Align with IntelliJ

[sideeffffect]

• groupedImports = Merge to prevent conflict with IntelliJ
• expandRelative = true to make converging with IntelliJ's Optimize imports faster

Maybe there are other changes necessary to match IntelliJ 100%, but from my experience over many months, using

OrganizeImports {
  expandRelative = true
  groupedImports = Merge
  groups = [
    "*"
    "re:(javax?|scala)\\."
  ]
}

doesn't cause any conflicts between IntelliJ and scalafix-organize-imports.

[codecov]

Codecov Report

Merging #146 (848cb50) into master (869e427) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #146   +/-   ##
=======================================
  Coverage   90.90%   90.90%           
=======================================
  Files           4        4           
  Lines         242      242           
  Branches       12       12           
=======================================
  Hits          220      220           
  Misses         22       22           

Impacted Files	Coverage Δ
...les/src/main/scala/fix/OrganizeImportsConfig.scala	100.00% <ø> (ø)

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[liancheng]

This change violates the original motivation of the test. It meant to test whether relative imports are grouped in a separate order-preserving group, but now they are expanded.

To avoid such issues, let's not change any output files but update the OrganizeImports configurations in all the input files to reflect the new default configuration values.

[liancheng]

Thanks, @sideeffffect. I left a comment about the changes in the tests, otherwise LGTM.

I'm afraid we won't be able to be 100% compatible with IntelliJ default configurations. OrganizeImports values correctness more than conciseness because it is supposed to be used in a batch manner in CI, and we don't want to break your code there. The default IntelliJ configuration values conciseness more even though sometimes it may produce wrong results. For example:

Class count to use import with '_': 5

The above configuration is equivalent to OrganizeImports.coalesceToWildcardImportThreshold = 5, which is not recommended and may result in compilation errors in corner cases (see here). This might be acceptable for IntelliJ since its import optimizer is mostly used in interactive ways and users can spot and fix any errors on the fly.

With that said, changes proposed in this PR are safe, though.

[liancheng]

Oh, actually, another issue: defaulting expandRelative to true may produce unused imports that cannot be removed even if you set removeUnused to true. See here. This means that if you set both expandRelative and removeUnused to true, then the output may not be idempotent unless you run OrganizeImports at least twice. It was the biggest reason why I didn't enable it by default.

I'm not quite sure whether it's a good idea to enable it by default.

Maybe leaving it disabled by default is fine? Because in that case, OrganizeImports doesn't do or complain anything, so it does not conflict with IntelliJ anyway.

[liancheng]

I'm thinking maybe we can add a basedOnStyle option to provide different sets of default configurations. Say:

OrganizeImports.basedOnStyle = INTELLIJ_2020_3

implies:

OrganizeImports {
  coalesceToWildcardImportThreshold = 5
  groups = [
    "*",
    "re:(javax?|scala)\\."
  ]
  groupedImports = Merge
}

Users can still override individual options.

[sideeffffect]

I've changed default expandRelative = false. I think this is good to go into master and then release. Then we can wait for feedback how it works in practice 😉

While in the future it may turn out handy to have a basedOnStyle setting, I don't think we're there yet. So far I would bet that we can get away without using it, so let's not add it just yet. We'll see how far we can get with just IntelliJ-aligned defaults after this PR is merged and a new scalafix-organize-imports version released.

[liancheng]

Thanks and merged!