Make string globals persist-able using fixed size allocations (#5296)

Co-authored-by: Daniel Dunn <dannydunn@eternityforest.com>

esphome/components/globals/__init__.py

@@ -15,8 +15,14 @@ CODEOWNERS = ["@esphome/core"]
 globals_ns = cg.esphome_ns.namespace("globals")
 GlobalsComponent = globals_ns.class_("GlobalsComponent", cg.Component)
 RestoringGlobalsComponent = globals_ns.class_("RestoringGlobalsComponent", cg.Component)
+RestoringGlobalStringComponent = globals_ns.class_(
+    "RestoringGlobalStringComponent", cg.Component
+)
 GlobalVarSetAction = globals_ns.class_("GlobalVarSetAction", automation.Action)
 
+CONF_MAX_RESTORE_DATA_LENGTH = "max_restore_data_length"
+
+
 MULTI_CONF = True
 CONFIG_SCHEMA = cv.Schema(
     {
@@ -24,6 +30,7 @@ CONFIG_SCHEMA = cv.Schema(
         cv.Required(CONF_TYPE): cv.string_strict,
         cv.Optional(CONF_INITIAL_VALUE): cv.string_strict,
         cv.Optional(CONF_RESTORE_VALUE, default=False): cv.boolean,
+        cv.Optional(CONF_MAX_RESTORE_DATA_LENGTH): cv.int_range(0, 254),
     }
 ).extend(cv.COMPONENT_SCHEMA)
 
@@ -32,12 +39,19 @@ CONFIG_SCHEMA = cv.Schema(
 @coroutine_with_priority(-100.0)
 async def to_code(config):
     type_ = cg.RawExpression(config[CONF_TYPE])
-    template_args = cg.TemplateArguments(type_)
     restore = config[CONF_RESTORE_VALUE]
 
-    type = RestoringGlobalsComponent if restore else GlobalsComponent
-    res_type = type.template(template_args)
+    # Special casing the strings to their own class with a different save/restore mechanism
+    if str(type_) == "std::string" and restore:
+        template_args = cg.TemplateArguments(
+            type_, config.get(CONF_MAX_RESTORE_DATA_LENGTH, 63) + 1
+        )
+        type = RestoringGlobalStringComponent
+    else:
+        template_args = cg.TemplateArguments(type_)
+        type = RestoringGlobalsComponent if restore else GlobalsComponent
 
+    res_type = type.template(template_args)
     initial_value = None
     if CONF_INITIAL_VALUE in config:
         initial_value = cg.RawExpression(config[CONF_INITIAL_VALUE])