Add error when switch does not have a source tree

lib/import.ml

@@ -42,10 +42,12 @@ let pp_cmd ppf cmd =
   Bos.Cmd.to_list cmd |> List.map quote_if_needed |> String.concat " "
   |> Format.pp_print_string ppf
 
-type error = [ `Command_failed of Bos.Cmd.t | `Unknown ]
+type error = [ `Command_failed of Bos.Cmd.t | `Unknown | `No_compiler_sources ]
 
 let translate_error s =
   let open Rresult.R in
   reword_error (function
     | `Unknown -> msgf "%s" s
-    | `Command_failed cmd -> msgf "%s - command failed: %a" s pp_cmd cmd)
+    | `Command_failed cmd -> msgf "%s - command failed: %a" s pp_cmd cmd
+    | `No_compiler_sources ->
+        msgf "%s - switch is not linked to compiler sources" s)

lib/import.mli

@@ -27,7 +27,7 @@ val pp_env : Format.formatter -> (string * string) list option -> unit
 
 val pp_cmd : Format.formatter -> Bos.Cmd.t -> unit
 
-type error = [ `Command_failed of Bos.Cmd.t | `Unknown ]
+type error = [ `Command_failed of Bos.Cmd.t | `Unknown | `No_compiler_sources ]
 
 val translate_error :
   string -> ('a, [< error ]) result -> ('a, [> Rresult.R.msg ]) result

lib/op.ml

@@ -39,7 +39,7 @@ let reinstall runner mode ~name =
   let open Let_syntax.Result in
   (let* compiler_sources_opt = Opam.get_compiler_sources runner ~name in
    match compiler_sources_opt with
-   | None -> (* XXX *) assert false
+   | None -> Error `No_compiler_sources
    | Some compiler_sources ->
        let* () = Opam.reinstall_compiler runner ~compiler_sources in
        reinstall_packages_if_needed runner mode)

test/unit/test_op.ml

@@ -14,6 +14,14 @@ let run_mock loc expectations =
   let run ?extra_env ?chdir cmd = run_mock (cmd, extra_env, chdir) in
   (run, check)
 
+let run_out_mock loc expectations =
+  let testable =
+    Alcotest.(pair (module Bos.Cmd) (option (list (pair string string))))
+  in
+  let run_out_mock, check = Mock.create testable loc expectations in
+  let run_out ?extra_env cmd = run_out_mock (cmd, extra_env) in
+  (run_out, check)
+
 let opam_cli_env = Some [ ("OPAMCLI", "2.0") ]
 
 let create_tests =
@@ -69,4 +77,29 @@ let create_tests =
             git+https://github.com/USER/REPO#BRANCH");
   ]
 
-let tests = [ ("Op create", create_tests) ]
+let reinstall_tests =
+  [
+    ( "reinstall: switch does not have sources",
+      `Quick,
+      fun () ->
+        let expectations =
+          [
+            Mock.expect
+              ( Bos.Cmd.(v "opam" % "config" % "expand" % "%{compiler-sources}%"),
+                opam_cli_env )
+              ~and_return:(Ok "");
+          ]
+        in
+        let run_out, check = run_out_mock __LOC__ expectations in
+        let runner = { Helpers.runner_fail_all with run_out } in
+        let got = Op.reinstall runner Quick ~name:None in
+        let expected =
+          Error
+            (`Msg
+              "Could not reinstall - switch is not linked to compiler sources")
+        in
+        Alcotest.check Alcotest.(result unit msg) __LOC__ expected got;
+        check () );
+  ]
+
+let tests = [ ("Op create", create_tests); ("Op reinstall", reinstall_tests) ]