strict option: no_duplicate_keys

[andreineculau]

as per https://tools.ietf.org/html/rfc7159#section-4

The names within an object SHOULD be unique.

yet JSX works like this:

1> jsx:decode(<<"{\"a\": \"b\", \"a\": \"c\"}">>).
[{<<"a">>,<<"b">>},{<<"a">>,<<"c">>}]

Consider adding no_duplicate_keys as as flag part of the strict option, or similar.

[talentdeficit]

i'll look at adding this to the in progress 3.0

probably won't backport it to 2.x tho, because there's no low impact way to track multiple keys when decoding to a map

[andreineculau]

how is "there's no low impact way..." relevant if we're talking about adding a flag? current performance can stay the same, but those who want no_duplicate_keys can deal with whatever "performance" loss?

[andreineculau]

a friendly bump. what's the status on this? thanks!

[paulo-ferraz-oliveira]

@andreineculau: is this still an issue (it's been more than 2 years)? How would you go about detecting the duplicates? I imagine a map, since a list would be even more performance-degrading. Is this what you mean by your question? You'd like a flag and then a runtime validation if that flag was active. Is that it?

[andreineculau]

@paulo-ferraz-oliveira I missed your comment, sorry. But yes, I think it's still an issue.

jsx@3.1.0 behaviour is unchanged

1> jsx:decode(<<"{\"a\": \"b\", \"a\": \"c\"}">>).
#{<<"a">> => <<"c">>}
2> jsx:decode(<<"{\"a\": \"b\", \"a\": \"c\"}">>, [{return_maps, false}]).
[{<<"a">>,<<"b">>},{<<"a">>,<<"c">>}]

from jsx@2.8.0

1> jsx:decode(<<"{\"a\": \"b\", \"a\": \"c\"}">>).
[{<<"a">>,<<"b">>},{<<"a">>,<<"c">>}]
2> jsx:decode(<<"{\"a\": \"b\", \"a\": \"c\"}">>, [{return_maps, true}]).
#{<<"a">> => <<"c">>}

For starters, it would be good if there's no behaviour difference dictated by return_maps.
At this point, it is "better" to return_maps: false and do the validation outside of JSX, because when returning maps, there's simply no way to detect duplicate keys.