** operator on a JS object produces the error "attr keys of obj undef"

[Denis Migdal]

Hi,

Somewhere in my code, I have opts which is a JS object.

BLISS(**opts)

Produces :

attr keys of obj undef
Uncaught (in promise) TypeError: obj is undefined
    $getattr http://127.0.0.1:5500/brython/www/src/brython.js:2903
    anonymous http://127.0.0.1:5500/brython/www/src/brython.js line 11966 > Function:55
    BLISS20 http://127.0.0.1:5500/brython/www/src/brython.js line 150 > Function:43
    call http://127.0.0.1:5500/brython/www/src/brython.js:1603
    BLISSAuto_defineWebComponent43 http://127.0.0.1:5500/brython/www/src/brython.js line 150 > Function:556
    defineWebComponent http://127.0.0.1:5500/index.js:48
    #addTag http://127.0.0.1:5500/LISS/index.js:603
    LISS_Auto http://127.0.0.1:5500/LISS/index.js:562
    BLISS_Auto http://127.0.0.1:5500/index.js:37
    init http://127.0.0.1:5500/LISS/index.js:239
    connectedCallback http://127.0.0.1:5500/LISS/index.js:190
    define http://127.0.0.1:5500/LISS/index.js:328
    async* http://127.0.0.1:5500/index.js:51
2 brython.js:2903:4

However, if I do :

opts = dict(opts)
BLISS(**opts)

It works properly.

I suggest either :

• raising an exception when using ** on a JS object Can't use ** operator on js object, use dict() to convert to dictionary.
• OR, when using ** operator, if used on a JS object, first convert to a dictionary ?

Cordially,

[Pierre Quentel]

With the commit above, an exception is raised:

Traceback (most recent call last):
  File "tests/test.html", line 24, in <module>
    f(**window.kw)
TypeError: s1.f() argument after ** must be a mapping, not Javascript Object

I think it's explicit enough, do you agree ?

[Denis Migdal]

I think it's explicit enough, do you agree ?

I think this is a good error message as it is very close to Python error messages, therefore we can find more information by searching the error message.

I think the error message could be more explicit, but that'd a Python issue, not a Brython issue.