Simplify setting model validation

src/openflexure_microscope_server/things/autofocus.py

@@ -16,7 +16,7 @@ from types import TracebackType
 from typing import Literal, Mapping, Optional, Self, Sequence
 
 import numpy as np
-from pydantic import BaseModel, computed_field, field_validator, model_validator
+from pydantic import BaseModel, Field, computed_field, field_validator, model_validator
 
 import labthings_fastapi as lt
 from labthings_fastapi.types.numpy import NDArray
@@ -59,12 +59,12 @@ class StackParams(BaseModel):
     """A class for holding stack parameters, and returning computed ones."""
 
     stack_dz: int
-    images_to_save: int
+    images_to_save: int = Field(gt=0)
 
     # Using docstrings under variables as this is how pdoc would expect
     # attributed to be documented
 
-    settling_time: float = 0.3
+    settling_time: float = Field(default=0.3, ge=0)
     """Time (in seconds) between moving and capturing an image"""
 
     backlash_correction: int = 250
@@ -75,22 +75,6 @@ class StackParams(BaseModel):
     origin: StackOrigin = StackOrigin.START
     """Where the stack is positioned relative to the current z position."""
 
-    @field_validator("images_to_save")
-    @classmethod
-    def validate_images_to_save(cls, value: int) -> int:
-        """Validate that the number of images to save is greater than zero."""
-        if value <= 0:
-            raise ValueError(f"Invalid number of images to save: {value}. Must be > 0.")
-        return value
-
-    @field_validator("settling_time")
-    @classmethod
-    def validate_settling_time(cls, value: float) -> float:
-        """Validate that settling time is zero or positive."""
-        if value < 0:
-            raise ValueError(f"Invalid settling time: {value}. Must be positive or 0.")
-        return value
-
 
 class SmartStackParams(StackParams):
     """A class for holding smart stack parameters, and returning computed ones."""

src/openflexure_microscope_server/things/camera/__init__.py

@@ -15,12 +15,12 @@ import tempfile
 import time
 from datetime import datetime
 from types import TracebackType
-from typing import Any, Literal, Mapping, Optional, Self, Tuple
+from typing import Annotated, Any, Literal, Mapping, Optional, Self, Tuple
 
 import numpy as np
 import piexif
 from PIL import Image
-from pydantic import BaseModel, field_validator
+from pydantic import BaseModel, Field
 
 import labthings_fastapi as lt
 from labthings_fastapi.types.numpy import NDArray
@@ -48,34 +48,15 @@ class CaptureError(RuntimeError):
     """An error trying to capture from a CameraThing."""
 
 
+PositiveInt = Annotated[int, Field(ge=1)]
+NonEmptyString = Annotated[str, Field(min_length=1)]
+
+
 class CaptureParams(BaseModel):
     """A class for capturing at least a single image."""
 
-    images_dir: str
-    save_resolution: tuple[int, int]
-
-    @field_validator("save_resolution")
-    @classmethod
-    def validate_save_resolution(cls, value: Tuple[int, int]) -> Tuple[int, int]:
-        """Validate that save_resolution is a tuple with exactly two positive integers."""
-        if not isinstance(value, tuple):
-            raise TypeError("Save resolution should be a tuple")
-        if len(value) != 2 or any(not isinstance(x, int) or x <= 0 for x in value):
-            raise ValueError(
-                f"Invalid save_resolution: {value}. "
-                "Must be a tuple of two positive integers."
-            )
-        return value
-
-    @field_validator("images_dir")
-    @classmethod
-    def validate_images_dir(cls, value: str) -> str:
-        """Validate that images_dir is a non-empty string."""
-        if not isinstance(value, str) or not value:
-            raise ValueError(
-                f"Invalid images_dir: {value}. Must be a non-empty string."
-            )
-        return value
+    images_dir: NonEmptyString
+    save_resolution: tuple[PositiveInt, PositiveInt]
 
 
 class NoImageInMemoryError(RuntimeError):

tests/unit_tests/test_stack.py

@@ -109,8 +109,8 @@ def test_stack_params_negative_images_to_save(save_ims, extra_ims):
     # Depending on the values multiple messages are possible
     match = (
         "(Can't test for focus with fewer than 3 images|"
-        "Images to save must be positive and odd)|"
-        "Invalid number of images to save"
+        "Images to save must be positive and odd|"
+        "Input should be greater than 0)"
     )
     with pytest.raises(ValueError, match=match):
         SmartStackParams(
@@ -154,8 +154,8 @@ def test_even_images_to_save(save_ims, extra_ims):
     """
     match = (
         "(Can't test for focus with fewer than 3 images|"
-        "Images to save must be positive and odd)|"
-        "Invalid number of images to save"
+        "Images to save must be positive and odd|"
+        "Input should be greater than 0)"
     )
     with pytest.raises(ValueError, match=match):
         SmartStackParams(
@@ -948,7 +948,7 @@ def test_run_basic_stack_end_origin(
 def test_invalid_stack_images_raises():
     """Test basic stack raises expected error for negative or zero image count."""
     for capture_count in [-3, 0]:
-        with pytest.raises(ValueError, match="Invalid number of images to save"):
+        with pytest.raises(ValueError, match="Input should be greater than 0"):
             StackParams(
                 stack_dz=10,
                 images_to_save=capture_count,
@@ -960,7 +960,7 @@ def test_invalid_stack_images_raises():
 
 def test_invalid_stack_settling_raises():
     """Test basic stack raises expected error for negative settling time."""
-    with pytest.raises(ValueError, match="Invalid settling time"):
+    with pytest.raises(ValueError, match="Input should be greater than or equal to 0"):
         StackParams(
             stack_dz=10,
             images_to_save=1,
@@ -973,7 +973,7 @@ def test_invalid_stack_settling_raises():
 @pytest.mark.parametrize(
     ("bad_path", "match_err"),
     [
-        ("", "Must be a non-empty string"),
+        ("", "String should have at least 1 character"),
         (None, "Input should be a valid string"),
         (67, "Input should be a valid string"),
     ],
@@ -987,8 +987,8 @@ def test_invalid_capture_dir_raises(bad_path, match_err):
 @pytest.mark.parametrize(
     ("bad_res", "match_err"),
     [
-        ((-100, 50), "Invalid save_resolution:"),
-        ((20, 0), "Invalid save_resolution:"),
+        ((-100, 50), "Input should be greater than or equal to 1"),
+        ((20, 0), "Input should be greater than or equal to 1"),
         ("", "Input should be a valid tuple"),
         (None, "Input should be a valid tuple"),
         (67, "Input should be a valid tuple"),