One more time...

Author: baronfel

src/FsAutoComplete.Core/SignatureFormatter.fs

@@ -43,7 +43,11 @@ module SignatureFormatter =
   let rec formatFSharpType (context: FSharpDisplayContext) (typ: FSharpType) : string =
     let context = context.WithPrefixGenericParameters()
 
-    let nullabilityClause = if typ.HasNullAnnotation then " | null" else ""
+    let nullabilityClause =
+      if typ.HasNullAnnotation || typ.IsNullAmbivalent then
+        " | null"
+      else
+        ""
 
     try
       if typ.IsTupleType || typ.IsStructTupleType then

test/FsAutoComplete.Tests.Lsp/CoreTests.fs

@@ -641,6 +641,7 @@ let tooltipTests state =
             106u
             7u
             (concatLines [ "val usesBCLNullable:"; "   key: string"; "     -> string | null" ])
+          verifySignature "simple value" 107u 7u ("val envKey: string | null")
 #endif
           ] ]
 

test/FsAutoComplete.Tests.Lsp/TestCases/Tooltips/Script.fsx

@@ -105,3 +105,4 @@ let usesConcreteNullable (x: string | null) = nonNull x
 let makesNullable (x: 'x): 'x | null = null
 let makesConcreteNullable (x: string): string | null = null
 let usesBCLNullable (key: string) = System.Environment.GetEnvironmentVariable(key)
+let envKey = System.Environment.GetEnvironmentVariable("PATH")