langchain[patch]: Mask API key for ForeFrontAI LLM (#14013)

- **Description:** Mask API key for ForeFrontAI LLM and associated unit
tests
  - **Issue:** https://github.com/langchain-ai/langchain/issues/12165
  - **Dependencies:** N/A
  - **Tag maintainer:** @eyurtsev 
  - **Twitter handle:** `__mmahmad__`

I made the API key non-optional since linting required adding validation
for None, but the key is required per documentation:
https://python.langchain.com/docs/integrations/llms/forefrontai

libs/langchain/langchain/llms/forefrontai.py

@@ -1,12 +1,12 @@
 from typing import Any, Dict, List, Mapping, Optional
 
 import requests
-from langchain_core.pydantic_v1 import Extra, root_validator
+from langchain_core.pydantic_v1 import Extra, SecretStr, root_validator
 
 from langchain.callbacks.manager import CallbackManagerForLLMRun
 from langchain.llms.base import LLM
 from langchain.llms.utils import enforce_stop_tokens
-from langchain.utils import get_from_dict_or_env
+from langchain.utils import convert_to_secret_str, get_from_dict_or_env
 
 
 class ForefrontAI(LLM):
@@ -41,7 +41,7 @@ class ForefrontAI(LLM):
     repetition_penalty: int = 1
     """Penalizes repeated tokens according to frequency."""
 
-    forefrontai_api_key: Optional[str] = None
+    forefrontai_api_key: SecretStr = None
 
     base_url: Optional[str] = None
     """Base url to use, if None decides based on model name."""
@@ -54,10 +54,9 @@ class ForefrontAI(LLM):
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that api key exists in environment."""
-        forefrontai_api_key = get_from_dict_or_env(
+        values["forefrontai_api_key"] = convert_to_secret_str(
-            values, "forefrontai_api_key", "FOREFRONTAI_API_KEY"
+            get_from_dict_or_env(values, "forefrontai_api_key", "FOREFRONTAI_API_KEY")
         )
-        values["forefrontai_api_key"] = forefrontai_api_key
         return values
 
     @property
@@ -102,10 +101,11 @@ class ForefrontAI(LLM):
 
                 response = ForefrontAI("Tell me a joke.")
         """
+        auth_value = f"Bearer {self.forefrontai_api_key.get_secret_value()}"
         response = requests.post(
             url=self.endpoint_url,
             headers={
-                "Authorization": f"Bearer {self.forefrontai_api_key}",
+                "Authorization": auth_value,
                 "Content-Type": "application/json",
             },
             json={"text": prompt, **self._default_params, **kwargs},

libs/langchain/tests/unit_tests/llms/test_forefrontai.py

@@ -0,0 +1,50 @@
+"""Test ForeFrontAI LLM"""
+from typing import cast
+
+from langchain_core.pydantic_v1 import SecretStr
+from pytest import CaptureFixture, MonkeyPatch
+
+from langchain.llms.forefrontai import ForefrontAI
+
+
+def test_forefrontai_api_key_is_secret_string() -> None:
+    """Test that the API key is stored as a SecretStr."""
+    llm = ForefrontAI(forefrontai_api_key="secret-api-key", temperature=0.2)
+    assert isinstance(llm.forefrontai_api_key, SecretStr)
+
+
+def test_forefrontai_api_key_masked_when_passed_from_env(
+    monkeypatch: MonkeyPatch, capsys: CaptureFixture
+) -> None:
+    """Test that the API key is masked when passed from an environment variable."""
+    monkeypatch.setenv("FOREFRONTAI_API_KEY", "secret-api-key")
+    llm = ForefrontAI(temperature=0.2)
+    print(llm.forefrontai_api_key, end="")
+    captured = capsys.readouterr()
+
+    assert captured.out == "**********"
+
+
+def test_forefrontai_api_key_masked_when_passed_via_constructor(
+    capsys: CaptureFixture,
+) -> None:
+    """Test that the API key is masked when passed via the constructor."""
+    llm = ForefrontAI(
+        forefrontai_api_key="secret-api-key",
+        temperature=0.2,
+    )
+    print(llm.forefrontai_api_key, end="")
+    captured = capsys.readouterr()
+
+    assert captured.out == "**********"
+
+
+def test_forefrontai_uses_actual_secret_value_from_secretstr() -> None:
+    """Test that the actual secret value is correctly retrieved."""
+    llm = ForefrontAI(
+        forefrontai_api_key="secret-api-key",
+        temperature=0.2,
+    )
+    assert (
+        cast(SecretStr, llm.forefrontai_api_key).get_secret_value() == "secret-api-key"
+    )