Add findDuplicateMappingFiles task

[supersaiyansubtlety]

Adds findDuplicateMappingFiles gradle task that checks for mapping files that map the same class.

Useful when merging/rebasing.
It just matches the first line of each file against "^CLASS net/minecraft/unmapped/C_\\w+" and if it finds any files with the same one it throws an exception listing them.

edit: it matches against this now:

"^CLASS (?:net/minecraft|com/mojang/blaze3d)/(?:\\w+/)*\\w+(?= )"

Also makes mappingLint depend on findDuplicateMappingFiles.

Edit: also removes current duplicate mapping files so the build run can complete.

[supersaiyansubtlety]

Output looks like this (these are actual duplicates currently on the 1.21 branch):
edit: see new logging below

> Found classes mapped by multiple files!
      CLASS net/minecraft/unmapped/C_zjsuejaf is mapped by:
          C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\datafixer\fix\AttributeIdFix.mapping
          C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\datafixer\fix\AttributeModifierIdFix.mapping
      CLASS net/minecraft/unmapped/C_dxtlxcwy is mapped by:
          C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\datafixer\fix\RemoveEmptyItemInSuspiciousBlockFix.mapping
          C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\datafixer\fix\RemoveEmptyItemInBrushableBlockFix.mapping

[supersaiyansubtlety]

It would also be trivial to add checking for empty files, files that don't match the regex, and files that don't have the mapping extension.
Do we care about those?

[supersaiyansubtlety]

Went ahead and added those checks.
It also checks non-obfuscated classes now and the logging is more similar to MappingLintTask.
The new logging:

Found 1 class mapped by multiple files!
	CLASS net/minecraft/unmapped/C_xyxorzsk is mapped by:
		C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersion.mapping
		C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersion2.mapping2
Found 1 empty file!
	C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersionEMPTY.mapping3
Found 1 file not mapping a class!
	C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersionNO_CLASS.mapping
Found 2 files without the mapping extension!
	C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersion2.mapping2
	C:\Users\super\Projects\Minecraft\Modding\Quilt\quilt-mappings\mappings\net\minecraft\WorldVersionEMPTY.mapping3

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':findDuplicateMappingFiles'.
> Found 1 class mapped by multiple files, 1 empty file, 1 file not mapping a class, and 2 files without the mapping extension! See the log for details.

[supersaiyansubtlety]

private static final Pattern MINECRAFT_CLASS = Pattern.compile("^CLASS net/minecraft/(?:\\w+/)*\\w+(?= )");
private static final Pattern BLAZE_CLASS = Pattern.compile("^CLASS com/mojang/blaze3d/(?:\\w+/)*\\w+(?= )");

these could be generalized to

private static final Pattern ANY_CLASS = Pattern.compile("^CLASS (?:\\w+/)+\\w+(?= )");

idk if we want to allow classes outside of net.minecraft and com.mojang.blaze3d though

[OroArmor]

Until a good reason comes, I think disallowing anything outside of those two root packages is a good idea.

[ix0rai]

fantastic work!

[OroArmor]

can we have the check task depend on this like the MappingsLint task?

[supersaiyansubtlety]

can we have the check task depend on this like the MappingsLint task?

Sure; instead of MappingsLint's dependency on findDuplicateMappingFiles, or in addition to it?

[OroArmor]

Oh! I missed that! Looks good!

[OroArmor]

@ix0rai with this, do we want to enforce that all PRs are up to date before merging (like QSL)? it'll make merging multiple PRs in a row annoying, but will make sure that this is caught in a PR and not once 3 branches are merged at once

[ix0rai]

@ix0rai with this, do we want to enforce that all PRs are up to date before merging (like QSL)? it'll make merging multiple PRs in a row annoying, but will make sure that this is caught in a PR and not once 3 branches are merged at once

I think we should, it's probably possible to automate checking them using actions and merge queue