Fix LSP compatibility - textDocument/didChange version is the number after all changes applied

This was broken since the original code drop (or may be an artefact of LSP 2.0)
Fixes #1024

Author: lukaszsamson

apps/language_server/lib/language_server/parser.ex

@@ -58,6 +58,7 @@ defmodule ElixirLS.LanguageServer.Parser do
   end
 
   def handle_cast({:parse_with_debounce, uri, source_file}, state) do
+    # TODO check source_file.language_id
     state = if String.ends_with?(uri, [".ex", ".exs", ".eex"]) do
       state = update_in(state.debounce_refs[uri], fn old_ref ->
         if old_ref do

apps/language_server/lib/language_server/server.ex

@@ -528,7 +528,7 @@ defmodule ElixirLS.LanguageServer.Server do
     state
   end
 
-  defp handle_notification(did_open(uri, _language_id, version, text), state = %__MODULE__{}) do
+  defp handle_notification(did_open(uri, language_id, version, text), state = %__MODULE__{}) do
     if Map.has_key?(state.source_files, uri) do
       # An open notification must not be sent more than once without a corresponding
       # close notification send before
@@ -551,7 +551,7 @@ defmodule ElixirLS.LanguageServer.Server do
         Logger.error("File not valid on open:\n#{inspect(text)}")
       end
 
-      source_file = %SourceFile{text: text, version: version}
+      source_file = %SourceFile{text: text, version: version, language_id: language_id}
 
       Parser.parse_with_debounce(uri, source_file)
 
@@ -593,6 +593,8 @@ defmodule ElixirLS.LanguageServer.Server do
     else
       state =
         update_in(state.source_files[uri], fn source_file ->
+          # LSP 3.17: The version number points to the version after all provided content changes have
+	        # been applied
           updated_source_file =
             %SourceFile{source_file | version: version, dirty?: true}
             |> SourceFile.apply_content_changes(content_changes)

apps/language_server/lib/language_server/source_file.ex

@@ -2,7 +2,7 @@ defmodule ElixirLS.LanguageServer.SourceFile do
   import ElixirLS.LanguageServer.Protocol
   require Logger
 
-  defstruct [:text, :version, dirty?: false]
+  defstruct [:text, :version, :language_id, dirty?: false]
 
   @endings ["\r\n", "\r", "\n"]
 
@@ -54,12 +54,6 @@ defmodule ElixirLS.LanguageServer.SourceFile do
           put_in(source_file.text, new_text)
       end
 
-    source_file =
-      update_in(source_file.version, fn
-        v when is_integer(v) -> v + 1
-        _ -> 1
-      end)
-
     apply_content_changes(source_file, rest)
   end
 

apps/language_server/test/server_test.exs

@@ -527,7 +527,8 @@ defmodule ElixirLS.LanguageServer.ServerTest do
 
         assert_receive notification("textDocument/publishDiagnostics", %{
                          "uri" => ^uri,
-                         "diagnostics" => [diagnostic]
+                         "diagnostics" => [diagnostic],
+                         "version" => 1
                        }),
                        1000
 
@@ -550,14 +551,15 @@ defmodule ElixirLS.LanguageServer.ServerTest do
 
         state = :sys.get_state(server)
 
-        assert %SourceFile{dirty?: false, text: ^code, version: 1} =
+        assert %SourceFile{dirty?: false, text: ^code, language_id: "elixir", version: 1} =
                  Server.get_source_file(state, uri)
 
         # Code.with_diagnostics is broken on elixir < 1.15.3
         if Version.match?(System.version(), ">= 1.15.3") do
           assert_receive notification("textDocument/publishDiagnostics", %{
                            "uri" => ^uri,
-                           "diagnostics" => [diagnostic]
+                           "diagnostics" => [diagnostic],
+                           "version" => 1
                          }),
                          1000
 
@@ -810,11 +812,12 @@ defmodule ElixirLS.LanguageServer.ServerTest do
                        }),
                        1000
 
-        Server.receive_packet(server, did_change(uri, 1, content_changes))
+        Server.receive_packet(server, did_change(uri, 2, content_changes))
 
         assert_receive notification("textDocument/publishDiagnostics", %{
                          "uri" => ^uri,
-                         "diagnostics" => [_]
+                         "diagnostics" => [_],
+                         "version" => 2
                        }),
                        1000
 
@@ -846,24 +849,26 @@ defmodule ElixirLS.LanguageServer.ServerTest do
         )
 
         fake_initialize(server)
-        Server.receive_packet(server, did_open(uri, "elixir", 1, code))
+        Server.receive_packet(server, did_open(uri, "elixir", 0, code))
 
         assert_receive notification("textDocument/publishDiagnostics", %{
                          "uri" => ^uri,
-                         "diagnostics" => [_]
+                         "diagnostics" => [_],
+                         "version" => 0
                        }),
                        1000
 
         Server.receive_packet(server, did_change(uri, 1, content_changes))
 
         assert_receive notification("textDocument/publishDiagnostics", %{
                          "uri" => ^uri,
-                         "diagnostics" => []
+                         "diagnostics" => [],
+                         "version" => 1
                        }),
                        1000
 
         state = :sys.get_state(server)
-        assert %SourceFile{dirty?: true, version: 2} = Server.get_source_file(state, uri)
+        assert %SourceFile{dirty?: true, version: 1} = Server.get_source_file(state, uri)
 
         wait_until_compiled(server)
       end)