feat(langchain): v1 scaffolding (#32166)

This PR adds scaffolding for langchain 1.0 entry package.

Most contents have been removed. 

Currently remaining entrypoints for:

* chat models
* embedding models
* memory -> trimming messages, filtering messages and counting tokens
[we may remove this]
* prompts -> we may remove some prompts
* storage: primarily to support cache backed embeddings, may remove the
kv store
* tools -> report tool primitives

Things to be added:

* Selected agent implementations
* Selected workflows
* Common primitives: messages, Document
* Primitives for type hinting: BaseChatModel, BaseEmbeddings
* Selected retrievers
* Selected text splitters

Things to be removed:

* Globals needs to be removed (needs an update in langchain core)


Todos: 

* TBD indexing api (requires sqlalchemy which we don't want as a
dependency)
* Be explicit about public/private interfaces (e.g., likely rename
chat_models.base.py to something more internal)
* Remove dockerfiles
* Update module doc-strings and README.md

Author: eyurtsev

.github/scripts/check_diff.py

@@ -16,6 +16,7 @@
     "libs/core",
     "libs/text-splitters",
     "libs/langchain",
+    "libs/langchain_v1",
 ]
 
 # when set to True, we are ignoring core dependents

libs/langchain_v1/.dockerignore

@@ -0,0 +1,6 @@
+.venv
+.github
+.git
+.mypy_cache
+.pytest_cache
+Dockerfile

libs/langchain_v1/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) LangChain, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

libs/langchain_v1/Makefile

@@ -0,0 +1,101 @@
+.PHONY: all clean docs_build docs_clean docs_linkcheck api_docs_build api_docs_clean api_docs_linkcheck format lint test tests test_watch integration_tests docker_tests help extended_tests
+
+# Default target executed when no arguments are given to make.
+all: help
+
+######################
+# TESTING AND COVERAGE
+######################
+
+# Define a variable for the test file path.
+TEST_FILE ?= tests/unit_tests/
+
+.EXPORT_ALL_VARIABLES:
+UV_FROZEN = true
+
+# Run unit tests and generate a coverage report.
+coverage:
+	uv run --group test pytest --cov \
+		--cov-config=.coveragerc \
+		--cov-report xml \
+		--cov-report term-missing:skip-covered \
+		$(TEST_FILE)
+
+test tests:
+	uv run --group test pytest -n auto --disable-socket --allow-unix-socket $(TEST_FILE)
+
+extended_tests:
+	uv run --group test pytest --disable-socket --allow-unix-socket --only-extended tests/unit_tests
+
+test_watch:
+	uv run --group test ptw --snapshot-update --now . -- -x --disable-socket --allow-unix-socket --disable-warnings tests/unit_tests
+
+test_watch_extended:
+	uv run --group test ptw --snapshot-update --now . -- -x --disable-socket --allow-unix-socket --only-extended tests/unit_tests
+
+integration_tests:
+	uv run --group test --group test_integration pytest tests/integration_tests
+
+docker_tests:
+	docker build -t my-langchain-image:test .
+	docker run --rm my-langchain-image:test
+
+check_imports: $(shell find langchain -name '*.py')
+	uv run python ./scripts/check_imports.py $^
+
+######################
+# LINTING AND FORMATTING
+######################
+
+# Define a variable for Python and notebook files.
+PYTHON_FILES=.
+MYPY_CACHE=.mypy_cache
+lint format: PYTHON_FILES=.
+lint_diff format_diff: PYTHON_FILES=$(shell git diff --relative=libs/langchain --name-only --diff-filter=d master | grep -E '\.py$$|\.ipynb$$')
+lint_package: PYTHON_FILES=langchain
+lint_tests: PYTHON_FILES=tests
+lint_tests: MYPY_CACHE=.mypy_cache_test
+
+lint lint_diff lint_package lint_tests:
+	[ "$(PYTHON_FILES)" = "" ] || uv run --all-groups ruff check $(PYTHON_FILES)
+	[ "$(PYTHON_FILES)" = "" ] || uv run --all-groups ruff format $(PYTHON_FILES) --diff
+	[ "$(PYTHON_FILES)" = "" ] || mkdir -p $(MYPY_CACHE) && uv run --all-groups mypy $(PYTHON_FILES) --cache-dir $(MYPY_CACHE)
+
+format format_diff:
+	[ "$(PYTHON_FILES)" = "" ] || uv run --all-groups ruff format $(PYTHON_FILES)
+	[ "$(PYTHON_FILES)" = "" ] || uv run --all-groups ruff check --fix $(PYTHON_FILES)
+
+spell_check:
+	uv run --all-groups codespell --toml pyproject.toml
+
+spell_fix:
+	uv run --all-groups codespell --toml pyproject.toml -w
+
+######################
+# HELP
+######################
+
+help:
+	@echo '===================='
+	@echo 'clean                        - run docs_clean and api_docs_clean'
+	@echo 'docs_build                   - build the documentation'
+	@echo 'docs_clean                   - clean the documentation build artifacts'
+	@echo 'docs_linkcheck               - run linkchecker on the documentation'
+	@echo 'api_docs_build               - build the API Reference documentation'
+	@echo 'api_docs_clean               - clean the API Reference documentation build artifacts'
+	@echo 'api_docs_linkcheck           - run linkchecker on the API Reference documentation'
+	@echo '-- LINTING --'
+	@echo 'format                       - run code formatters'
+	@echo 'lint                         - run linters'
+	@echo 'spell_check               	- run codespell on the project'
+	@echo 'spell_fix               		- run codespell on the project and fix the errors'
+	@echo '-- TESTS --'
+	@echo 'coverage                     - run unit tests and generate coverage report'
+	@echo 'test                         - run unit tests'
+	@echo 'tests                        - run unit tests (alias for "make test")'
+	@echo 'test TEST_FILE=<test_file>   - run all tests in file'
+	@echo 'extended_tests               - run only extended unit tests'
+	@echo 'test_watch                   - run unit tests in watch mode'
+	@echo 'integration_tests            - run integration tests'
+	@echo 'docker_tests                 - run unit tests in docker'
+	@echo '-- DOCUMENTATION tasks are from the top-level Makefile --'

