Fix some blocking in incremental builder

src/Compiler/Service/IncrementalBuild.fs

@@ -914,7 +914,7 @@ module IncrementalBuilderStateHelpers =
             return! prevBoundModel.Next(syntaxTree)
         })
 
-    let rec createFinalizeBoundModelGraphNode (initialState: IncrementalBuilderInitialState) (boundModels: GraphNode<BoundModel> seq) =
+    let createFinalizeBoundModelGraphNode (initialState: IncrementalBuilderInitialState) (boundModels: GraphNode<BoundModel> seq) =
         GraphNode(node {
             use _ = Activity.start "GetCheckResultsAndImplementationsForProject" [|Activity.Tags.project, initialState.outfile|]
             let! result = 
@@ -928,7 +928,7 @@ module IncrementalBuilderStateHelpers =
             return result, DateTime.UtcNow
         })
 
-    and computeStampedFileNames (initialState: IncrementalBuilderInitialState) (state: IncrementalBuilderState) (cache: TimeStampCache) =
+    let computeStampedFileNames (initialState: IncrementalBuilderInitialState) (state: IncrementalBuilderState) (cache: TimeStampCache) =
         let slots = 
             if initialState.useChangeNotifications then
                 state.slots
@@ -967,7 +967,7 @@ module IncrementalBuilderStateHelpers =
         else
             state
 
-    and computeStampedReferencedAssemblies (initialState: IncrementalBuilderInitialState) state canTriggerInvalidation (cache: TimeStampCache) =
+    let computeStampedReferencedAssemblies (initialState: IncrementalBuilderInitialState) state canTriggerInvalidation (cache: TimeStampCache) =
         let stampedReferencedAssemblies = state.stampedReferencedAssemblies.ToBuilder()
 
         let mutable referencesUpdated = false
@@ -1132,11 +1132,6 @@ type IncrementalBuilder(initialState: IncrementalBuilderInitialState, state: Inc
             do! setCurrentState currentState cache ct
         }
 
-    let checkFileTimeStampsSynchronously cache =
-        checkFileTimeStamps cache
-        |> Async.AwaitNodeCode
-        |> Async.RunSynchronously
-
     do IncrementalBuilderEventTesting.MRU.Add(IncrementalBuilderEventTesting.IBECreated)
 
     member _.TcConfig = tcConfig
@@ -1192,10 +1187,10 @@ type IncrementalBuilder(initialState: IncrementalBuilderInitialState, state: Inc
 
     member builder.TryGetCheckResultsBeforeFileInProject fileName =
         let cache = TimeStampCache defaultTimeStamp
-        checkFileTimeStampsSynchronously cache
+        let tmpState = computeStampedFileNames initialState currentState cache
 
         let slotOfFile = builder.GetSlotOfFileName fileName
-        match tryGetBeforeSlot currentState slotOfFile with
+        match tryGetBeforeSlot tmpState slotOfFile with
         | Some(boundModel, timestamp) ->
             let projectTimeStamp = builder.GetLogicalTimeStampForFileInProject(fileName)
             Some (PartialCheckResults (boundModel, timestamp, projectTimeStamp))
@@ -1277,12 +1272,12 @@ type IncrementalBuilder(initialState: IncrementalBuilderInitialState, state: Inc
 
     member _.GetLogicalTimeStampForFileInProject(slotOfFile: int) =
         let cache = TimeStampCache defaultTimeStamp
-        checkFileTimeStampsSynchronously cache
-        computeProjectTimeStamp currentState slotOfFile
+        let tempState = computeStampedFileNames initialState currentState cache
+        computeProjectTimeStamp tempState slotOfFile
 
     member _.GetLogicalTimeStampForProject(cache) =
-        checkFileTimeStampsSynchronously cache
-        computeProjectTimeStamp currentState -1
+        let tempState = computeStampedFileNames initialState currentState cache
+        computeProjectTimeStamp tempState -1
 
     member _.TryGetSlotOfFileName(fileName: string) =
         // Get the slot of the given file and force it to build.

src/Compiler/Service/IncrementalBuild.fsi

@@ -185,15 +185,18 @@ type internal IncrementalBuilder =
     /// This is safe for use from non-compiler threads but the objects returned must in many cases be accessed only from the compiler thread.
     member GetCheckResultsForFileInProjectEvenIfStale: fileName: string -> PartialCheckResults option
 
+    // TODO: Looks like the following doc does not match the actual method or it's signature.
+
     /// Get the preceding typecheck state of a slot, but only if it is up-to-date w.r.t.
     /// the timestamps on files and referenced DLLs prior to this one. Return None if the result is not available.
     /// This is a relatively quick operation.
     ///
     /// This is safe for use from non-compiler threads
     member AreCheckResultsBeforeFileInProjectReady: fileName: string -> bool
 
-    /// Get the preceding typecheck state of a slot, WITH checking if it is up-to-date w.r.t. However, files will not be parsed or checked.
-    /// the timestamps on files and referenced DLLs prior to this one. Return None if the result is not available or if it is not up-to-date.
+    /// Get the preceding typecheck state of a slot, WITH checking if it is up-to-date w.r.t. the timestamps of files and referenced DLLs prior to this one.
+    /// However, files will not be parsed or checked.
+    /// Return None if the result is not available or if it is not up-to-date.
     ///
     /// This is safe for use from non-compiler threads but the objects returned must in many cases be accessed only from the compiler thread.
     member TryGetCheckResultsBeforeFileInProject: fileName: string -> PartialCheckResults option