Add missing file

stellarphot/settings/astropy_pydantic.py

@@ -0,0 +1,106 @@
+from astropy.units import Quantity, Unit
+
+__all__ = ["UnitType", "QuantityType", "PixelScaleType"]
+
+# Approach to validation of units was inspired by the GammaPy project
+# which did it before we did:
+# https://docs.gammapy.org/dev/_modules/gammapy/analysis/config.html
+
+
+class UnitType(Unit):
+    # Validator for Unit type
+    @classmethod
+    def __get_validators__(cls):
+        yield cls.validate
+
+    @classmethod
+    def validate(cls, v):
+        return Unit(v)
+
+    @classmethod
+    def __modify_schema__(cls, field_schema, field):
+        # Set default values for the schema in case the field doesn't provide them
+        name = "Unit"
+        description = "An astropy unit"
+
+        name = field.name or name
+        description = field.field_info.description or description
+        examples = field.field_info.extra.get("examples", [])
+
+        field_schema.update(
+            {
+                "title": name,
+                "description": description,
+                "examples": examples,
+                "type": "string",
+            }
+        )
+
+
+class QuantityType(Quantity):
+    # Validator for Quantity type
+    @classmethod
+    def __get_validators__(cls):
+        yield cls.validate
+
+    @classmethod
+    def validate(cls, v):
+        try:
+            v = Quantity(v)
+        except TypeError as err:
+            raise ValueError(f"Invalid value for Quantity: {v}") from err
+        else:
+            if not v.unit.bases:
+                raise ValueError("Must provided a unit")
+        return v
+
+    @classmethod
+    def __modify_schema__(cls, field_schema, field):
+        # Set default values for the schema in case the field doesn't provide them
+        name = "Quantity"
+        description = "An astropy Quantity with units"
+
+        name = field.name or name
+        description = field.field_info.description or description
+        examples = field.field_info.extra.get("examples", [])
+
+        field_schema.update(
+            {
+                "title": name,
+                "description": description,
+                "examples": examples,
+                "type": "string",
+            }
+        )
+
+
+class PixelScaleType(Quantity):
+    # Validator for pixel scale type
+    @classmethod
+    def __get_validators__(cls):
+        yield cls.validate
+
+    @classmethod
+    def validate(cls, v):
+        try:
+            v = Quantity(v)
+        except TypeError as err:
+            raise ValueError(f"Invalid value for Quantity: {v}") from err
+        if (
+            len(v.unit.bases) != 2
+            or v.unit.bases[0].physical_type != "angle"
+            or v.unit.bases[1].name != "pix"
+        ):
+            raise ValueError(f"Invalid unit for pixel scale: {v.unit!r}")
+        return v
+
+    @classmethod
+    def __modify_schema__(cls, field_schema):
+        field_schema.update(
+            {
+                "title": "PixelScale",
+                "description": "An astropy Quantity with units of angle per pixel",
+                "examples": ["0.563 arcsec / pix"],
+                "type": "string",
+            }
+        )