feat: port various nit changes from wip-v0.4 (#32506)

Lots of work that wasn't directly related to core
improvements/messages/testing functionality

docs/api_reference/create_api_rst.py

@@ -97,7 +97,7 @@ def _load_module_members(module_path: str, namespace: str) -> ModuleMembers:
             if type(type_) is typing_extensions._TypedDictMeta:  # type: ignore
                 kind: ClassKind = "TypedDict"
             elif type(type_) is typing._TypedDictMeta:  # type: ignore
-                kind: ClassKind = "TypedDict"
+                kind = "TypedDict"
             elif (
                 issubclass(type_, Runnable)
                 and issubclass(type_, BaseModel)
@@ -189,7 +189,7 @@ def _load_package_modules(
         if isinstance(package_directory, str)
         else package_directory
     )
-    modules_by_namespace = {}
+    modules_by_namespace: Dict[str, ModuleMembers] = {}
 
     # Get the high level package name
     package_name = package_path.name
@@ -283,7 +283,7 @@ def _construct_doc(
 .. toctree::
     :hidden:
     :maxdepth: 2
-    
+
 """
     index_autosummary = """
 """
@@ -365,9 +365,9 @@ def _construct_doc(
 
                 module_doc += f"""\
     :template: {template}
-    
+
     {class_["qualified_name"]}
-    
+
 """
                 index_autosummary += f"""
     {class_["qualified_name"]}
@@ -550,8 +550,8 @@ def _build_index(dirs: List[str]) -> None:
     integrations = sorted(dir_ for dir_ in dirs if dir_ not in main_)
     doc = """# LangChain Python API Reference
 
-Welcome to the LangChain Python API reference. This is a reference for all 
-`langchain-x` packages. 
+Welcome to the LangChain Python API reference. This is a reference for all
+`langchain-x` packages.
 
 For user guides see [https://python.langchain.com](https://python.langchain.com).
 

docs/docs/contributing/how_to/testing.mdx

@@ -124,6 +124,47 @@ start "" htmlcov/index.html || open htmlcov/index.html
 
 ```
 
+## Snapshot Testing
+
+Some tests use [syrupy](https://github.com/tophat/syrupy) for snapshot testing, which captures the output of functions and compares them to stored snapshots. This is particularly useful for testing JSON schema generation and other structured outputs.
+
+### Updating Snapshots
+
+To update snapshots when the expected output has legitimately changed:
+
+```bash
+uv run --group test pytest path/to/test.py --snapshot-update
+```
+
+### Pydantic Version Compatibility Issues
+
+Pydantic generates different JSON schemas across versions, which can cause snapshot test failures in CI when tests run with different Pydantic versions than what was used to generate the snapshots.
+
+**Symptoms:**
+- CI fails with snapshot mismatches showing differences like missing or extra fields.
+- Tests pass locally but fail in CI with different Pydantic versions
+
+**Solution:**
+Locally update snapshots using the same Pydantic version that CI uses:
+
+1. **Identify the failing Pydantic version** from CI logs (e.g., `2.7.0`, `2.8.0`, `2.9.0`)
+
+2. **Update snapshots with that version:**
+   ```bash
+   uv run --with "pydantic==2.9.0" --group test pytest tests/unit_tests/path/to/test.py::test_name --snapshot-update
+   ```
+
+3. **Verify compatibility across supported versions:**
+   ```bash
+   # Test with the version you used to update
+   uv run --with "pydantic==2.9.0" --group test pytest tests/unit_tests/path/to/test.py::test_name
+
+   # Test with other supported versions
+   uv run --with "pydantic==2.8.0" --group test pytest tests/unit_tests/path/to/test.py::test_name
+   ```
+
+**Note:** Some tests use `@pytest.mark.skipif` decorators to only run with specific Pydantic version ranges (e.g., `PYDANTIC_VERSION_AT_LEAST_210`). Make sure to understand these constraints when updating snapshots.
+
 ## Coverage
 
 Code coverage (i.e. the amount of code that is covered by unit tests) helps identify areas of the code that are potentially more or less brittle.