From 2bd058257b703062c6d8473027142db01329ccb9 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Tue, 1 Apr 2025 09:43:42 +0200
Subject: [PATCH 01/11] Prevent emitting optimizer warnings twice in the REPL

---
 Lib/_pyrepl/console.py                | 43 ++++++++++++++++++++++-----
 Lib/test/test_pyrepl/test_interact.py | 25 ++++++++++++++++
 2 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/Lib/_pyrepl/console.py b/Lib/_pyrepl/console.py
index 8956fb1242e52a..bd10edf36c14df 100644
--- a/Lib/_pyrepl/console.py
+++ b/Lib/_pyrepl/console.py
@@ -28,6 +28,7 @@
 from dataclasses import dataclass, field
 import os.path
 import sys
+import warnings
 
 
 TYPE_CHECKING = False
@@ -188,16 +189,19 @@ def runcode(self, code):
 
     def runsource(self, source, filename="<input>", symbol="single"):
         try:
-            tree = self.compile.compiler(
-                source,
-                filename,
-                "exec",
-                ast.PyCF_ONLY_AST,
-                incomplete_input=False,
-            )
+            with warnings.catch_warnings(record=True) as all_warnings:
+                warnings.simplefilter("always")
+                tree = self.compile.compiler(
+                    source,
+                    filename,
+                    "exec",
+                    ast.PyCF_ONLY_AST,
+                    incomplete_input=False,
+                )
         except (SyntaxError, OverflowError, ValueError):
             self.showsyntaxerror(filename, source=source)
             return False
+        _replay_warnings(all_warnings)
         if tree.body:
             *_, last_stmt = tree.body
         for stmt in tree.body:
@@ -205,7 +209,9 @@ def runsource(self, source, filename="<input>", symbol="single"):
             the_symbol = symbol if stmt is last_stmt else "exec"
             item = wrapper([stmt])
             try:
-                code = self.compile.compiler(item, filename, the_symbol)
+                with warnings.catch_warnings(record=True) as stmt_warnings:
+                    warnings.simplefilter("always")
+                    code = self.compile.compiler(item, filename, the_symbol)
                 linecache._register_code(code, source, filename)
             except SyntaxError as e:
                 if e.args[0] == "'await' outside function":
@@ -220,6 +226,16 @@ def runsource(self, source, filename="<input>", symbol="single"):
                 self.showsyntaxerror(filename, source=source)
                 return False
 
+            # Only emit new warnings and throw away those
+            # which were already emitted when the source
+            # was compiled to AST.
+            # This prevents emitting duplicate warnings which are
+            # raised in the AST optimizer.
+            all_warnings = {str(w.message) for w in all_warnings}
+            new_warnings = [w for w in stmt_warnings
+                            if str(w.message) not in all_warnings]
+            _replay_warnings(new_warnings)
+
             if code is None:
                 return True
 
@@ -227,3 +243,14 @@ def runsource(self, source, filename="<input>", symbol="single"):
             if result is self.STATEMENT_FAILED:
                 break
         return False
+
+
+def _replay_warnings(ws):
+    for w in ws:
+        warnings.warn_explicit(
+            message=w.message,
+            category=w.category,
+            filename=w.filename,
+            lineno=w.lineno,
+            source=w.source,
+        )
diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index af5d4d0e67632a..2fecd22069b325 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -273,3 +273,28 @@ def test_incomplete_statement(self):
         code = "if foo:"
         console = InteractiveColoredConsole(namespace, filename="<stdin>")
         self.assertTrue(_more_lines(console, code))
+
+
+class TestWarnings(unittest.TestCase):
+    def test_pep_765_warning(self):
+        """
+        Test that a SyntaxWarning emitted from the
+        AST optimizer is only shown once in the REPL.
+        """
+        # gh-131927
+        console = InteractiveColoredConsole()
+        code = dedent("""\
+        def f():
+            try:
+                return 1
+            finally:
+                return 2
+        """)
+
+        f = io.StringIO()
+        with contextlib.redirect_stderr(f):
+            result = console.runsource(code)
+        self.assertFalse(result)
+        self.assertEqual(f.getvalue(),
+                         "<input>:5: SyntaxWarning: "
+                         "'return' in a 'finally' block\n")

