[ethernet] Check the manual IP table layout

The extern declaration now has its size, so a longer generated table fails to compile, and a codegen test checks the 20 octets and their order.

esphome/components/ethernet/ethernet_component.cpp

@@ -12,7 +12,7 @@ EthernetComponent::EthernetComponent() { global_eth_component = this; }
 
 #ifdef USE_ETHERNET_MANUAL_IP
 ManualIP load_manual_ip() {
-  uint8_t b[5 * 4];  // five IPv4 addresses
+  uint8_t b[ETHERNET_MANUAL_IP_SIZE];
   progmem_memcpy(b, ETHERNET_MANUAL_IP, sizeof(b));
   auto ip = [&b](size_t i) { return network::IPAddress(b[i], b[i + 1], b[i + 2], b[i + 3]); };
   return ManualIP{ip(0), ip(4), ip(8), ip(12), ip(16)};

esphome/components/ethernet/ethernet_component.h

@@ -106,7 +106,8 @@ struct ManualIP {
 #ifdef USE_ETHERNET_MANUAL_IP
 /// The configured static IP, gateway, subnet, dns1 and dns2 as 4 octets each, generated by codegen
 /// (components/ethernet/__init__.py) and kept in flash.
-extern const uint8_t ETHERNET_MANUAL_IP[] PROGMEM;
+static constexpr size_t ETHERNET_MANUAL_IP_SIZE = 5 * 4;
+extern const uint8_t ETHERNET_MANUAL_IP[ETHERNET_MANUAL_IP_SIZE] PROGMEM;
 ManualIP load_manual_ip();
 #endif
 

tests/component_tests/ethernet/config/manual_ip.yaml

@@ -0,0 +1,18 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+ethernet:
+  type: LAN8720
+  mdc_pin: GPIO23
+  mdio_pin: GPIO18
+  clk:
+    mode: CLK_EXT_IN
+    pin: GPIO0
+  manual_ip:
+    static_ip: 192.168.1.50
+    gateway: 192.168.1.1
+    subnet: 255.255.255.0
+    dns1: 1.1.1.1

tests/component_tests/ethernet/test_manual_ip.py

@@ -0,0 +1,29 @@
+"""The manual IP table codegen emits must match the ETHERNET_MANUAL_IP layout in ethernet_component.h."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+
+def test_manual_ip_table_layout(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    """Twenty octets: static IP, gateway, subnet, dns1, dns2 (unset DNS is zero)."""
+    main_cpp = generate_main(component_config_path("manual_ip.yaml"))
+
+    expected = (
+        "192, 168, 1, 50, 192, 168, 1, 1, 255, 255, 255, 0, 1, 1, 1, 1, 0, 0, 0, 0"
+    )
+    assert (
+        f"esphome::ethernet::ETHERNET_MANUAL_IP[] PROGMEM = {{{expected}}};" in main_cpp
+    )
+    assert "set_manual_ip(" not in main_cpp
+
+
+def test_no_manual_ip_emits_no_table(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    main_cpp = generate_main(component_config_path("rmii_defaults.yaml"))
+
+    assert "ETHERNET_MANUAL_IP" not in main_cpp