Problem re-raising Python error to surrounding Javascript code (Brython 3.2.3)

[André]

I just upgraded to Brython 3.2.3 from 3.2.0 alpha and encountered a problem.  I found a workaround solution and would like to know if it is the best way to proceed and if it is likely to be future-proof.

[Note: I am working with Brython 3.2.3 only on a locally hosted private version of my site.]

In Reeborg's World (http://reeborg.ca/world.html) I run Python code from a Javascript context as follows (greatly simplified):

try {

    eval_python(src);

} catch (e) {

    //  console.log(e)

    process(e)

}

where eval_python(src) can be thought of being

def eval_python(src):

   exec(src, some_dict)

Up until now (Brython 3.2.0 and many earlier), "e" would be an object with various attributes including in particular  __name__ and "$message".  I also defined my own custom errors, with attributes, and could get them.

With Brython 3.2.3, I do not get this.  If I log the error in the console, instead of a "nice" error object with the relevant attributes, I get a "native error" raised at line 6423 of brython.js with the following information available

Error

  at Error (native)

  at _b_.SyntaxError (<anonymous>:105:390)

  at eval (<anonymous>:16:81)

  at $eval (http://localhost:8000/src/libraries/brython3.2.3/brython.js:5124:9)

  at exec (http://localhost:8000/src/libraries/brython3.2.3/brython.js:5137:42)

  ...

Line 6423 of brython .js is var result=js_attr.apply(self.js,args)

So, no more "nice" javascript object to decipher...

=====

After much experimentation, I arrived at this workaround solution (again, simplified).  I catch any error in eval_python as follows:

def eval_python(src):

    window.__python_error = ""

    try:

        exec(src, some_dict)

    except Exception as e:

        window.__python_error = e

and I modified the way I run the code from Javascript as follows:

try {

    eval_python(src);

    if (window.__python_error) {

        throw window.__python_error;

    }

} catch (e) {

    //  console.log(e)

    process(e)

}

====

Is there a better way to have errors be lifted from the Python context to the surrounding Javascript context and handling them?

André

[Pierre Quentel]

Le lundi 23 novembre 2015 01:20:04 UTC+1, André a écrit :

I just upgraded to Brython 3.2.3 from 3.2.0 alpha and encountered a problem.  I found a workaround solution and would like to know if it is the best way to proceed and if it is likely to be future-proof.

[Note: I am working with Brython 3.2.3 only on a locally hosted private version of my site.]

In Reeborg's World (http://reeborg.ca/world.html) I run Python code from a Javascript context as follows (greatly simplified):

try {

    eval_python(src);

} catch (e) {

    //  console.log(e)

    process(e)

}

where eval_python(src) can be thought of being

def eval_python(src):

   exec(src, some_dict)

Up until now (Brython 3.2.0 and many earlier), "e" would be an object with various attributes including in particular  __name__ and "$message".  I also defined my own custom errors, with attributes, and could get them.

With Brython 3.2.3, I do not get this.  If I log the error in the console, instead of a "nice" error object with the relevant attributes, I get a "native error" raised at line 6423 of brython.js with the following information available

I didn't think of such use cases when rewriting parts of the exception management. I have restored the previous behaviour in todays commit ; does it work for your application ?

[Andre Roberge]

Well... the way I do things is a bit unusual, I do admit.

I've tried it and it works.   However, for this case, since I would (apparently) have a workaround solution, if the new exception handling proves to be more useful, do not feel obliged to keep the old behaviour simply on my behalf.

André

 

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