[log] Remove null check indirection from log functions

Call global_logger->log_vprintf_() directly without null-checking
global_logger on every log call. Logger::pre_setup() sets global_logger
before any other component is created in the generated setup() function,
so it is guaranteed to be valid by the time any log function is invoked.

Also removes the __FlashStringHelper* esp_log_vprintf_ overload which
was dead code (only called from esp_log_printf_, never directly).

Add a Python codegen test to verify the ordering invariant, and a
comment on App.pre_setup() documenting the constraint.

esphome/core/application.h

@@ -138,6 +138,7 @@ static constexpr uint32_t TEARDOWN_TIMEOUT_REBOOT_MS = 1000;  // 1 second for qu
 
 class Application {
  public:
+  // Called before Logger::pre_setup() — must not log (global_logger is not yet set).
   void pre_setup(const std::string &name, const std::string &friendly_name, bool name_add_mac_suffix) {
     arch_init();
     this->name_add_mac_suffix_ = name_add_mac_suffix;

esphome/core/log.cpp

@@ -8,52 +8,37 @@
 
 namespace esphome {
 
-// Call log_vprintf_ directly to avoid extra indirection through esp_log_vprintf_
+// No null check on global_logger — Logger::pre_setup() sets global_logger
+// before any other component is created in the generated setup() function,
+// so it is guaranteed to be valid by the time any log function is invoked.
 void HOT esp_log_printf_(int level, const char *tag, int line, const char *format, ...) {  // NOLINT
 #ifdef USE_LOGGER
-  auto *log = logger::global_logger;
-  if (log == nullptr)
-    return;
-
   va_list arg;
   va_start(arg, format);
-  log->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, arg);
+  logger::global_logger->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, arg);
   va_end(arg);
 #endif
 }
+
 #ifdef USE_STORE_LOG_STR_IN_FLASH
 void HOT esp_log_printf_(int level, const char *tag, int line, const __FlashStringHelper *format, ...) {
-#ifdef USE_LOGGER
-  auto *log = logger::global_logger;
-  if (log == nullptr)
-    return;
-
   va_list arg;
   va_start(arg, format);
-  log->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, arg);
+  logger::global_logger->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, arg);
   va_end(arg);
-#endif
 }
 #endif
 
 void HOT esp_log_vprintf_(int level, const char *tag, int line, const char *format, va_list args) {  // NOLINT
 #ifdef USE_LOGGER
-  auto *log = logger::global_logger;
-  if (log == nullptr)
-    return;
-
-  log->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, args);
+  logger::global_logger->log_vprintf_(static_cast<uint8_t>(level), tag, line, format, args);
 #endif
 }
 
 #ifdef USE_ESP32
 int HOT esp_idf_log_vprintf_(const char *format, va_list args) {  // NOLINT
 #ifdef USE_LOGGER
-  auto *log = logger::global_logger;
-  if (log == nullptr)
-    return 0;
-
-  log->log_vprintf_(ESPHOME_LOG_LEVEL, "esp-idf", 0, format, args);
+  logger::global_logger->log_vprintf_(ESPHOME_LOG_LEVEL, "esp-idf", 0, format, args);
 #endif
   return 0;
 }

tests/component_tests/logger/test_logger.py

@@ -0,0 +1,43 @@
+"""Tests for the logger component."""
+
+import re
+
+
+def test_logger_pre_setup_before_other_components(generate_main):
+    """Logger::pre_setup() must be called before any other component is created.
+
+    Log functions call global_logger->log_vprintf_() without a null check,
+    so global_logger must be set before anything can log.
+    """
+    main_cpp = generate_main("tests/component_tests/logger/test_logger.yaml")
+
+    # Find the position of logger pre_setup
+    pre_setup_match = re.search(r"->pre_setup\(\)", main_cpp)
+    assert pre_setup_match is not None, "Logger pre_setup() not found in generated code"
+
+    # Find all "new " allocations (component creation)
+    new_allocations = list(re.finditer(r"\bnew [\w:]+", main_cpp))
+    assert len(new_allocations) > 0, "No component allocations found"
+
+    # Find the logger allocation
+    logger_new = None
+    for alloc in new_allocations:
+        if "logger" in alloc.group():
+            logger_new = alloc
+            break
+
+    assert logger_new is not None, (
+        f"Logger allocation not found in: {[a.group() for a in new_allocations]}"
+    )
+
+    # All non-logger allocations must appear after pre_setup()
+    for alloc in new_allocations:
+        if alloc == logger_new:
+            continue
+        # Skip "new (&App)" placement new which is before logger
+        if "(&App)" in main_cpp[max(0, alloc.start() - 5) : alloc.start()]:
+            continue
+        assert alloc.start() > pre_setup_match.start(), (
+            f"Component allocation '{alloc.group()}' at position {alloc.start()} "
+            f"appears before logger pre_setup() at position {pre_setup_match.start()}"
+        )

tests/component_tests/logger/test_logger.yaml

@@ -0,0 +1,9 @@
+---
+esphome:
+  name: test
+
+esp8266:
+  board: d1_mini_lite
+
+logger:
+  level: DEBUG