chore: enable ANN ruff ruleset for elasticsearch integration (#2986)

Add ANN (flake8-annotations) to ruff select, ignore ANN401 (Any is used
legitimately for **kwargs and ES SDK boundaries), exclude tests from ANN
checks, and add missing -> None return type annotations to __init__ and
_ensure_initialized.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: julian-risch

integrations/elasticsearch/pyproject.toml

@@ -85,6 +85,7 @@ line-length = 120
 [tool.ruff.lint]
 select = [
   "A",
+  "ANN",
   "ARG",
   "B",
   "C",
@@ -125,6 +126,8 @@ ignore = [
   "PLR0912",
   "PLR0913",
   "PLR0915",
+  # Allow `Any` - used legitimately for dynamic types and SDK boundaries
+  "ANN401",
 ]
 
 [tool.ruff.lint.isort]
@@ -134,8 +137,8 @@ known-first-party = ["haystack_integrations"]
 ban-relative-imports = "parents"
 
 [tool.ruff.lint.per-file-ignores]
-# Tests can use magic values, assertions, and relative imports
-"tests/**/*" = ["PLR2004", "S101", "TID252"]
+# Tests can use magic values, assertions, relative imports, and don't need type annotations
+"tests/**/*" = ["PLR2004", "S101", "TID252", "ANN"]
 
 [tool.coverage.run]
 source = ["haystack_integrations"]

integrations/elasticsearch/src/haystack_integrations/components/retrievers/elasticsearch/bm25_retriever.py

@@ -52,7 +52,7 @@ def __init__(
         top_k: int = 10,
         scale_score: bool = False,
         filter_policy: str | FilterPolicy = FilterPolicy.REPLACE,
-    ):
+    ) -> None:
         """
         Initialize ElasticsearchBM25Retriever with an instance ElasticsearchDocumentStore.
 

integrations/elasticsearch/src/haystack_integrations/components/retrievers/elasticsearch/embedding_retriever.py

@@ -53,7 +53,7 @@ def __init__(
         top_k: int = 10,
         num_candidates: int | None = None,
         filter_policy: str | FilterPolicy = FilterPolicy.REPLACE,
-    ):
+    ) -> None:
         """
         Create the ElasticsearchEmbeddingRetriever component.
 

integrations/elasticsearch/src/haystack_integrations/components/retrievers/elasticsearch/sql_retriever.py

@@ -42,7 +42,7 @@ def __init__(
         document_store: ElasticsearchDocumentStore,
         raise_on_failure: bool = True,
         fetch_size: int | None = None,
-    ):
+    ) -> None:
         """
         Creates the ElasticsearchSQLRetriever component.
 

integrations/elasticsearch/src/haystack_integrations/document_stores/elasticsearch/document_store.py

@@ -86,7 +86,7 @@ def __init__(
         api_key_id: Secret | str | None = Secret.from_env_var("ELASTIC_API_KEY_ID", strict=False),
         embedding_similarity_function: Literal["cosine", "dot_product", "l2_norm", "max_inner_product"] = "cosine",
         **kwargs: Any,
-    ):
+    ) -> None:
         """
         Creates a new ElasticsearchDocumentStore instance.
 
@@ -156,7 +156,7 @@ def __init__(
                 ],
             }
 
-    def _ensure_initialized(self):
+    def _ensure_initialized(self) -> None:
         """
         Ensures both sync and async clients are initialized and the index exists.
         """