[flow] make autocompleteService_js return non-lazy result

Summary:
The only difference between
* `ServerProt.Response.Completion.completion_item`
* `AutocompleteService_js.AcCompletion.completion_item`

is that the former computes `documentation_and_tags` lazily. By the time `autocomplete_get_results` is done, we should have determined that final list of items that will be included in the response. It is safe at that point to force documentation and tags into evaluation without doing redundant work. In other words, the perf fix of D52670618 still applies.

Motivation for this change is to allow be able to compare the result of completion between "typed-AST" and "on-demand" modes. To do so, I plan to use `eq` which cannot be expressed over lazy values. This also allows us to hide `AcCompletion` as an implementation detail of `AutocompleteService_js`.

Changelog: [internal]

Reviewed By: SamChou19815

Differential Revision: D55231178

fbshipit-source-id: 7c70c139a513a6645600c808c5998dfa1b267917

src/server/command_handler/commandHandler.ml

@@ -402,7 +402,6 @@ let autocomplete
         let open Hh_json in
         match results_res with
         | AcResult { result; errors_to_log } ->
-          let result = AcCompletion.to_server_prot_completion_t result in
           let { ServerProt.Response.Completion.items; is_incomplete = _ } = result in
           let result_string =
             match (items, errors_to_log) with

src/services/autocomplete/autocompleteService_js.ml

@@ -374,16 +374,19 @@ let mk_typing_artifacts ~options ~reader ~cx ~file_sig ~ast ~available_ast ~expo
   in
   { options; reader; cx; file_sig; ast; available_ast; exports; norm_genv }
 
-type ac_result = {
-  result: AcCompletion.t;
+type 'r ac_result = {
+  result: 'r;
   errors_to_log: string list;
 }
 
-type autocomplete_service_result =
-  | AcResult of ac_result
+type 'r autocomplete_service_result_generic =
+  | AcResult of 'r ac_result
   | AcEmpty of string
   | AcFatalError of string
 
+type autocomplete_service_result =
+  ServerProt.Response.Completion.t autocomplete_service_result_generic
+
 let jsdoc_of_def_loc { reader; ast; _ } def_loc =
   loc_of_aloc ~reader def_loc |> Find_documentation.jsdoc_of_getdef_loc ~ast ~reader
 
@@ -2109,7 +2112,7 @@ let autocomplete_get_results typing ac_options trigger_character cursor =
   match process_location cx ~trigger_character ~cursor ~available_ast with
   | Error err -> (None, None, "None", AcFatalError err)
   | Ok None ->
-    let result = { AcCompletion.items = []; is_incomplete = false } in
+    let result = { ServerProt.Response.Completion.items = []; is_incomplete = false } in
     ( None,
       None,
       "None",
@@ -2268,4 +2271,11 @@ let autocomplete_get_results typing ac_options trigger_character cursor =
       | Ac_qualified_type qtype ->
         autocomplete_module_exports ~typing ~edit_locs ~token ~kind:`Type qtype
     in
+    let result =
+      match result with
+      | AcResult { result; errors_to_log } ->
+        AcResult { result = AcCompletion.to_server_prot_completion_t result; errors_to_log }
+      | AcEmpty s -> AcEmpty s
+      | AcFatalError e -> AcFatalError e
+    in
     (Some token, Some ac_loc, string_of_autocomplete_type autocomplete_type, result)

src/services/autocomplete/autocompleteService_js.mli

@@ -5,30 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  *)
 
-module AcCompletion : sig
-  type completion_item = {
-    kind: Lsp.Completion.completionItemKind option;
-    name: string;
-    labelDetail: string option;  (** LSP's CompletionItemLabelDetails.detail *)
-    description: string option;  (** LSP's CompletionItemLabelDetails.description *)
-    itemDetail: string option;  (** LSP's CompletionItem.detail *)
-    text_edit: ServerProt.Response.insert_replace_edit option;
-    additional_text_edits: ServerProt.Response.textedit list;
-    sort_text: string option;
-    preselect: bool;
-    documentation_and_tags: (string option * Lsp.CompletionItemTag.t list option) Lazy.t;
-    log_info: string;
-    insert_text_format: Lsp.Completion.insertTextFormat;
-  }
-
-  type t = {
-    items: completion_item list;
-    is_incomplete: bool;
-  }
-
-  val to_server_prot_completion_t : t -> ServerProt.Response.Completion.t
-end
-
 type ac_options = {
   imports: bool;
   imports_min_characters: int;
@@ -37,8 +13,8 @@ type ac_options = {
   show_ranking_info: bool;
 }
 
-type ac_result = {
-  result: AcCompletion.t;
+type 'r ac_result = {
+  result: 'r;
   errors_to_log: string list;
 }
 
@@ -54,11 +30,14 @@ val mk_typing_artifacts :
   exports:Export_search.t ->
   typing
 
-type autocomplete_service_result =
-  | AcResult of ac_result
+type 'r autocomplete_service_result_generic =
+  | AcResult of 'r ac_result
   | AcEmpty of string
   | AcFatalError of string
 
+type autocomplete_service_result =
+  ServerProt.Response.Completion.t autocomplete_service_result_generic
+
 val autocomplete_get_results :
   typing ->
   ac_options ->