[emontx] Fix sensor state_class defaults not being applied correctly (#17610)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/component_tests/emontx/test_sensor_defaults.py

@@ -0,0 +1,100 @@
+"""Tests for emontx sensor tag defaults."""
+
+import pytest
+
+from esphome.components import sensor
+from esphome.components.emontx.sensor import CONFIG_SCHEMA, apply_tag_defaults
+from esphome.const import (
+    CONF_ACCURACY_DECIMALS,
+    CONF_STATE_CLASS,
+    STATE_CLASS_MEASUREMENT,
+    STATE_CLASS_TOTAL_INCREASING,
+)
+
+
+def _resolve_via_config_schema(tag: str) -> dict:
+    """Run a minimal config through the real CONFIG_SCHEMA pipeline, the
+    same path a user's YAML goes through."""
+    return CONFIG_SCHEMA(
+        {"tag_name": tag, "emontx_id": "my_emontx", "name": f"{tag} sensor"}
+    )
+
+
+def test_config_schema_applies_tag_default_state_class():
+    """If sensor_schema(state_class=...) is reintroduced, the schema-level
+    default wins over apply_tag_defaults' per-prefix value, and E1 would
+    resolve to measurement instead of total_increasing. Driving the real
+    CONFIG_SCHEMA (not just apply_tag_defaults) catches that, since
+    sensor_schema() runs before apply_tag_defaults in the cv.All() chain.
+    """
+    result = _resolve_via_config_schema("E1")
+    assert result[CONF_STATE_CLASS] == sensor.validate_state_class(
+        STATE_CLASS_TOTAL_INCREASING
+    )
+
+
+def test_config_schema_applies_tag_default_accuracy_decimals():
+    """Same root cause as the state_class regression: reintroducing
+    sensor_schema(accuracy_decimals=...) would make V1 resolve to the
+    schema-level default instead of the prefix-specific value of 2.
+    """
+    result = _resolve_via_config_schema("V1")
+    assert result[CONF_ACCURACY_DECIMALS] == 2
+
+
+def _make_config(tag: str) -> dict:
+    """Minimal config dict with only tag_name set — no overrides."""
+    return {"tag_name": tag}
+
+
+@pytest.mark.parametrize(
+    ("tag", "expected_state_class", "expected_decimals"),
+    [
+        # Known numeric-index prefixes
+        ("E1", STATE_CLASS_TOTAL_INCREASING, 0),
+        ("E12", STATE_CLASS_TOTAL_INCREASING, 0),
+        ("P1", STATE_CLASS_MEASUREMENT, 0),
+        ("V1", STATE_CLASS_MEASUREMENT, 2),
+        ("I1", STATE_CLASS_MEASUREMENT, 2),
+        ("T1", STATE_CLASS_MEASUREMENT, 2),
+        # Known patterns
+        ("PULSE1", STATE_CLASS_TOTAL_INCREASING, 0),
+        ("PULSE12", STATE_CLASS_TOTAL_INCREASING, 0),
+        ("PF1", STATE_CLASS_MEASUREMENT, 2),
+        # Unknown / free-form tags fall back to generic defaults
+        ("CUSTOM1", STATE_CLASS_MEASUREMENT, 0),
+        ("X", STATE_CLASS_MEASUREMENT, 0),
+    ],
+)
+def test_apply_tag_defaults(tag, expected_state_class, expected_decimals):
+    """apply_tag_defaults must inject the correct state_class and accuracy_decimals
+    for each tag type when no user overrides are present."""
+    config = _make_config(tag)
+    result = apply_tag_defaults(config)
+
+    assert result[CONF_STATE_CLASS] == sensor.validate_state_class(expected_state_class)
+    assert result[CONF_ACCURACY_DECIMALS] == expected_decimals
+
+
+@pytest.mark.parametrize(
+    ("tag", "user_state_class", "user_decimals"),
+    [
+        # User overrides must not be clobbered by defaults
+        ("E1", STATE_CLASS_MEASUREMENT, 3),
+        ("PULSE1", STATE_CLASS_MEASUREMENT, 1),
+        ("V1", STATE_CLASS_TOTAL_INCREASING, 0),
+        ("CUSTOM1", STATE_CLASS_TOTAL_INCREASING, 4),
+    ],
+)
+def test_apply_tag_defaults_respects_user_overrides(
+    tag, user_state_class, user_decimals
+):
+    """apply_tag_defaults must not overwrite values already set by the user."""
+    config = _make_config(tag)
+    config[CONF_STATE_CLASS] = sensor.validate_state_class(user_state_class)
+    config[CONF_ACCURACY_DECIMALS] = user_decimals
+
+    result = apply_tag_defaults(config)
+
+    assert result[CONF_STATE_CLASS] == sensor.validate_state_class(user_state_class)
+    assert result[CONF_ACCURACY_DECIMALS] == user_decimals

