Postel's Law or the "Robustness Principle" is an anti-pattern in general. Accepting trailing commas in JSON isn't as big a deal as having two different opinion

Postel's Law or the "Robustness Principle" is an anti-pattern in general. Accepting trailing commas in JSON isn't as big a deal as having two different opinions about what a valid document is. But you might think a trailing comma could indicate a hand-edited document that's missing an important field or array element.