From 08eab527599dbc2b349532f9e9d197feaffefae7 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Wed, 2 Apr 2025 19:58:40 +0200
Subject: [PATCH 02/11] Improve test

---
 Lib/test/test_pyrepl/test_interact.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index 2fecd22069b325..a8ebe2b884f3f7 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -295,6 +295,7 @@ def f():
         with contextlib.redirect_stderr(f):
             result = console.runsource(code)
         self.assertFalse(result)
-        self.assertEqual(f.getvalue(),
-                         "<input>:5: SyntaxWarning: "
-                         "'return' in a 'finally' block\n")
+        warning = "<input>:5: SyntaxWarning: 'return' in a 'finally' block"
+        output = f.getvalue()
+        # Check that the warning is shown only once
+        self.assertEqual(output.count(warning), 1)

From 2049da302ec4c5b89f5abea0c29d523487d2c602 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Wed, 2 Apr 2025 22:08:00 +0200
Subject: [PATCH 03/11] Fix tests

---
 Lib/_pyrepl/console.py                |  4 ++--
 Lib/test/test_pyrepl/test_interact.py | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/Lib/_pyrepl/console.py b/Lib/_pyrepl/console.py
index bd10edf36c14df..3b5496e513f79a 100644
--- a/Lib/_pyrepl/console.py
+++ b/Lib/_pyrepl/console.py
@@ -231,9 +231,9 @@ def runsource(self, source, filename="<input>", symbol="single"):
             # was compiled to AST.
             # This prevents emitting duplicate warnings which are
             # raised in the AST optimizer.
-            all_warnings = {str(w.message) for w in all_warnings}
+            all_warnings = {str(w) for w in all_warnings}
             new_warnings = [w for w in stmt_warnings
-                            if str(w.message) not in all_warnings]
+                            if str(w) not in all_warnings]
             _replay_warnings(new_warnings)
 
             if code is None:
diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index a8ebe2b884f3f7..36301d08b39298 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -1,6 +1,7 @@
 import contextlib
 import io
 import unittest
+import warnings
 from unittest.mock import patch
 from textwrap import dedent
 
@@ -291,11 +292,10 @@ def f():
                 return 2
         """)
 
-        f = io.StringIO()
-        with contextlib.redirect_stderr(f):
-            result = console.runsource(code)
-        self.assertFalse(result)
-        warning = "<input>:5: SyntaxWarning: 'return' in a 'finally' block"
-        output = f.getvalue()
-        # Check that the warning is shown only once
-        self.assertEqual(output.count(warning), 1)
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            console.runsource(code)
+
+        count = sum("'return' in a 'finally' block" in str(w.message)
+                    for w in caught)
+        self.assertEqual(count, 1)
\ No newline at end of file

From a922e165fcc4a9ad3c1b789c11fed4ea8d8d72f6 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Wed, 2 Apr 2025 22:34:57 +0200
Subject: [PATCH 04/11] Lint fix

---
 Lib/test/test_pyrepl/test_interact.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index 36301d08b39298..62e4a7c3c4da65 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -298,4 +298,4 @@ def f():
 
         count = sum("'return' in a 'finally' block" in str(w.message)
                     for w in caught)
-        self.assertEqual(count, 1)
\ No newline at end of file
+        self.assertEqual(count, 1)

From 742a4b1b8852ffafa4b52bd5f621741465b9bba4 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Sat, 5 Apr 2025 12:57:07 +0200
Subject: [PATCH 05/11] Revert REPL changes

---
 Lib/_pyrepl/console.py | 43 ++++++++----------------------------------
 1 file changed, 8 insertions(+), 35 deletions(-)

diff --git a/Lib/_pyrepl/console.py b/Lib/_pyrepl/console.py
index 3b5496e513f79a..8956fb1242e52a 100644
--- a/Lib/_pyrepl/console.py
+++ b/Lib/_pyrepl/console.py
@@ -28,7 +28,6 @@
 from dataclasses import dataclass, field
 import os.path
 import sys
-import warnings
 