libs/langchain_v1/README.md

@@ -0,0 +1,91 @@
+# 🦜️🔗 LangChain
+
+⚡ Building applications with LLMs through composability ⚡
+
+[![Release Notes](https://img.shields.io/github/release/langchain-ai/langchain)](https://github.com/langchain-ai/langchain/releases)
+[![lint](https://github.com/langchain-ai/langchain/actions/workflows/lint.yml/badge.svg)](https://github.com/langchain-ai/langchain/actions/workflows/lint.yml)
+[![test](https://github.com/langchain-ai/langchain/actions/workflows/test.yml/badge.svg)](https://github.com/langchain-ai/langchain/actions/workflows/test.yml)
+[![Downloads](https://static.pepy.tech/badge/langchain/month)](https://pepy.tech/project/langchain)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![Twitter](https://img.shields.io/twitter/url/https/twitter.com/langchainai.svg?style=social&label=Follow%20%40LangChainAI)](https://twitter.com/langchainai)
+[![Open in Dev Containers](https://img.shields.io/static/v1?label=Dev%20Containers&message=Open&color=blue&logo=visualstudiocode)](https://vscode.dev/redirect?url=vscode://ms-vscode-remote.remote-containers/cloneInVolume?url=https://github.com/langchain-ai/langchain)
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/langchain-ai/langchain)
+[![GitHub star chart](https://img.shields.io/github/stars/langchain-ai/langchain?style=social)](https://star-history.com/#langchain-ai/langchain)
+[![Dependency Status](https://img.shields.io/librariesio/github/langchain-ai/langchain)](https://libraries.io/github/langchain-ai/langchain)
+[![Open Issues](https://img.shields.io/github/issues-raw/langchain-ai/langchain)](https://github.com/langchain-ai/langchain/issues)
+
+
+Looking for the JS/TS version? Check out [LangChain.js](https://github.com/langchain-ai/langchainjs).
+
+To help you ship LangChain apps to production faster, check out [LangSmith](https://smith.langchain.com). 
+[LangSmith](https://smith.langchain.com) is a unified developer platform for building, testing, and monitoring LLM applications. 
+Fill out [this form](https://www.langchain.com/contact-sales) to speak with our sales team.
+
+## Quick Install
+
+`pip install langchain`
+or
+`pip install langsmith && conda install langchain -c conda-forge`
+
+## 🤔 What is this?
+
+Large language models (LLMs) are emerging as a transformative technology, enabling developers to build applications that they previously could not. However, using these LLMs in isolation is often insufficient for creating a truly powerful app - the real power comes when you can combine them with other sources of computation or knowledge.
+
+This library aims to assist in the development of those types of applications. Common examples of these applications include:
+
+**❓ Question answering with RAG**
+
+- [Documentation](https://python.langchain.com/docs/use_cases/question_answering/)
+- End-to-end Example: [Chat LangChain](https://chat.langchain.com) and [repo](https://github.com/langchain-ai/chat-langchain)
+
+**🧱 Extracting structured output**
+
+- [Documentation](https://python.langchain.com/docs/use_cases/extraction/)
+- End-to-end Example: [SQL Llama2 Template](https://github.com/langchain-ai/langchain-extract/)
+
+**🤖 Chatbots**
+
+- [Documentation](https://python.langchain.com/docs/use_cases/chatbots)
+- End-to-end Example: [Web LangChain (web researcher chatbot)](https://weblangchain.vercel.app) and [repo](https://github.com/langchain-ai/weblangchain)
+
+## 📖 Documentation
+
+Please see [here](https://python.langchain.com) for full documentation on:
+
+- Getting started (installation, setting up the environment, simple examples)
+- How-To examples (demos, integrations, helper functions)
+- Reference (full API docs)
+- Resources (high-level explanation of core concepts)
+
+## 🚀 What can this help with?
+
+There are five main areas that LangChain is designed to help with.
+These are, in increasing order of complexity:
+
+**📃 Models and Prompts:**
+
+This includes prompt management, prompt optimization, a generic interface for all LLMs, and common utilities for working with chat models and LLMs.
+
+**🔗 Chains:**
+
+Chains go beyond a single LLM call and involve sequences of calls (whether to an LLM or a different utility). LangChain provides a standard interface for chains, lots of integrations with other tools, and end-to-end chains for common applications.
+
+**📚 Retrieval Augmented Generation:**
+
+Retrieval Augmented Generation involves specific types of chains that first interact with an external data source to fetch data for use in the generation step. Examples include summarization of long pieces of text and question/answering over specific data sources.
+
+**🤖 Agents:**
+
+Agents involve an LLM making decisions about which Actions to take, taking that Action, seeing an Observation, and repeating that until done. LangChain provides a standard interface for agents, a selection of agents to choose from, and examples of end-to-end agents.
+
+**🧐 Evaluation:**
+
+[BETA] Generative models are notoriously hard to evaluate with traditional metrics. One new way of evaluating them is using language models themselves to do the evaluation. LangChain provides some prompts/chains for assisting in this.
+
+For more information on these concepts, please see our [full documentation](https://python.langchain.com).
+
+## 💁 Contributing
+
+As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.
+
+For detailed information on how to contribute, see the [Contributing Guide](https://python.langchain.com/docs/contributing/).

