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

[Jason Andryuk <jason.andryuk@xxxxxxx>]

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@xxxxxxx>
---
Here's an alternative approach to workaround removeprefix.

 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
 
+    sub_scope_object = "jso_sub_%d" % depth
     if isinstance(ty, idl.Array):
         if parent is None:
             raise Exception("Array type must have a parent")
@@ -398,7 +399,8 @@ def libxl_C_type_gen_jso(ty, v, indent = "    ", parent = 
None, scope_object = "
         s += "        json_object *%s;\n" % (sub_scope_object)
         # remove some indent, it's over indented at least in one case 
libxl_vcpu_sched_params_gen_json
         s += libxl_C_type_gen_jso(ty.elem_type, v+"[i]",
-                                   indent + "    ", parent, sub_scope_object)
+                                  indent + "    ", parent, sub_scope_object,
+                                  depth)
         s += "        if (json_object_array_add(%s, %s)) {\n" % (scope_object, 
sub_scope_object)
         s += "            json_object_put(%s);\n" % (sub_scope_object)
         s += "            goto out;\n"
@@ -417,7 +419,7 @@ def libxl_C_type_gen_jso(ty, v, indent = "    ", parent = 
None, scope_object = "
             (nparent,fexpr) = ty.member(v, f, parent is None)
             s += "case %s:\n" % f.enumname
             if f.type is not None:
-                s += libxl_C_type_gen_jso(f.type, fexpr, indent + "    ", 
nparent, scope_object)
+                s += libxl_C_type_gen_jso(f.type, fexpr, indent + "    ", 
nparent, scope_object, depth)
             else:
                 s += "    %s = json_object_new_object();\n" % (scope_object)
                 s += "    if (!%s)\n" % (scope_object)
@@ -433,7 +435,7 @@ def libxl_C_type_gen_jso(ty, v, indent = "    ", parent = 
None, scope_object = "
             default_expr = get_default_expr(f, nparent, fexpr)
             s += "if (%s) {\n" % default_expr
             s += "    json_object *%s = NULL;\n" % (sub_scope_object)
-            s += libxl_C_type_gen_jso(f.type, fexpr, "    ", nparent, 
sub_scope_object)
+            s += libxl_C_type_gen_jso(f.type, fexpr, "    ", nparent, 
sub_scope_object, depth)
             s += libxl_C_type_gen_jso_map_key(f, nparent, "    ", 
scope_object, sub_scope_object)
 
             s += "}\n"
-- 
2.51.0