From d7ebe2e6fcd32e4c9c32e007aaa0b130e40a9829 Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Mon, 13 Jan 2025 15:25:09 -0800
Subject: [PATCH] Fix crash with `--cache-fine-grained --cache-dir=/dev/null`
 (#18457)

Fixes #18454

Couldn't easily repro in test suite
---
 mypy/build.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mypy/build.py b/mypy/build.py
index 342331243b96..a7a76a51f958 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}