changeset 49253:4c57ce494a4e

worker: stop relying on garbage collection to release memoryview

On CPython, before resizing the bytearray, all memoryviews referencing it must
be released. Before this change, we ensured that all references to them were
deleted. On CPython, this was enough to set the reference count to zero, which
results in garbage collecting and releasing them.

On PyPy, releasing the memoryviews is not necessary because they are implemented
differently. If it would be necessary however, ensuring that all references are
deleted would not be suffient because PyPy doesn’t use reference counting.

By using with statements that take care of releasing the memoryviews, we ensure
that the bytearray is resizable without relying on implementation details. So
while this doesn’t fix any observable bug, it increases compatiblity with other
and future Python implementations.

--- a/mercurial/worker.py	Sat May 21 22:24:02 2022 +0200
+++ b/mercurial/worker.py	Sat May 21 23:31:30 2022 +0200
@@ -107,16 +107,16 @@
             return self._wrapped.readall()
 
         buf = bytearray(size)
-        view = memoryview(buf)
         pos = 0
 
-        while pos < size:
-            ret = self._wrapped.readinto(view[pos:])
-            if not ret:
-                break
-            pos += ret
+        with memoryview(buf) as view:
+            while pos < size:
+                with view[pos:] as subview:
+                    ret = self._wrapped.readinto(subview)
+                if not ret:
+                    break
+                pos += ret
 
-        del view
         del buf[pos:]
         return bytes(buf)