#40509 InMemoryVectorStore.delete(None) 不会删除所有文档

Submission checklist

This is a bug, not a usage question.
I added a clear and descriptive title that summarizes this issue.
I used the GitHub search to find a similar question and didn't find it.
I am sure that this is a bug in LangChain rather than my code.
The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
This is not related to the LangChain-community package.
I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Package (Required)

LangChain
LangChain-OpenAI
LangChain-Anthropic
LangChain-classic
LangChain-core
LangChain-model-profiles
LangChain-tests
LangChain-text-splitters
LangChain-chroma
LangChain-DeepSeek
LangChain-exa
LangChain-fireworks
LangChain-groq
LangChain-huggingface
LangChain-mistralai
LangChain-nomic
LangChain-ollama
LangChain-openrouter
LangChain-Perplexity
LangChain-qdrant
LangChain-xai
Other / not sure / general

Related Issues / PRs

No response

Reproduction Steps / Example Code (Python)

from langchain_core.documents import Document
from langchain_core.embeddings import Embeddings
from langchain_core.vectorstores import InMemoryVectorStore


class FakeEmbeddings(Embeddings):
    def embed_documents(self, texts: list[str]) -> list[list[float]]:
        return [[1.0, 0.0] for _ in texts]

    def embed_query(self, text: str) -> list[float]:
        return [1.0, 0.0]


vectorstore = InMemoryVectorStore(FakeEmbeddings())

vectorstore.add_documents(
    [Document(page_content="document A")],
    ids=["doc-a"],
)

print("IDs before delete:", list(vectorstore.store))
vectorstore.delete(ids=None)
print("IDs after delete:", list(vectorstore.store))

Error Message and Stack Trace (if applicable)

Description

VectorStore.delete() documents that passing ids=None should delete all vectors. However, InMemoryVectorStore.delete() only performs deletion when ids is truthy. The implementation currently uses:

def delete(
    self,
    ids: Sequence[str] | None = None,
    **kwargs: Any,
) -> None:
    if ids:
        for identifier in ids:
            self.store.pop(identifier, None)
### System Info
System Information
------------------
> OS:  Windows
> OS Version:  10.0.26200
> Python Version:  3.13.3 (main, May 30 2025, 05:37:00) [MSC v.1943 64 bit (AMD64)]

Package Information
-------------------
> langchain_core: 1.6.3
> langsmith: 0.12.5
> langchain_classic: 1.0.8
> langchain_huggingface: 1.2.2
> langchain_protocol: 0.0.19
> langchain_text_splitters: 1.1.2