Fix some bugs in fg cache loading

Author: msullivan

mypy/dmypy_server.py

@@ -265,6 +265,7 @@ def initialize_fine_grained(self, sources: List[mypy.build.BuildSource]) -> Dict
         messages = result.errors
         manager = result.manager
         graph = result.graph
+        manager.options.cache_dir = os.devnull  # XXX: HACK
         self.fine_grained_manager = mypy.server.update.FineGrainedBuildManager(manager, graph)
         self.fine_grained_initialized = True
         self.previous_sources = sources
@@ -285,7 +286,7 @@ def initialize_fine_grained(self, sources: List[mypy.build.BuildSource]) -> Dict
             # Run an update
             changed = self.find_changed(sources)
             if changed:
-                messages += self.fine_grained_manager.update(changed)
+                messages = self.fine_grained_manager.update(changed)
 
         status = 1 if messages else 0
         self.previous_messages = messages[:]

mypy/server/update.py

@@ -378,7 +378,7 @@ def update_single_isolated(module: str,
     sources = get_sources(previous_modules, [(module, path)])
     invalidate_stale_cache_entries(manager.saved_cache, [(module, path)])
 
-    manager.missing_modules = set()
+    manager.missing_modules.clear()
     try:
         graph = load_graph(sources, manager)
     except CompileError as err:
@@ -497,7 +497,8 @@ def delete_module(module_id: str,
     # TODO: Remove deps for the module (this only affects memory use, not correctness)
     assert module_id not in graph
     new_graph = graph.copy()
-    del manager.modules[module_id]
+    if module_id in manager.modules:
+        del manager.modules[module_id]
     if module_id in manager.saved_cache:
         del manager.saved_cache[module_id]
     components = module_id.split('.')

test-data/unit/fine-grained-modules.test

@@ -245,7 +245,6 @@ from p import q
 main:1: error: Cannot find module named 'p.q'
 -- TODO: The following messages are different compared to non-incremental mode
 main:1: note: (Perhaps setting MYPYPATH or using the "--ignore-missing-imports" flag would help)
-main:1: error: Module 'p' has no attribute 'q'
 ==
 
 [case testDeletionOfSubmoduleTriggersImportFrom2]