Do not add Kotlin and Groovy sources from build/ to LST

[timtebeek]

What's changed?

Reuse the mechanism we added for protos/build/generated for build/generated-sources.

What's your motivation?

Files like build-src/build/generated-sources are parsed into the LST, and modified by recipes. That last part is undesirable, as the diffs would then target files not part of the git repository, and fail to apply from a dryRun fix.patch file.

n	sourcePath	sourceFileType	buildTool	buildToolVersion	checksum	lineCount
1	build-src/build/generated-sources/kotlin-dsl-external-plugin-spec-builders/kotlin/gradle/kotlin/dsl/plugins/_12895b5fa930feaf40eec89923f04a18/PluginSpecBuilders.kt	K.CompilationUnit	modgradle	3.17.0	55d3a6f819a2d911e8dc50fcdba328c6	1186
2	build-src/build/generated-sources/kotlin-dsl-accessors/kotlin/gradle/kotlin/dsl/accessors/_f68e08f112e4a379392eaca54506dc98/Accessorsct2ylp5ktt4rxe14s34wgi9de.kt	K.CompilationUnit	modgradle	3.17.0	f4d3580d463adfe088c5cc21c590086f	76
3	build-src/build/generated-sources/kotlin-dsl-accessors/kotlin/gradle/kotlin/dsl/accessors/_f68e08f112e4a379392eaca54506dc98/Accessorsd6fwhfk2ip9kv56d7w2vygrh6.kt	K.CompilationUnit	modgradle	3.17.0	1a203f1b9aaeb9223e2565c7cd25fa37	76

Anything in particular you'd like reviewers to focus on?

There's likely a better way, but I'm having a bit of trouble working that out. Figured open this PR to start the discussion.

Have you considered any alternatives or workarounds?

What I'd done previously in an attempt to exclude these files is add them to Git ignore:
openrewrite/rewrite-recipe-bom@9f5840c
But somehow they are still picked up; I had thought we already excluded files ignored in git.

Any additional context

I know in the Maven plugin we explicitly exclude generated sources, but I'm not immediately seeing an equivalent here.
https://github.com/ammachado/rewrite-maven-plugin/blob/f900a9a6365a4d02c0083dd29e14927d6ffa6576/src/main/java/org/openrewrite/maven/MavenMojoProjectParser.java#L425-L430

[shanman190]

I suspect that we're actually including all types of generated sources that are produced by various plugins as they will appear within the source files from sourceSet.getAllSources(). I think the current proto implementation was a bandaid around the problem, but never actually addressed it.

What should probably be being done is a filter operation when collecting all of the unparsed sources and excluding them when they are contained within subproject.getLayout().getBuildDirectory() (already confirmed that this is also available on the baseline Gradle 4.10, so no special logic is required for old versions). This would be directly akin to what was done within the Maven plugin.

[timtebeek]

Thanks for the hint! Noticed we only had that pattern for Java; now also for Kotlin & Groovy + Kotlin multi platform. Should help I think, although it's a bit cumbersome to test.

[shanman190]

Do we want to even be parsing these files at all with OpenRewrite?

[timtebeek]

I thought we did so for the type attribution; that's at least the comment over on the Maven plugin. Hadn't thought to change that here just yet. Just excluding them after they are parsed to prevent them ending up in the LST themselves.

[shanman190]

So we have so far, yeah, but we also trigger the compile phases in Gradle as well prior to the rewrite tasks, so technically we could put the source set's own output classes onto the parser's classpath to still get the necessary type attribution and bypass parsing the generated types.

Just a thought though.

[timtebeek]

Could indeed be a nice improvement to stop ourselves from parsing source files whose LSTs we'll discard anyway, or perhaps even having two sources of the same type information; compiled vs source.