generator: Introduce error code (errcode) concept.

There was a lot of repeated code to map return types (eg. RErr)
to error cases (eg. -1 or NULL).

This commit introduces an error code type and two functions to
map return types to error codes and error codes to strings.

1 files changed, 27 insertions, 19 deletions

diff --git a/generator/generator_python.ml b/generator/generator_python.ml
index bc570a88..937c092d 100644
--- a/generator/generator_python.ml
+++ b/generator/generator_python.ml
@@ -293,21 +293,20 @@ py_guestfs_close (PyObject *self, PyObject *args)
         pr "  struct guestfs_%s_argv *optargs = &optargs_s;\n" name;
       );
 
-      let error_code =
-        match ret with
-        | RErr | RInt _ | RBool _ -> pr "  int r;\n"; "-1"
-        | RInt64 _ -> pr "  int64_t r;\n"; "-1"
-        | RConstString _ | RConstOptString _ ->
-            pr "  const char *r;\n"; "NULL"
-        | RString _ -> pr "  char *r;\n"; "NULL"
-        | RStringList _ | RHashtable _ -> pr "  char **r;\n"; "NULL"
-        | RStruct (_, typ) -> pr "  struct guestfs_%s *r;\n" typ; "NULL"
-        | RStructList (_, typ) ->
-            pr "  struct guestfs_%s_list *r;\n" typ; "NULL"
-        | RBufferOut _ ->
-            pr "  char *r;\n";
-            pr "  size_t size;\n";
-            "NULL" in
+      (match ret with
+       | RErr | RInt _ | RBool _ -> pr "  int r;\n"
+       | RInt64 _ -> pr "  int64_t r;\n"
+       | RConstString _ | RConstOptString _ ->
+           pr "  const char *r;\n"
+       | RString _ -> pr "  char *r;\n"
+       | RStringList _ | RHashtable _ -> pr "  char **r;\n"
+       | RStruct (_, typ) -> pr "  struct guestfs_%s *r;\n" typ
+       | RStructList (_, typ) ->
+           pr "  struct guestfs_%s_list *r;\n" typ
+       | RBufferOut _ ->
+           pr "  char *r;\n";
+           pr "  size_t size;\n"
+      );
 
       List.iter (
         function
@@ -457,10 +456,19 @@ py_guestfs_close (PyObject *self, PyObject *args)
             pr "  free (%s);\n" n
       ) args;
 
-      pr "  if (r == %s) {\n" error_code;
-      pr "    PyErr_SetString (PyExc_RuntimeError, guestfs_last_error (g));\n";
-      pr "    return NULL;\n";
-      pr "  }\n";
+      (match errcode_of_ret ret with
+       | `CannotReturnError -> ()
+       | `ErrorIsMinusOne ->
+           pr "  if (r == -1) {\n";
+           pr "    PyErr_SetString (PyExc_RuntimeError, guestfs_last_error (g));\n";
+           pr "    return NULL;\n";
+           pr "  }\n"
+       | `ErrorIsNULL ->
+           pr "  if (r == NULL) {\n";
+           pr "    PyErr_SetString (PyExc_RuntimeError, guestfs_last_error (g));\n";
+           pr "    return NULL;\n";
+           pr "  }\n"
+      );
       pr "\n";
 
       (match ret with