[ENH] RFC9457 compliant errors (#238)

Support [RFC9457](https://datatracker.ietf.org/doc/html/rfc9457) compliant errors.
There are some improvements left out of scope: more consistent terminology in error details, changing some errors to normal responses (e.g., empty list instead of error).

Author: PGijsbers

src/core/errors.py

@@ -1,7 +1,354 @@
-from enum import IntEnum
+"""RFC 9457 Problem Details for HTTP APIs.
 
+This module provides RFC 9457 compliant error handling for the OpenML REST API.
+See: https://www.rfc-editor.org/rfc/rfc9457.html
+"""
 
-class DatasetError(IntEnum):
-    NOT_FOUND = 111
-    NO_ACCESS = 112
-    NO_DATA_FILE = 113
+from http import HTTPStatus
+
+from fastapi import Request
+from fastapi.responses import JSONResponse
+
+# =============================================================================
+# Base Exception
+# =============================================================================
+
+
+class ProblemDetailError(Exception):
+    """Base exception for RFC 9457 compliant error responses.
+
+    Subclasses should define class attributes:
+        - uri: The problem type URI
+        - title: Human-readable title
+        - _default_status_code: HTTP status code
+        - _default_code: Legacy error code (optional)
+
+    The status_code and code can be overridden per-instance.
+    """
+
+    uri: str = "about:blank"
+    title: str = "An error occurred"
+    _default_status_code: HTTPStatus = HTTPStatus.INTERNAL_SERVER_ERROR
+    _default_code: int | None = None
+
+    def __init__(
+        self,
+        detail: str,
+        *,
+        code: int | str | None = None,
+        instance: str | None = None,
+        status_code: HTTPStatus | None = None,
+    ) -> None:
+        self.detail = detail
+        self._code_override = code
+        self.instance = instance
+        self._status_code_override = status_code
+        super().__init__(detail)
+
+    @property
+    def status_code(self) -> HTTPStatus:
+        """Return the status code, preferring instance override over class default."""
+        if self._status_code_override is not None:
+            return self._status_code_override
+        return self._default_status_code
+
+    @property
+    def code(self) -> int | str | None:
+        """Return the code, preferring instance override over class default."""
+        if self._code_override is not None:
+            return self._code_override
+        return self._default_code
+
+
+def problem_detail_exception_handler(
+    request: Request,  # noqa: ARG001
+    exc: ProblemDetailError,
+) -> JSONResponse:
+    """FastAPI exception handler for ProblemDetailError.
+
+    Returns a response with:
+    - Content-Type: application/problem+json
+    - RFC 9457 compliant JSON body
+    """
+    content: dict[str, str | int] = {
+        "type": exc.uri,
+        "title": exc.title,
+        "status": int(exc.status_code),
+        "detail": exc.detail,
+    }
+    if exc.code is not None:
+        content["code"] = str(exc.code)
+    if exc.instance is not None:
+        content["instance"] = exc.instance
+
+    return JSONResponse(
+        status_code=int(exc.status_code),
+        content=content,
+        media_type="application/problem+json",
+    )
+
+
+# =============================================================================
+# Dataset Errors
+# =============================================================================
+
+
+class DatasetNotFoundError(ProblemDetailError):
+    """Raised when a dataset cannot be found."""
+
+    uri = "https://openml.org/problems/dataset-not-found"
+    title = "Dataset Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+    _default_code = 111
+
+
+class DatasetNoAccessError(ProblemDetailError):
+    """Raised when user doesn't have access to a dataset."""
+
+    uri = "https://openml.org/problems/dataset-no-access"
+    title = "Dataset Access Denied"
+    _default_status_code = HTTPStatus.FORBIDDEN
+    _default_code = 112
+
+
+class DatasetNoDataFileError(ProblemDetailError):
+    """Raised when a dataset's data file is missing."""
+
+    uri = "https://openml.org/problems/dataset-no-data-file"
+    title = "Dataset Data File Missing"
+    _default_status_code = HTTPStatus.PRECONDITION_FAILED
+    _default_code = 113
+
+
+class DatasetNotProcessedError(ProblemDetailError):
+    """Raised when a dataset has not been processed yet."""
+
+    uri = "https://openml.org/problems/dataset-not-processed"
+    title = "Dataset Not Processed"
+    _default_status_code = HTTPStatus.PRECONDITION_FAILED
+    _default_code = 273
+
+
+class DatasetProcessingError(ProblemDetailError):
+    """Raised when a dataset had an error during processing."""
+
+    uri = "https://openml.org/problems/dataset-processing-error"
+    title = "Dataset Processing Error"
+    _default_status_code = HTTPStatus.PRECONDITION_FAILED
+    _default_code = 274
+
+
+class DatasetNoFeaturesError(ProblemDetailError):
+    """Raised when a dataset has no features available."""
+
+    uri = "https://openml.org/problems/dataset-no-features"
+    title = "Dataset Features Not Available"
+    _default_status_code = HTTPStatus.PRECONDITION_FAILED
+    _default_code = 272
+
+
+class DatasetStatusTransitionError(ProblemDetailError):
+    """Raised when an invalid dataset status transition is attempted."""
+
+    uri = "https://openml.org/problems/dataset-status-transition"
+    title = "Invalid Status Transition"
+    _default_status_code = HTTPStatus.PRECONDITION_FAILED
+    _default_code = 694
+
+
+class DatasetNotOwnedError(ProblemDetailError):
+    """Raised when user tries to modify a dataset they don't own."""
+
+    uri = "https://openml.org/problems/dataset-not-owned"
+    title = "Dataset Not Owned"
+    _default_status_code = HTTPStatus.FORBIDDEN
+    _default_code = 693
+
+
+class DatasetAdminOnlyError(ProblemDetailError):
+    """Raised when a non-admin tries to perform an admin-only action."""
+
+    uri = "https://openml.org/problems/dataset-admin-only"
