Patch CharField/TextField to handle None as empty string and add none_to_empty converter

Author: pangpang20

gaussdb_django/base.py

@@ -11,7 +11,7 @@
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.db import DatabaseError as WrappedDatabaseError
-from django.db import connections
+from django.db import connections, models
 from django.db.backends.base.base import NO_DB_ALIAS, BaseDatabaseWrapper
 from django.db.backends.utils import CursorDebugWrapper as BaseCursorDebugWrapper
 from django.utils.asyncio import async_unsafe
@@ -70,6 +70,15 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
+        
+        def fix_field(value):
+            return "" if value is None else str(value)
+        def patched_get_prep_value(self, value):
+            result = fix_field(value)
+            return result
+        models.CharField.get_prep_value = patched_get_prep_value
+        models.TextField.get_prep_value = patched_get_prep_value
+
 
     # This dictionary maps Field objects to their associated Gaussdb column
     # types, as strings. Column-type strings can contain format strings; they'll

gaussdb_django/operations.py

@@ -1,6 +1,5 @@
 import json
 from functools import lru_cache, partial
-from datetime import datetime, date
 from django.conf import settings
 from django.db.backends.base.operations import BaseDatabaseOperations
 from .compiler import InsertUnnest, GaussDBSQLCompiler, SQLInsertCompiler
@@ -15,6 +14,7 @@
 from django.db.models.functions import Cast
 from django.utils.regex_helper import _lazy_re_compile
 from django.db.models import JSONField, IntegerField
+from django.db import models
 
 
 @lru_cache
@@ -28,7 +28,6 @@ class DatabaseOperations(BaseDatabaseOperations):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
-    # compiler_module = "gaussdb_django.compiler"
     cast_char_field_without_max_length = "varchar"
     explain_prefix = "EXPLAIN"
     explain_options = frozenset(
@@ -439,7 +438,6 @@ def converter(value, expression, connection):
 
             return [converter] + converters
         if isinstance(expression.output_field, IntegerField):
-
             def int_safe_converter(value, expression, connection):
                 if value is None:
                     return None
@@ -451,5 +449,10 @@ def int_safe_converter(value, expression, connection):
                     return None
 
             return [int_safe_converter] + converters
-
+        if isinstance(expression.output_field, (models.CharField, models.TextField)):
+            def none_to_empty(value, expression, connection):
+                if value is None:
+                    return ""
+                return value
+            converters.append(none_to_empty)
         return converters