Improve README

Author: henribru

README.md

@@ -23,13 +23,6 @@ The stubs should be automatically picked up by your editor or typechecker.
 
 ## Caveats
 
-### Performance
-The stubs contain a separate overload of `googleapiclient.discovery.build` for each service and version (see `discovery.pyi`). 
-This can lead to slow type inference for this function. Mypy will generally be pretty fast after the first run,
-but you might experience slow autocomplete in your editor. If you're experiencing this problem you can bypass type inference with explicit annotations, 
-e.g. `sheets_service: SheetsResource = build("sheets", "v4")` instead of `sheets_service = build("sheets", "v4")`.
-See the next section for some caveats to this approach.
-
 ### Explicit annotations
 The `google-api-python-client-stubs` is quite dynamic. 
 All resources are just instances of a single class with dynamically attached methods
@@ -42,11 +35,24 @@ annotate a variable, argument or return type in your code with one of these type
 This ensures that Python doesn't attempt to evaluate the types at runtime. 
 Note that the import is only supported in Python 3.7 and above.
 2. Only import the types inside an `if typing.TYPE_CHECKING` block. This ensures that the imports are only evaluated during
-type checking. Note that any type not available at runtime is located under the `googleapiclient._apis` package. 
-For example, `SheetsResource` should be imported from `googleapiclient._apis.sheets.v4`. Note that nested resources have a nested class structure, e.g. the return type of `sheets_service.spreadsheets().values()` is `SheetsResource.SpreadsheetsResource.ValuesResource`.
+type checking, not at runtime.
+
+Any type not available at runtime is located under the `googleapiclient._apis` package, with a subpackage for the API and a subpackage for the API version.
+For example, the return type of `build("sheets", "v4")`, `SheetsResource`, should be imported from `googleapiclient._apis.sheets.v4`. Nested resources have a nested class structure, e.g. the return type of `build("sheets", "v4").spreadsheets().values()` is `SheetsResource.SpreadsheetsResource.ValuesResource`.
 If autocompleting import paths doesn't work you can find the correct path by using Mypy's [reveal_type](https://mypy.readthedocs.io/en/stable/common_issues.html#reveal-type)
 on the thing you want to explicitly annotate. For `TypedDict`s this will also give you useful info about the structure of the dictionary.
 
+If you use Pyright/Pylance, you'll get a [reportMissingModuleSource](https://github.com/microsoft/pyright/blob/main/docs/configuration.md#reportMissingModuleSource) error at the import site, which indicates that the stub file doesn't have a corresponding source file. As long as the import only occurs during typechecking, this can be safely ignored. Autocomplete and typechecking will still work.
+
+Note that since the types don't exist at runtime, they're not compatible with libraries that evaluate annotations at runtime. For example, you can't use them to annotate a field in a Pydantic model.
+
+### Performance
+The stubs contain a separate overload of `googleapiclient.discovery.build` for each service and version (see `discovery.pyi`). 
+This can lead to slow type inference for this function. Mypy will generally be pretty fast after the first run,
+but you might experience slow autocomplete in your editor. If you're experiencing this problem you can bypass type inference with explicit annotations, 
+e.g. `sheets_service: SheetsResource = build("sheets", "v4")` instead of `sheets_service = build("sheets", "v4")`.
+Note the caveats to this approach in the previous section.
+
 ### Recursive types
 The stubs previously didn't include recursive type definitions due to a lack of type checker support, but this is now included. Note that if you're using Mypy, v0.990 or higher is required for this to work.