Fix a bug with F to K conversion

src/corva_unit_converter/converter.py

@@ -76,9 +76,6 @@ def convert(self, unit_from: str, unit_to: str,  # noqa: CCR001, CFQ004
         result = value * origin["unit"]["to_anchor"]
 
         # for some units it's a simple shift (e.g. C to K)
-        if "anchor_shift" in destination["unit"]:
-            result += destination["unit"]["anchor_shift"]
-
         if "anchor_shift" in origin["unit"]:
             result -= origin["unit"]["anchor_shift"]
 
@@ -87,10 +84,15 @@ def convert(self, unit_from: str, unit_to: str,  # noqa: CCR001, CFQ004
             # Convert through transformation
             transform = measures[origin["measure"]]["_anchors"][origin["system"]].get("transform")
             if transform and callable(transform):
-                return transform(result)
+                result = transform(result)
+
             # Convert through the anchor ratio
             result *= measures[origin["measure"]]["_anchors"][origin["system"]]["ratio"]
 
+        # Apply shift after transformation for F to K
+        if "anchor_shift" in destination["unit"]:
+            result += destination["unit"]["anchor_shift"]
+
         # Convert to another unit inside the destination system
         return result / destination["unit"]["to_anchor"]
 

src/corva_unit_converter/definitions/temperature.py

@@ -45,11 +45,13 @@
    "_anchors": {
       "metric": {
          "unit": "C",
-         "transform": lambda c: c / (5 / 9) + 32
+         "transform": lambda c: c / (5 / 9) + 32,
+         "ratio": 1
       },
       "imperial": {
          "unit": "F",
-         "transform": lambda f: (f - 32) * (5 / 9)
+         "transform": lambda f: (f - 32) * (5 / 9),
+         "ratio": 1
       }
    }
 }

tests/test_temperature.py

@@ -6,6 +6,8 @@
     {"from": "F", "amount": 32, "to": "C", "expected": 0},
     {"from": "K", "amount": 0, "to": "C", "expected": -273.15},
     {"from": "C", "amount": 0, "to": "K", "expected": 273.15},
+    {"from": "F", "amount": 32, "to": "K", "expected": 273.15},
+    {"from": "K", "amount": 0, "to": "F", "expected": -459.67},
 ]