Improve absolute path handling

[lukastaegert]

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 relevant issue numbers:
Resolves #3940
Resolves #3693
Resolves #3024

Description

This will very much extend the handling of external imports to allow having absolute external imports in the output. There are several parts to this:

• A new option makeAbsoluteExternalsRelative that controls how absolute resolved ids are handled. By default it is true, which is the current behaviour. Switching it to false will keep them as absolute in the output while the third value "ifRelativeSource" will only convert them to a relative import if the original import has been relative (even though the resolved import might not have anything to do with the original import).

  "IfRelativeSource" will become the new default in the next major version

• An extension of the resolveId plugin hook: When plugins return an object for their resolveId hook, they can now not only make the id "external" by returning external: true, they can also override the user's choice for the makeAbsoluteExternalsRelative option. By returning external: "absolute", they can force an absolute id to remain absolute in the output while by returning external: "relative", they can force it to become relative. For non-absolute ids, these choices will be treated as true.

• A new value for the external property when using the this.resolve plugin context function. When an absolute id should opt out of becoming relative, the external property will have the value "absolute" instead of true. While this could be considered a breaking change, this will only happen if either the user or a plugin makes use of the new option. For that reason, this will still be a minor release.

See also the included doc updates.

[codecov]

Codecov Report

Merging #4021 (8560404) into master (443dc97) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4021   +/-   ##
=======================================
  Coverage   97.47%   97.47%           
=======================================
  Files         192      192           
  Lines        6775     6785   +10     
  Branches     1985     1994    +9     
=======================================
+ Hits         6604     6614   +10     
  Misses         84       84           
  Partials       87       87           

Impacted Files	Coverage Δ
src/Chunk.ts	100.00% <ø> (ø)
src/utils/options/mergeOptions.ts	100.00% <ø> (ø)
src/ExternalModule.ts	100.00% <100.00%> (ø)
src/ModuleLoader.ts	100.00% <100.00%> (ø)
src/utils/options/normalizeInputOptions.ts	100.00% <100.00%> (ø)

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[github-actions]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#improve-absolute-path-handling

or load it into the REPL:
https://rollupjs.org/repl/?circleci=14888

[Oleksandr-prog]

?

[lukastaegert]

While the question is rather vague, the answer to the three "fixed" issues is to add makeAbsoluteExternalsRelative: "ifRelativeSource". This will also become the default eventually. The complexity arises from the need to make it non-breaking as some libraries depend on the old behaviour.