Disable signature merging unless decompiler is active, closes SpongeP…

…owered#254

src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java

@@ -238,6 +238,15 @@ public static enum Option {
          */
         DEBUG_EXPORT_DECOMPILE_THREADED(Option.DEBUG_EXPORT_DECOMPILE, Inherit.ALLOW_OVERRIDE, "async"),
 
+        /**
+         * By default, if the runtime export decompiler is active, mixin generic
+         * signatures are merged into target classes. However this can cause
+         * problems with some runtime subsystems which attempt to reify generics
+         * using the signature data. Set this option to <tt>false</tt> to
+         * disable generic signature merging. 
+         */
+        DEBUG_EXPORT_DECOMPILE_MERGESIGNATURES(Option.DEBUG_EXPORT_DECOMPILE, Inherit.ALLOW_OVERRIDE, "mergeGenericSignatures"),
+
         /**
          * Run the CheckClassAdapter on all classes after mixins are applied,
          * also enables stricter checks on mixins for use at dev-time, promotes

src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java

@@ -56,6 +56,7 @@
 import org.spongepowered.asm.mixin.injection.ModifyVariable;
 import org.spongepowered.asm.mixin.injection.Redirect;
 import org.spongepowered.asm.mixin.transformer.ClassInfo.Field;
+import org.spongepowered.asm.mixin.transformer.ext.extensions.ExtensionClassExporter;
 import org.spongepowered.asm.mixin.transformer.meta.MixinMerged;
 import org.spongepowered.asm.mixin.transformer.meta.MixinRenamed;
 import org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException;
@@ -237,10 +238,22 @@ public String toString() {
      */
     protected final Profiler profiler = MixinEnvironment.getProfiler();
 
+    /**
+     * Flag to track whether signatures from applied mixins should be merged
+     * into target classes. This is only true when the runtime decompiler is
+     * active. If this is disabled, signatures on merged mixin methods are
+     * stripped instead of remapped.
+     */
+    protected final boolean mergeSignatures;
+
     MixinApplicatorStandard(TargetClassContext context) {
         this.context = context;
         this.targetName = context.getClassName();
         this.targetClass = context.getClassNode();
+
+        ExtensionClassExporter exporter = context.getExtensions().<ExtensionClassExporter>getExtension(ExtensionClassExporter.class);
+        this.mergeSignatures = exporter.isDecompilerActive()
+                && MixinEnvironment.getCurrentEnvironment().getOption(Option.DEBUG_EXPORT_DECOMPILE_MERGESIGNATURES);
     }
 
     /**
@@ -316,7 +329,9 @@ protected final void applyMixin(MixinTargetContext mixin, ApplicatorPass pass) {
     }
 
     protected void applySignature(MixinTargetContext mixin) {
-        this.context.mergeSignature(mixin.getSignature());
+        if (this.mergeSignatures) {
+            this.context.mergeSignature(mixin.getSignature());
+        }
     }
 
     /**
@@ -389,6 +404,16 @@ protected void mergeNewFields(MixinTargetContext mixin) {
             if (target == null) {
                 // This is just a local field, so add it
                 this.targetClass.fields.add(field);
+
+                if (field.signature != null) {
+                    if (this.mergeSignatures) {
+                        SignatureVisitor sv = mixin.getSignature().getRemapper();
+                        new SignatureReader(field.signature).accept(sv);
+                        field.signature = sv.toString();
+                    } else {
+                        field.signature = null;
+                    }
+                }
             }
         }
     }
@@ -468,9 +493,13 @@ protected void mergeMethod(MixinTargetContext mixin, MethodNode method) {
         mixin.methodMerged(method);
 
         if (method.signature != null) {
-            SignatureVisitor sv = mixin.getSignature().getRemapper();
-            new SignatureReader(method.signature).accept(sv);
-            method.signature = sv.toString();
+            if (this.mergeSignatures) {
+                SignatureVisitor sv = mixin.getSignature().getRemapper();
+                new SignatureReader(method.signature).accept(sv);
+                method.signature = sv.toString();
+            } else {
+                method.signature = null;
+            }
         }
     }
 

src/main/java/org/spongepowered/asm/mixin/transformer/ext/extensions/ExtensionClassExporter.java

@@ -75,6 +75,10 @@ public ExtensionClassExporter(MixinEnvironment env) {
         }
     }
 
+    public boolean isDecompilerActive() {
+        return this.decompiler != null;
+    }
+
     private IDecompiler initDecompiler(MixinEnvironment env, File outputPath) {
         if (!env.getOption(Option.DEBUG_EXPORT_DECOMPILE)) {
             return null;