Try to improve handling for '{}' schemas

In some cases nova/cinder (at least) report the body as '{}' (i.e.
server stop/start). On the cli side it makes absolutely no sense to
expose it to the user since it generally stands for the "null" body.

Change-Id: I4aa4f786d3cd60caa404a1850e87fb0167824b6a
Signed-off-by: Artem Goncharov <artem.goncharov@gmail.com>

codegenerator/model.py

@@ -380,6 +380,10 @@ class JsonSchemaParser:
                     field = StructField(data_type=data_type)
 
                 field.description = v.get("description")
+                if not field.description and isinstance(
+                    data_type, PrimitiveAny
+                ):
+                    field.description = "OpenAPI specifies the field as '{}'."
                 if k in required:
                     field.is_required = True
                 if min_ver:

codegenerator/rust_cli.py

@@ -11,17 +11,18 @@
 #   under the License.
 #
 import logging
-from pathlib import Path
-import subprocess
 import re
+import subprocess
+from pathlib import Path
 
+from codegenerator import common, model
 from codegenerator.base import BaseGenerator
-from codegenerator import common
-from codegenerator import model
+from codegenerator.common import (
+    BaseCombinedType,
+    BaseCompoundType,
+    BasePrimitiveType,
+)
 from codegenerator.common import rust as common_rust
-from codegenerator.common import BasePrimitiveType
-from codegenerator.common import BaseCombinedType
-from codegenerator.common import BaseCompoundType
 
 BASIC_FIELDS = [
     "id",
@@ -86,6 +87,17 @@ class JsonValue(common_rust.JsonValue):
         return imports
 
 
+class JsonValueDefaultNull(JsonValue):
+    """Arbitrary JSON value"""
+
+    clap_macros: set[str] = {
+        'value_name="JSON"',
+        "value_parser=crate::common::parse_json",
+        "default_value_t=Value::Null",
+    }
+    original_data_type: BaseCombinedType | BaseCompoundType | None = None
+
+
 class StructInputField(common_rust.StructField):
     """Structure field of the CLI input"""
 
@@ -592,6 +604,16 @@ class RequestTypeManager(common_rust.TypeManager):
                     simplified_data_type.original_data_type = field_data_type
                     field_data_type = simplified_data_type
                     self.ignored_models.append(field.data_type)
+            if (
+                field.is_required
+                and isinstance(field.data_type, model.PrimitiveAny)
+                and len(type_model.fields) == 1
+            ):
+                # When a only field of the struct is mandatory and is defined as
+                # '{}' most likely it is expecting the Null. We cannot trust
+                # this 100% but we can define the default value as Value::Null
+                # while still giving the user possibility to pass a real value.
+                field_data_type = JsonValueDefaultNull()
             f = field_class(
                 local_name=self.get_local_attribute_name(field_name),
                 remote_name=self.get_remote_attribute_name(field_name),

codegenerator/templates/rust_macros.j2

@@ -199,7 +199,8 @@ Some({{ val }})
 {%- elif param.data_type.__class__.__name__ in ["ArrayInput"] %}
     {{ sdk_plain_array_setter(param, val_var.replace("&", ""), dst_var, by_ref=by_ref) }}
 
-{%- elif param.data_type.__class__.__name__ in ["JsonValue"] %}
+{%- elif param.data_type.__class__.__name__ in ["JsonValue",
+"JsonValueDefaultNull"] %}
 
     {%- set original_type = param.data_type.original_data_type %}
     {%- if original_type and original_type.__class__.__name__ == "StructInput" %}
@@ -300,7 +301,7 @@ Some({{ val }})
     {{ dst_var }}.{{ param.remote_name }}({{ builder_name }}.build().wrap_err("error preparing the request data")?);
     }
 
-  {%- elif param.data_type.item_type.__class__.__name__ == "JsonValue" %}
+  {%- elif param.data_type.item_type.__class__.__name__ in ["JsonValue", "JsonValueDefaultNull"] %}
   {#- atm it is not possible to pass ownership of Option<Json> #}
     if let Some(val) = {{ val_var }} {
       {{ dst_var }}.{{ param.remote_name }}(val.clone());