings.catch_warnings(record=True) as caught:
-            warnings.simplefilter("default")
+            warnings.simplefilter("always")
             compile(source, '<stdin>', 'exec')
 
-        self.assertEqual(len(caught), 1)
-        self.assertEqual(caught[0].category, SyntaxWarning)
-        self.assertIn("\"is\" with 'int' literal", str(caught[0].message))
+        self.assertEqual(sorted(wm.lineno for wm in caught), [5, 9])
+        for wm in caught:
+            self.assertEqual(wm.category, SyntaxWarning)
+            self.assertIn("\"is\" with 'int' literal", str(wm.message))
+
+        # Other code path is used for "try" with "except*".
+        source = textwrap.dedent("""
+            try:
+                pass
+            except *Exception:
+                pass
+            finally:
+                1 is 1  # line 7
+                try:
+                    pass
+                except *Exception:
+                    pass
+                finally: # nested
+                    1 is 1  # line 13
+        """)
+
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            compile(source, '<stdin>', 'exec')
+
+        self.assertEqual(sorted(wm.lineno for wm in caught), [7, 13])
+        for wm in caught:
+            self.assertEqual(wm.category, SyntaxWarning)
+            self.assertIn("\"is\" with 'int' literal", str(wm.message))
+
 
 class TestBooleanExpression(unittest.TestCase):
     class Value:

Lib/test/test_pyrepl/test_interact.py

@@ -293,7 +293,7 @@ def f():
         """)
 
         with warnings.catch_warnings(record=True) as caught:
-            warnings.simplefilter("default")
+            warnings.simplefilter("always")
             console.runsource(code)
 
         count = sum("'return' in a 'finally' block" in str(w.message)

Misc/NEWS.d/next/Core_and_Builtins/2025-10-06-10-03-37.gh-issue-139640.gY5oTb.rst

@@ -0,0 +1,2 @@
+Fix swallowing some syntax warnings in different modules if they
+accidentally have the same message and are emitted from the same line.

Python/_warnings.c

@@ -1473,28 +1473,6 @@ PyErr_WarnExplicitObject(PyObject *category, PyObject *message,
     return 0;
 }
 
-/* Like PyErr_WarnExplicitObject, but automatically sets up context */
-int
-_PyErr_WarnExplicitObjectWithContext(PyObject *category, PyObject *message,
-                                     PyObject *filename, int lineno)
-{
-    PyObject *unused_filename, *module, *registry;
-    int unused_lineno;
-    int stack_level = 1;
-
-    if (!setup_context(stack_level, NULL, &unused_filename, &unused_lineno,
-                       &module, &registry)) {
-        return -1;
-    }
-
-    int rc = PyErr_WarnExplicitObject(category, message, filename, lineno,
-                                      module, registry);
-    Py_DECREF(unused_filename);
-    Py_DECREF(registry);
-    Py_DECREF(module);
-    return rc;
-}
-
 int
 PyErr_WarnExplicit(PyObject *category, const char *text,
                    const char *filename_str, int lineno,

Python/compile.c

@@ -103,6 +103,7 @@ typedef struct _PyCompiler {
     bool c_save_nested_seqs;     /* if true, construct recursive instruction sequences
                                   * (including instructions for nested code objects)
                                   */
+    int c_disable_warning;
 } compiler;
 
 static int
@@ -765,6 +766,9 @@ _PyCompile_PushFBlock(compiler *c, location loc,
     f->fb_loc = loc;
     f->fb_exit = exit;
     f->fb_datum = datum;
+    if (t == COMPILE_FBLOCK_FINALLY_END) {
+        c->c_disable_warning++;
+    }
     return SUCCESS;
 }
 
@@ -776,6 +780,9 @@ _PyCompile_PopFBlock(compiler *c, fblocktype t, jump_target_label block_label)
     u->u_nfblocks--;
     assert(u->u_fblock[u->u_nfblocks].fb_type == t);
     assert(SAME_JUMP_TARGET_LABEL(u->u_fblock[u->u_nfblocks].fb_block, block_label));
+    if (t == COMPILE_FBLOCK_FINALLY_END) {
+        c->c_disable_warning--;
+    }
 }
 
 fblockinfo *
@@ -1203,6 +1210,9 @@ _PyCompile_Error(compiler *c, location loc, const char *format, ...)
 int
 _PyCompile_Warn(compiler *c, location loc, const char *format, ...)
 {
+    if (c->c_disable_warning) {
+        return 0;
+    }
     va_list vargs;
     va_start(vargs, format);
     PyObject *msg = PyUnicode_FromFormatV(format, vargs);

Python/errors.c

@@ -1962,8 +1962,8 @@ int
 _PyErr_EmitSyntaxWarning(PyObject *msg, PyObject *filename, int lineno, int col_offset,
                          int end_lineno, int end_col_offset)
 {
-    if (_PyErr_WarnExplicitObjectWithContext(PyExc_SyntaxWarning, msg,
-                                             filename, lineno) < 0)
+    if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning, msg,
+                                 filename, lineno, NULL, NULL) < 0)
     {
         if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
             /* Replace the SyntaxWarning exception with a SyntaxError