bpo-44859: Improve error handling in sqlite3 and and raise more accurate exceptions. (GH-27654)

* MemoryError is now raised instead of sqlite3.Warning when
  memory is not enough for encoding a statement to UTF-8
  in Connection.__call__() and Cursor.execute().
* UnicodEncodeError is now raised instead of sqlite3.Warning when
  the statement contains surrogate characters
  in Connection.__call__() and Cursor.execute().
* TypeError is now raised instead of ValueError for non-string
  script argument in Cursor.executescript().
* ValueError is now raised for script containing the null
  character instead of truncating it in Cursor.executescript().
* Correctly handle exceptions raised when getting boolean value
  of the result of the progress handler.
* Add many tests covering different corner cases.

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@innova.no>

Lib/sqlite3/test/userfunctions.py

@@ -33,28 +33,37 @@
 from test.support import bigmemtest
 
 
-def with_tracebacks(strings):
+def with_tracebacks(strings, traceback=True):
     """Convenience decorator for testing callback tracebacks."""
-    strings.append('Traceback')
+    if traceback:
+        strings.append('Traceback')
 
     def decorator(func):
         @functools.wraps(func)
         def wrapper(self, *args, **kwargs):
             # First, run the test with traceback enabled.
-            sqlite.enable_callback_tracebacks(True)
-            buf = io.StringIO()
-            with contextlib.redirect_stderr(buf):
+            with check_tracebacks(self, strings):
                 func(self, *args, **kwargs)
-            tb = buf.getvalue()
-            for s in strings:
-                self.assertIn(s, tb)
 
             # Then run the test with traceback disabled.
-            sqlite.enable_callback_tracebacks(False)
             func(self, *args, **kwargs)
         return wrapper
     return decorator
 
+@contextlib.contextmanager
+def check_tracebacks(self, strings):
+    """Convenience context manager for testing callback tracebacks."""
+    sqlite.enable_callback_tracebacks(True)
+    try:
+        buf = io.StringIO()
+        with contextlib.redirect_stderr(buf):
+            yield
+        tb = buf.getvalue()
+        for s in strings:
+            self.assertIn(s, tb)
+    finally:
+        sqlite.enable_callback_tracebacks(False)
+
 def func_returntext():
     return "foo"
 def func_returntextwithnull():
@@ -408,9 +417,26 @@ def md5sum(t):
         del x,y
         gc.collect()
 
+    def test_func_return_too_large_int(self):
+        cur = self.con.cursor()
+        for value in 2**63, -2**63-1, 2**64:
+            self.con.create_function("largeint", 0, lambda value=value: value)
+            with check_tracebacks(self, ['OverflowError']):
+                with self.assertRaises(sqlite.DataError):
+                    cur.execute("select largeint()")
+
+    def test_func_return_text_with_surrogates(self):
+        cur = self.con.cursor()
+        self.con.create_function("pychr", 1, chr)
+        for value in 0xd8ff, 0xdcff:
+            with check_tracebacks(self,
+                    ['UnicodeEncodeError', 'surrogates not allowed']):
+                with self.assertRaises(sqlite.OperationalError):
+                    cur.execute("select pychr(?)", (value,))
+
     @unittest.skipUnless(sys.maxsize > 2**32, 'requires 64bit platform')
     @bigmemtest(size=2**31, memuse=3, dry_run=False)
-    def test_large_text(self, size):
+    def test_func_return_too_large_text(self, size):
         cur = self.con.cursor()
         for size in 2**31-1, 2**31:
             self.con.create_function("largetext", 0, lambda size=size: "b" * size)
@@ -419,7 +445,7 @@ def test_large_text(self, size):
 
     @unittest.skipUnless(sys.maxsize > 2**32, 'requires 64bit platform')
     @bigmemtest(size=2**31, memuse=2, dry_run=False)
-    def test_large_blob(self, size):
+    def test_func_return_too_large_blob(self, size):
         cur = self.con.cursor()
         for size in 2**31-1, 2**31:
             self.con.create_function("largeblob", 0, lambda size=size: b"b" * size)