Does SWC Respect an Initial Source Map?

[stahlbauer]

SWC can be applied to files that already have a source map (either inlined or as an external file). Is this mapping information maintained throughout all transformation passes of chained plugins?

I hope nobody is offended too much by all the questions regarding source maps :-D Thanks in advance.

[stahlbauer]

Minimizing a file that contained an initial source map with the swc config fragment

   "minify": {
      "compress": {
        "unused": true
      },
      "mangle": true
    }

results in a minimized version with an empty source map, that is, with

//#sourceMappingURL=data:application/json;charset=utf-8;base64,IntcInZlcnNpb25cIjozLFwic291cmNlc1wiOltdLFwibmFtZXNcIjpbXSxcIm1hcHBpbmdzXCI6XCJcIixcImZpbGVcIjpcInN0ZG91dFwifSI=

which can be decoded to

"{\"version\":3,\"sources\":[],\"names\":[],\"mappings\":\"\",\"file\":\"stdout\"}"

[stahlbauer]

Passing the argument --source-maps results in a non-empty source map.

[stahlbauer]

(but at least the https://evanw.github.io/source-map-visualization/ cannot parse and visualize it)

[stahlbauer]

To contribute, it would be helpful for me to know where I can find unit/integration/system tests that test this functionality in the code base.

[jridgewell]

Using this (which I generated from TS playground), it seems the input sourcemap is maintained throughout the plugins.

It seems it does not propagate the sourcesContent field (instead, it uses the content input into SWC).