diag: Do not emit cross-file diag for single-file folders

Marksman/Diag.fs

@@ -42,6 +42,13 @@ let checkNonBreakingWhitespace (doc: Doc) =
 
             [ NonBreakableWhitespace(whitespaceRange) ])
 
+let isCrossFileLink uref =
+    match uref with
+    | Uref.Doc _ -> true
+    | Uref.Heading(doc = Some _) -> true
+    | Uref.Heading(doc = None) -> false
+    | Uref.LinkDef _ -> false
+
 let checkLink (folder: Folder) (doc: Doc) (link: Element) : seq<Entry> =
     let uref = Uref.ofElement link
 
@@ -50,7 +57,9 @@ let checkLink (folder: Folder) (doc: Doc) (link: Element) : seq<Entry> =
     | Some uref ->
         let refs = Dest.tryResolveUref uref doc folder |> Array.ofSeq
 
-        if refs.Length = 1 then
+        if Folder.isSingleFile folder && isCrossFileLink uref then
+            []
+        else if refs.Length = 1 then
             []
         else if refs.Length = 0 then
             match link with

Marksman/Workspace.fs

@@ -149,6 +149,11 @@ module Folder =
 
     let singleFile doc = SingleFile doc
 
+    let isSingleFile =
+        function
+        | SingleFile _ -> true
+        | MultiFile _ -> false
+
     let multiFile name root docs = MultiFile(name, root, docs)
 
     let docs: Folder -> seq<Doc> =

Marksman/Workspace.fsi

@@ -56,6 +56,7 @@ module Folder =
 
     val singleFile: Doc -> Folder
     val multiFile: name: string -> root: RootPath -> docs: Map<PathUri, Doc> -> Folder
+    val isSingleFile: Folder -> bool
 
     val withDoc: Doc -> Folder -> Folder
     val withoutDoc: PathUri -> Folder -> option<Folder>

Tests/DiagTest.fs

@@ -85,3 +85,20 @@ let noDiagOnNonMarkdownFiles () =
           "fake.md", "Link to non-existent document at 'another%20bad.md'" ],
         diag
     )
+
+[<Fact>]
+let noCrossFileDiagOnSingleFileFolders () =
+    let doc =
+        FakeDoc.Mk(
+            [| "[](bad.md)" //
+               "[[another-bad]]"
+               "[bad-ref][bad-ref]" |]
+        )
+
+    let folder = Folder.singleFile doc
+    let diag = checkFolder folder |> diagToHuman
+
+    Assert.Equal<string * string>(
+        [ "fake.md", "Link to non-existent link definition with the label 'bad-ref'" ],
+        diag
+    )