tests/components/emontx/test.esp32-idf.yaml

@@ -1,4 +1,3 @@
 packages:
   uart_115200: !include ../../test_build_components/common/uart_115200/esp32-idf.yaml
-
-<<: !include common.yaml
+  emontx: !include common.yaml

tests/components/emontx/test.esp8266-ard.yaml

@@ -1,4 +1,3 @@
 packages:
   uart_115200: !include ../../test_build_components/common/uart_115200/esp8266-ard.yaml
-
-<<: !include common.yaml
+  emontx: !include common.yaml

tests/components/emontx/test.rp2040-ard.yaml

@@ -1,4 +1,3 @@
 packages:
   uart_115200: !include ../../test_build_components/common/uart_115200/rp2040-ard.yaml
-
-<<: !include common.yaml
+  emontx: !include common.yaml

tests/components/emontx/validate.esp32-idf.yaml

@@ -0,0 +1,73 @@
+packages:
+  uart_115200: !include ../../test_build_components/common/uart_115200/esp32-idf.yaml
+  emontx: !include common.yaml
+
+# Validate that each sensor type gets the correct default state_class,
+# unit_of_measurement, device_class, and accuracy_decimals when NO overrides
+# are provided. The values are intentionally omitted so apply_tag_defaults is
+# exercised, not the user-override path.
+
+sensor:
+  # Energy sensor (E prefix): expects state_class=total_increasing, unit=Wh,
+  # device_class=energy, accuracy_decimals=0
+  - platform: emontx
+    tag_name: E1
+    name: Energy 1
+    emontx_id: test_emontx
+
+  # Power sensor (P prefix): expects state_class=measurement, unit=W,
+  # device_class=power, accuracy_decimals=0
+  - platform: emontx
+    tag_name: P1
+    name: Power 1
+    emontx_id: test_emontx
+
+  # Voltage sensor (V prefix): expects state_class=measurement, unit=V,
+  # device_class=voltage, accuracy_decimals=2
+  - platform: emontx
+    tag_name: V1
+    name: Voltage 1
+    emontx_id: test_emontx
+
+  # Current sensor (I prefix): expects state_class=measurement, unit=A,
+  # device_class=current, accuracy_decimals=2
+  - platform: emontx
+    tag_name: I1
+    name: Current 1
+    emontx_id: test_emontx
+
+  # Temperature sensor (T prefix): expects state_class=measurement, unit=°C,
+  # device_class=temperature, accuracy_decimals=2
+  - platform: emontx
+    tag_name: T1
+    name: Temperature 1
+    emontx_id: test_emontx
+
+  # Pulse sensor (PULSE pattern): expects state_class=total_increasing,
+  # unit=pulses, device_class=energy, accuracy_decimals=0
+  - platform: emontx
+    tag_name: PULSE1
+    name: Pulse 1
+    emontx_id: test_emontx
+
+  # Power factor sensor (PF pattern): expects state_class=measurement,
+  # device_class=power_factor, accuracy_decimals=2
+  - platform: emontx
+    tag_name: PF1
+    name: Power Factor 1
+    emontx_id: test_emontx
+
+  # Unknown tag: no prefix match, falls back to state_class=measurement,
+  # accuracy_decimals=0
+  - platform: emontx
+    tag_name: CUSTOM1
+    name: Custom sensor
+    emontx_id: test_emontx
+
+  # User override: verify that explicit values are respected and not clobbered
+  - platform: emontx
+    tag_name: E2
+    name: Energy 2 (user override)
+    emontx_id: test_emontx
+    state_class: measurement
+    accuracy_decimals: 3