Added option to transform the paths within a sourcemap.

[sebinsua]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevent issue numbers:

• Customize sourcemap sources paths #2168

Description

@pgn-vole wrote:
It doesn't seem possible at the moment to customize the path the sources within the sourcemap.

I added a OutputOption#sourcemapPathTransform function which can be used to transform the source paths outputted into the sourcemaps. This helps in situations in which multiple rollup generated libraries sourcemaps are being consumed in a browser and you do not want all package's files to be grouped within the same src/ directory.

I do not think it's necessary to supply a base directory as was mentioned in the original GitHub issue. A transformation function can also handle making the path relative to a base directory. If you're able to pass a transform function in through a rollup.config.js you will also be able to pass a base path into your transformation function using a closure.

What do others think?

/cc @pgn-vole @teohhanhui

[sebinsua]

Can anybody help me work out why the AppVeyor build isn't working?

Edit: It was a cross-environment problem in my test.

[teohhanhui]

I do not think it's necessary to supply a base directory as was mentioned in the original GitHub issue. A transformation function can also handle making the path relative to a base directory. If you're able to pass a transform function in through a rollup.config.js you will also be able to pass a base path into your transformation function using a closure.

True, if they're all absolute paths, then it's fine.

[sebinsua]

True, if they're all absolute paths, then it's fine.

@teohhanhui Can you explain what you mean (or what you're trying to achieve), because in the unit test within this PR I have a relative path which I can then apply a transformation to.

e.g.

const path = require('path');
const pkg = require('./package.json');

module.exports = {
  description: 'transform sourcemap paths (#2168)',
  options: {
    output: {
      name: 'myModule',
      file: path.resolve(__dirname, '_actual', 'bundle.js'),
      sourcemapPathTransform: sourcePath => sourcePath.replace(
        // To demonstrate, sourcePath is a relative path and I am doing a string-replace on it. 
        `..${path.sep}`,
        // I'm replacing it with the package name followed by a slash.
        `${pkg.name}${path.sep}`
      )
    }
  }
};

[teohhanhui]

Sorry, I'm not familiar with how it works in rollup. But do see my gulp example in the previous issue to understand what I mean...

Anyway, as long as all the paths are already normalized to be relative to the same base directory, there's no problem.

[pgn-vole]

Looks good @sebinsua!
Thanks for that!

[lukastaegert]

Thank you very much! Could not find any issues from my side, code looks good, too. Will put this into the next release!

[lukastaegert]

Good thinking!

[lukastaegert]

One note: Once this is released, it should be documented on the website. As this tends to be forgotten and we are somewhat short-staffed, if someone would open a PR on https://github.com/rollup/rollupjs.org adding this to the big list of options (maybe with a simple example where all files paths are changed to a different base path?) this would be a great help and I will merge it once we release.

Thanks!