gh-96052: codeop: fix handling compiler warnings in incomplete input (GH-96132)

Previously codeop.compile_command() emitted compiler warnings (SyntaxWarning or
DeprecationWarning) and raised a SyntaxError for incomplete input containing
a potentially incorrect code. Now it always returns None for incomplete input
without emitting any warnings.
(cherry picked from commit 426d72e7ddb0af5cf851914ac75127186dd1ff04)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/Lib/codeop.py b/Lib/codeop.py
index 45a378b..2213b69 100644
--- a/Lib/codeop.py
+++ b/Lib/codeop.py
@@ -56,22 +56,22 @@ def _maybe_compile(compiler, source, filename, symbol):
         if symbol != "eval":
             source = "pass"     # Replace it with a 'pass' statement
 
-    try:
-        return compiler(source, filename, symbol)
-    except SyntaxError:  # Let other compile() errors propagate.
-        pass
-
-    # Catch syntax warnings after the first compile
-    # to emit warnings (SyntaxWarning, DeprecationWarning) at most once.
+    # Disable compiler warnings when checking for incomplete input.
     with warnings.catch_warnings():
-        warnings.simplefilter("error")
-
+        warnings.simplefilter("ignore", (SyntaxWarning, DeprecationWarning))
         try:
-            compiler(source + "\n", filename, symbol)
-        except SyntaxError as e:
-            if "incomplete input" in str(e):
+            compiler(source, filename, symbol)
+        except SyntaxError:  # Let other compile() errors propagate.
+            try:
+                compiler(source + "\n", filename, symbol)
                 return None
-            raise
+            except SyntaxError as e:
+                if "incomplete input" in str(e):
+                    return None
+                # fallthrough
+
+    return compiler(source, filename, symbol)
+
 
 def _is_syntax_error(err1, err2):
     rep1 = repr(err1)