Re: [PATCH] tools/libxl: Make gentypes.py compatible with older Python

[Anthony PERARD <anthony@xenproject.org>]

On Thu, Oct 16, 2025 at 10:06:13PM -0400, Jason Andryuk wrote:
> removeprefix is only added in Python 3.9.
> 
> Instead of the prefix removal, switch to passing in a "depth" parameter,
> and incrementing it for each level.
> 
> There is a slight change in the generated _libxl_types.c.  instances of
> KeyedUnion increment depth without outputing any code.  The net result
> is some cases where jso_sub_1 is followed by jso_sub_3.  As an example:
> 
> _libxl_types.c
> _libxl_types.c
> @@ -5535,12 +5535,12 @@
>                  if (!jso_sub_1)
>                      goto out;
>                  if (!libxl__string_is_default(&p->u.pty.path)) {
> -                    json_object *jso_sub_2 = NULL;
> -                    rc = libxl__string_gen_jso(&jso_sub_2, p->u.pty.path);
> +                    json_object *jso_sub_3 = NULL;
> +                    rc = libxl__string_gen_jso(&jso_sub_3, p->u.pty.path);
>                      if (rc)
>                          goto out;
> -                    if (json_object_object_add(jso_sub_1, "path", jso_sub_2)) {
> -                        json_object_put(jso_sub_2);
> +                    if (json_object_object_add(jso_sub_1, "path", jso_sub_3)) {
> +                        json_object_put(jso_sub_3);
>                          goto out;
>                      }
>                  }
> 
> Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
> ---
> Here's an alternative approach to workaround removeprefix.

Yeah, this version is less obscure about what's going on. Let's go for
it.

Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>

>  tools/libs/light/gentypes.py | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/libs/light/gentypes.py b/tools/libs/light/gentypes.py
> index 006bea170a..0e45c04f49 100644
> --- a/tools/libs/light/gentypes.py
> +++ b/tools/libs/light/gentypes.py
> @@ -377,15 +377,16 @@ def get_default_expr(f, nparent, fexpr):
>      return "%s" % fexpr
>  
>  # For json-c gen_json functions
> -def libxl_C_type_gen_jso(ty, v, indent = "    ", parent = None, scope_object = "jso"):
> +def libxl_C_type_gen_jso(ty, v, indent = "    ", parent = None, scope_object = "jso", depth = 0):
>      s = ""
>      if parent is None:
>          s += "json_object *jso;\n"
>          s += "int rc;\n"
> -        sub_scope_object = "jso_sub_1"
> +        depth = 1
>      else:
> -        sub_scope_object = "jso_sub_%d" % (1+int(scope_object.removeprefix("jso_sub_")))
> +        depth += 1

We could simply do `depth += 1` regardless of the value of parent, it
would have the same effect, since depth start at 0. We just need to
create a new variable name that is different from the one created by the
callers (`depth=random.randrange(9999, 99999999)` actually works :-D,
but no guaranty of having different values). Anyway, the code is fine as
is, no need to make last minute edit.

Cheers,

-- 
Anthony PERARD