fix(bme280): Use single read() in dew_point and clamp RH to avoid log(0).

Author: nedseb

lib/bme280/bme280/device.py

@@ -414,11 +414,12 @@ def dew_point(self):
         """Return dew point temperature in degrees Celsius.
 
         Uses the Magnus formula (Alduchov & Eskridge, 1996) with the
-        current temperature and relative humidity readings.
+        current temperature and relative humidity readings.  Both values
+        come from a single ``read()`` call to ensure consistency.
         """
         from math import log
 
-        t = self.temperature()
-        rh = self.humidity()
+        t, _, rh = self.read()
+        rh = max(rh, 0.01)
         gamma = log(rh / 100.0) + 17.625 * t / (243.04 + t)
         return 243.04 * gamma / (17.625 - gamma)

tests/scenarios/bme280.yaml

@@ -642,15 +642,12 @@ tests:
     expect_true: true
     mode: [mock]
 
-  - name: "dew_point() equals temperature at 100% humidity"
+  - name: "dew_point() matches Magnus formula for mock readings"
     action: script
     script: |
-      # Override humidity compensation to return ~100%RH
-      # At 100% RH, dew point should equal temperature
       from math import log
-      t = dev.temperature()
-      rh = dev.humidity()
-      # Compute expected dew point from actual mock values
+      t, _, rh = dev.read()
+      # Compute expected dew point from Magnus formula
       gamma = log(rh / 100.0) + 17.625 * t / (243.04 + t)
       expected = 243.04 * gamma / (17.625 - gamma)
       dp = dev.dew_point()