Source map support

[pavelkukov]

This is not an issue, it is question.
Did Rhino support source maps?
If not, is it planned?

[gbrail]

There's not reason why we couldn't implement those in Rhino, but at the
same time we don't have any plans. There are only a few people working on
Rhino, and they're all working very sporadically, so any help is
appreciated and we take pull requests ;-)

With that said, as I understand it, the Closure Compiler supports source
maps, and furthermore the Closure Compiler is based on a fork of Rhino:

https://github.com/google/closure-compiler/wiki/Source-Maps

Perhaps someone from that team can help.

On Fri, Jan 29, 2016 at 5:33 AM, Pavel Kukov notifications@github.com
wrote:

This is not an issue, it is question
Did Rhino support source maps?
If not, is it planned?

—
Reply to this email directly or view it on GitHub
#260.

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[pavelkukov]

Thank you @gbrail !
Very helpful info about closure compiler. I will check out what is possible.

[pastelmind]

I landed here while looking for source map-driven exception stack traces, similar to node-source-map-support.

TL;DR: source map-driven stack traces are impossible in Rhino.

All source map-consuming tools need both the line and column numbers of the transformed code to retrieve the corresponding position from the original source. For example, Mozilla's own source-map expects the line and column parameters. However, Rhino does not provide a column number, even if V8-style stack traces are enabled. It simply prints a 0.

Rhino depends heavily on Java's own stack trace mechanism to generate JavaScript stack traces. See here where the built-in StackTraceElement object is used to create a ScriptStackTrace object. Unfortunately, Java doesn't support column numbers either.

To make source maps work for stack traces, I expect we'll need to somehow attach column numbers to every JavaScript function and extract that information when constructing a stack trace.