Allow easier configuration of groovy.antlr4

[jamesdh]

I'm trying to make use of Spotless code formatter (within gradle) for formatting our Java + Groovy code. Unfortunately, when setting it up today I encountered some issues with lambda syntax in Groovy 3+ code. A bit of googling lead me to groovy-eclipse, since Spotless uses it to perform its groovy parsing. Eventually I stumbled on the 4.2.0 release notes with the following:

The new antlr4-based Parrot Parser is disabled by default. To enable it, add -Dgroovy.antlr4=true to your eclipse.ini file after the -vmargs line or add a compiler config script to your project with configuration.pluginFactory = org.codehaus.groovy.control.ParserPluginFactory.antlr4()

There doesn't seem to be any way to enable antlr4 from gradle directly. I was able to get things working by passing a JVM option to gradle directly, but I was hoping to configure this in such a way that doesn't require active input from other team members.

Initially I opened an issue at diffplug/spotless#975, inquiring as to whether or not I was missing something. Ultimately, they think this would be better served by making it more configurable from within groovy-eclipse itself.

[eric-milles]

It is configurable through CompilerConfiguration as well. I don't really know what sort of interface spotless provides for you.

[jamesdh]

Since Groovy 4 is just around the corner and removes the Antlr2 based parser completely, is there any plans to just switch to the Antlr4 parser by default?

[eric-milles]

Groovy 4 does indeed remove its antlr2-based parser. But it does not remove the mechanism for supplying any compatible parser to the compiler. So this project continues to supply a patched antlr2-based parser to keep code completion and other editor features working.

Plans for transition to the antlr40based parser as the default can be tracked here:
#1011
#1107