Uncaught TypeError: Cannot assign to read only property 'attrDef' of [object Object]

[kenvunz]

Hi,

Not sure if it's a bug or a feature but if I use the new attributes method to define component and mixin default attributes, an error is thrown but only when the Debug mode is turned on.

Uncaught TypeError: Cannot assign to read only property 'attrDef' of [object Object]

Example

// with-mixin.js

define([], function() {
    'use strict';

    return (function() {
        this.attributes({
            foo: 'baz1'
        });

        this.after('initialize', function() {
            console.log(this.attr);
        });
    });
});

// component.js

define(['flight/lib/component', 'with-mixin'], function(component, withMixin) {
    'use strict';

    return component(function() {

        this.attributes({
            foo: 'baz'
        });

        this.after('initialize', function() {
            console.log(this.attr);
            this.on(document, 'click', function(event) {
                console.log(event);
            });
        });
    }, withMixin);
});

Full error stack

Uncaught TypeError: Cannot assign to read only property 'attrDef' of [object Object] base.js:256
attributes base.js:256
(anonymous function) with-mixin.js:5
mixin compose.js:34
define component.js:123
(anonymous function) component.js:4
context.execCb require.js:1650
Module.check require.js:866
(anonymous function) require.js:1113
(anonymous function) require.js:132
(anonymous function) require.js:1156
each require.js:57
Module.emit require.js:1155
Module.check require.js:917
(anonymous function) require.js:1113
(anonymous function) require.js:132
(anonymous function) require.js:1156
each require.js:57
Module.emit require.js:1155
Module.check require.js:917
Module.enable require.js:1143
Module.init require.js:774
callGetModule require.js:1170
context.completeLoad require.js:1544
context.onScriptLoad

Any clarifications, pointers of how to avoid this error during Debug mode would be great

Cheers
Ken

[necolas]

Is this still an issue in the stable release (1.2.0) that includes this.attributes?

[prashaantt]

Yes it is. I just ran into this issue too.

Attempting to define this.attributes on a component that also has a mixin that defines its own this.attributes throws this error — and it doesn't matter if the attrs defined are completely different. Reverting to using this.defaultAttrs for both resolves this issue.

[angus-c]

looks like we need to whitelist attrDef when write protecting. cc @danwrong

[angus-c]

fixed in branch: attributes_in_debug.
However looking at test failure in master before I PR

[angus-c]

Fixed: #279