+    title = "Administrator Only"
+    _default_status_code = HTTPStatus.FORBIDDEN
+    _default_code = 696
+
+
+# =============================================================================
+# Authentication/Authorization Errors
+# =============================================================================
+
+
+class AuthenticationRequiredError(ProblemDetailError):
+    """Raised when authentication is required but not provided."""
+
+    uri = "https://openml.org/problems/authentication-required"
+    title = "Authentication Required"
+    _default_status_code = HTTPStatus.UNAUTHORIZED
+
+
+class AuthenticationFailedError(ProblemDetailError):
+    """Raised when authentication credentials are invalid."""
+
+    uri = "https://openml.org/problems/authentication-failed"
+    title = "Authentication Failed"
+    _default_status_code = HTTPStatus.UNAUTHORIZED
+    _default_code = 103
+
+
+class ForbiddenError(ProblemDetailError):
+    """Raised when user is authenticated but not authorized."""
+
+    uri = "https://openml.org/problems/forbidden"
+    title = "Forbidden"
+    _default_status_code = HTTPStatus.FORBIDDEN
+
+
+# =============================================================================
+# Tag Errors
+# =============================================================================
+
+
+class TagAlreadyExistsError(ProblemDetailError):
+    """Raised when trying to add a tag that already exists."""
+
+    uri = "https://openml.org/problems/tag-already-exists"
+    title = "Tag Already Exists"
+    _default_status_code = HTTPStatus.CONFLICT
+    _default_code = 473
+
+
+# =============================================================================
+# Search/List Errors
+# =============================================================================
+
+
+class NoResultsError(ProblemDetailError):
+    """Raised when a search returns no results."""
+
+    uri = "https://openml.org/problems/no-results"
+    title = "No Results Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+    _default_code = 372
+
+
+# =============================================================================
+# Study Errors
+# =============================================================================
+
+
+class StudyNotFoundError(ProblemDetailError):
+    """Raised when a study cannot be found."""
+
+    uri = "https://openml.org/problems/study-not-found"
+    title = "Study Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+
+
+class StudyPrivateError(ProblemDetailError):
+    """Raised when trying to access a private study without permission."""
+
+    uri = "https://openml.org/problems/study-private"
+    title = "Study Is Private"
+    _default_status_code = HTTPStatus.FORBIDDEN
+
+
+class StudyLegacyError(ProblemDetailError):
+    """Raised when trying to access a legacy study that's no longer supported."""
+
+    uri = "https://openml.org/problems/study-legacy"
+    title = "Legacy Study Not Supported"
+    _default_status_code = HTTPStatus.GONE
+
+
+class StudyAliasExistsError(ProblemDetailError):
+    """Raised when trying to create a study with an alias that already exists."""
+
+    uri = "https://openml.org/problems/study-alias-exists"
+    title = "Study Alias Already Exists"
+    _default_status_code = HTTPStatus.CONFLICT
+
+
+class StudyInvalidTypeError(ProblemDetailError):
+    """Raised when study type configuration is invalid."""
+
+    uri = "https://openml.org/problems/study-invalid-type"
+    title = "Invalid Study Type"
+    _default_status_code = HTTPStatus.BAD_REQUEST
+
+
+class StudyNotEditableError(ProblemDetailError):
+    """Raised when trying to edit a study that cannot be edited."""
+
+    uri = "https://openml.org/problems/study-not-editable"
+    title = "Study Not Editable"
+    _default_status_code = HTTPStatus.FORBIDDEN
+
+
+class StudyConflictError(ProblemDetailError):
+    """Raised when there's a conflict with study data (e.g., duplicate attachment)."""
+
+    uri = "https://openml.org/problems/study-conflict"
+    title = "Study Conflict"
+    _default_status_code = HTTPStatus.CONFLICT
+
+
+# =============================================================================
+# Task Errors
+# =============================================================================
+
+
+class TaskNotFoundError(ProblemDetailError):
+    """Raised when a task cannot be found."""
+
+    uri = "https://openml.org/problems/task-not-found"
+    title = "Task Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+
+
+class TaskTypeNotFoundError(ProblemDetailError):
+    """Raised when a task type cannot be found."""
+
+    uri = "https://openml.org/problems/task-type-not-found"
+    title = "Task Type Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+    _default_code = 241
+
+
+# =============================================================================
+# Flow Errors
+# =============================================================================
+
+
+class FlowNotFoundError(ProblemDetailError):
+    """Raised when a flow cannot be found."""
+
+    uri = "https://openml.org/problems/flow-not-found"
+    title = "Flow Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+
+
+# =============================================================================
+# Service Errors
+# =============================================================================
+
+
+class ServiceNotFoundError(ProblemDetailError):
+    """Raised when a service cannot be found."""
+
+    uri = "https://openml.org/problems/service-not-found"
+    title = "Service Not Found"
+    _default_status_code = HTTPStatus.NOT_FOUND
+
+
+# =============================================================================
+# Internal Errors
+# =============================================================================
+
+
+class InternalError(ProblemDetailError):
+    """Raised for unexpected internal server errors."""
+
+    uri = "https://openml.org/problems/internal-error"
+    title = "Internal Server Error"
+    _default_status_code = HTTPStatus.INTERNAL_SERVER_ERROR

