Add config flow title placeholder update infrastructure (home-assistant#154353)

Author: bdraco

homeassistant/config_entries.py

@@ -2859,6 +2859,29 @@ def async_get_supported_subentry_types(
         """Return subentries supported by this handler."""
         return {}
 
+    @callback
+    def async_update_title_placeholders(
+        self, title_placeholders: Mapping[str, str]
+    ) -> None:
+        """Update title placeholders for the discovery notification and notify listeners.
+
+        This updates the flow context title_placeholders and notifies listeners
+        (such as the frontend) to reload the flow state, updating the discovery
+        notification title.
+
+        Only call this method when the flow is not progressing to a new step
+        (e.g., from a callback that receives updated data). If the flow is
+        progressing to a new step, set title_placeholders directly in context
+        before returning the step result, as the step change will trigger
+        listener notification automatically.
+        """
+        # Context is typed as TypedDict but is mutable dict at runtime
+        current_placeholders = cast(
+            dict[str, str], self.context.setdefault("title_placeholders", {})
+        )
+        current_placeholders.update(title_placeholders)
+        self.async_notify_flow_changed()
+
     @callback
     def _async_abort_entries_match(
         self, match_dict: dict[str, Any] | None = None

homeassistant/data_entry_flow.py

@@ -432,11 +432,7 @@ async def _async_configure(
                     != result.get("description_placeholders")
                 )
             ):
-                # Tell frontend to reload the flow state.
-                self.hass.bus.async_fire_internal(
-                    EVENT_DATA_ENTRY_FLOW_PROGRESSED,
-                    {"handler": flow.handler, "flow_id": flow_id, "refresh": True},
-                )
+                flow.async_notify_flow_changed()
 
         return result
 
@@ -886,6 +882,17 @@ def async_update_progress(self, progress: float) -> None:
             {"handler": self.handler, "flow_id": self.flow_id, "progress": progress},
         )
 
+    @callback
+    def async_notify_flow_changed(self) -> None:
+        """Notify listeners that the flow has changed.
+
+        This notifies listeners (such as the frontend) to reload the flow state.
+        """
+        self.hass.bus.async_fire_internal(
+            EVENT_DATA_ENTRY_FLOW_PROGRESSED,
+            {"handler": self.handler, "flow_id": self.flow_id, "refresh": True},
+        )
+
     @callback
     def async_show_progress_done(self, *, next_step_id: str) -> _FlowResultT:
         """Mark the progress done."""

tests/test_config_entries.py

@@ -9434,3 +9434,74 @@ async def async_step_user(self, user_input=None):
         "working in Home Assistant 2026.3, please create a bug report at https:"
     )
     assert (log_text in caplog.text) == expected_log
+
+
+async def test_async_update_title_placeholders(hass: HomeAssistant) -> None:
+    """Test async_update_title_placeholders updates context and notifies listeners."""
+
+    class TestFlow(config_entries.ConfigFlow):
+        """Test flow."""
+
+        VERSION = 1
+
+        async def async_step_user(self, user_input=None):
+            """Test user step."""
+            self.context["title_placeholders"] = {"initial": "value"}
+            return self.async_show_form(step_id="user")
+
+    mock_integration(hass, MockModule("comp"))
+    mock_platform(hass, "comp.config_flow", None)
+
+    with patch.dict(config_entries.HANDLERS, {"comp": TestFlow}):
+        result = await hass.config_entries.flow.async_init(
+            "comp", context={"source": config_entries.SOURCE_USER}
+        )
+        assert result["type"] is FlowResultType.FORM
+
+        # Get the flow to check initial title_placeholders
+        flow = hass.config_entries.flow.async_get(result["flow_id"])
+        assert flow["context"]["title_placeholders"] == {"initial": "value"}
+
+        # Get the flow instance to call methods
+        flow_instance = hass.config_entries.flow._progress[result["flow_id"]]
+
+        # Capture events to verify frontend notification
+        events = async_capture_events(
+            hass, data_entry_flow.EVENT_DATA_ENTRY_FLOW_PROGRESSED
+        )
+
+        # Update title placeholders
+        flow_instance.async_update_title_placeholders({"name": "updated"})
+        await hass.async_block_till_done()
+
+        # Verify placeholders were updated (preserving existing values)
+        flow = hass.config_entries.flow.async_get(result["flow_id"])
+        assert flow["context"]["title_placeholders"] == {
+            "initial": "value",
+            "name": "updated",
+        }
+
+        # Verify frontend was notified
+        assert len(events) == 1
+        assert events[0].data == {
+            "handler": "comp",
+            "flow_id": result["flow_id"],
+            "refresh": True,
+        }
+
+        # Update again with overlapping key
+        flow_instance.async_update_title_placeholders(
+            {"initial": "new_value", "another": "key"}
+        )
+        await hass.async_block_till_done()
+
+        # Verify placeholders were updated correctly
+        flow = hass.config_entries.flow.async_get(result["flow_id"])
+        assert flow["context"]["title_placeholders"] == {
+            "initial": "new_value",
+            "name": "updated",
+            "another": "key",
+        }
+
+        # Verify frontend was notified again
+        assert len(events) == 2