[uart_mux] New component to share a UART between a CDC-ACM bridge and local consumers (#19066)

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>
Co-authored-by: J. Nick Koston <nick@koston.org>

tests/component_tests/uart_mux/test_init.py

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+"""Tests for the uart_mux component's final validation."""
+
+import pytest
+
+from esphome import config_validation as cv
+from esphome.const import CONF_ID, PlatformFramework
+from esphome.core import ID
+from esphome.types import ConfigType
+from tests.component_tests.types import SetCoreConfigCallable
+
+CONF_BRIDGE_ID = "bridge_id"
+
+
+def _set_esp32_s3(set_core_config: SetCoreConfigCallable) -> None:
+    from esphome.components.esp32 import KEY_VARIANT, VARIANT_ESP32S3
+
+    set_core_config(
+        PlatformFramework.ESP32_IDF, platform_data={KEY_VARIANT: VARIANT_ESP32S3}
+    )
+
+
+def _mux_conf(mux_id: str, bridge_id: str) -> ConfigType:
+    return {CONF_ID: ID(mux_id), CONF_BRIDGE_ID: ID(bridge_id)}
+
+
+def test_accepts_one_mux_per_bridge(set_core_config: SetCoreConfigCallable) -> None:
+    _set_esp32_s3(set_core_config)
+    from esphome.components import uart_mux
+
+    uart_mux._final_validate(_mux_conf("mux_0", "bridge_0"))
+    uart_mux._final_validate(_mux_conf("mux_1", "bridge_1"))
+
+
+def test_rejects_two_muxes_on_one_bridge(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    _set_esp32_s3(set_core_config)
+    from esphome.components import uart_mux
+
+    uart_mux._final_validate(_mux_conf("mux_0", "bridge_0"))
+    with pytest.raises(cv.Invalid, match="already routed by another 'uart_mux'"):
+        uart_mux._final_validate(_mux_conf("mux_1", "bridge_0"))

tests/components/uart_mux/common.yaml

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+tinyusb:
+  id: tinyusb_test
+  on_mount:
+    - uart_mux.select_bridge: mux_0
+  on_unmount:
+    - uart_mux.select_local: mux_0
+  usb_manufacturer_str: ESPHomeTestManufacturer
+  usb_product_id: 0x1234
+  usb_product_str: ESPHomeTestProduct
+  usb_vendor_id: 0x2345
+
+uart:
+  - id: uart_0
+    tx_pin: 14
+    rx_pin: 13
+    baud_rate: 115200
+
+usb_cdc_acm:
+  interfaces:
+    - id: cdc_acm_1
+
+bridge:
+  - platform: cdc_acm_uart
+    id: bridge_0
+    uart_id: uart_0
+    usb_cdc_acm_id: cdc_acm_1
+
+uart_mux:
+  - id: mux_0
+    bridge_id: bridge_0
+    initial_route: local
+
+interval:
+  - interval: 60s
+    then:
+      - if:
+          condition:
+            uart_mux.is_local: mux_0
+          then:
+            - lambda: |-
+                uint8_t byte;
+                if (id(mux_0).available() && id(mux_0).read_byte(&byte)) {
+                  id(mux_0).write_byte(byte);
+                }

tests/components/uart_mux/test.esp32-p4-idf.yaml

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+packages:
+  uart_mux: !include common.yaml

tests/components/uart_mux/test.esp32-s2-idf.yaml

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+# ESP32-S2 has no USB_SERIAL_JTAG, so the logger defaults to USB_CDC, which shares
+# the USB OTG peripheral with tinyusb. Use a hardware UART for logging instead.
+logger:
+  hardware_uart: UART0
+
+packages:
+  uart_mux: !include common.yaml

tests/components/uart_mux/test.esp32-s3-idf.yaml

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+packages:
+  uart_mux: !include common.yaml