Allow enabling experimental and/or custom ruleset for ktlint

[tbroyer]

kotlin and kotlinGradle (in Gradle plugin, haven't looked at other usages or Spotless) don't seem to allow using the experimental ruleset of Ktlint (enabling import ordering and indentation rules), and/or custom rulesets (e.g. to re-enable the "no wildcard import" rule that's now disabled by default in Ktlint 0.33.0)

[amadeu01]

@nedtwigg Do you know who could answer that? or, this feature is not possible currently?

[nedtwigg]

It's not possible currently, but could be added. Here's the code that would need to change:

spotless/lib/src/main/java/com/diffplug/spotless/kotlin/KtLintStep.java

Lines 109 to 114 in 6c7db83

	// String KtLint::format(String input, Iterable<RuleSet> rules, Function2 errorCallback)
	// first, we get the standard rules
	Class<?> standardRuleSetProviderClass = classLoader.loadClass(pkg + ".ktlint.ruleset.standard.StandardRuleSetProvider");
	Object standardRuleSet = standardRuleSetProviderClass.getMethod("get").invoke(standardRuleSetProviderClass.newInstance());
	Iterable<?> ruleSets = Collections.singletonList(standardRuleSet);

[nedtwigg]

Fixing this with reflection is doable, but tricky. It would be a lot easier with #524.

[aphexcx]

Hi there! Curious if there's an update on this. I really want to use spotless with https://github.com/cqfn/diKTat (which is a custom ktlint ruleset along with its own config.)

If this isn't usable yet, perhaps I could help. I've read a bunch of other issues to figure out how hard this would be to implement myself, possibly as a custom Step that calls the diKTat formatter?

[nedtwigg]

Happy to take a PR which adds support for custom ktlint rulesets, and/or happy to take a PR with diKTat support. The challenge for both is that the integration code is currently written using reflection, though that can be fixed with #524.

If you decide submit a PR for either, I would recommend doing the documentation first, and submitting a draft PR with the documentation. Then build to the docs.

[nedtwigg]

diKTat is a one way to accomplish this, and it is now available in plugin-gradle 5.10.0 and plugin-maven 2.8.0.

[nedtwigg]

Now that #1012 has merged, it should be easier to build this if anybody wants to contribute a PR.

[st-hocnguyen]

Any progress on this?

[nedtwigg]

@st-hocnguyen nope, PR's welcome :)