REST API JSON Parsing in Racket - json

Question

I'm developing rest service in Racket in educational purposes and facing problem with JSON parsing.
I have POST request with following body
"{\"word\": \"a\", \"desc\": \"b\"}"
Also I have request handler for this request such as
(define (add-word-req req)
(define post-data (request-post-data/raw req))
(display post-data)
(newline)
(define post-data-expr1 (bytes->jsexpr post-data))
(display post-data-expr1)
(newline)
(display (jsexpr? post-data-expr1))
(display (hash? post-data-expr1))
(newline)
(define post-data-expr (string->jsexpr "{\"word\": \"a\", \"desc\": \"b\"}"))
(display post-data-expr)
(newline)
(display (hash? post-data-expr))
(newline)
(for (((key val) (in-hash post-data-expr)))
(printf "~a = ~a~%" key val))
(cond
[(jsexpr? post-data-expr)
;; some conditional work
...
]
[else
...]
)
)
As you can see, request body and hard-coded JSON are same.
While processing request I get next output:
"{\"word\": \"a\", \"desc\": \"b\"}"
{"word": "a", "desc": "b"}
#t#f
#hasheq((desc . b) (word . a))
#t
desc = b
word = a
Body is transmitted in one piece and even transformed into jsexpr, but still it is not hash! And because of it I can't use hash methods for post-data-expr1.
What is the best way to get hash from such jsexpr? Or should I use another method to obtain key/values?
Regards.

Answer 1

This program:
#lang racket
(require json)
(string->jsexpr "{\"word\": \"a\", \"desc\": \"b\"}")
(bytes->jsexpr #"{\"word\": \"a\", \"desc\": \"b\"}")
has the output:
'#hasheq((desc . "b") (word . "a"))
'#hasheq((desc . "b") (word . "a"))
This means that bytes->jsexpr ought to work.
Can you change:
(define post-data (request-post-data/raw req))
(display post-data)
(newline)
to
(define post-data (request-post-data/raw req))
(write post-data)
(newline)
?
I have a feeling that the contents of the byte string is slightly different than the one you use later on.
Note:
> (displayln "{\\\"word\\\": \\\"a\\\", \\\"desc\\\": \\\"b\\\"}")
{\"word\": \"a\", \"desc\": \"b\"}
> (displayln "{\"word\": \"a\", \"desc\": \"b\"}")
{"word": "a", "desc": "b"}
The output of your (display post-data-expr1) matches the first interaction above. My guess is therefore that both backslashes and quotes are escaped in your input.