Display iterables as arrays (if “pure”)

[mbostock]

If a value is iterable (implements [Symbol.iterator] method), and the resulting iterator is a different object than the value (so as to avoid mutating common map and Set iterators that return this), we should display it in the inspector like an array.

[tmcw]

To clarify here:

For native types - Set, Map, Array - switching to treating everything as just an 'iterable' wouldn't constitute much of an improvement. A Map would be displayed as an array of [key, value] pairs, instead of as a key => value mapping as it is currently displayed. Additionally, for arrays with extra non-numeric properties, like [1, 2, key: 'value'], relying solely on the iterator method would regress our current ability to display those properties - the iterator doesn't iterate over extra properties.

But for new types that implement Symbol.iterator, this would be a nice convenience - this will make debugging frame objects easier.

[mbostock]

Moved to observablehq/inspector#13.