The way I would decode a stream of JSON objects is to use `view
Pipes.Aeson.Unchecked.decoded`:
view Pipes.Aeson.Unchecked.decoded
:: (Monad m, FromJSON a, ToJSON a)
=> Producer ByteString m r
-> Producer a m (Either (DecodingError, Producer ByteString mr) r)
That will take care of skipping blanks between and after parsed JSON
elements:
https://github.com/k0001/pipes-aeson/blob/66d3773a50de27188018e53732a076bf804064f3/src/Pipes/Aeson/Internal.hs#L63
What's happening in your example is that you are parsing one element at
a time, so after parsing the last element you are left with "\n" as the
remaining input and then asking `pipes-aeson` to decode that single
newline character as a JSON object, which causes it to fail. You can
either use the `decoded` lens to handle skipping white space when
parsing a stream or you can skip the whitespace within your own loop.
On 11/15/15 8:27 PM, Erik Rantapaa wrote:
I'm trying to use pipes-aeson to consume a "line-delimited" JSON file
- this is a text file which has one JSON object per line. Some
examples of this kind of file may be found
at http://jsonstudio.com/resources/
You can see how I'm trying to use Pipes.Aeon.decode to do this
at https://gist.github.com/erantapaa/4bf55d38865863529659#file-lib-hs-L90
The problem I'm running into is that Pipes.Aeson.decode seems to give
a parse error if it begins parsing at the trailing whitespace at the
end of the file. Since almost all text files end with a newline, I get
a parse error after successfully parsing all of the objects in the file.
The function test2a in the gist demonstrates this problem -- calling
test2a with the empty string returns "got Nothing", but test2a on a
bunch of spaces produces "got a parse error".
So I'm thinking that Pipes.Aeson.decode isn't handling whitespace
correctly. Or should I be doing something else?
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