libs/langchain_v1/extended_testing_deps.txt

@@ -0,0 +1,5 @@
+-e ../partners/openai
+-e ../partners/anthropic
+-e ../partners/fireworks
+-e ../partners/mistralai
+-e ../partners/groq

libs/langchain_v1/langchain/__init__.py

@@ -0,0 +1,29 @@
+"""Main entrypoint into package."""
+
+from importlib import metadata
+from typing import Any
+
+try:
+    __version__ = metadata.version(__package__)
+except metadata.PackageNotFoundError:
+    # Case where package metadata is not available.
+    __version__ = ""
+del metadata  # optional, avoids polluting the results of dir(__package__)
+
+
+def __getattr__(name: str) -> Any:  # noqa: ANN401
+    """Get an attribute from the package."""
+    if name == "verbose":
+        from langchain.globals import _verbose
+
+        return _verbose
+    if name == "debug":
+        from langchain.globals import _debug
+
+        return _debug
+    if name == "llm_cache":
+        from langchain.globals import _llm_cache
+
+        return _llm_cache
+    msg = f"Could not find: {name}"
+    raise AttributeError(msg)

libs/langchain_v1/langchain/chat_models/__init__.py

@@ -0,0 +1,24 @@
+"""**Chat Models** are a variation on language models.
+
+While Chat Models use language models under the hood, the interface they expose
+is a bit different. Rather than expose a "text in, text out" API, they expose
+an interface where "chat messages" are the inputs and outputs.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseLanguageModel --> BaseChatModel --> <name>  # Examples: ChatOpenAI, ChatGooglePalm
+
+**Main helpers:**
+
+.. code-block::
+
+    AIMessage, BaseMessage, HumanMessage
+"""  # noqa: E501
+
+from langchain.chat_models.base import init_chat_model
+
+__all__ = [
+    "init_chat_model",
+]