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Add support for native ES6 class Symbol #880

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lgersman opened this issue Nov 4, 2014 · 13 comments
Closed

Add support for native ES6 class Symbol #880

lgersman opened this issue Nov 4, 2014 · 13 comments
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@jmesserly

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@lgersman
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lgersman commented Nov 4, 2014

I play a lot with ES6 and recognized that current Polymer (version 0.4.2) does'nt handle native Symbol usage properly.
ES6 class Symbol arrived natively in Chrome 38. Current Chrome is 39.

When you run the following example in Chrome(>=38) you'll get an error

Uncaught TypeError: Cannot convert a Symbol value to a string

Example code :

<!doctype html>
<html>
<head>
  <script src="http://www.polymer-project.org/components/platform/platform.js"></script>
  <link rel="import" href="http://www.polymer-project.org/components/polymer/polymer.html">
</head>
<body>
  <polymer-element name="es6-symboltest">
    <template>
      <pre>options[Symbol(foo)] = {{options[property]}}</pre>
    </template>
    <script>
      var symbol = Symbol('foo');

      Polymer({
        attached : function() {
          this.options[symbol] = "bar";
        },
        property : symbol,
        options : {

        }
      });
    </script>
  </polymer-element>

  <es6-symboltest></es6-symboltest>
</body>
</html>

I guess the polymer-expression-to-function-conversion compiler provocates this error.

Live example (press F12 to see error in webinspector!) : http://jsbin.com/wegero/1/edit?html,output
@ebidel
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ebidel commented Nov 6, 2014

@jmesserly is this something you could look in to?

@jmesserly
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Sure thing. Sounds neat.

@jmesserly jmesserly self-assigned this Nov 6, 2014
@jmesserly
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hmmm. My first thought was a PolymerExpressions issue but it seems to work:
http://jsbin.com/ginonacata/1/edit?html,output

@jmesserly
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aha. The example works if you use created event: http://jsbin.com/fokawetabe/1/edit

so it's not an issue of Symbols not working in the index expr, what seems to be happening is that modifying the object doesn't trigger a change event.

@jmesserly
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... and/or the change event isn't handled correctly.

@jmesserly
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Try this in the console:

var o = {}; Object.observe(o, function(r) { console.log(r); }); o['abc'] = 123; o[5] = 6; o[Symbol('foo')] = 'bar';

there's no change event for the symbol, even though the contents of o are Object {5: 6, abc: 123, Symbol(foo): "bar"}

@jmesserly
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opened a V8 bug: https://code.google.com/p/v8/issues/detail?id=3682

@lgersman
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lgersman commented Nov 6, 2014

if i try your examplecreated example (http://jsbin.com/fokawetabe/1/edit) in chrome 39 I get the
Cannot convert a Symbol value to a string error too.

no difference. there might be 2 problems.

could you please reopen the bug because it fails also when using the created callback ?

@jmesserly
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hmm, really? I'm also running Chrome Version 39.0.2171.52 beta (64-bit)
that link displays for me options[Symbol(foo)] = bar

I don't think I have any experimental flags turned on...

@jmesserly
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More info that might help:

@lgersman
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lgersman commented Nov 6, 2014

  • i have Chrome (currently @home) 38.0.2125.111 (64-bit).
  • this example works !

@jmesserly
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Nice!

I wonder if maybe it's fixed in the latest Chrome beta then. Since Symbol is very new, I imagine there are changes from release to release as they find & fix bugs.

I just tried Version 40.0.2211.0 canary (64-bit), and this link works there too http://jsbin.com/fokawetabe/1/edit?html,output

@lgersman
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lgersman commented Nov 6, 2014

Okay - thats good news !

So its the best to keep this issue closed for now.

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@lgersman @ebidel @jmesserly