Avoid redundant shallow copy when getting read-only map fields #741
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`_FieldSet._$getMap` unnecessarily shallow-copies the map field when the message is read-only. If a message is read-only then all of its fields are read-only, so the map fields are read-only. We don't need to copy them. Copying map fields on every access can be expensive depending on the map size, so this will potentially be a significant performance win. (Also, if we had to copy, we would have to deep-copy, rather than shallow-copy, so the code would be buggy if we needed to copy the field) Also fix `_isReadonly` field initialization in `PbMap.unmodifiable`. We actually do not use `PbMap.unmodifiable` and we don't have any users of it, but I think that method will be useful when fixing google#705, so I'm not removing it for now.
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I'll add changelog entries. |
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This was broken in google#741
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_FieldSet._$getMapunnecessarily shallow-copies the map field when themessage is read-only.
If a message is read-only then all of its fields are read-only, so the
map fields are read-only. We don't need to copy them.
Copying map fields on every access can be expensive depending on the map
size, so this will potentially be a significant performance win.
(Also, if we had to copy, we would have to deep-copy, rather than
shallow-copy, so the code would be buggy if we needed to copy the field)
Also fix
_isReadonlyfield initialization inPbMap.unmodifiable.We actually do not use
PbMap.unmodifiableand we don't have any usersof it, but I think that method will be useful when fixing #705, so I'm
not removing it for now.