From ea9641f9808e0ab789aa3067831d3a699efdfd49 Mon Sep 17 00:00:00 2001
From: jan iversen <jancasacondor@gmail.com>
Date: Fri, 16 Apr 2021 22:33:58 +0200
Subject: [PATCH] Apply Precision/Scale/Offset to struct in modbus sensor
 (#48544)

The single values in struct are corrected with presicion, scale and offset,
just as it is done with single values.
---
 homeassistant/components/modbus/sensor.py     | 14 ++++++-
 tests/components/modbus/test_modbus_sensor.py | 41 +++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/homeassistant/components/modbus/sensor.py b/homeassistant/components/modbus/sensor.py
index 21069d86427..dcc68b52db8 100644
--- a/homeassistant/components/modbus/sensor.py
+++ b/homeassistant/components/modbus/sensor.py
@@ -319,7 +319,19 @@ class ModbusRegisterSensor(RestoreEntity, SensorEntity):
             # If unpack() returns a tuple greater than 1, don't try to process the value.
             # Instead, return the values of unpack(...) separated by commas.
             if len(val) > 1:
-                self._value = ",".join(map(str, val))
+                # Apply scale and precision to floats and ints
+                v_result = []
+                for entry in val:
+                    v_temp = self._scale * entry + self._offset
+
+                    # We could convert int to float, and the code would still work; however
+                    # we lose some precision, and unit tests will fail. Therefore, we do
+                    # the conversion only when it's absolutely necessary.
+                    if isinstance(v_temp, int) and self._precision == 0:
+                        v_result.append(str(v_temp))
+                    else:
+                        v_result.append(f"{float(v_temp):.{self._precision}f}")
+                self._value = ",".join(map(str, v_result))
             else:
                 val = val[0]
 
diff --git a/tests/components/modbus/test_modbus_sensor.py b/tests/components/modbus/test_modbus_sensor.py
index ce9889d8aaa..b81cc9c4c1e 100644
--- a/tests/components/modbus/test_modbus_sensor.py
+++ b/tests/components/modbus/test_modbus_sensor.py
@@ -12,6 +12,7 @@ from homeassistant.components.modbus.const import (
     CONF_REGISTERS,
     CONF_REVERSE_ORDER,
     CONF_SCALE,
+    DATA_TYPE_CUSTOM,
     DATA_TYPE_FLOAT,
     DATA_TYPE_INT,
     DATA_TYPE_STRING,
@@ -26,6 +27,7 @@ from homeassistant.const import (
     CONF_OFFSET,
     CONF_SENSORS,
     CONF_SLAVE,
+    CONF_STRUCTURE,
 )
 
 from .conftest import base_config_test, base_test
@@ -338,6 +340,7 @@ async def test_config_sensor(hass, do_discovery, do_config):
 )
 async def test_all_sensor(hass, cfg, regs, expected):
     """Run test for sensor."""
+
     sensor_name = "modbus_test_sensor"
     state = await base_test(
         hass,
@@ -352,3 +355,41 @@ async def test_all_sensor(hass, cfg, regs, expected):
         scan_interval=5,
     )
     assert state == expected
+
+
+async def test_struct_sensor(hass):
+    """Run test for sensor struct."""
+
+    sensor_name = "modbus_test_sensor"
+    # floats: 7.931250095367432, 10.600000381469727,
+    #         1.000879611487865e-28, 10.566553115844727
+    expected = "7.93,10.60,0.00,10.57"
+    state = await base_test(
+        hass,
+        {
+            CONF_NAME: sensor_name,
+            CONF_REGISTER: 1234,
+            CONF_COUNT: 8,
+            CONF_PRECISION: 2,
+            CONF_DATA_TYPE: DATA_TYPE_CUSTOM,
+            CONF_STRUCTURE: ">4f",
+        },
+        sensor_name,
+        SENSOR_DOMAIN,
+        CONF_SENSORS,
+        CONF_REGISTERS,
+        [
+            0x40FD,
+            0xCCCD,
+            0x4129,
+            0x999A,
+            0x10FD,
+            0xC0CD,
+            0x4129,
+            0x109A,
+        ],
+        expected,
+        method_discovery=False,
+        scan_interval=5,
+    )
+    assert state == expected