[FEATURE] Add module_alias resolution capabilities - round 2

src/commands/commandUtils.ml

@@ -678,6 +678,7 @@ let file_options =
       module_file_exts = FlowConfig.module_file_exts flowconfig;
       module_resource_exts = FlowConfig.module_resource_exts flowconfig;
       node_resolver_dirnames = FlowConfig.node_resolver_dirnames flowconfig;
+      node_resolver_aliases = FlowConfig.node_resolver_aliases flowconfig;
     }
 
 let ignore_flag prev =

src/commands/config/flowConfig.ml

@@ -93,6 +93,7 @@ module Opts = struct
     no_flowlib: bool;
     node_resolver_allow_root_relative: bool;
     node_resolver_dirnames: string list;
+    node_resolver_aliases: string list;
     node_resolver_root_relative_dirnames: string list;
     recursion_limit: int;
     root_name: string option;
@@ -192,6 +193,7 @@ module Opts = struct
       no_flowlib = false;
       node_resolver_allow_root_relative = false;
       node_resolver_dirnames = ["node_modules"];
+      node_resolver_aliases = [];
       node_resolver_root_relative_dirnames = [""];
       recursion_limit = 10000;
       root_name = None;
@@ -472,6 +474,13 @@ module Opts = struct
             else
               let node_resolver_dirnames = v :: opts.node_resolver_dirnames in
               Ok { opts with node_resolver_dirnames }) );
+      ( "module.system.node.resolve_alias",
+        string
+          ~init:(fun opts -> { opts with node_resolver_aliases = [] })
+          ~multiple:true
+          (fun opts v ->
+            let node_resolver_aliases = v :: opts.node_resolver_aliases in
+            Ok { opts with node_resolver_aliases }) );
       ( "module.system.node.root_relative_dirname",
         string
           ~init:(fun opts -> { opts with node_resolver_root_relative_dirnames = [] })
@@ -1008,7 +1017,7 @@ let is_not_comment =
       (* Line starts with ; *)
         Str.regexp_string "\240\159\146\169";
         (* Line starts with poop emoji *)
-      
+
     ]
   in
   fun (_, line) ->
@@ -1200,6 +1209,8 @@ let node_resolver_allow_root_relative c = c.options.Opts.node_resolver_allow_roo
 
 let node_resolver_dirnames c = c.options.Opts.node_resolver_dirnames
 
+let node_resolver_aliases c = c.options.Opts.node_resolver_aliases
+
 let node_resolver_root_relative_dirnames c = c.options.Opts.node_resolver_root_relative_dirnames
 
 let recursion_limit c = c.options.Opts.recursion_limit

src/commands/config/flowConfig.mli

@@ -142,6 +142,8 @@ val node_resolver_allow_root_relative : config -> bool
 
 val node_resolver_dirnames : config -> string list
 
+val node_resolver_aliases: config -> string list
+
 val node_resolver_root_relative_dirnames : config -> string list
 
 val required_version : config -> string option

src/common/files.ml

@@ -17,6 +17,7 @@ type options = {
   module_file_exts: SSet.t;
   module_resource_exts: SSet.t;
   node_resolver_dirnames: string list;
+  node_resolver_aliases: string list;
 }
 
 let default_lib_dir options = options.default_lib_dir
@@ -37,6 +38,8 @@ let module_resource_exts options = options.module_resource_exts
 
 let node_resolver_dirnames options = options.node_resolver_dirnames
 
+let node_resolver_aliases options = options.node_resolver_aliases
+
 (* During node module resolution, we need to look for node_modules/ directories
  * as we walk up the path. But checking each directory for them would be expensive.
  * So instead we memorize which directories contain node_modules/ directories.
@@ -114,6 +117,8 @@ let is_valid_path =
 
 let is_node_module options path = List.mem (Filename.basename path) options.node_resolver_dirnames
 
+let is_module_alias options path = List.mem (Filename.basename path) options.node_resolver_aliases
+
 let is_flow_file ~options =
   let is_valid_path = is_valid_path ~options in
   (fun path -> is_valid_path path && not (is_directory path))
@@ -193,7 +198,7 @@ let max_files = 1000
 