 
 TYPE_CHECKING = False
@@ -189,19 +188,16 @@ def runcode(self, code):
 
     def runsource(self, source, filename="<input>", symbol="single"):
         try:
-            with warnings.catch_warnings(record=True) as all_warnings:
-                warnings.simplefilter("always")
-                tree = self.compile.compiler(
-                    source,
-                    filename,
-                    "exec",
-                    ast.PyCF_ONLY_AST,
-                    incomplete_input=False,
-                )
+            tree = self.compile.compiler(
+                source,
+                filename,
+                "exec",
+                ast.PyCF_ONLY_AST,
+                incomplete_input=False,
+            )
         except (SyntaxError, OverflowError, ValueError):
             self.showsyntaxerror(filename, source=source)
             return False
-        _replay_warnings(all_warnings)
         if tree.body:
             *_, last_stmt = tree.body
         for stmt in tree.body:
@@ -209,9 +205,7 @@ def runsource(self, source, filename="<input>", symbol="single"):
             the_symbol = symbol if stmt is last_stmt else "exec"
             item = wrapper([stmt])
             try:
-                with warnings.catch_warnings(record=True) as stmt_warnings:
-                    warnings.simplefilter("always")
-                    code = self.compile.compiler(item, filename, the_symbol)
+                code = self.compile.compiler(item, filename, the_symbol)
                 linecache._register_code(code, source, filename)
             except SyntaxError as e:
                 if e.args[0] == "'await' outside function":
@@ -226,16 +220,6 @@ def runsource(self, source, filename="<input>", symbol="single"):
                 self.showsyntaxerror(filename, source=source)
                 return False
 
-            # Only emit new warnings and throw away those
-            # which were already emitted when the source
-            # was compiled to AST.
-            # This prevents emitting duplicate warnings which are
-            # raised in the AST optimizer.
-            all_warnings = {str(w) for w in all_warnings}
-            new_warnings = [w for w in stmt_warnings
-                            if str(w) not in all_warnings]
-            _replay_warnings(new_warnings)
-
             if code is None:
                 return True
 
@@ -243,14 +227,3 @@ def runsource(self, source, filename="<input>", symbol="single"):
             if result is self.STATEMENT_FAILED:
                 break
         return False
-
-
-def _replay_warnings(ws):
-    for w in ws:
-        warnings.warn_explicit(
-            message=w.message,
-            category=w.category,
-            filename=w.filename,
-            lineno=w.lineno,
-            source=w.source,
-        )

From bbefbf8d3de6e2b66d8f35bed52915b368c31e48 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Sat, 5 Apr 2025 13:01:47 +0200
Subject: [PATCH 06/11] Set up a warning registry for syntax warnings

---
 Include/cpython/warnings.h            |  6 ++++++
 Lib/test/test_pyrepl/test_interact.py |  1 -
 Python/_warnings.c                    | 19 +++++++++++++++++++
 Python/errors.c                       |  4 ++--
 4 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/Include/cpython/warnings.h b/Include/cpython/warnings.h
index 4e3eb88e8ff447..f590f3232692ad 100644
--- a/Include/cpython/warnings.h
+++ b/Include/cpython/warnings.h
@@ -18,3 +18,9 @@ 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);
\ No newline at end of file
diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index 62e4a7c3c4da65..261540f4d4aae0 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -293,7 +293,6 @@ def f():
         """)
 
         with warnings.catch_warnings(record=True) as caught:
-            warnings.simplefilter("always")
             console.runsource(code)
 
         count = sum("'return' in a 'finally' block" in str(w.message)
diff --git a/Python/_warnings.c b/Python/_warnings.c
index f9dd00f3ec23aa..efbe46c476a4a0 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -1366,6 +1366,25 @@ 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(module);
+    return rc;
+}
+
 int
 PyErr_WarnExplicit(PyObject *category, const char *text,
                    const char *filename_str, int lineno,
diff --git a/Python/errors.c b/Python/errors.c
index 14999d6dbaf72e..2b088e2f3888a1 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -1906,8 +1906,8 @@ int
 _PyErr_EmitSyntaxWarning(PyObject *msg, PyObject *filename, int lineno, int col_offset,
                          int end_lineno, int end_col_offset)
 {
-    if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning, msg, filename,
-                                 lineno, NULL, NULL) < 0)
+    if (_PyErr_WarnExplicitObjectWithContext(PyExc_SyntaxWarning, msg,
+                                             filename, lineno) < 0)
     {
         if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
             /* Replace the SyntaxWarning exception with a SyntaxError

