Adding SourceMap option

[Constellation]

Esprima can provide range / loc information, so we can create SourceMap from this.

[Constellation]

Reference

• V3 Spec Draft
• HTML5Rocks

[zaach]

Also relevant: https://github.com/mozilla/source-map

[rinon]

What do you think of passing SourceNodes back from generateStatements, instead of plain JS strings? This would allow source map information to be passed up to generate() and allow for creation of a Source Map. I'm actually looking at doing this myself, for another project that is using escodegen. This would create a dependence on the referenced source-map project, so...

[zaach]

+1 @rinon

[Constellation]

@rinon
Thanks, this is very interesting and exciting! +1.
Do you think about enabling it by option flag is possible? such as

escodegen.generate(tree, {
    sourceMap: true
});

[rinon]

Yes, that's exactly what I'm doing. I wish it was easier to completely switch between passing SourceNodes back and passing plain strings back, but I don't think that's feasible. At the moment I'm passing SourceNodes back exclusively, and then only generating the source map data at the end if the option is enabled. I'd still like to figure out a way to switch source map support off entirely so there will no performance overhead with source maps disabled.

@Constellation: What do you think of the dependency on source-map project? I can build it into a single source file for inclusion.

[Constellation]

@rinon

I can build it into a single source file for inclusion.

Great!

What do you think of the dependency on source-map project?

If separating source-map and escodegen is impossible, I think it is OK that adding source-map dependency to this project :-)

Personally I think following way to implement switching.

Passing source map namespace to escodegen like

escodegen.generate(tree, {
    sourceMap: require('source-map')
});

then, escodegen uses this namespace to create source-map.
And we wrap plain string with mock or SourceNode. By switching wrapping function, we can switch mode.

generateStatement = wrapWithMock(generateStatement);

or

generateStatement = wrapWithSourceNode(generateStatement)

Do you think that it is possible to implement?

[Constellation]

Added in d58f875