support for file I/O (JS_EvaluateScript)

A grep on the repository reveals occurrences of JS_EvaluateScript in spidermonkey/libjs/jsapi.c - however, there's no hint in the documentation ($ pydoc spidermonkey) on how that might be exposed via the API.

Thanks for the quick response!

You're absolutely correct - I don't actually need JS_EvaluateScript.
I had no idea you could provide access to Python functions from within Spidermonkey!

That, I assume, shows a fundamental lack of understanding of python-spidermonkey.
Sorry about that, I will review the README in more detail.

Also thanks for the clarification on the different version of python-spidermonkey.
If the previous maintainer is still around, it would be useful if he added a note to the Google Code page.

I tried to make the library interaction as transparent as possible so you should be able to do most anything that comes to mind in terms of passing objects back and forth.

I hate to be a pain and abuse this ticket for support - but I can't seem to pass objects between Python and JavaScript:

import spidermonkey







myVar1 = { "p1": 123, "p2": "abc" }
myVar2 = {}







rt = spidermonkey.Runtime()
cx = rt.new_context()







cx.add_global("myVar1", myVar1)
cx.add_global("myVar2", myVar2)







cx.execute("myVar1.p2 = 'xxx'");
cx.execute("delete myVar1.p1");
assert myVar1["p2"] == "xxx", "test myVar1 (a)"
assert not myVar1.has_key("p1"), "test myVar1 (b)"







cx.execute("myVar2 = { aaa: 'yyy' }");
assert myVar2.has_key("aaa"), "test myVar2 (a)"
assert myVar2["aaa"] == "yyy", "test myVar2 (b)"

AnC,

If you're wanting to create a variable in JS and return it to Python, the proper method is to make that variable the result of the last expression, like such:

myvar = cx.execute('var foo = {"foo": "bar"}; foo;')
assert myvar["foo"] == "bar"

Passing Python variables into JavaScript can be done using the Context.add_global method, or you can create a function and call it with python parameters, like such:

jsfunc = cx.execute("function(obj) {if(obj.key === null) throw("is null!"); return 2;}")
assert jsfunc({"key": "bar"}) == 2

There are more examples on passing data in and out of JavaScript in the README and in the unit tests. Though I should probably write up a clearer document that describes the different methods for passing data in and out. And as a matter of fact I had another idea for passing data in and out...

For this though:

myVar2 = {"bb": "cc"}
cx.add_global("myVar2", myVar2)
cx.execute("myVar2 = { aaa: 'yyy' }");
assert myVar2.has_key("aaa"), "test myVar2 (a)"
assert myVar2["aaa"] == "yyy", "test myVar2 (b)"

Assigning a value to the name 'myVar2' in the JavaScript interperter shouldn't affect the value of the Python 'myVar2'. The fact that you're naming them the same in both places does not confer any sort of relation between them. As you show above, you can affect the value that 'myVar1' refers to, but you're not affecting the name->value assignment.

Paul

Thanks again for your considerate response, Paul!

I had actually tried using return values early on, but objects are returned as "[object Object]":

import spidermonkey







rt = spidermonkey.Runtime()
cx = rt.new_context()







myVar = cx.execute("var obj = { aaa: 'yyy' }; obj;");
print myVar # DEBUG; outputs "[object Object]"
assert myVar.has_key("aaa"), "test #1" # fails
assert myVar["aaa"] == "yyy", "test #2" # fails

import spidermonkey







rt = spidermonkey.Runtime()
cx = rt.new_context()







myVar = { "aaa": "yyy" }
cx.add_global("obj", myVar)
myVar = cx.execute("obj;");
print myVar # DEBUG; outputs "{'aaa': 'yyy'}"
myVar = cx.execute("obj.bbb = 'zzz'; obj;");
print myVar # DEBUG; outputs "{'aaa': 'yyy', u'bbb': u'zzz'}"
assert myVar.has_key("aaa"), "test #1" # passes
assert myVar["aaa"] == "yyy", "test #2" # passes

Perhaps this is because I'm using the somewhat outdated spidermonkey-bin package from the Ubuntu repositories (version info: JavaScript-C 1.7.0 2007-10-03)?