     If kind_of_path fails, then we only emit a warning if error_filter passes *)
 let make_next_files_and_symlinks
-    ~node_module_filter ~path_filter ~realpath_filter ~error_filter paths =
+    ~node_module_filter ~module_alias_filter ~path_filter ~realpath_filter ~error_filter paths =
   let prefix_checkers = Base.List.map ~f:is_prefix paths in
   let rec process sz (acc, symlinks) files dir stack =
     if sz >= max_files then
@@ -215,7 +220,7 @@ let make_next_files_and_symlinks
           else
             process sz (acc, symlinks) files dir stack
         | Dir (path, is_symlink) ->
-          if node_module_filter file then
+          if node_module_filter file || module_alias_filter file then
             node_modules_containers :=
               SMap.add
                 ~combine:SSet.union
@@ -256,12 +261,13 @@ let make_next_files_and_symlinks
    and including any directories that are symlinked to even if they are outside
    of `paths`. *)
 let make_next_files_following_symlinks
-    ~node_module_filter ~path_filter ~realpath_filter ~error_filter paths =
+    ~node_module_filter ~module_alias_filter ~path_filter ~realpath_filter ~error_filter paths =
   let paths = Base.List.map ~f:Path.to_string paths in
   let cb =
     ref
       (make_next_files_and_symlinks
          ~node_module_filter
+         ~module_alias_filter
          ~path_filter
          ~realpath_filter
          ~error_filter
@@ -294,6 +300,7 @@ let make_next_files_following_symlinks
       cb :=
         make_next_files_and_symlinks
           ~node_module_filter
+          ~module_alias_filter
           ~path_filter:realpath_filter
           ~realpath_filter
           ~error_filter
@@ -315,6 +322,7 @@ let get_all =
 
 let init ?(flowlibs_only = false) (options : options) =
   let node_module_filter = is_node_module options in
+  let module_alias_filter = is_module_alias options in
   let libs =
     if flowlibs_only then
       []
@@ -341,6 +349,7 @@ let init ?(flowlibs_only = false) (options : options) =
         let filter' path = (path = lib_str || filter path) && not (is_json_file path) in
         make_next_files_following_symlinks
           ~node_module_filter
+          ~module_alias_filter
           ~path_filter:filter'
           ~realpath_filter:filter'
           ~error_filter:(fun _ -> true)
@@ -416,6 +425,7 @@ let watched_paths options = Path_matcher.stems options.includes
  *)
 let make_next_files ~root ~all ~subdir ~options ~libs =
   let node_module_filter = is_node_module options in
+  let module_alias_filter = is_module_alias options in
   let filter =
     if all then
       fun _ ->
@@ -454,6 +464,7 @@ let make_next_files ~root ~all ~subdir ~options ~libs =
   in
   make_next_files_following_symlinks
     ~node_module_filter
+    ~module_alias_filter
     ~path_filter
     ~realpath_filter
     ~error_filter:filter
@@ -585,6 +596,14 @@ let is_within_node_modules ~root ~options path =
   let node_resolver_dirnames = node_resolver_dirnames options |> SSet.of_list in
   not (SSet.inter directories node_resolver_dirnames |> SSet.is_empty)
 
+(* Given a path, we want to know if it's a resolve alias. *)
+let is_within_alias_directory ~root ~options path =
+  (* We use paths that are relative to the root, so that we ignore ancestor directories *)
+  let path = relative_path (Path.to_string root) path in
+  let directories = Str.split dir_sep path |> SSet.of_list in
+  let node_resolver_aliases = node_resolver_aliases options |> SSet.of_list in
+  not (SSet.inter directories node_resolver_aliases |> SSet.is_empty)
+
 (* realpath doesn't work for non-existent paths. So let's find the longest existent prefix, run
  * realpath on that, and then append the rest to it
  *)

src/common/files.mli

@@ -17,6 +17,7 @@ type options = {
   module_file_exts: SSet.t;
   module_resource_exts: SSet.t;
   node_resolver_dirnames: string list;
+  node_resolver_aliases: string list;
 }
 
