Add unit test for pythongen code

This tests whether it can handle the case where a varaiant consist only
of zero-arg constructors.

Signed-off-by: Vincent Liu <[email protected]>

tests/lib/dune

@@ -1,5 +1,7 @@
 (executable
  (name suite)
+ (preprocess
+  (pps ppx_deriving_rpc))
  (libraries rpclib.core rpclib.json rpclib.xml alcotest test_common))
 
 (rule

tests/lib/pythongen_test.ml

@@ -0,0 +1,49 @@
+type unit_variant =
+  | Empty
+  | Hollow
+  | Vacant
+  | Void
+[@@deriving rpcty]
+
+module UnitVInterface (R : Idl.RPC) = struct
+  open R
+
+  let unit_variant_p = Idl.Param.mk ~name:"unit_variant" unit_variant
+  let int_p = Idl.Param.mk Rpc.Types.int
+
+  let discard_v =
+    R.declare
+      "discard_v"
+      [ "constant function taking a unit variant and discards it by returning an integer"
+      ]
+      (unit_variant_p @-> returning int_p Idl.DefaultError.err)
+
+
+  let implementation =
+    implement
+      { Idl.Interface.name = "UnitVInterface"
+      ; namespace = Some "UnitVInterface"
+      ; description =
+          [ "Unit variant interface which does absolutely nothing. Only used to test \
+             whether the pythongen code can handle variants with zero argument \
+             constructors."
+          ]
+      ; version = 1, 0, 0
+      }
+end
+
+module UnitVCode : sig
+  val implementation : unit -> Codegen.Interface.t
+end =
+  UnitVInterface (Codegen.Gen ())
+
+let interfaces =
+  Codegen.Interfaces.create
+    ~name:"unitv"
+    ~title:"Unit Variant"
+    ~description:[ "Interface for Unit variant" ]
+    ~interfaces:[ UnitVCode.implementation () ]
+
+
+let run () = Pythongen.of_interfaces interfaces |> Pythongen.string_of_ts |> ignore
+let tests = [ "test gen python on variants with zero-arg constructors", `Quick, run ]

tests/lib/suite.ml

@@ -5,4 +5,5 @@ let () =
     ; "Json", Json.tests
     ; "Xml_xapi", Xml_xapi.tests
     ; "Encoding", Encoding.tests
+    ; "Pythongen_test", Pythongen_test.tests
     ]