Let json:decode/3 keep whitespaces #8809
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@michalmuskala Can you take a look.. |
lib/stdlib/src/json.erl
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| @@ -1386,16 +1386,18 @@ object_key(_, Original, Skip, Acc, Stack, Decode) -> | |||
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| continue(<<Rest/bits>>, Original, Skip, Acc, Stack0, Decode, Value) -> | |||
| case Stack0 of | |||
| [] -> terminate(Rest, Original, Skip, Acc, Value); | |||
| [] -> terminate(Rest, Rest, Acc, Value); | |||
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This breaks the binary pattern optimisation since the tail is now used in two paces - I'm fairly sure it will significantly affect performance
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From what we could see, looking at the beam asm,
the only difference was that it creates a sub-binary in the case when Stack = [],
which should be ok since that is only for the last "term" in the json string.
But I'm not fluent in beam-asm.
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It looks fine, the optimization is disabled for this particular call but not the others. Should this become a performance problem, it's not a huge deal for the compiler to allow the reused Rest context to be passed alongside a new tail binary representing Rest.
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I pushed up a new variant that postpones the creation and only does when necessary.
`json:decode/3` always stripped leading whitespaces in the `Rest` binary,
which could be problematic if user expected them.
E.g `json:decode(<<"foo\n bar">>, ok, #{})` returned:
`{<<"foo">>, ok, <<"bar">>}` instead of
`{<<"foo">>, ok, <<"\n bar">>}`.
If `Rest` only contains whitespaces they are removed, so that the user
can match on empty binary to know if they should continue the decoding loop.
E.g `json:decode(<<"foo\n ">>, ok, #{})` still returns:
`{<<"foo">>, ok, <<>>}`
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json:decode/3always stripped leading whitespaces in theRestbinary, which could be problematic if user expected them.E.g
json:decode(<<"foo\n bar">>, ok, #{})returned:{<<"foo">>, ok, <<"bar">>}instead of{<<"foo">>, ok, <<"\n bar">>}.If
Restonly contains whitespaces they are removed, so that the user can match on empty binary to know if they should continue the decoding loop.E.g
json:decode(<<"foo\n ">>, ok, #{})still returns:{<<"foo">>, ok, <<>>}