From d047dd3d07f5aa3d162974a2d370ee9f8fddc47c Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Sat, 5 Apr 2025 13:04:06 +0200
Subject: [PATCH 07/11] newline

---
 Include/cpython/warnings.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Include/cpython/warnings.h b/Include/cpython/warnings.h
index f590f3232692ad..8731fd2e96b716 100644
--- a/Include/cpython/warnings.h
+++ b/Include/cpython/warnings.h
@@ -23,4 +23,4 @@ int _PyErr_WarnExplicitObjectWithContext(
     PyObject *category,
     PyObject *message,
     PyObject *filename,
-    int lineno);
\ No newline at end of file
+    int lineno);

From c4a27bce5e3910a048e2bd6a0fd5facb51045978 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Mon, 7 Apr 2025 22:54:49 +0200
Subject: [PATCH 08/11] Fix test

---
 Lib/test/test_pyrepl/test_interact.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Lib/test/test_pyrepl/test_interact.py b/Lib/test/test_pyrepl/test_interact.py
index 261540f4d4aae0..a20719033fc9b7 100644
--- a/Lib/test/test_pyrepl/test_interact.py
+++ b/Lib/test/test_pyrepl/test_interact.py
@@ -293,6 +293,7 @@ def f():
         """)
 
         with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("default")
             console.runsource(code)
 
         count = sum("'return' in a 'finally' block" in str(w.message)

From 7f8d1afa471fd1975dfd9d092ecd1b788b91695b Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Mon, 7 Apr 2025 22:55:27 +0200
Subject: [PATCH 09/11] PEP7 + missing decref

---
 Python/_warnings.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Python/_warnings.c b/Python/_warnings.c
index efbe46c476a4a0..681e764d23d6b0 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -1369,18 +1369,20 @@ PyErr_WarnExplicitObject(PyObject *category, PyObject *message,
 /* Like PyErr_WarnExplicitObject, but automatically sets up context */
 int
 _PyErr_WarnExplicitObjectWithContext(PyObject *category, PyObject *message,
-                                  PyObject *filename, int lineno)
+                                     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))
+                       &module, &registry)) {
         return -1;
+    }
 
     int rc = PyErr_WarnExplicitObject(category, message, filename, lineno,
                                       module, registry);
+    Py_DECREF(unused_filename);
     Py_DECREF(module);
     return rc;
 }

From c15635bc06ef4ec8c5116ad72545425a3740cf31 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Sat, 12 Apr 2025 11:26:10 +0200
Subject: [PATCH 10/11] Add missing decref

---
 Python/_warnings.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Python/_warnings.c b/Python/_warnings.c
index 681e764d23d6b0..e16153ef254cd0 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -1383,6 +1383,7 @@ _PyErr_WarnExplicitObjectWithContext(PyObject *category, PyObject *message,
     int rc = PyErr_WarnExplicitObject(category, message, filename, lineno,
                                       module, registry);
     Py_DECREF(unused_filename);
+    Py_DECREF(registry);
     Py_DECREF(module);
     return rc;
 }

From 97d028e239a44f5c9d9c9a6da80661bd41c79c63 Mon Sep 17 00:00:00 2001
From: Tomas Roun <tomas.roun8@gmail.com>
Date: Sat, 12 Apr 2025 11:43:11 +0200
Subject: [PATCH 11/11] Add more tests

---
 Lib/test/test_compile.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index ce9c060641d6c5..fb784898669f04 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -1636,6 +1636,24 @@ async def name_4():
                     pass
             [[]]
 
+    def test_compile_warnings(self):
+        # See gh-131927
+        # Compile warnings originating from the same file and
+        # line are now only emitted once.
+        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)
+
+        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)
+
 class TestBooleanExpression(unittest.TestCase):
     class Value:
         def __init__(self):

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