fix: don't fail when document is missing (#266)

There is a report of the document being nil, which is causing the server
to crash. The document should never be nil, but we can figure that out
later. The server not crashing should make that easier.

lib/next_ls.ex

@@ -451,41 +451,52 @@ defmodule NextLS do
     document = lsp.assigns.documents[uri]
 
     [resp] =
-      dispatch(lsp.assigns.registry, :runtimes, fn entries ->
-        for {runtime, %{uri: wuri}} <- entries, String.starts_with?(uri, wuri) do
-          with {:ok, {formatter, _}} <-
-                 Runtime.call(runtime, {Mix.Tasks.Format, :formatter_for_file, [URI.parse(uri).path]}),
-               {:ok, response} when is_binary(response) or is_list(response) <-
-                 Runtime.call(runtime, {Kernel, :apply, [formatter, [Enum.join(document, "\n")]]}) do
-            {:reply,
-             [
-               %TextEdit{
-                 new_text: IO.iodata_to_binary(response),
-                 range: %Range{
-                   start: %Position{line: 0, character: 0},
-                   end: %Position{
-                     line: length(document),
-                     character: document |> List.last() |> String.length() |> Kernel.-(1) |> max(0)
+      if is_list(document) do
+        dispatch(lsp.assigns.registry, :runtimes, fn entries ->
+          for {runtime, %{uri: wuri}} <- entries, String.starts_with?(uri, wuri) do
+            with {:ok, {formatter, _}} <-
+                   Runtime.call(runtime, {Mix.Tasks.Format, :formatter_for_file, [URI.parse(uri).path]}),
+                 {:ok, response} when is_binary(response) or is_list(response) <-
+                   Runtime.call(runtime, {Kernel, :apply, [formatter, [Enum.join(document, "\n")]]}) do
+              {:reply,
+               [
+                 %TextEdit{
+                   new_text: IO.iodata_to_binary(response),
+                   range: %Range{
+                     start: %Position{line: 0, character: 0},
+                     end: %Position{
+                       line: length(document),
+                       character: document |> List.last() |> String.length() |> Kernel.-(1) |> max(0)
+                     }
                    }
                  }
-               }
-             ], lsp}
-          else
-            {:error, :not_ready} ->
-              GenLSP.notify(lsp, %GenLSP.Notifications.WindowShowMessage{
-                params: %GenLSP.Structures.ShowMessageParams{
-                  type: GenLSP.Enumerations.MessageType.info(),
-                  message: "The NextLS runtime is still initializing!"
-                }
-              })
+               ], lsp}
+            else
+              {:error, :not_ready} ->
+                GenLSP.notify(lsp, %GenLSP.Notifications.WindowShowMessage{
+                  params: %GenLSP.Structures.ShowMessageParams{
+                    type: GenLSP.Enumerations.MessageType.info(),
+                    message: "The NextLS runtime is still initializing!"
+                  }
+                })
+
+                {:reply, nil, lsp}
 
-              {:reply, nil, lsp}
+              _ ->
+                GenLSP.warning(lsp, "[Next LS] Failed to format the file: #{uri}")
 
-            _ ->
-              {:reply, nil, lsp}
+                {:reply, nil, lsp}
+            end
           end
-        end
-      end)
+        end)
+      else
+        GenLSP.warning(
+          lsp,
+          "[Next LS] The file #{uri} was not found in the server's process state. Something must have gone wrong when opening, changing, or saving the file."
+        )
+
+        [{:reply, nil, lsp}]
+      end
 
     resp
   end