src/core/formatting.py

@@ -3,7 +3,6 @@
 from sqlalchemy.engine import Row
 
 from config import load_routing_configuration
-from core.errors import DatasetError
 from schemas.datasets.openml import DatasetFileFormat
 
 
@@ -16,11 +15,6 @@ def _str_to_bool(string: str) -> bool:
     raise ValueError(msg)
 
 
-def _format_error(*, code: DatasetError, message: str) -> dict[str, str]:
-    """Formatter for JSON bodies of OpenML error codes."""
-    return {"code": str(code), "message": message}
-
-
 def _format_parquet_url(dataset: Row) -> str | None:
     if dataset.format.lower() != DatasetFileFormat.ARFF:
         return None

src/database/users.py

@@ -7,11 +7,10 @@
 
 from config import load_configuration
 
-# Enforces str is 32 hexadecimal characters, does not check validity.
 # If `allow_test_api_keys` is set, the key may also be one of `normaluser`,
 # `normaluser2`, or `abc` (admin).
 api_key_pattern = r"^[0-9a-fA-F]{32}$"
-if load_configuration()["development"].get("allow_test_api_keys"):
+if load_configuration().get("development", {}).get("allow_test_api_keys"):
     api_key_pattern = r"^([0-9a-fA-F]{32}|normaluser|normaluser2|abc)$"
 
 APIKey = Annotated[