Compute abspath once

mypy/build.py

@@ -1699,6 +1699,7 @@ class State:
     order = None  # type: int  # Order in which modules were encountered
     id = None  # type: str  # Fully qualified module name
     path = None  # type: Optional[str]  # Path to module source
+    abspath = None  # type: Optional[str]  # Absolute path to module source
     xpath = None  # type: str  # Path or '<string>'
     source = None  # type: Optional[str]  # Module source code
     source_hash = None  # type: Optional[str]  # Hash calculated based on the source code
@@ -1800,6 +1801,8 @@ def __init__(self,
             if follow_imports == 'silent':
                 self.ignore_all = True
         self.path = path
+        if path:
+            self.abspath = os.path.abspath(path)
         self.xpath = path or '<string>'
         if path and source is None and self.manager.fscache.isdir(path):
             source = ''
@@ -2758,7 +2761,7 @@ def load_graph(sources: List[BuildSource], manager: BuildManager,
 
     # Note: Running this each time could be slow in the daemon. If it's a problem, we
     # can do more work to maintain this incrementally.
-    seen_files = {os.path.abspath(st.path): st for st in graph.values() if st.path}
+    seen_files = {st.abspath: st for st in graph.values() if st.path}
 
     # Collect dependencies.  We go breadth-first.
     # More nodes might get added to new as we go, but that's fine.