gh-111366: Correctly show custom syntax error messages in the codeop module functions

Author: pablogsal

Lib/codeop.py

@@ -70,10 +70,14 @@ def _maybe_compile(compiler, source, filename, symbol):
                     return None
                 # fallthrough
 
-    return compiler(source, filename, symbol)
+    return compiler(source, filename, symbol, incomplete_input=False)
 
-def _compile(source, filename, symbol):
-    return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT | PyCF_ALLOW_INCOMPLETE_INPUT)
+def _compile(source, filename, symbol, incomplete_input=True):
+    flags = 0
+    if incomplete_input:
+        flags |= PyCF_ALLOW_INCOMPLETE_INPUT
+        flags |= PyCF_DONT_IMPLY_DEDENT
+    return compile(source, filename, symbol, flags)
 
 def compile_command(source, filename="<input>", symbol="single"):
     r"""Compile a command and determine whether it is incomplete.
@@ -104,8 +108,12 @@ class Compile:
     def __init__(self):
         self.flags = PyCF_DONT_IMPLY_DEDENT | PyCF_ALLOW_INCOMPLETE_INPUT
 
-    def __call__(self, source, filename, symbol):
-        codeob = compile(source, filename, symbol, self.flags, True)
+    def __call__(self, source, filename, symbol, **kwargs):
+        flags = self.flags
+        if kwargs.get('incomplete_input', True) is False:
+            flags &= ~PyCF_DONT_IMPLY_DEDENT
+            flags &= ~PyCF_ALLOW_INCOMPLETE_INPUT
+        codeob = compile(source, filename, symbol, flags, True)
         for feature in _features:
             if codeob.co_flags & feature.compiler_flag:
                 self.flags |= feature.compiler_flag

Lib/test/test_codeop.py

@@ -5,6 +5,7 @@
 import unittest
 import warnings
 from test.support import warnings_helper
+from textwrap import dedent
 
 from codeop import compile_command, PyCF_DONT_IMPLY_DEDENT
 
@@ -307,6 +308,19 @@ def test_invalid_warning(self):
         self.assertEqual(w[0].category, SyntaxWarning)
         self.assertRegex(str(w[0].message), 'invalid escape sequence')
         self.assertEqual(w[0].filename, '<input>')
+    
+    def assertSyntaxErrorMatches(self, code, message):
+        with self.subTest(code):
+            with self.assertRaisesRegex(SyntaxError, message):
+                compile_command(code, symbol='exec')
+
+    def test_syntax_errors(self):
+        self.assertSyntaxErrorMatches(
+            dedent("""\
+                def foo(x,x):
+                   pass
+            """), "duplicate argument 'x' in function definition")
+
 
 
 if __name__ == "__main__":

Misc/NEWS.d/next/Core and Builtins/2023-10-27-12-17-49.gh-issue-111366._TSknV.rst

@@ -0,0 +1,3 @@
+Fix an issue in the :mod:`codeop` that was causing :exc:`SyntaxError`
+exceptions raised in the presence of invalid syntax to not contain precise
+error messages. Patch by Pablo Galindo