Fix missing extension method parameters names during code completion

src/eclipseAgent/lombok/eclipse/agent/ExtensionMethodCompletionProposal.java

@@ -26,7 +26,11 @@ import static org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants.AccV
 
 import java.util.Arrays;
 
+import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.jdt.core.CompletionProposal;
+import org.eclipse.jdt.core.IMethod;
+import org.eclipse.jdt.core.JavaModelException;
+import org.eclipse.jdt.core.Signature;
 import org.eclipse.jdt.core.compiler.CharOperation;
 import org.eclipse.jdt.internal.codeassist.CompletionEngine;
 import org.eclipse.jdt.internal.codeassist.InternalCompletionProposal;
@@ -36,20 +40,29 @@ import org.eclipse.jdt.internal.codeassist.complete.CompletionOnSingleNameRefere
 import org.eclipse.jdt.internal.compiler.ast.ASTNode;
 import org.eclipse.jdt.internal.compiler.lookup.MethodBinding;
 import org.eclipse.jdt.internal.compiler.lookup.TypeBinding;
+import org.eclipse.jdt.internal.core.NameLookup;
 
 public class ExtensionMethodCompletionProposal extends InternalCompletionProposal {
+	private char[] fullSignature;
+	private char[][] parameterNames;
+	
 	public ExtensionMethodCompletionProposal(final int replacementOffset) {
 		super(CompletionProposal.METHOD_REF, replacementOffset - 1);
 	}
 	
 	public void setMethodBinding(final MethodBinding method, final ASTNode node) {
+		// Add proposal parameter names, sometimes its empty...
+		if (method.parameterNames != null && method.parameterNames.length > 0) {
+			setParameterNames(Arrays.copyOfRange(method.parameterNames, 1, method.parameterNames.length));
+		} else {
+			// Copy signature for parameter name resolution, this is more reliable but slower
+			fullSignature = CompletionEngine.getSignature(method);
+		}
+
 		MethodBinding original = method.original();
 		TypeBinding[] parameters = Arrays.copyOf(method.parameters, method.parameters.length);
 		method.parameters = Arrays.copyOfRange(method.parameters, 1, method.parameters.length);
-		// Add proposal parameter names, sometimes its still empty...
-		if (method.parameterNames != null && method.parameterNames.length > 0) {
-			setParameterNames(Arrays.copyOfRange(method.parameterNames, 1, method.parameterNames.length));
-		}
+
 		TypeBinding[] originalParameters = null;
 		if (original != method) {
 			originalParameters = Arrays.copyOf(method.original().parameters, method.original().parameters.length);
@@ -105,4 +118,58 @@ public class ExtensionMethodCompletionProposal extends InternalCompletionProposa
 			method.original().parameters = originalParameters;
 		}
 	}
+	
+	@Override
+	public char[][] findParameterNames(IProgressMonitor monitor) {
+		if (parameterNames != null) {
+			return parameterNames;
+		}
+		
+		NameLookup.Answer answer = this.nameLookup.findType(
+			new String(this.declarationTypeName),
+			new String(this.declarationPackageName),
+			false,
+			NameLookup.ACCEPT_CLASSES & NameLookup.ACCEPT_INTERFACES,
+			true/* consider secondary types */,
+			false/* do NOT wait for indexes */,
+			false/*don't check restrictions*/,
+			null);
+		
+		if (answer != null && answer.type != null) {
+			char[][] parameterTypes = Signature.getParameterTypes(fullSignature);
+			
+			String[] args = new String[parameterTypes.length];
+			for (int i = 0; i < parameterTypes.length; i++) {
+				args[i] = new String(parameterTypes[i]);
+			}
+			IMethod method = answer.type.getMethod(new String(this.getName()), args);
+			IMethod[] methods = answer.type.findMethods(method);
+			if (methods != null && methods.length > 0) {
+				method = methods[0];
+			}
+			if (method != null) {
+				try {
+					String[] parameterNames = method.getParameterNames();
+					char[][] parameterNamesAsChar = new char[parameterNames.length - 1][];
+					for (int i = 0; i < parameterNamesAsChar.length; i++) {
+						parameterNamesAsChar[i] = parameterNames[i + 1].toCharArray();
+					}
+					setParameterNames(parameterNamesAsChar);
+				} catch (JavaModelException e) {
+					// Nope
+				}
+			}
+		}
+		// Seems like we failed, fallback
+		if (parameterNames == null) {
+			parameterNames = super.findParameterNames(monitor);
+		}
+		return parameterNames;
+	}
+	
+	@Override
+	public void setParameterNames(char[][] parameterNames) {
+		this.parameterNames = parameterNames;
+		super.setParameterNames(parameterNames);
+	}
 }