From 77180a73b7bbc6aa2b1d9b7b063a1cc7be38763c Mon Sep 17 00:00:00 2001
From: jan iversen <jancasacondor@gmail.com>
Date: Thu, 7 Sep 2023 20:56:00 +0200
Subject: [PATCH] Modbus scale parameter cuts decimals (#99758)

---
 .../components/modbus/base_platform.py        |  2 ++
 tests/components/modbus/test_sensor.py        | 32 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/homeassistant/components/modbus/base_platform.py b/homeassistant/components/modbus/base_platform.py
index b71f8c20215..672250790da 100644
--- a/homeassistant/components/modbus/base_platform.py
+++ b/homeassistant/components/modbus/base_platform.py
@@ -160,6 +160,8 @@ class BaseStructPlatform(BasePlatform, RestoreEntity):
         self._structure: str = config[CONF_STRUCTURE]
         self._precision = config[CONF_PRECISION]
         self._scale = config[CONF_SCALE]
+        if self._scale < 1 and not self._precision:
+            self._precision = 2
         self._offset = config[CONF_OFFSET]
         self._slave_count = config.get(CONF_SLAVE_COUNT, 0)
         self._slave_size = self._count = config[CONF_COUNT]
diff --git a/tests/components/modbus/test_sensor.py b/tests/components/modbus/test_sensor.py
index a746bcda3ba..551398c898b 100644
--- a/tests/components/modbus/test_sensor.py
+++ b/tests/components/modbus/test_sensor.py
@@ -596,6 +596,38 @@ async def test_config_wrong_struct_sensor(
             False,
             "1.23",
         ),
+        (
+            {
+                CONF_DATA_TYPE: DataType.INT32,
+                CONF_SCALE: 10,
+                CONF_OFFSET: 0,
+                CONF_PRECISION: 0,
+            },
+            [0x00AB, 0xCDEF],
+            False,
+            "112593750",
+        ),
+        (
+            {
+                CONF_DATA_TYPE: DataType.INT32,
+                CONF_SCALE: 0.01,
+                CONF_OFFSET: 0,
+                CONF_PRECISION: 2,
+            },
+            [0x00AB, 0xCDEF],
+            False,
+            "112593.75",
+        ),
+        (
+            {
+                CONF_DATA_TYPE: DataType.INT32,
+                CONF_SCALE: 0.01,
+                CONF_OFFSET: 0,
+            },
+            [0x00AB, 0xCDEF],
+            False,
+            "112593.75",
+        ),
     ],
 )
 async def test_all_sensor(hass: HomeAssistant, mock_do_cycle, expected) -> None: