Fix scheduler race conditions and add comprehensive test suite (#9348)

tests/integration/fixtures/external_components/scheduler_recursive_timeout_component/__init__.py

@@ -0,0 +1,21 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ID
+
+scheduler_recursive_timeout_component_ns = cg.esphome_ns.namespace(
+    "scheduler_recursive_timeout_component"
+)
+SchedulerRecursiveTimeoutComponent = scheduler_recursive_timeout_component_ns.class_(
+    "SchedulerRecursiveTimeoutComponent", cg.Component
+)
+
+CONFIG_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(): cv.declare_id(SchedulerRecursiveTimeoutComponent),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+async def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    await cg.register_component(var, config)

tests/integration/fixtures/external_components/scheduler_recursive_timeout_component/recursive_timeout_component.cpp

@@ -0,0 +1,40 @@
+#include "recursive_timeout_component.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace scheduler_recursive_timeout_component {
+
+static const char *const TAG = "scheduler_recursive_timeout";
+
+void SchedulerRecursiveTimeoutComponent::setup() { ESP_LOGCONFIG(TAG, "SchedulerRecursiveTimeoutComponent setup"); }
+
+void SchedulerRecursiveTimeoutComponent::run_recursive_timeout_test() {
+  ESP_LOGI(TAG, "Starting recursive timeout test - scheduling timeout from within timeout");
+
+  // Reset state
+  this->nested_level_ = 0;
+
+  // Schedule the initial timeout with 1ms delay
+  this->set_timeout(1, [this]() {
+    ESP_LOGI(TAG, "Executing initial timeout");
+    this->nested_level_ = 1;
+
+    // From within this timeout, schedule another timeout with 1ms delay
+    this->set_timeout(1, [this]() {
+      ESP_LOGI(TAG, "Executing nested timeout 1");
+      this->nested_level_ = 2;
+
+      // From within this nested timeout, schedule yet another timeout with 1ms delay
+      this->set_timeout(1, [this]() {
+        ESP_LOGI(TAG, "Executing nested timeout 2");
+        this->nested_level_ = 3;
+
+        // Test complete
+        ESP_LOGI(TAG, "Recursive timeout test complete - all %d levels executed", this->nested_level_);
+      });
+    });
+  });
+}
+
+}  // namespace scheduler_recursive_timeout_component
+}  // namespace esphome

tests/integration/fixtures/external_components/scheduler_recursive_timeout_component/recursive_timeout_component.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include "esphome/core/component.h"
+
+namespace esphome {
+namespace scheduler_recursive_timeout_component {
+
+class SchedulerRecursiveTimeoutComponent : public Component {
+ public:
+  void setup() override;
+  float get_setup_priority() const override { return setup_priority::LATE; }
+
+  void run_recursive_timeout_test();
+
+ private:
+  int nested_level_{0};
+};
+
+}  // namespace scheduler_recursive_timeout_component
+}  // namespace esphome