Nice custom error wrapper for pydanic issues. Adds a "message" field …

…with user readable errors, while keeping the source_errors as well

app/web_ui/src/lib/utils/form_container.svelte

@@ -110,9 +110,11 @@
       </div>
     {/if}
     {#if custom_error_message}
-      <div class="text-sm text-center text-error">
-        {custom_error_message}
-      </div>
+      {#each custom_error_message.split("\n") as error_line}
+        <div class="text-sm text-center text-error">
+          {error_line}
+        </div>
+      {/each}
     {/if}
     <button
       type="submit"

libs/studio/kiln_studio/custom_errors.py

@@ -0,0 +1,24 @@
+from fastapi import FastAPI, Request, status
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
+
+
+def connect_custom_errors(app: FastAPI):
+    @app.exception_handler(RequestValidationError)
+    async def validation_exception_handler(
+        request: Request, exc: RequestValidationError
+    ):
+        # Write user friendly error messages
+        error_messages = []
+        for error in exc.errors():
+            field = error["loc"][-1]  # Get the field name
+            message = error["msg"]
+            error_messages.append(f"{field.capitalize()}: {message}")
+
+        return JSONResponse(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            content={
+                "message": ".\n".join(error_messages),
+                "source_errors": exc.errors(),
+            },
+        )

libs/studio/kiln_studio/server.py

@@ -4,6 +4,7 @@
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
+from .custom_errors import connect_custom_errors
 from .project_management import connect_project_management
 from .provider_management import connect_provider_management
 from .settings import connect_settings
@@ -30,6 +31,7 @@ def ping():
     connect_provider_management(app)
     connect_settings(app)
     connect_webhost(app)
+    connect_custom_errors(app)
 
     return app
 

libs/studio/kiln_studio/test_custom_error.py

@@ -0,0 +1,74 @@
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from pydantic import BaseModel, Field
+
+from libs.studio.kiln_studio.custom_errors import connect_custom_errors
+
+
+@pytest.fixture
+def app():
+    app = FastAPI()
+    connect_custom_errors(app)
+
+    class Item(BaseModel):
+        name: str = Field(..., min_length=3)
+        price: float = Field(..., gt=0)
+
+    @app.post("/items")
+    async def create_item(item: Item):
+        return item
+
+    return app
+
+
+@pytest.fixture
+def client(app):
+    return TestClient(app)
+
+
+def test_validation_error_single_field(client):
+    response = client.post("/items", json={"name": "ab", "price": 10})
+    assert response.status_code == 422
+    assert response.json() == {
+        "message": "Name: String should have at least 3 characters",
+        "source_errors": [
+            {
+                "type": "string_too_short",
+                "loc": ["body", "name"],
+                "msg": "String should have at least 3 characters",
+                "input": "ab",
+                "ctx": {"min_length": 3},
+            }
+        ],
+    }
+
+
+def test_validation_error_multiple_fields(client):
+    response = client.post("/items", json={"name": "ab", "price": -5})
+    assert response.status_code == 422
+    assert response.json() == {
+        "message": "Name: String should have at least 3 characters.\nPrice: Input should be greater than 0",
+        "source_errors": [
+            {
+                "type": "string_too_short",
+                "loc": ["body", "name"],
+                "msg": "String should have at least 3 characters",
+                "input": "ab",
+                "ctx": {"min_length": 3},
+            },
+            {
+                "type": "greater_than",
+                "loc": ["body", "price"],
+                "msg": "Input should be greater than 0",
+                "input": -5,
+                "ctx": {"gt": 0},
+            },
+        ],
+    }
+
+
+def test_valid_input(client):
+    response = client.post("/items", json={"name": "abc", "price": 10})
+    assert response.status_code == 200
+    assert response.json() == {"name": "abc", "price": 10}