Mercury is a source code transformation library for Java codebases, with an included remapper - built on Eclipse's JDT and Lorenz. Mercury is licensed under the Eclipse Public License 2.0.

While Mercury is yet to see a proper release (we're working on it), it has been successfully used by the following projects:

• The Fabric Project uses Mercury in their Gradle build tools to remap mods to their latest yarn mappings.
• The Sponge Project uses Mercury for their cross-version mapping migration tool, saving hundreds of man-hours of work - and with greater accuracy.

Mercury is centred around the Mercury class, which is the effective control centre. See the following example, for a demonstration of remapping a codebase using Lorenz.

final Mercury mercury = new Mercury();

// Due to the nature of how mercury works, it is essential that we have
// the full binary classpath.
mercury.getClassPath().add(Paths.get("example.jar"));

// To remap the codebase using Lorenz, we must install a MercuryRemapper,
// with our MappingSet.
mercury.getProcessors().add(MercuryRemapper.create(mappings));

// Lets rewrite our codebase at "a/" to "b/".
mercury.rewrite(Paths.get("a"), Paths.get("b"));

Mercury also has an optional dependency on at, allowing access transformers to be applied to source, and be updated to reflect changes in the structure of the codebase. See the following example to see how this could work.

final Mercury mercury = new Mercury();
mercury.getClassPath().add(Paths.get("example.jar"));
mercury.getProcessors().add(MercuryRemapper.create(mappings));

// Since we run after MercuryRemapper, the access transformer needs to be
// remapped - fortunately, at provides an optional dependency on Lorenz,
// and a utility to do just that!
final AccessTransformSet remappedTransforms =
            AccessTransformSetMapper.remap(transforms, mappings);
// We can then use AccessTransformerRewriter with the remapped access
// transform set.
mercury.getProcessors()
            .add(AccessTransformerRewriter.create(remappedTransforms));

mercury.rewrite(Paths.get("a"), Paths.get("b"));

There is beginning to be tooling designed to work with Mercury, these may be helpful in your project:

• CadixDev/MercuryMixin which remaps Mixins when remapping.

Found an issue with Mercury? Make an issue! We'd rather close invalid reports than have bugs go unreported :)

We have an IRC channel on EsperNet, #cadix, which is available for all registered users to join and discuss Mercury and other Cadix projects.