Add re-authentication for transmission (#73124)

* Add reauth flow to transmission

* fix async_setup

* add strings

* fix test coverage

homeassistant/components/transmission/config_flow.py

@@ -1,6 +1,9 @@
 """Config flow for Transmission Bittorent Client."""
 from __future__ import annotations
 
+from collections.abc import Mapping
+from typing import Any
+
 import voluptuous as vol
 
 from homeassistant import config_entries
@@ -13,6 +16,7 @@ from homeassistant.const import (
     CONF_USERNAME,
 )
 from homeassistant.core import callback
+from homeassistant.data_entry_flow import FlowResult
 
 from . import get_api
 from .const import (
@@ -43,6 +47,7 @@ class TransmissionFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
     """Handle Tansmission config flow."""
 
     VERSION = 1
+    _reauth_entry: config_entries.ConfigEntry | None
 
     @staticmethod
     @callback
@@ -87,6 +92,48 @@ class TransmissionFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
             errors=errors,
         )
 
+    async def async_step_reauth(self, data: Mapping[str, Any]) -> FlowResult:
+        """Perform reauth upon an API authentication error."""
+        self._reauth_entry = self.hass.config_entries.async_get_entry(
+            self.context["entry_id"]
+        )
+        return await self.async_step_reauth_confirm()
+
+    async def async_step_reauth_confirm(
+        self, user_input: dict[str, str] | None = None
+    ) -> FlowResult:
+        """Confirm reauth dialog."""
+        errors = {}
+        assert self._reauth_entry
+        if user_input is not None:
+            user_input = {**self._reauth_entry.data, **user_input}
+            try:
+                await get_api(self.hass, user_input)
+
+            except AuthenticationError:
+                errors[CONF_PASSWORD] = "invalid_auth"
+            except (CannotConnect, UnknownError):
+                errors["base"] = "cannot_connect"
+            else:
+                self.hass.config_entries.async_update_entry(
+                    self._reauth_entry, data=user_input
+                )
+                await self.hass.config_entries.async_reload(self._reauth_entry.entry_id)
+                return self.async_abort(reason="reauth_successful")
+
+        return self.async_show_form(
+            description_placeholders={
+                CONF_USERNAME: self._reauth_entry.data[CONF_USERNAME]
+            },
+            step_id="reauth_confirm",
+            data_schema=vol.Schema(
+                {
+                    vol.Required(CONF_PASSWORD): str,
+                }
+            ),
+            errors=errors,
+        )
+
 
 class TransmissionOptionsFlowHandler(config_entries.OptionsFlow):
     """Handle Transmission client options."""