Add suggested_value helper for FlowHandler (#82491)

* Add suggested_value helper for ConfigFlow

* Move helper function to FlowHandler

* Rename and adjust docstring

* Fix rebase

homeassistant/data_entry_flow.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 import abc
 import asyncio
 from collections.abc import Iterable, Mapping
+import copy
 from dataclasses import dataclass
 import logging
 from types import MappingProxyType
@@ -443,6 +444,34 @@ class FlowHandler:
         """If we should show advanced options."""
         return self.context.get("show_advanced_options", False)
 
+    def add_suggested_values_to_schema(
+        self, data_schema: vol.Schema, suggested_values: Mapping[str, Any]
+    ) -> vol.Schema:
+        """Make a copy of the schema, populated with suggested values.
+
+        For each schema marker matching items in `suggested_values`,
+        the `suggested_value` will be set. The existing `suggested_value` will
+        be left untouched if there is no matching item.
+        """
+        schema = {}
+        for key, val in data_schema.schema.items():
+            if isinstance(key, vol.Marker):
+                # Exclude advanced field
+                if (
+                    key.description
+                    and key.description.get("advanced")
+                    and not self.show_advanced_options
+                ):
+                    continue
+
+            new_key = key
+            if key in suggested_values and isinstance(key, vol.Marker):
+                # Copy the marker to not modify the flow schema
+                new_key = copy.copy(key)
+                new_key.description = {"suggested_value": suggested_values[key]}
+            schema[new_key] = val
+        return vol.Schema(schema)
+
     @callback
     def async_show_form(
         self,

homeassistant/helpers/schema_config_entry_flow.py

@@ -210,25 +210,9 @@ class SchemaCommonFlowHandler:
 
         if data_schema.schema:
             # Make a copy of the schema with suggested values set to saved options
-            schema = {}
-            for key, val in data_schema.schema.items():
-
-                if isinstance(key, vol.Marker):
-                    # Exclude advanced field
-                    if (
-                        key.description
-                        and key.description.get("advanced")
-                        and not self._handler.show_advanced_options
-                    ):
-                        continue
-
-                new_key = key
-                if key in suggested_values and isinstance(key, vol.Marker):
-                    # Copy the marker to not modify the flow schema
-                    new_key = copy.copy(key)
-                    new_key.description = {"suggested_value": suggested_values[key]}
-                schema[new_key] = val
-            data_schema = vol.Schema(schema)
+            data_schema = self._handler.add_suggested_values_to_schema(
+                data_schema, suggested_values
+            )
 
         errors = {"base": str(error)} if error else None