How to convert embedded (quoted) json string to json

Question

I'm familiar with "jq" for parsing json.

I work with one service that produces a json response where one of the properties is itself a json string. How do I convert that quoted value to a valid json string so I can then process it with jq?

For instance, if I just view the plain pretty-printed json from "jq .", here's a short excerpt of the output:

"someJsonString": "{\"date\":\"2018-01-08\", ...

I can use jq to get the value of that property, but I need to convert the quoted string to valid json by "unescaping" it.

I suppose I could pipe it into sed, removing the opening and ending double quotes, and removing all backslashes ("sed -e 's/^"//' -e 's/"$//' -e 's/\\//g'"). That seems to work, but that doesn't seem like the most robust solution.

Update:

Just to be a little clearer on what I'm doing, here are a couple of elided samples that show what I've tried:

% curl -s -q -L 'http://.../1524.json' | jq '.results[0].someJsonString' | jq .
"{\"date\":\"2018-01-08\",...
% echo $(curl -s -q -L 'http:/.../1524.json' | jq '.results[0].someJsonString') | jq .
"{\"date\":\"2018-01-08\",...

Update:

Here's a completely standalone example:

% cat stuff.json | jq .
{
  "stuff": "{\"date\":\"2018-01-08\"}"
}
% cat stuff.json | jq '.stuff'
"{\"date\":\"2018-01-08\"}"
% cat stuff.json | jq '.stuff' | jq .
"{\"date\":\"2018-01-08\"}"

Update:

If I tried to process that last output with a real jq expression, it does something like this:

% cat stuff.json | jq '.stuff' | jq '.date'
assertion "cb == jq_util_input_next_input_cb" failed: file "/usr/src/ports/jq/jq-1.5-3.x86_64/src/jq-1.5/util.c", line 371, function: jq_util_input_get_position
Aborted (core dumped)

Answer 1

With jq's fromjson function:

Sample stuff.json contents:

{
  "stuff": "{\"date\":\"2018-01-08\"}"
}

---

jq -c '.stuff | fromjson' stuff.json

The output:

{"date":"2018-01-08"}

Answer 2

There is a raw flag for this

    -r      output raw strings, not JSON texts;

jq -rc .stuff stuff.json

Output

{"date":"2018-01-08"}