python - Django 1.7 makemigrations - ValueError : Cannot serialize function: lambda

Question

我切换到 Django 1.7。当我为我的应用程序尝试 makemigrations 时，它崩溃了。崩溃报告是:

Migrations for 'roadmaps':
  0001_initial.py:
    - Create model DataQualityIssue
    - Create model MonthlyChange
    - Create model Product
    - Create model ProductGroup
    - Create model RecomendedStack
    - Create model RecomendedStackMembership
    - Create model RoadmapMarket
    - Create model RoadmapUser
    - Create model RoadmapVendor
    - Create model SpecialEvent
    - Create model TimelineEvent
    - Create model UserStack
    - Create model UserStackMembership
    - Add field products to userstack
    - Add field viewers to userstack
    - Add field products to recomendedstack
    - Add field product_group to product
    - Add field vendor to product
    - Add field product to dataqualityissue
Traceback (most recent call last):
  File "manage.py", line 29, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/makemigrations.py", line 124, in handle
    self.write_migration_files(changes)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/makemigrations.py", line 152, in write_migration_files
    migration_string = writer.as_string()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 129, in as_string
    operation_string, operation_imports = OperationWriter(operation).serialize()
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 80, in serialize
    arg_string, arg_imports = MigrationWriter.serialize(item)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 245, in serialize
    item_string, item_imports = cls.serialize(item)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 310, in serialize
    return cls.serialize_deconstructed(path, args, kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 221, in serialize_deconstructed
    arg_string, arg_imports = cls.serialize(arg)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/writer.py", line 323, in serialize
    raise ValueError("Cannot serialize function: lambda")
ValueError: Cannot serialize function: lambda

我在这里找到了一个注释 https://code.djangoproject.com/ticket/22892

还有指向文档的链接 https://docs.djangoproject.com/en/dev/topics/migrations/#serializing-values

但这并没有让我更清楚。错误消息没有给我在哪里寻找问题的线索。

有没有办法检测到底是哪一行导致了问题？

有什么提示吗？

Answer 1

我们在自定义字段定义中使用 lambda 时遇到了这个问题。

很难发现，因为它没有在回溯中列出，并且在使用此类自定义字段的特定模型上不会引发错误。

我们的解决方法:

• 检查所有自定义字段(甚至在第 3 方库中)
• 将 lambda 更改为可调用的，这是在模块中定义的(即不在自定义字段类中)