Replace exceptions by result types for the requests (#11)

CHANGES.md

@@ -1,3 +1,11 @@
+## unreleased
+
+### Changed
+
+- Replace exceptions by result types for the requests (#11, @gpetiot)
+  + `Graphql.exec` now returns `_ result Lwt.t`
+  + `Contributions.fetch` now returns `_ result`
+
 ## 0.2.0
 
 ### Added

bin/main.ml

@@ -8,6 +8,8 @@ let or_die = function
       Fmt.epr "%s@." m;
       exit 1
 
+let ( let* ) x y = y @@ or_die x
+
 let home =
   match Sys.getenv_opt "HOME" with
   | None -> Fmt.failwith "$HOME is not set!"
@@ -73,13 +75,14 @@ let run period : unit =
   | `Normal ->
       Period.with_period period ~last_fetch_file ~f:(fun period ->
           (* Fmt.pr "period: %a@." Fmt.(pair string string) period; *)
-          let token = get_token () |> or_die in
-          show ~from:(fst period) @@ Contributions.fetch ~period ~token)
+          let* token = get_token () in
+          let* contributions = Contributions.fetch ~period ~token in
+          show ~from:(fst period) contributions)
   | `Save ->
       Period.with_period period ~last_fetch_file ~f:(fun period ->
-          let token = get_token () |> or_die in
-          Contributions.fetch ~period ~token
-          |> Yojson.Safe.to_file "activity.json")
+          let* token = get_token () in
+          let* contributions = Contributions.fetch ~period ~token in
+          Yojson.Safe.to_file "activity.json" contributions)
   | `Load ->
       (* When testing formatting changes, it is quicker to fetch the data once and then load it again for each test: *)
       let from =

lib/contributions.mli

@@ -15,7 +15,10 @@ module Repo_map : Map.S with type key = string
 
 type t = { username : string; activity : item list Repo_map.t }
 
-val fetch : period:string * string -> token:Token.t -> Yojson.Safe.t
+val fetch :
+  period:string * string ->
+  token:Token.t ->
+  (Yojson.Safe.t, [ `Msg of string ]) result
 
 val of_json : from:string -> Yojson.Safe.t -> t
 (** We pass [from] again here so we can filter out anything that GitHub included by accident. *)

lib/graphql.ml

@@ -21,12 +21,17 @@ let exec ?variables ~token ~query () =
   | `OK -> (
       let json = Yojson.Safe.from_string body in
       match json / "errors" with
-      | `Null -> json
+      | `Null -> Ok json
       | _errors ->
-          Fmt.failwith "@[<v2>GitHub returned errors: %a@]"
-            (Yojson.Safe.pretty_print ~std:true)
-            json)
+          Error
+            (`Msg
+              (Format.asprintf "@[<v2>GitHub returned errors: %a@]"
+                 (Yojson.Safe.pretty_print ~std:true)
+                 json)))
   | err ->
-      Fmt.failwith "@[<v2>Error performing GraphQL query on GitHub: %s@,%s@]"
-        (Cohttp.Code.string_of_status err)
-        body
+      Error
+        (`Msg
+          (Format.asprintf
+             "@[<v2>Error performing GraphQL query on GitHub: %s@,%s@]"
+             (Cohttp.Code.string_of_status err)
+             body))

lib/graphql.mli

@@ -3,4 +3,4 @@ val exec :
   token:string ->
   query:string ->
   unit ->
-  Yojson.Safe.t Lwt.t
+  (Yojson.Safe.t, [ `Msg of string ]) result Lwt.t