Plugin API feature requests

I recently wrote a plugin that used get_function_hook() to intercept instantiations of a certain set of classes (recognized by name), and found a bunch of functionality missing. Here's a list.

• I needed the names of the arguments but they were not directly available. I ended up using rtype.type.names['__init__'].node.arg_names (with various type and None guards) and subtracting 1 to compensate for self, which looked very hacky. It would be nice if FunctionContext also has an arg_names argument.

• CheckerPluginInterface has no fail() method. It exists on the implementation, and the similar TypeAnalyzerPluginInterface does define it.

• I needed to look up a name in the module's global namespace; I ended up calling ctx.api.lookup_qualified() but that's not in the interface, and perhaps it's not the thing to use.

• I needed the functionality of parse_bool() but it's not there (it only exists on SemanticAnalyzerPluginInterface).

• I needed something similar to what's in mypy/plugins/common.py as _get_bool_argument() _get_argument() but had to write my own because the starting point was a FunctionContext instead of a ClassDefContext.

• (Not directly a plugin issue, but this happened.) I was also bitten by the error message The type alias{} is invalid in runtime context -- this seems a bit inconsistent because expanding the Union that the alias references makes it go away. I.e. if A = Optional[int], foo(A) gives that error, but foo(Optional[int]) doesn't.

FunctionContext、CheckerPluginInterface、SemanticAnalyzerPluginInterface に関連するプラグインインターフェースと、mypy/plugins/common.py、および報告されている実行時の型エイリアスの動作を確認してください。この issue には、単一の範囲が定められた変更ではなく、複数の個別の API リクエストが含まれています。完了するには、どのリクエストをサポートするかを判断し、それらの期待される動作を定義する必要があります。