Fix .fantomasignore support (fsprojects#1920)

* Fix .fantomasignore support

- Don't call MAB.DotIgnore.IgnoreList.IsIgnored() with absolute paths
- Remove path prefix (".\" or: "./") when calling MAB.DotIgnore.IgnoreList.IsIgnored()

* add unit test 'ignore specific file in subfolder'

- extend TestHelpers.TemporaryFileCodeSample to support multiple sub folders
  otherwise we would call --recurse in Path.GetTempPath(), which might contain unrelated .fs files
- adjust other tests

* Add back the original subFolder ctr parameter alongside the new subFolders parameter.

- Internally use an array and let subfolders take precedence over subfolder

* Remove now superfluous blank lines

* Call Directory.Delete() with the topmost subfolder and recursive = true

Co-authored-by: David Schaefer <david.schaefer@rhein-spree.com>

src/Fantomas.CoreGlobalTool.Tests/IgnoreFilesTests.fs

@@ -43,6 +43,24 @@ let ``ignore specific file`` () =
 
     output |> should contain "was ignored"
 
+[<Test>]
+let ``ignore specific file in subfolder`` () =
+    let fileName = "A"
+    let sub1 = System.Guid.NewGuid().ToString("N")
+    let sub2 = System.Guid.NewGuid().ToString("N")
+    let subFolders = [| sub1; sub2 |]
+
+    use inputFixture =
+        new TemporaryFileCodeSample(Source, fileName = fileName, subFolders = subFolders)
+
+    use ignoreFixture =
+        new FantomasIgnoreFile(sprintf "%s/%s/A.fs" sub1 sub2)
+
+    let { ExitCode = exitCode; Output = output } =
+        runFantomasTool (sprintf "--recurse --check .%c%s" Path.DirectorySeparatorChar sub1)
+
+    exitCode |> should equal 0
+
 [<Test>]
 let ``don't ignore other files`` () =
     let fileName = "B"

src/Fantomas.CoreGlobalTool.Tests/TestHelpers.fs

@@ -12,19 +12,29 @@ type TemporaryFileCodeSample
         codeSnippet: string,
         ?hasByteOrderMark: bool,
         ?fileName: string,
-        ?subFolder: string
+        ?subFolder: string,
+        ?subFolders: string array
     ) =
     let hasByteOrderMark = defaultArg hasByteOrderMark false
 
+    let internalSubFolders =
+        match subFolders with
+        | Some sf -> Some sf
+        | None ->
+            match subFolder with
+            | Some sf -> Array.singleton sf |> Some
+            | None -> None
+
     let filename =
         let name =
             match fileName with
             | Some fn -> fn
             | None -> Guid.NewGuid().ToString()
 
-        match subFolder with
+        match internalSubFolders with
         | Some sf ->
-            let tempFolder = Path.Join(Path.GetTempPath(), sf)
+            let tempFolder =
+                Path.Join(Path.GetTempPath(), Path.Join(sf))
 
             if not (Directory.Exists(tempFolder)) then
                 Directory.CreateDirectory(tempFolder) |> ignore
@@ -44,11 +54,11 @@ type TemporaryFileCodeSample
         member this.Dispose() : unit =
             File.Delete(filename)
 
-            subFolder
+            internalSubFolders
             |> Option.iter
                 (fun sf ->
-                    Path.Join(Path.GetTempPath(), sf)
-                    |> Directory.Delete)
+                    let path = Path.Join(Path.GetTempPath(), sf.[0])
+                    Directory.Delete(path, true))
 
 type OutputFile internal () =
     let filename =

src/Fantomas.Extras/IgnoreFile.fs

@@ -18,13 +18,22 @@ module IgnoreFile =
         let path = getIgnoreFilePath ()
         File.Exists path |> not
 
+    let private relativePathPrefix =
+        sprintf ".%c" Path.DirectorySeparatorChar
+
+    let private removeRelativePathPrefix (path: string) =
+        if path.StartsWith(relativePathPrefix) then
+            path.Substring(2)
+        else
+            path
+
     let isIgnoredFile (file: string) =
         if hasNoIgnoreFile () then
             false
         else
             try
-                let fullPath = Path.GetFullPath(file)
-                ignores.Value.IsIgnored(fullPath, false)
+                let path = removeRelativePathPrefix file
+                ignores.Value.IsIgnored(path, false)
             with
             | ex ->
                 printfn "%A" ex