AnC,

Hey, these two cases do seem quite similar, but they're quite different.

import spidermonkey

rt = spidermonkey.Runtime()
cx = rt.new_context()

# myVar is a wrapper to a JSObject* in the JavaScript virtual
# machine. As such, it only has access to the JS functions and
# a few special cases that are faked for Python.
myVar = cx.execute("var obj = { aaa: 'yyy' }; obj;");

# Here I could try and do something like pretty printing the object
# or similar, but I'm not sure its such a good idea as it starts
# to blur the line a bit too far between what is JS and what is Py
print myVar # DEBUG; outputs "[object Object]"

# Alternatively for debugging, you can call:
print myVar.toSource()

# Part of being a JavaScript object means it doesn't have all of
# the Python dict methods. To test whether the key "aaa" is in the
# object, you can use the 'in' keyword that has been proxied.
# assert myVar.has_key("aaa"), "test [#1](/projects/26898/tickets/1 "Ticket #1")" # fails
assert "aaa" in myVar

# This test passes just fine for me.
assert myVar["aaa"] == "yyy", "test [#2](/projects/26898/tickets/2 "Ticket #2")" # fails

For the other case you're creating a Python object and modifying that object from JavaScript

import spidermonkey

rt = spidermonkey.Runtime()
cx = rt.new_context()

# myVar is a Python dict here
myVar = { "aaa": "yyy" }
cx.add_global("obj", myVar)

myVar2 = cx.execute("obj;");
# You should even be able to go further and say:
assert id(myVar) == id(myVar2), "myVar2 refers to the same object as myVar1"

# myVar is still a python dict. Using myVar2 above should hopefully make this
# more clear.
print myVar # DEBUG; outputs "{'aaa': 'yyy'}"

# To point out that you're editing the original myVar live
# I'm not returning it so you can see we can assert against
# the original.
# myVar = cx.execute("obj.bbb = 'zzz'; obj;");
cx.execute("obj.bbb = 'zzz';")
assert myVar["aaa"] == "yyy"
assert myVar["bbb"] == "zzz"

# and to make it more clear:
assert myVar2["aaa"] == "yyy"
assert myVar2["bbb"] == "zzz"

Let me know if that helps.

Right, I shouldn't just assume that a JavaScript object is identical to a Python dictionary - I can see that now.

In my particular case, I have a complex JS object like this:

[

{
    id: 123,
    name: "my item",
    description: "hello world",
    attributes: {
        shape: "square",
        color: "red"
    }
},
{
    id: 789,
    [...]
}

]

AnC,

A thought just occurred to me, you might look into something like
copy.deepcopy to see if you can use that to convert the object
recrusively.

AnC,

Yeah, I was putting off the upgrade to 1.8 because I wanted to go directly to 1.8.1. In fact I don't even know if the native JSON methods are in 1.8. Either way, the Mozilla folks haven't put out a 1.8.1 tarball to use in building which is probably why almost everyone is still using 1.7 when embedding JavaScript.

JSON is awesome, the reason I'd avoid it in this case though is that python-spidermonkey is trying to be transparent to the caller. Obviously, getting a spidermonkey.Array is a bit different than getting a native array but that's an implementation detail so that your objects are live in the JS VM. Ie, if you edit a spidermonkey.Array object, it's value in the JS vm should be updated as well. (I should probably write a test for that though).

The deepcopy was to do similar to the function the code that marc posted above. Using a tad bit of python to convert spidermonkey.Object and spidermonkey.Array into Python dicts and arrays should be pretty simple.

I looked back but I never said anything about not liking json.dumps near as I can tell. I don't like the obj -> JSON -> obj approach because its unnecessary, but then again, a working implementation is always better than a theoretical one :)