FileContext.open() / close(): Only call wrapped once

FileContext's _open() and _close() are called everytime their wrapper is called, which tasks the caller with keeping track of whether they were already called or not. Be a little easier on the caller, keep track in an open count, and call _open() only once for multiple calls to open(), and close() likewise. The caller still needs to make sure the number of open() and close() calls matches.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/FileContext.py

@@ -37,6 +37,7 @@ class FileContext(abc.ABC):
         self.__log_name: str|None = None
         self.__in_pipe = in_pipe
         self.__out_pipe = out_pipe
+        self.__open_count = 0
         assert verbose_default is not None
 
     async def __aenter__(self):
@@ -75,13 +76,18 @@ class FileContext(abc.ABC):
         pass
 
     async def open(self) -> None:
+        self.__open_count += 1
+        if self.__open_count == 1:
             await self._open()
 
     async def _close(self) -> None:
         pass
 
     async def close(self) -> None:
+        if self.__open_count == 1:
             await self._close()
+        self.__open_count -= 1
+        assert self.__open_count >= 0
 
     @classmethod
     def schema_from_uri(cls, uri: str) -> str: