Do not emit redundant flowlint comments error in libdef

Summary:
Library definitions don't have control over where the configuration where it is used, and it might need to use features that are considered as bad by flow lints (e.g. getters and setters). Flow currently complains about flowlint comments that do nothing, which makes the beforementioned use cases impossible to achieve.

Instead of rejecting this, which is too strict, or do not emit any lint errors in libdef, which is too loose, we need to at least let the users know what they are doing and give them a way to shut Flow up, which is what's being done in this diff.

Changelog: [fix] We will no longer emit redundant flowlint disable errors in library definitions.

Reviewed By: williewillus

Differential Revision: D46165188

fbshipit-source-id: a4c1544876fe3ef9dafb2e68dee6dbb95e5165fc

Author: SamChou19815

src/common/lints/exactCover.ml

@@ -125,7 +125,7 @@ let update_settings =
   (fun range setting_list builder -> update_range range (map_fun setting_list) builder)
 
 let update_settings_and_running =
-  let update_settings_and_error err_fun settings settings_list =
+  let update_settings_and_error ~in_libdef err_fun settings settings_list =
     match settings_list with
     | (_, (_, loc)) :: _ ->
       let (new_settings, all_redundant) =
@@ -139,18 +139,18 @@ let update_settings_and_running =
           (settings, true)
           settings_list
       in
-      if all_redundant then err_fun (loc, LintSettings.Redundant_argument);
+      if (not in_libdef) && all_redundant then err_fun (loc, LintSettings.Redundant_argument);
       new_settings
     | [] -> settings
   in
-  let update_settings_and_error_from_list err_fun settings_list_list settings =
-    List.fold_left (update_settings_and_error err_fun) settings settings_list_list
+  let update_settings_and_error_from_list ~in_libdef err_fun settings_list_list settings =
+    List.fold_left (update_settings_and_error ~in_libdef err_fun) settings settings_list_list
   in
-  fun running_settings err_fun range settings_list_list builder ->
+  fun ~in_libdef running_settings err_fun range settings_list_list builder ->
     let flat_settings_list = List.flatten settings_list_list in
     let updated_builder = update_settings range flat_settings_list builder in
     let updated_running_settings =
-      update_settings_and_error_from_list err_fun settings_list_list running_settings
+      update_settings_and_error_from_list ~in_libdef err_fun settings_list_list running_settings
     in
     (updated_builder, updated_running_settings)
 

src/common/lints/exactCover.mli

@@ -90,6 +90,7 @@ val update_settings :
  * anything. It doesn't check for settings that are redundant because they are
  * immediately overwritten. (That's done elsewhere.) *)
 val update_settings_and_running :
+  in_libdef:bool ->
   'a LintSettings.t ->
   ((* Running lint settings *)
    Loc.t * LintSettings.lint_parse_error -> unit) ->

src/services/inference/merge_service.ml

@@ -367,7 +367,7 @@ let merge_component ~mutator ~options ~for_find_all_refs ~reader component =
             Parsing_heaps.read_ast_unsafe file parse
           in
           let (_, suppressions, _) =
-            Type_inference_js.scan_for_suppressions file lint_severities comments
+            Type_inference_js.scan_for_suppressions ~in_libdef:false file lint_severities comments
           in
           Error_suppressions.union suppressions acc)
         Error_suppressions.empty

src/typing/type_inference_js.ml

@@ -250,7 +250,7 @@ let scan_for_lint_suppressions =
         { loc = new_loc; value = s }
     )
   in
-  let process_comment acc comment =
+  let process_comment ~in_libdef acc comment =
     let (severity_cover_builder, running_settings, suppression_locs, errs) = acc in
     let loc_comment = comment |> convert_comment |> trim_and_stars_locational in
     match parse_keyword loc_comment with
@@ -262,6 +262,7 @@ let scan_for_lint_suppressions =
       let (new_builder, new_running_settings) =
         let covered_range = get_range keyword in
         ExactCover.update_settings_and_running
+          ~in_libdef
           running_settings
           (fun err ->
             error_encountered := true;
@@ -330,23 +331,23 @@ let scan_for_lint_suppressions =
       (severity_cover_builder, running_settings, suppression_locs, errs)
     | None -> acc
   in
-  fun file_key base_settings acc errs comments ->
+  fun ~in_libdef file_key base_settings acc errs comments ->
     let severity_cover_builder = ExactCover.new_builder file_key base_settings in
     let (severity_cover_builder, _, suppression_locs, errs) =
       List.fold_left
-        process_comment
+        (process_comment ~in_libdef)
         (severity_cover_builder, base_settings, Loc_collections.LocSet.empty, errs)
         comments
     in
     let severity_cover = ExactCover.bake severity_cover_builder in
     let acc = Error_suppressions.add_lint_suppressions suppression_locs acc in
     (severity_cover, acc, errs)
 
-let scan_for_suppressions file_key lint_severities comments =
+let scan_for_suppressions ~in_libdef file_key lint_severities comments =
   let comments = List.sort (fun (loc1, _) (loc2, _) -> Loc.compare loc1 loc2) comments in
   let acc = Error_suppressions.empty in
   let (acc, errs) = scan_for_error_suppressions acc [] comments in
-  scan_for_lint_suppressions file_key lint_severities acc errs comments
+  scan_for_lint_suppressions ~in_libdef file_key lint_severities acc errs comments
 
 module Statement = Fix_statement.Statement_
 
@@ -454,7 +455,7 @@ let infer_ast ~lint_severities cx filename comments aloc_ast =
     let typed_statements = infer_core cx aloc_statements in
 
     let (severity_cover, suppressions, suppression_errors) =
-      scan_for_suppressions filename lint_severities comments
+      scan_for_suppressions ~in_libdef:false filename lint_severities comments
     in
     Context.add_severity_cover cx filename severity_cover;
     Context.add_error_suppressions cx suppressions;
@@ -507,7 +508,7 @@ let infer_lib_file ~exclude_syms ~lint_severities ~file_sig cx ast =
     let t_stmts = infer_core cx aloc_statements in
 
     let (severity_cover, suppressions, suppression_errors) =
-      scan_for_suppressions (Context.file cx) lint_severities all_comments
+      scan_for_suppressions ~in_libdef:true (Context.file cx) lint_severities all_comments
     in
     Context.add_severity_cover cx (Context.file cx) severity_cover;
     Context.add_error_suppressions cx suppressions;

src/typing/type_inference_js.mli

@@ -6,6 +6,7 @@
  *)
 
 val scan_for_suppressions :
+  in_libdef:bool ->
   File_key.t ->
   Severity.severity LintSettings.t ->
   Loc.t Flow_ast.Comment.t list ->