Passing no providers to FullRepoMetadataConfig causes exception

[lisroach]

My ultimate goal is to use Fixit without Pyre, and without having to pass timeout=0 to the TypeInferenceProvider to force a breakage in the pyre subprocess call.

Created a simple repro:

from pathlib import Path
import logging
import sys
import libcst as cst
from fixit._version import FIXIT_VERSION
from fixit.common.config import get_lint_config
from fixit.common.config import get_rules_from_config
from fixit.common.full_repo_metadata import FullRepoMetadataConfig, get_repo_caches
from fixit.rule_lint_engine import lint_file
from libcst.metadata import MetadataWrapper, TypeInferenceProvider


def main(filename):
    full_repo_metadata_config = FullRepoMetadataConfig(
        providers=set(),  # <--- passing in no provider here instead of TypeInferenceProvider
        timeout_seconds=120,  # <--- If I were passing TypeInferenceProvider I would set this to 0
        logger=logging.getLogger("Metadata"),
    )

    with open(filename, "rb") as f:
        source = f.read()
    metadata_caches = get_repo_caches([filename], full_repo_metadata_config)
    try:
        cst_wrapper = MetadataWrapper(
            cst.parse_module(source),
            True,
            metadata_caches[filename],
        )
    except Exception:
        cst_wrapper = None
    rules = get_rules_from_config()
    config = get_lint_config()
    results = lint_file(
        Path(filename),
        source,
        rules=rules,
        config=config,
        cst_wrapper=cst_wrapper,
        find_unused_suppressions=True,
    )
    print(results)

if __name__ == "__main__":
    filename = sys.argv[0]
    main(filename)

Running this file results in:

(fixit-env) lisroach@lisroach-mbp Fixit % python3 hey.py hey.py
Traceback (most recent call last):
  File "hey.py", line 45, in <module>
    main(filename)
  File "hey.py", line 39, in main
    find_unused_suppressions=True,
  File "/Users/lisroach/Fixit/fixit/rule_lint_engine.py", line 115, in lint_file
    _visit_cst_rules_with_context(cst_wrapper, cst_rules, cst_context)
  File "/Users/lisroach/Fixit/fixit/rule_lint_engine.py", line 50, in _visit_cst_rules_with_context
    rule_instances, before_visit=before_visit, after_leave=after_leave
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/wrapper.py", line 222, in visit_batched
    stack.enter_context(v.resolve(self))
  File "/opt/homebrew/Cellar/python37/3.7.5_3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/contextlib.py", line 427, in enter_context
    result = _cm_type.__enter__(cm)
  File "/opt/homebrew/Cellar/python37/3.7.5_3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/contextlib.py", line 112, in __enter__
    return next(self.gen)
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/_metadata_dependent.py", line 85, in resolve
    self.metadata = wrapper.resolve_many(self.get_inherited_dependencies())
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/wrapper.py", line 196, in resolve_many
    _resolve_impl(self, providers)
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/wrapper.py", line 97, in _resolve_impl
    p(wrapper._cache.get(p)) if p.gen_cache else p() for p in batchable
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/wrapper.py", line 97, in <listcomp>
    p(wrapper._cache.get(p)) if p.gen_cache else p() for p in batchable
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/type_inference_provider.py", line 75, in __init__
    super().__init__(cache)
  File "/Users/lisroach/fixit-env/lib/python3.7/site-packages/libcst/metadata/base_provider.py", line 69, in __init__
    f"Cache is required for initializing {self.__class__.__name__}."