Crash on schemathesis with `--cache-dir=/dev/null`

[hauntsaninja]

Bisects to 3999ab88 in schemathesis

git clone https://github.com/schemathesis/schemathesis
cd schemathesis
mypy src/schemathesis --cache-dir=/dev/null

Traceback (most recent call last):
  File "/Users/shantanujain/.virtualenvs/mypy-wxtm/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
             ~~~~~~~~~~~~~^^
  File "/Users/shantanujain/dev/mypy/mypy/__main__.py", line 15, in console_entry
    main()
    ~~~~^^
  File "/Users/shantanujain/dev/mypy/mypy/main.py", line 119, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
                              ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/shantanujain/dev/mypy/mypy/main.py", line 203, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/shantanujain/dev/mypy/mypy/build.py", line 191, in build
    result = _build(
        sources, options, alt_lib_path, flush_errors, fscache, stdout, stderr, extra_plugins
    )
  File "/Users/shantanujain/dev/mypy/mypy/build.py", line 267, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/shantanujain/dev/mypy/mypy/build.py", line 2947, in dispatch
    write_deps_cache(rdeps, manager, graph)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/shantanujain/dev/mypy/mypy/build.py", line 976, in write_deps_cache
    assert st.meta, "Module must be either parsed or cached"
           ^^^^^^^
AssertionError: Module must be either parsed or cached

[hauntsaninja]

This would fix, but would be good to make a small repro. Looks related to schemathesis.internal

diff --git a/mypy/build.py b/mypy/build.py
index 342331243..a7a76a51f 100644
--- a/mypy/build.py
+++ b/mypy/build.py
@@ -973,8 +973,10 @@ def write_deps_cache(
         if st.source_hash:
             hash = st.source_hash
         else:
-            assert st.meta, "Module must be either parsed or cached"
-            hash = st.meta.hash
+            if st.meta:
+                hash = st.meta.hash
+            else:
+                hash = ""
         meta_snapshot[id] = hash
 
     meta = {"snapshot": meta_snapshot, "deps_meta": fg_deps_meta}

[hauntsaninja]

Needs --cache-fine-grained to repro

λ tree                 
.
└── s
    ├── __init__.py
    └── internal
        └── checks.py

3 directories, 2 files
λ cat s/__init__.py
λ cat s/internal/checks.py 
from ..types import foo

λ mypy s --cache-dir=/dev/null --cache-fine-grained
s/internal/checks.py:1: error: Cannot find implementation or library stub for module named "s.types"  [import-not-found]
s/internal/checks.py:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Traceback (most recent call last):
  File "/Users/shantanu/.virtualenvs/mypy-crxl/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
             ^^^^^^^^^^^^^^^
  File "/Users/shantanu/dev/mypy/mypy/__main__.py", line 15, in console_entry
    main()
  File "/Users/shantanu/dev/mypy/mypy/main.py", line 119, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/shantanu/dev/mypy/mypy/main.py", line 203, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/shantanu/dev/mypy/mypy/build.py", line 191, in build
    result = _build(
             ^^^^^^^
  File "/Users/shantanu/dev/mypy/mypy/build.py", line 267, in _build
    graph = dispatch(sources, manager, stdout)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/shantanu/dev/mypy/mypy/build.py", line 2947, in dispatch
    write_deps_cache(rdeps, manager, graph)
  File "/Users/shantanu/dev/mypy/mypy/build.py", line 976, in write_deps_cache
    assert st.meta, "Module must be either parsed or cached"
AssertionError: Module must be either parsed or cached