Server not compatible with marshmallow-dataclass>8.5.3

marshmallow-dataclass 8.5.3 works.

With marshmallow-dataclass 8.5.4 through 8.5.8, we get

$ lektor server
/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py:353: UserWarning: ****** WARNING ****** marshmallow_dataclass was called on the class <function NewType.<locals>.new_type at 0x7f0af2e076d0>, which is not a dataclass. It is going to try and convert the class into a dataclass, which may have undesirable side effects. To avoid this message, make sure all your classes and all the classes of their fields are either explicitly supported by marshmallow_dataclass, or define the schema explicitly using field(metadata=dict(marshmallow_field=...)). For more information, see https://github.com/lovasoa/marshmallow_dataclass/issues/51 ****** WARNING ******
  warnings.warn(
Traceback (most recent call last):
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/dataclasses.py", line 1197, in fields
    fields = getattr(class_or_instance, _FIELDS)
AttributeError: 'function' object has no attribute '__dataclass_fields__'. Did you mean: '__dataclass_params__'?

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 350, in _internal_class_schema
    fields: Tuple[dataclasses.Field, ...] = dataclasses.fields(clazz)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/dataclasses.py", line 1199, in fields
    raise TypeError('must be called with a dataclass type or instance')
TypeError: must be called with a dataclass type or instance

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 364, in _internal_class_schema
    created_dataclass: type = dataclasses.dataclass(clazz)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/dataclasses.py", line 1185, in dataclass
    return wrap(cls)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/dataclasses.py", line 1176, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash,
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/dataclasses.py", line 909, in _process_class
    for b in cls.__mro__[-1:0:-1]:
AttributeError: 'function' object has no attribute '__mro__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/joe/miniconda3/envs/lektor/bin/lektor", line 8, in <module>
    sys.exit(main())
  File "/home/joe/wrkspc/lktr/lektor/lektor/cli.py", line 621, in main
    cli.main(args=args, prog_name=name)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/decorators.py", line 84, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/joe/wrkspc/lktr/lektor/lektor/cli.py", line 336, in server_cmd
    from lektor.devserver import run_server
  File "/home/joe/wrkspc/lktr/lektor/lektor/devserver.py", line 9, in <module>
    from lektor.admin import WebAdmin
  File "/home/joe/wrkspc/lktr/lektor/lektor/admin/__init__.py", line 1, in <module>
    from .webui import WebAdmin
  File "/home/joe/wrkspc/lktr/lektor/lektor/admin/webui.py", line 12, in <module>
    from lektor.admin.modules import api
  File "/home/joe/wrkspc/lktr/lektor/lektor/admin/modules/api.py", line 137, in <module>
    @_with_validated(_PathAndAlt)
  File "/home/joe/wrkspc/lktr/lektor/lektor/admin/modules/api.py", line 97, in _with_validated
    schema_class = mdcls.class_schema(param_type, base_schema=_SchemaBase)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 339, in class_schema
    return _internal_class_schema(clazz, base_schema, clazz_frame)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 382, in _internal_class_schema
    attributes.update(
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 385, in <genexpr>
    field_for_schema(
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 707, in field_for_schema
    or _internal_class_schema(typ, base_schema, typ_frame)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 367, in _internal_class_schema
    raise TypeError(
TypeError: _PathType is not a dataclass and cannot be turned into one.

[nixjdm]

Yeah, I’m not sure where exactly this is a problem either, but I can at least confirm your fix!

# a git diff
-    typing.inspect < 0.8.0
+    typing-inspect < 0.8.0

works.

[nixjdm]

@dairiki It doesn’t look like that works, possibly because of some other issue with pkg_resources. Constraining marshmallow-dataclass directly might be the better option.

$ lektor s
Traceback (most recent call last):
  File "/home/joe/miniconda3/envs/lektor/bin/lektor", line 8, in <module>
    sys.exit(main())
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/lektor/cli.py", line 621, in main
    cli.main(args=args, prog_name=name)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/decorators.py", line 84, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/lektor/cli.py", line 341, in server_cmd
    ctx.load_plugins(extra_flags=extra_flags)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/lektor/cli_utils.py", line 140, in load_plugins
    initialize_plugins(self.get_env())
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/lektor/pluginsystem.py", line 127, in initialize_plugins
    plugins = load_plugins()
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/lektor/pluginsystem.py", line 121, in load_plugins
    rv[ep.name] = ep.load()
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/pkg_resources/__init__.py", line 2470, in load
    self.require(*args, **kwargs)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/pkg_resources/__init__.py", line 2493, in require
    items = working_set.resolve(reqs, env, installer, extras=self.extras)
  File "/home/joe/miniconda3/envs/lektor/lib/python3.10/site-packages/pkg_resources/__init__.py", line 795, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'typing.inspect<0.8.0' distribution was not found and is required by Lektor