jq flags -r effect seems can't cancel between calls ?

[yurenchen000]

version: release-0.5.1 jq.wasm.js

run in chrome F12.

// ------ worked well
> jq.raw('{"a":"hello"}', '.a')
< ""hello""

> jq.raw('{"a":"hello"}', '.a', ['-c'])
< ""hello""

// ------ once call with `-r`, 
> jq.raw('{"a":"hello"}', '.a', ['-r'])
< "hello"

// ------ somethings err? following call can't cancel `-r` flag
> jq.raw('{"a":"hello"}', '.a')
< "hello"

> jq.raw('{"a":"hello"}', '.a', ['-c'])
< "hello"

then refresh page,
and worked well again.

[fiatjaf]

Oh, you mean once you pass a flag it keeps being applied to next calls?

[yurenchen000]

Oh, you mean once you pass a flag it keeps being applied to next calls?

yes

[yurenchen000]

seems some parse error state also persist:

// run in linux chrome 74.0.3729.131 64bit
// linux/win10 firefox 72.0.2 64bit also occur

> jq.raw('{"a":"hello"}', '.a')
< ""hello""

// try parse err
> jq.raw('{"a":,"hello"}', '.a')
< jq.wasm.js:6 Uncaught parse error: Expected value before ',' at line 1, column 6

// following call is sick, infected
> jq.raw('{"a":"hello"}', '.a')
< ""

[fiatjaf]

This is very odd. I took a look at it but can't see where the error is. Maybe we need an Emscripten specialist.

[yurenchen000]

// init bin arr once
var res = await fetch('jq_github/jq.wasm.wasm')
var arr = await res.arrayBuffer()


// reload asm when necessary
var mod = await WebAssembly.instantiate(arr, info) //info from jq.wasm.js createWasm()
Module.asm = mod.instance.exports   //Module from jq.wasm.js 

I use this code reload the asm, which can fix the parse err state,
but -r effect still exist.

[yurenchen000]

> jq.raw('\n12', '.')
< "12"

> jq.raw('123\n', '.')
< "123"

>  jq.raw('1234', '.')
< ""

input end with '\n' also fall into unexpected state,
and no any err detect/throw out.

// reload asm also can fix this, but we can't detect this state normally,
// unless check with an additional test call.

[yurenchen000]

had a glance at jq c code.

jq@341a5fc main.c:147

static int options = 0;

I guess the global static var options ( without re-init with 0 )
cause flags remain every time we call main()

maybe need clean the stack & heap before next time call main

[fiatjaf]

Wow, I guess we've found our Emscripten specialist!

I have no idea of how to do that. It would be great if you could open a pull request.

[yurenchen000]

sorry for late response, busy year after year.

options var residue

AFAIK, wasm no api to reset stack or global var.
so as workaround, patched the src/main.c to reset the options.

why?

-r output raw strings, not JSON texts

but there no way to cancel it's effect, once called with -r:

> jq.raw('"abc"', '.')
'"abc"'
> jq.raw('"abc"', '.', ['-r'])
'abc'

//--- jq into bad state: we didn't pass '-r' anymore, but it still effect
//    no way to get non-raw output (json string)
> jq.raw('"abc"', '.')
'abc'
> jq.raw('"abc"', '.', ['-c'])
'abc'

cause in jq/src/main.c
options is a global var, and only bit set, no bit clear operate in main
https://github.com/jqlang/jq/blob/341a5fcab3/src/main.c#L333

the RP here
#27

[yurenchen000]

stdin broken after error

first mentioned here:
#15 (comment)

> jq.raw('123', '.')
'123'
> jq.raw(',123', '.')
jq.wasm.js:6 Uncaught parse error: Expected value before ',' at line 1, column 1

raw @ jq.wasm.js:6
(anonymous) @ VM824:1

//----- jq into a bad state, no response anymore //I found it's about stdin broken
> jq.raw('123', '.')
''
> jq.raw('123', '.')
''

cause after main, c may close stdin. (and next call it read nothing)
we use explicit position arg /dev/stdin, so that c main will open it at every call.

ref: man 3 exit

All open stdio(3) streams are flushed and closed

I made a PR here to fix stdin,
also clear un-closed FS.streams[] after main call.

#28

[yurenchen000]

about stdout, stderr

current code only show err when stdout got nothing
https://github.com/fiatjaf/jq-web/blob/0.5.1/post.js#L23

but, sometimes it can output both stdout,stderr.
then the err msg can't see in jq-web

$ echo '"abc",' | jq
"abc"
parse error: Expected value before ',' at line 1, column 6

a PR here,
I didn't do much, just print to console on demand

#29