 val default_lib_dir : options -> Path.t option
@@ -37,6 +38,8 @@ val module_resource_exts : options -> SSet.t
 
 val node_resolver_dirnames : options -> string list
 
+val node_resolver_aliases : options -> string list
+
 val node_modules_containers : SSet.t SMap.t ref
 
 val global_file_name : string
@@ -124,6 +127,8 @@ val mkdirp : string -> Unix.file_perm -> unit
 
 val is_within_node_modules : root:Path.t -> options:options -> string -> bool
 
+val is_within_alias_directory : root:Path.t -> options:options -> string -> bool
+
 val imaginary_realpath : string -> string
 
 val canonicalize_filenames :

src/services/inference/module/module_js.ml

@@ -61,6 +61,9 @@ let choose_provider_and_warn_about_duplicates =
       in
       (defn, errmap)
 
+let get_root ~options =
+  Options.root options |> Path.to_string |> Sys_utils.normalize_filename_dir_sep
+
 (**
  * A set of module.name_mapper config entry allows users to specify regexp
  * matcher strings each with a template string in order to map the names of a
@@ -74,7 +77,7 @@ let choose_provider_and_warn_about_duplicates =
 let module_name_candidates ~options =
   Module_hashtables.memoize_with_module_name_candidates_cache ~f:(fun name ->
       let mappers = Options.module_name_mappers options in
-      let root = Options.root options |> Path.to_string |> Sys_utils.normalize_filename_dir_sep in
+      let root = get_root options in
       let map_name mapped_names (regexp, template) =
         let new_name =
           name
@@ -318,26 +321,47 @@ module Node = struct
 
   let rec node_module ~options ~reader node_modules_containers file loc resolution_acc dir r =
     let file_options = Options.file_options options in
+    let root = get_root options in
     lazy_seq
       [
         lazy
           (match SMap.get dir node_modules_containers with
           | Some existing_node_modules_dirs ->
             lazy_seq
-              ( Files.node_resolver_dirnames file_options
-              |> Base.List.map ~f:(fun dirname ->
-                     lazy
-                       ( if SSet.mem dirname existing_node_modules_dirs then
-                         resolve_relative
-                           ~options
-                           ~reader
-                           loc
-                           ?resolution_acc
-                           dir
-                           (spf "%s%s%s" dirname Filename.dir_sep r)
-                       else
-                         None )) )
-          | None -> None);
+              [
+                lazy
+                  (lazy_seq
+                     ( Files.node_resolver_aliases file_options
+                     |> Base.List.map ~f:(fun dirname ->
+                            let modified_dirname =
+                              dirname
+                              |> Str.split_delim Files.project_root_token
+                              |> String.concat root
+                            in
+                            lazy
+                              (resolve_relative
+                                 ~options
+                                 ~reader
+                                 loc
+                                 ?resolution_acc
+                                 dir
+                                 (spf "%s%s%s" modified_dirname Filename.dir_sep r))) ));
+                lazy
+                  (lazy_seq
+                     ( Files.node_resolver_dirnames file_options
+                     |> Base.List.map ~f:(fun dirname ->
+                            lazy
+                              ( if SSet.mem dirname existing_node_modules_dirs then
+                                resolve_relative
+                                  ~options
+                                  ~reader
+                                  loc
+                                  ?resolution_acc
+                                  dir
+                                  (spf "%s%s%s" dirname Filename.dir_sep r))) ));
+              ]
+          else
+            None );
         lazy
           (let parent_dir = Filename.dirname dir in
            if dir = parent_dir then

tests/config_module_system_node_resolve_alias/.flowconfig

@@ -0,0 +1,5 @@
+[options]
+module.system.node.resolve_dirname=node_modules
+module.system.node.resolve_dirname=custom_node_modules
+module.system.node.resolve_alias=custom_resolve_dir
+module.system.node.resolve_alias=<PROJECT_ROOT>/root_resolve_dir

tests/config_module_system_node_resolve_alias/.testconfig

@@ -0,0 +1 @@
+shell: test.sh