This change fixes all sphinx warnings when building the fiddle docs with only one exception: the warning that both index.rst and index.md exist.

Note: this has been tested with a clean virtualenv + install (which caught the missing graphviz dependency).

Skip copying HistoryEntry dataclasses, which are immutable. This should be correct almost all of the time, though it may have different behavior if a sub-configuration (stored in the new_value field of a HistoryEntry) is mutated later. But this is perhaps a more general problem for the API; if we wanted to solve it then we should deepcopy the value stored in the new_value field when creating HistoryEntry's.

Python doesn't do this automatically because it can't guarantee that a dataclass is actually/effectively immutable just because it is frozen.

Update replace_unconfigured_partials_with_callables to replace Partials with their Callables if the only arguments that are passed are equivalent to the corresponding default argument.

Get rid of BuildError and adopt solution from Gin, which uses subclassing to attach some additional error information.

We have chosen to go with this slightly magical approach, since the stack traces from Python's raise new_error from old_error feature shows the user Fiddle internal stack trace lines first, even when the error is clearly from user code.

Configurator pattern, which might be a useful mid-level API option when auto_config is too magical.

The configurator is inspired by (basically a Fiddle version of) https://detectron2.readthedocs.io/en/latest/tutorials/lazyconfigs.html , though we also pass through technically-incorrect type signatures so that we get static type checking of arguments similar to auto_config.

Example usage:

encoder = C(Encoder)( embedders={ "tokens": shared_token_embedder, "position": None }, attention=C(Attention)(dtype, kernel_init, bias_init), mlp=C(Mlp)(dtype, False, ["embed", "num_heads", "head_dim"]), )

I am trying to run this colab from the documentation but importing fails when running the first cell.

Collecting fiddle
  Downloading fiddle-0.2.2-py3-none-any.whl (233 kB)
     |████████████████████████████████| 233 kB 7.6 MB/s 
Requirement already satisfied: typing-extensions in /usr/local/lib/python3.7/dist-packages (from fiddle) (4.1.1)
Collecting libcst
  Downloading libcst-0.4.7-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (2.7 MB)
     |████████████████████████████████| 2.7 MB 54.7 MB/s 
Requirement already satisfied: pyyaml>=5.2 in /usr/local/lib/python3.7/dist-packages (from libcst->fiddle) (6.0)
Collecting typing-inspect>=0.4.0
  Downloading typing_inspect-0.8.0-py3-none-any.whl (8.7 kB)
Collecting mypy-extensions>=0.3.0
  Downloading mypy_extensions-0.4.3-py2.py3-none-any.whl (4.5 kB)
Installing collected packages: mypy-extensions, typing-inspect, libcst, fiddle
Successfully installed fiddle-0.2.2 libcst-0.4.7 mypy-extensions-0.4.3 typing-inspect-0.8.0
Traceback (most recent call last):

  File "/usr/local/lib/python3.7/dist-packages/IPython/core/interactiveshell.py", line 3326, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)

  File ["<ipython-input-1-ba42286d1387>"](https://localhost:8080/#), line 3, in <module>
    import fiddle as fdl

  File "/usr/local/lib/python3.7/dist-packages/fiddle/__init__.py", line 18, in <module>
    from fiddle.building import build

  File "/usr/local/lib/python3.7/dist-packages/fiddle/building.py", line 22, in <module>
    from fiddle import config

  File "/usr/local/lib/python3.7/dist-packages/fiddle/config.py", line 86
    def __init__(self, fn_or_cls: Union['Buildable', TypeOrCallableProducingT], /,
                                                                                ^
SyntaxError: invalid syntax

Fiddle intends to drop support for Python 3.7 as it is beyond EoL. Additionally, by dropping Py3.7, we can better support all sorts of argument names.

Fix bug where applying auto_config to a lambda could fail if the lambda expression was wrapped in a larger multi-line expression, such that inspect.getsource(fn) does not form a valid python statement.

Fix bug where applying auto_config to a lambda could fail if the lambda expression was wrapped in a larger multi-line expression, such that inspect.getsource(fn) does not form a valid python statement. E.g.:

foo = ( lambda: f(3))

(Note that "lambda: f(3))" is not valid Python because of the trailing close-paren.)