Lots of whitespace differences introduced by endo bundler

On the right is the original lockdown-shim.js. On the left is the corresponding portion of lockdown.umd.js aligned for a visual line by line comparison. There are lots of little divergences. I do not remember seeing these divergences when we were using some previous bundler (rollup?).

These differences will impede the debugging experience. It means that at least the columns are different, and so we cannot simply sourceURL the original source file to appear in the debugger in lieu of the bundled source.

[erights]

Actually, the current babel output seems to differ on more than whitespace, for example unnecessary parens, so that a correspondence verifier for babel output is no longer such a trivial exercise. This pushes harder for us to convert to CSTs.

[erights]

Thanks! If the cst works (it looks like a great find!), I prefer it to the sourcemap path. With sourcemaps, the programmer is often looking at their original source text which can differ from the code actually being executed in devious ways. Even with the cst, I’d expect programmers to often be looking at their original source test, via sourceURL rather than text being executed. But, since these are supposed to differ only on import and export,

• programmers can avoid the sourceURL view and have essentially the same experience
• differences on lines other than import and export can be trivially caught by a diff.

CST FTW! Thanks much. I hope this works!

All that said, if we do sourcemaps, we can easily write a checker to ensure that the pre vs post source text differs only on import, export, and whitespace. We should probably do that anyway. Once that’s verified, debugging through a sourcemap view would be safe.