Fix review issues: tags validation, size nullability, type annotation, hash mismatch check, and add tag histogram tests

- Remove contradictory min_length=1 from CreateFromHashBody.tags default
- Restore size field to int|None=None for proper null semantics
- Add Union type annotation to _build_asset_response result param
- Add hash mismatch validation on idempotent upload path (409 HASH_MISMATCH)
- Add unit tests for list_tag_histogram service function

Amp-Thread-ID: https://ampcode.com/threads/T-019cd993-f43c-704e-b3d7-6cfc3d4d4a80
Co-authored-by: Amp <amp@ampcode.com>

app/assets/api/routes.py

@@ -13,6 +13,7 @@ from pydantic import ValidationError
 import folder_paths
 from app import user_manager
 from app.assets.api import schemas_in, schemas_out
+from app.assets.services import schemas
 from app.assets.api.schemas_in import (
     AssetValidationError,
     UploadError,
@@ -123,7 +124,7 @@ def _validate_sort_field(requested: str | None) -> str:
     return "created_at"
 
 
-def _build_asset_response(result) -> schemas_out.Asset:
+def _build_asset_response(result: schemas.AssetDetailResult | schemas.UploadResult) -> schemas_out.Asset:
     """Build an Asset response from a service result."""
     preview_url = None
     if result.ref.preview_id:
@@ -132,7 +133,7 @@ def _build_asset_response(result) -> schemas_out.Asset:
         id=result.ref.id,
         name=result.ref.name,
         asset_hash=result.asset.hash if result.asset else None,
-        size=int(result.asset.size_bytes) if result.asset else 0,
+        size=int(result.asset.size_bytes) if result.asset else None,
         mime_type=result.asset.mime_type if result.asset else None,
         tags=result.tags,
         preview_url=preview_url,
@@ -386,6 +387,14 @@ async def upload_asset(request: web.Request) -> web.Response:
                 owner_id=owner_id,
             )
             if existing:
+                # Validate that uploaded content matches existing asset
+                if spec.hash and existing.asset and existing.asset.hash != spec.hash:
+                    delete_temp_file_if_exists(parsed.tmp_path)
+                    return _build_error_response(
+                        409,
+                        "HASH_MISMATCH",
+                        "Uploaded file hash does not match existing asset.",
+                    )
                 delete_temp_file_if_exists(parsed.tmp_path)
                 asset = _build_asset_response(existing)
                 payload_out = schemas_out.AssetCreated(

app/assets/api/schemas_in.py

@@ -121,7 +121,7 @@ class CreateFromHashBody(BaseModel):
 
     hash: str
     name: str | None = None
-    tags: list[str] = Field(default_factory=list, min_length=1)
+    tags: list[str] = Field(default_factory=list)
     user_metadata: dict[str, Any] = Field(default_factory=dict)
     mime_type: str | None = None
 

app/assets/api/schemas_out.py

@@ -8,7 +8,7 @@ class Asset(BaseModel):
     id: str
     name: str
     asset_hash: str | None = None
-    size: int = 0
+    size: int | None = None
     mime_type: str | None = None
     tags: list[str] = Field(default_factory=list)
     preview_url: str | None = None