Adding Perplexity extra and deprecating the community version of ChatPerplexity (#30649)

Plus, some accompanying docs updates

Some compelling usage:

```py
from langchain_perplexity import ChatPerplexity


chat = ChatPerplexity(model="llama-3.1-sonar-small-128k-online")
response = chat.invoke(
    "What were the most significant newsworthy events that occurred in the US recently?",
    extra_body={"search_recency_filter": "week"},
)
print(response.content)
# > Here are the top significant newsworthy events in the US recently: ...
```

Also, some confirmation of structured outputs:

```py
from langchain_perplexity import ChatPerplexity
from pydantic import BaseModel


class AnswerFormat(BaseModel):
    first_name: str
    last_name: str
    year_of_birth: int
    num_seasons_in_nba: int


messages = [
    {"role": "system", "content": "Be precise and concise."},
    {
        "role": "user",
        "content": (
            "Tell me about Michael Jordan. "
            "Please output a JSON object containing the following fields: "
            "first_name, last_name, year_of_birth, num_seasons_in_nba. "
        ),
    },
]

llm = ChatPerplexity(model="llama-3.1-sonar-small-128k-online")
structured_llm = llm.with_structured_output(AnswerFormat)
response = structured_llm.invoke(messages)
print(repr(response))
#> AnswerFormat(first_name='Michael', last_name='Jordan', year_of_birth=1963, num_seasons_in_nba=15)
```

libs/community/langchain_community/chat_models/perplexity.py

@@ -18,6 +18,7 @@ from typing import (
     Union,
 )
 
+from langchain_core._api.deprecation import deprecated
 from langchain_core.callbacks import CallbackManagerForLLMRun
 from langchain_core.language_models import LanguageModelInput
 from langchain_core.language_models.chat_models import (
@@ -71,6 +72,11 @@ def _create_usage_metadata(token_usage: dict) -> UsageMetadata:
     )
 
 
+@deprecated(
+    since="0.3.21",
+    removal="1.0",
+    alternative_import="langchain_perplexity.ChatPerplexity",
+)
 class ChatPerplexity(BaseChatModel):
     """`Perplexity AI` Chat models API.
 

libs/langchain/pyproject.toml

@@ -38,6 +38,7 @@ groq = ["langchain-groq"]
 aws = ["langchain-aws"]
 deepseek = ["langchain-deepseek"]
 xai = ["langchain-xai"]
+perplexity = ["langchain-perplexity"]
 
 [project.urls]
 "Source Code" = "https://github.com/langchain-ai/langchain/tree/master/libs/langchain"

libs/langchain/uv.lock

@@ -1,4 +1,5 @@
 version = 1
+revision = 1
 requires-python = ">=3.9, <4.0"
 resolution-markers = [
     "python_full_version >= '3.13' and platform_python_implementation == 'PyPy'",
@@ -2400,6 +2401,9 @@ ollama = [
 openai = [
     { name = "langchain-openai" },
 ]
+perplexity = [
+    { name = "langchain-perplexity" },
+]
 together = [
     { name = "langchain-together" },
 ]
@@ -2493,6 +2497,7 @@ requires-dist = [
     { name = "langchain-mistralai", marker = "extra == 'mistralai'" },
     { name = "langchain-ollama", marker = "extra == 'ollama'" },
     { name = "langchain-openai", marker = "extra == 'openai'", editable = "../partners/openai" },
+    { name = "langchain-perplexity", marker = "extra == 'perplexity'" },
     { name = "langchain-text-splitters", editable = "../text-splitters" },
     { name = "langchain-together", marker = "extra == 'together'" },
     { name = "langchain-xai", marker = "extra == 'xai'" },
@@ -2502,6 +2507,7 @@ requires-dist = [
     { name = "requests", specifier = ">=2,<3" },
     { name = "sqlalchemy", specifier = ">=1.4,<3" },
 ]
+provides-extras = ["community", "anthropic", "openai", "azure-ai", "cohere", "google-vertexai", "google-genai", "fireworks", "ollama", "together", "mistralai", "huggingface", "groq", "aws", "deepseek", "xai", "perplexity"]
 
 [package.metadata.requires-dev]
 codespell = [{ name = "codespell", specifier = ">=2.2.0,<3.0.0" }]
@@ -2659,7 +2665,7 @@ wheels = [
 
 [[package]]
 name = "langchain-core"
-version = "0.3.49"
+version = "0.3.50"
 source = { editable = "../core" }
 dependencies = [
     { name = "jsonpatch" },
@@ -2836,7 +2842,7 @@ wheels = [
 
 [[package]]
 name = "langchain-openai"
-version = "0.3.11"
+version = "0.3.12"
 source = { editable = "../partners/openai" }
 dependencies = [
     { name = "langchain-core" },
@@ -2883,6 +2889,19 @@ typing = [
     { name = "types-tqdm", specifier = ">=4.66.0.5,<5.0.0.0" },
 ]
 
+[[package]]
+name = "langchain-perplexity"
+version = "0.1.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "langchain-core" },
+    { name = "openai" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/fb/66/ccdce60458111a1118d8107c106c65fa40e93fe358c61f9cb2b87b9a5eca/langchain_perplexity-0.1.0.tar.gz", hash = "sha256:947648a223cf1cbbc5b26efcf29d5483443be222fd803da1cff9c2923d6063d6", size = 10069 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/31/82/d6bad72aed8dde4c3cdba5e51554f8978fc5d1ec43ba2f23611474673079/langchain_perplexity-0.1.0-py3-none-any.whl", hash = "sha256:7e18fa4c28e25240a9e57c613bf75737d2767d63dc92979de2db51f4e40127e0", size = 8669 },
+]
+
 [[package]]
 name = "langchain-tests"
 version = "0.3.17"

libs/packages.yml

@@ -567,4 +567,7 @@ packages:
   repo: vectara/langchain-vectara
 - name: langchain-oxylabs
   path: .
-  repo: oxylabs/langchain-oxylabs
+  repo: oxylabs/langchain-oxylabs
+- name: langchain-perplexity
+  path: libs/partners/perplexity
+  repo: langchain-ai/langchain