If found package.json doesn't have engines, continue traversing

bin/run.ml

@@ -43,18 +43,26 @@ let program_version_env_var program =
   let s = String.uppercase_ascii (Program.to_string program) in
   Printf.sprintf "NODE_SHIM_%s_VERSION" s
 
-let get_version_from_package_json program =
-  match Package.find_package_json_res () with
+let rec get_version_from_package_json ?(dir = Sys.getcwd ()) program =
+  match Package.find_package_json_res dir with
   | Error _ -> None
   | Ok path -> (
       Logger.debug ("Found package.json: " ^ path);
       let ch = open_in path in
       let engines = Package.parse_engines_from_chan ch in
-      Logger.debug ("Found engines: " ^ Package.string_of_engines engines);
-      match get_version engines program with
-      | None -> None
-      | Some semver ->
-          Some (Shim.find_highest_available_version program semver) )
+      match engines with
+      | None ->
+          if path = File.root_dir then None
+          else (
+            Logger.debug "Found package.json without engines. Traversing up...";
+            let parent_dir = File.parent_dir (Filename.dirname path) in
+            get_version_from_package_json ~dir:parent_dir program )
+      | Some engines -> (
+          Logger.debug ("Found engines: " ^ Package.string_of_engines engines);
+          match get_version engines program with
+          | None -> None
+          | Some semver ->
+              Some (Shim.find_highest_available_version program semver) ) )
 
 let get_executable_path program =
   let global_exec = "/usr/local/bin/" ^ Program.to_string program in

lib/file.mli

@@ -18,6 +18,10 @@
 
 val home_dir : string
 
+val root_dir : string
+
 val find_file_by_traversing_up : string -> string -> string
 
 val join : string list -> string
+
+val parent_dir : string -> string

lib/package.ml

@@ -27,21 +27,25 @@ let string_of_engines e =
   let s o = match o with Some s -> Semver.to_string s | None -> "None" in
   Printf.sprintf "node: %s, npm: %s, yarn: %s" (s e.node) (s e.npm) (s e.yarn)
 
-let find_package_json () =
-  File.find_file_by_traversing_up (Sys.getcwd ()) "package.json"
+let find_package_json dir = File.find_file_by_traversing_up dir "package.json"
 
-let find_package_json_res () =
-  try Ok (find_package_json ()) with e -> Error e
+let find_package_json_res dir =
+  try Ok (find_package_json dir) with e -> Error e
 
 let parse_engines_from_chan ch =
   let json = J.from_channel ch in
   let open J.Util in
   let engines_member = json |> member "engines" in
-  let parse_semver_from m =
-    try Some (Semver.of_string (engines_member |> member m |> to_string))
-    with _ -> None
+  let engines_missing =
+    match engines_member with `Null -> true | _ -> false
   in
-  let node = parse_semver_from "node" in
-  let npm = parse_semver_from "npm" in
-  let yarn = parse_semver_from "yarn" in
-  make_engines node npm yarn
+  if engines_missing then None
+  else
+    let parse_semver_from m =
+      try Some (Semver.of_string (engines_member |> member m |> to_string))
+      with _ -> None
+    in
+    let node = parse_semver_from "node" in
+    let npm = parse_semver_from "npm" in
+    let yarn = parse_semver_from "yarn" in
+    Some (make_engines node npm yarn)