nickva commented on code in PR #4394:
URL: https://github.com/apache/couchdb/pull/4394#discussion_r1081579998
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src/mango/src/mango_cursor_view.erl:
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@@ -248,6 +266,19 @@ view_cb({row, Row}, #mrargs{extra = Options} = Acc) ->
key = couch_util:get_value(key, Row),
doc = couch_util:get_value(doc, Row)
},
+ % This supports receiving our "arguments" either as just the `selector`
+ % or in the new record in `callback_args`. This is to support mid-upgrade
+ % clusters where the non-upgraded coordinator nodes will send the older
style.
+ % TODO remove this in a couple of couchdb versions.
+ {Selector, Fields} =
+ case couch_util:get_value(callback_args, Options) of
+ % old style
+ undefined ->
+ {couch_util:get_value(selector, Options), undefined};
+ % new style - assume a viewcbargs
+ Args ->
Review Comment:
It's a balance, but I think it's slightly better to leak some of the
implementation for a stronger assert in the case. It also tells the reader what
the types are in that snippet right away ("we are dealing with a map or
undefined only") so serves as a shorthand reminder in a way.
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