Error on invalid matcher option

lib/matchers/languages.ml

@@ -715,11 +715,8 @@ let all : (module Types.Matcher.S) list =
   ; (module Generic)
   ]
 
-let select_with_extension extension : (module Types.Matcher.S) =
+let select_with_extension extension : (module Types.Matcher.S) option =
   List.find all ~f:(fun (module M) -> List.exists M.extensions ~f:((=) extension))
-  |> function
-  | Some matcher -> matcher
-  | None -> (module Generic)
 
 let create
     Types.Syntax.

src/main.ml

@@ -4,12 +4,6 @@ open Hack_parallel
 
 open Pipeline.Command_configuration
 
-type json_result =
-  { matches : Match.t list
-  ; source : string
-  }
-[@@deriving yojson]
-
 let verbose_out_file = "/tmp/comby.out"
 
 let debug =
@@ -32,7 +26,16 @@ let select_matcher custom_matcher override_matcher configuration =
         Format.eprintf "%s@." error;
         exit 1
   else if Option.is_some override_matcher then
-    Matchers.select_with_extension (Option.value_exn override_matcher), None
+    let matcher_override = Option.value_exn override_matcher in
+    let matcher =
+      match Matchers.select_with_extension matcher_override with
+      | Some matcher -> matcher
+      | None when matcher_override <> ".generic" ->
+        Format.eprintf "The matcher %S is not supported. See -list for supported matchers@." matcher_override;
+        exit 1
+      | None -> (module Matchers.Generic)
+    in
+    matcher, None
   else
     let extension =
       match configuration.file_filters with
@@ -42,7 +45,9 @@ let select_matcher custom_matcher override_matcher configuration =
         | _, Some extension -> "." ^ extension
         | extension, None -> "." ^ extension
     in
-    Matchers.select_with_extension extension, Some extension
+    match Matchers.select_with_extension extension with
+    | Some matcher -> matcher, Some extension
+    | None -> (module Matchers.Generic), Some extension
 
 let paths_with_file_size paths =
   List.map paths ~f:(fun path ->

src/server.ml

@@ -38,7 +38,11 @@ let perform_match request =
   >>| function
   | Ok ({ source; match_template; rule; language; id } as request) ->
     if debug then Format.printf "Received %s@." (Yojson.Safe.pretty_to_string (In.match_request_to_yojson request));
-    let matcher = Matchers.select_with_extension language in
+    let matcher =
+      match Matchers.select_with_extension language with
+      | Some matcher -> matcher
+      | None -> (module Matchers.Generic)
+    in
     let run ?rule () =
       let configuration = Configuration.create ~match_kind:Fuzzy () in
       Pipeline.timed_run matcher ?rule ~configuration ~template:match_template ~source ()
@@ -64,7 +68,11 @@ let perform_rewrite request =
   >>| function
   | Ok ({ source; match_template; rewrite_template; rule; language; substitution_kind; id } as request) ->
     if debug then Format.printf "Received %s@." (Yojson.Safe.pretty_to_string (In.rewrite_request_to_yojson request));
-    let matcher = Matchers.select_with_extension language in
+    let matcher =
+      match Matchers.select_with_extension language with
+      | Some matcher -> matcher
+      | None -> (module Matchers.Generic)
+    in
     let source_substitution, substitute_in_place =
       match substitution_kind with
       | "newline_separated" -> None, false

test/test_cli.ml

@@ -836,3 +836,35 @@ let ()
   [%expect_exact {|3 matches
 WARNING: -count only works with -match-only. Performing -match-only -count.
 |}]
+
+let%expect_test "unrecognized_matcher" =
+  let source = {|dont care|} in
+  let match_template = "dont care" in
+  let rewrite_template = "dont care" in
+  let command_args =
+    Format.sprintf "-stdin '%s' '%s' -matcher invalid"
+      match_template rewrite_template
+  in
+  let command = Format.sprintf "%s %s" binary_path command_args in
+  read_expect_stdin_and_stdout command source
+  |> print_string;
+  [%expect_exact {|The matcher "invalid" is not supported. See -list for supported matchers
+|}]
+
+let%expect_test "generic_matcher_ok" =
+  let source = {|dont care|} in
+  let match_template = "dont care" in
+  let rewrite_template = "blah" in
+  let command_args =
+    Format.sprintf "-stdin '%s' '%s' -matcher .generic"
+      match_template rewrite_template
+  in
+  let command = Format.sprintf "%s %s" binary_path command_args in
+  read_expect_stdin_and_stdout command source
+  |> print_string;
+  [%expect_exact {|------ /dev/null
+++++++ /dev/null
+@|-1,1 +1,1 ============================================================
+-|dont care
++|blah
+|}]