Declare supported IntelliJ IDEA versions in plugin metadata

[snicoll]

Given that we have to release the plugin quite often as they are breaking change in a lower-level API we have to use, it would be better to actually document the versions that are compatible.

The plugin metadata can use build number ranges for this.

[snicoll]

There is actually a since-build in there but it is outdated.

[snicoll]

I am tempted to go with <idea-version since-build="201" until-build="202.*"/> that would enable the plugin for IJ
2020.1 and 2020.2. I've tested on both and it works fine.

The plugin will disable itself when 2020.3 is released but we have a chance to test the EAP and have an extra release beforehand. The other option is to not put a until-build and process the feedback if any.

paging @YannCebron for insights

[YannCebron]

"it depends" if a plugin uses only small parts/very "stable" part of APIs, then usually omitting until-build will work
we recommend using Plugin Verifier to check binary compatibility against all supported versions https://jetbrains.org/intellij/sdk/docs/reference_guide/api_changes_list.html#plugin-verifier

[philwebb]

Most of the compatibility issues appear in our DelegatingCodeStyleManager class. I guess com.intellij.psi.codeStyle.CodeStyleManager is somewhat internal, so it's not that surprising. We only need to override the reformat... methods, and those generally don't change much. More often than not it's just methods added in CodeStyleManager that we need to add to the delegate.

I seem to remember finding a few other IntelliJ plugins that have similar problems. Perhaps if there was a DelegatingCodeStyleManager API already provided by IntelliJ it would help a little?

[YannCebron]

Unfortunately there exists no (stable) API yet for delegating code formatting. Please follow https://youtrack.jetbrains.com/issue/IDEA-203568 for progress.

[krasa]

Using cglib proxy is much better than extending CodeStyleManager - you will break the IDE pretty much with every API change while the proxy will always work.

https://github.com/krasa/EclipseCodeFormatter/blob/master/src/java/krasa/formatter/plugin/ProxyUtils.java
https://github.com/krasa/EclipseCodeFormatter/blob/master/src/java/krasa/formatter/plugin/ProxyCodeStyleManagerDelegator.java

[philwebb]

Thanks for the suggestion @krasa. I've opened #255 to investigate.

[philwebb]

With #359 we've switched to use the DocumentFormattingService which should be a more stable API.