> > Is the on-demand nature of conflict detection (for traits built with >> Object.create) somehow unavoidable, or was that simply a design choice? >> > > It actually was a design choice dating from before we switched to > Object.create. Originally, we had a high-vs-low integrity switch in > Traits.create. As Tom was implementing our design, he noticed that the low > integrity case simplified down to being identical to Object.create. Seeing > that, Tom realized that we didn't actually need a switch as people could > just use Object.create directly. > > Tom, do I have the history of that right? >
Yes, that's an accurate summary. It also brings me back to Dave's earlier question about the limited choices provided by the Traits library. Initially, our Traits provided more fine-grained control over freezing, |this|-binding, etc. Performing some code archaeology on the traits.js source code reveals these options: We started out with a set of knobs to configure whether trait composition errors would be flagged early or not: http://code.google.com/p/es-lab/source/browse/trunk/src/traits/traits.js?spec=svn177&r=177#211 We later switched to a different set of knobs to configure whether the new trait instance should be frozen & |this|-bound or not: http://code.google.com/p/es-lab/source/browse/trunk/src/traits/traits.js?spec=svn232&r=232#418 As you can see from the code comments, we lumped together various options into a single switch, based on what we thought were the common use cases. Eventually, we realized that instead of such a switch, we could use Object.create vs Trait.create for similar effect. Long story short: it's definitely possible for a Traits library to offer more knobs, although I'm not sure whether the increased complexity is worth it. Judging from earlier comments, it seems there is at least a niche for the combination of 'early conflict detection' + 'non-frozen, non-|this|-bound objects'.
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