Take the full path into account when sanitizing file name. Fixes fspr…

…ojects#1337.

src/Fantomas.Tests/CodeFormatterTests.fs

@@ -31,3 +31,30 @@ let main argv _ =
     )
     |> Async.RunSynchronously
     |> ignore
+
+[<Test>]
+let ``sanitize filename if path with Program.fs`` () =
+    let fileName = @"d:\dev\bootcamp\src\Program.fs"
+
+    let source = """
+open System
+open Poker.Main
+
+[<EntryPoint>]
+let main _ =
+    processInput Console.In Console.Out
+    0
+"""
+
+    let parsingOptions =
+        FakeHelpers.createParsingOptionsFromFile fileName
+
+    CodeFormatter.FormatDocumentAsync(
+        fileName,
+        SourceOrigin.SourceString source,
+        config,
+        parsingOptions,
+        sharedChecker.Value
+    )
+    |> Async.RunSynchronously
+    |> ignore

src/Fantomas/CodeFormatterImpl.fs

@@ -41,11 +41,13 @@ type FormatContext =
       SourceText: ISourceText }
 
 // Some file names have a special meaning for the F# compiler and the AST cannot be parsed.
-let safeFileName fileName =
+let safeFileName file =
+    let fileName = Path.GetFileName(file)
+
     if fileName = "Program.fs" then
         "tmp.fsx"
     else
-        fileName
+        file
 
 let createFormatContext fileName (source: SourceOrigin) =
     let (sourceText, sourceCode) = getSourceTextAndCode source