gh-108590: Fix sqlite3.iterdump for invalid Unicode in TEXT columns (#108657)

Co-authored-by: Erlend E. Aasland <erlend@python.org>

Lib/sqlite3/dump.py

@@ -7,6 +7,10 @@
 # future enhancements, you should normally quote any identifier that
 # is an English language word, even if you do not have to."
 
+
+from contextlib import contextmanager
+
+
 def _quote_name(name):
     return '"{0}"'.format(name.replace('"', '""'))
 
@@ -15,6 +19,24 @@ def _quote_value(value):
     return "'{0}'".format(value.replace("'", "''"))
 
 
+def _force_decode(bs, *args, **kwargs):
+    # gh-108590: Don't fail if the database contains invalid Unicode data.
+    try:
+        return bs.decode(*args, **kwargs)
+    except UnicodeDecodeError:
+        return "".join([chr(c) for c in bs])
+
+
+@contextmanager
+def _text_factory(con, factory):
+    saved_factory = con.text_factory
+    con.text_factory = factory
+    try:
+        yield
+    finally:
+        con.text_factory = saved_factory
+
+
 def _iterdump(connection):
     """
     Returns an iterator to the dump of the database in an SQL text format.
@@ -74,8 +96,9 @@ def _iterdump(connection):
             )
         )
         query_res = cu.execute(q)
-        for row in query_res:
-            yield("{0};".format(row[0]))
+        with _text_factory(connection, bytes):
+            for row in query_res:
+                yield("{0};".format(_force_decode(row[0])))
 
     # Now when the type is 'index', 'trigger', or 'view'
     q = """