refactor(api): Separate SegmentType for Integer/Float to Enable Pydantic Serialization (#22025)

refactor(api): Separate SegmentType for Integer/Float to Enable Pydantic Serialization (#22025)

This PR addresses serialization issues in the VariablePool model by separating the `value_type` tags for `IntegerSegment`/`FloatSegment` and `IntegerVariable`/`FloatVariable`. Previously, both Integer and Float types shared the same `SegmentType.NUMBER` tag, causing conflicts during serialization.

Key changes:
- Introduce distinct `value_type` tags for Integer and Float segments/variables
- Add `VariableUnion` and `SegmentUnion` types for proper type discrimination
- Leverage Pydantic's discriminated union feature for seamless serialization/deserialization
- Enable accurate serialization of data structures containing these types

Closes #22024.

api/fields/workflow_fields.py

@@ -5,6 +5,8 @@ from core.variables import SecretVariable, SegmentType, Variable
 from fields.member_fields import simple_account_fields
 from libs.helper import TimestampField
 
+from ._value_type_serializer import serialize_value_type
+
 ENVIRONMENT_VARIABLE_SUPPORTED_TYPES = (SegmentType.STRING, SegmentType.NUMBER, SegmentType.SECRET)
 
 
@@ -24,11 +26,16 @@ class EnvironmentVariableField(fields.Raw):
                 "id": value.id,
                 "name": value.name,
                 "value": value.value,
-                "value_type": value.value_type.value,
+                "value_type": value.value_type.exposed_type().value,
                 "description": value.description,
             }
         if isinstance(value, dict):
-            value_type = value.get("value_type")
+            value_type_str = value.get("value_type")
+            if not isinstance(value_type_str, str):
+                raise TypeError(
+                    f"unexpected type for value_type field, value={value_type_str}, type={type(value_type_str)}"
+                )
+            value_type = SegmentType(value_type_str).exposed_type()
             if value_type not in ENVIRONMENT_VARIABLE_SUPPORTED_TYPES:
                 raise ValueError(f"Unsupported environment variable value type: {value_type}")
             return value
@@ -37,7 +44,7 @@ class EnvironmentVariableField(fields.Raw):
 conversation_variable_fields = {
     "id": fields.String,
     "name": fields.String,
-    "value_type": fields.String(attribute="value_type.value"),
+    "value_type": fields.String(attribute=serialize_value_type),
     "value": fields.Raw,
     "description": fields.String,
 }