Please upgrade source-map to 0.7.2 to get speed improvements

[andreicristianpetcu]

The latest source-map which is v0.7.2 got support for WebAssembly and it is 10 times faster than the old one. More info here:

https://github.com/mozilla/source-map/blob/master/CHANGELOG.md#072
http://fitzgeraldnick.com/2018/02/26/speed-without-wizardry.html
https://hacks.mozilla.org/2018/01/oxidizing-source-maps-with-rust-and-webassembly/
firefox-devtools/debugger#5598

Please update so you would get 10 times speed improvements for your library in Firefox, 9 times in Safari and 5 times in Chrome.

[bcoe]

@andreicristianpetcu the new soure-map API is unfortunately async, which would require a fairly major refector of the Istanbul API to support:

https://github.com/mozilla/source-map/blob/master/CHANGELOG.md#070

I'm open to help on this front, if you feel like taking a look. I can also look into whether it would be easier to update in nyc first (which has its own implementation of source-map handling).

[coreyfarrell]

@andreicristianpetcu Just want to mention I've upgraded source-map from 0.5 to 0.6 (in master, not yet released). I didn't try updating to 0.7 because it says that it requires node.js 8 while node.js 6 isn't EOL for another 10 months.

[coreyfarrell]

I've looked into this and think it's impossible. nyc needs to process source-map's during process exit hooks where code must be sync. Unless a future version of source-map finds a way to support a sync API we will never be able to upgrade.