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.

Cherry picked from commit 8037da06feea097716ce700f38c0eac0d5411a7c
and rebased against stable 1.8 branch.

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