Resolve review comments

src/state/opamEnv.ml

@@ -348,16 +348,8 @@ let shell_eval_invocation shell cmd =
 (** Returns "opam env" invocation string together with optional root and switch
     overrides *)
 let opam_env_invocation ?root ?switch ?(set_opamswitch=false) () =
-  let root =
-    match root with
-    | None -> ""
-    | Some r -> Printf.sprintf " --root=%s" r
-  in
-  let switch =
-    match switch with
-    | None -> ""
-    | Some s -> Printf.sprintf " --switch=%s" s
-  in
+  let root = OpamStd.Option.map_default (Printf.sprintf " --root=%s") "" root in
+  let switch = OpamStd.Option.map_default (Printf.sprintf " --switch=%s") "" switch in
   let setswitch = if set_opamswitch then " --set-switch" else "" in
   Printf.sprintf "opam env%s%s%s" root switch setswitch
 
@@ -374,21 +366,21 @@ let eval_string gt ?(set_opamswitch=false) switch =
     else
       None
   in
-  let switch =
-    match switch with
-    | None -> None
-    | Some sw ->
-      let sw_cur = OpamSwitch.to_string sw in
-      let sw_env =
-        OpamStd.Option.Op.(
-          OpamStd.Env.getopt "OPAMSWITCH" ++
-          (OpamStateConfig.get_current_switch_from_cwd gt.root >>|
-           OpamSwitch.to_string) ++
-          (OpamFile.Config.switch gt.config >>| OpamSwitch.to_string)
-        )
-      in
-      if Some sw_cur <> sw_env then Some sw_cur else None
+  (* Returns the switch only if it is different from the one determined by the
+     environment *)
+  let overriden_switch sw =
+    let sw_cur = OpamSwitch.to_string sw in
+    let sw_env =
+      OpamStd.Option.Op.(
+        OpamStd.Env.getopt "OPAMSWITCH" ++
+        (OpamStateConfig.get_current_switch_from_cwd gt.root >>|
+          OpamSwitch.to_string) ++
+        (OpamFile.Config.switch gt.config >>| OpamSwitch.to_string)
+      )
+    in
+    if Some sw_cur <> sw_env then Some sw_cur else None
   in
+  let switch = OpamStd.Option.replace overriden_switch switch in
   let shell = OpamStd.Sys.guess_shell_compat () in
   shell_eval_invocation shell (opam_env_invocation ?root ?switch ~set_opamswitch ())