feature/mx-1649 more rule editing prep (#212)

### PR Context
- prep for robert-koch-institut/mex-editor#192

### Changes
- harmonize error handling for transforming raw rule-sets to responses
- return 404 on GET rule-set endpoint, when no rules are found

### Removed
- removed not needed `mex.backend.constants` module

CHANGELOG.md

@@ -11,10 +11,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changes
 
+- harmonize error handling for transforming raw rule-sets to responses
+- return 404 on GET rule-set endpoint, when no rules are found
+
 ### Deprecated
 
 ### Removed
 
+- removed not needed `mex.backend.constants` module
+
 ### Fixed
 
 ### Security

mex/backend/merged/helpers.py

@@ -2,7 +2,6 @@
 
 from pydantic import Field, TypeAdapter, ValidationError
 
-from mex.backend.constants import NUMBER_OF_RULE_TYPES
 from mex.backend.fields import MERGEABLE_FIELDS_BY_CLASS_NAME
 from mex.backend.graph.connector import GraphConnector
 from mex.backend.graph.exceptions import InconsistentGraphError
@@ -153,23 +152,20 @@ def merge_search_result_item(item: dict[str, Any]) -> AnyMergedModel:
         for component in item["components"]
         if component["entityType"] in EXTRACTED_MODEL_CLASSES_BY_NAME
     ]
-    rules_raw = [
+    raw_rules = [
         component
         for component in item["components"]
         if component["entityType"] in RULE_MODEL_CLASSES_BY_NAME
     ]
-    if len(rules_raw) == NUMBER_OF_RULE_TYPES:
-        rule_set_response = transform_raw_rules_to_rule_set_response(rules_raw)
-    elif len(rules_raw) == 0:
-        rule_set_response = None
+    if raw_rules:
+        rule_set = transform_raw_rules_to_rule_set_response(raw_rules)
     else:
-        msg = f"Unexpected number of rules found in graph: {len(rules_raw)}"
-        raise InconsistentGraphError(msg)
+        rule_set = None
 
     return create_merged_item(
         identifier=item["identifier"],
         extracted_items=extracted_items,
-        rule_set=rule_set_response,
+        rule_set=rule_set,
     )
 
 

mex/backend/rules/helpers.py

@@ -1,8 +1,8 @@
 from collections.abc import Mapping
 from typing import Any, Final
 
-from mex.backend.constants import NUMBER_OF_RULE_TYPES
 from mex.backend.graph.connector import GraphConnector
+from mex.backend.graph.exceptions import InconsistentGraphError
 from mex.common.exceptions import MExError
 from mex.common.models import (
     ADDITIVE_MODEL_CLASSES_BY_NAME,
@@ -32,9 +32,9 @@ def transform_raw_rules_to_rule_set_response(
     response: dict[str, Any] = {}
     model: type[AnyRuleModel] | None
 
-    if len(raw_rules) != NUMBER_OF_RULE_TYPES:
-        msg = "inconsistent rule item count"
-        raise MExError(msg)
+    if (num_raw_rules := len(raw_rules)) != len(MODEL_CLASS_LOOKUP_BY_FIELD_NAME):
+        msg = f"inconsistent number of rules found: {num_raw_rules}"
+        raise InconsistentGraphError(msg)
 
     for rule in raw_rules:
         for field_name, model_class_lookup in MODEL_CLASS_LOOKUP_BY_FIELD_NAME.items():
@@ -45,10 +45,10 @@ def transform_raw_rules_to_rule_set_response(
 
     if len(set(stem_types)) != 1:
         msg = "inconsistent rule item stem types"
-        raise MExError(msg)
+        raise InconsistentGraphError(msg)
     if len(set(stable_target_ids)) != 1:
-        msg = "inconsistent rule item stableTargetIds"
-        raise MExError(msg)
+        msg = f"inconsistent rule item stableTargetIds: {', '.join(stable_target_ids)}"
+        raise InconsistentGraphError(msg)
 
     response["stableTargetId"] = stable_target_ids[0]
     response_class_name = ensure_postfix(stem_types[0], "RuleSetResponse")
@@ -83,7 +83,7 @@ def create_and_get_rule_set(
 
 def get_rule_set_from_graph(
     stable_target_id: Identifier,
-) -> AnyRuleSetResponse:
+) -> AnyRuleSetResponse | None:
     """Read a rule set from the graph."""
     connector = GraphConnector.get()
     graph_result = connector.fetch_rule_items(
@@ -93,7 +93,9 @@ def get_rule_set_from_graph(
         0,
         3,
     )
-    return transform_raw_rules_to_rule_set_response(graph_result.one()["items"])
+    if raw_rules := graph_result.one()["items"]:
+        return transform_raw_rules_to_rule_set_response(raw_rules)
+    return None
 
 
 def update_and_get_rule_set(

mex/backend/rules/main.py

@@ -1,4 +1,4 @@
-from fastapi import APIRouter
+from fastapi import APIRouter, HTTPException
 from starlette import status
 
 from mex.backend.rules.helpers import (
@@ -21,7 +21,9 @@ def create_rule_set(rule_set: AnyRuleSetRequest) -> AnyRuleSetResponse:
 @router.get("/rule-set/{stableTargetId}", tags=["editor"])
 def get_rule_set(stableTargetId: Identifier) -> AnyRuleSetResponse:
     """Get a rule set."""
-    return get_rule_set_from_graph(stableTargetId)
+    if rule_set := get_rule_set_from_graph(stableTargetId):
+        return rule_set
+    raise HTTPException(status.HTTP_404_NOT_FOUND, "no rules found")
 
 
 @router.put("/rule-set/{stableTargetId}", tags=["editor"])

mex/backend/utils.py

@@ -57,4 +57,6 @@ def reraising(
     try:
         return fn(*args, **kwargs)
     except original_error as error:
+        if isinstance(reraise_as, type):
+            reraise_as = reraise_as(*error.args)
         raise reraise_as from error