Add support for outsourcing of a constructor to JavaScript

src/de/inetsoftware/jwebassembly/module/ImportSyntheticFunctionName.java

@@ -0,0 +1,62 @@
+/*
+   Copyright 2019 Volker Berlin (i-net software)
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+*/
+package de.inetsoftware.jwebassembly.module;
+
+import java.util.function.Function;
+
+/**
+ * Synthetic/dynamic method based on import annotation.
+ * 
+ * @author Volker Berlin
+ */
+class ImportSyntheticFunctionName extends SyntheticFunctionName {
+
+    private final Function<String, Object> importAnannotation;
+
+    /**
+     * create a new instance
+     * 
+     * @param className
+     *            the Java class name
+     * @param name
+     *            the function name
+     * @param signature
+     *            the method signature, first the parameters, then null and the the return types
+     * @param importAnannotation
+     *            the annotations
+     */
+    ImportSyntheticFunctionName( String className, String name, String signature, Function<String, Object> importAnannotation ) {
+        super( className, name, signature );
+        this.importAnannotation = importAnannotation;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected boolean hasWasmCode() {
+        return false;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected Function<String, Object> getAnnotation() {
+        return importAnannotation;
+    }
+}

src/de/inetsoftware/jwebassembly/module/WasmCodeBuilder.java

@@ -18,6 +18,7 @@ package de.inetsoftware.jwebassembly.module;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Function;
 
 import javax.annotation.Nonnegative;
 import javax.annotation.Nonnull;
@@ -358,7 +359,35 @@ public abstract class WasmCodeBuilder {
      *            the line number in the Java source code
      */
     protected void addCallInstruction( FunctionName name, int javaCodePos, int lineNumber ) {
-        instructions.add( new WasmCallInstruction( name, javaCodePos, lineNumber, types ) );
+        WasmCallInstruction instruction = new WasmCallInstruction( name, javaCodePos, lineNumber, types );
+
+        if( "<init>".equals( name.methodName ) ) {
+            Function<String, Object> importAnannotation = functions.getImportAnannotation( name );
+            if( importAnannotation != null ) {
+                // if there a JavaScript replacement for a constructor we need also replace the create instance instruction
+                List<WasmInstruction> instructions = this.instructions;
+                for( int i = instructions.size() - 1; i >= 0; i-- ) {
+                    WasmInstruction instr = instructions.get( i );
+                    if( instr.getType() == Type.Struct ) {
+                        WasmStructInstruction struct = (WasmStructInstruction)instr;
+                        if( struct.getOperator() == StructOperator.NEW_DEFAULT ) {
+                            instructions.remove( i ); // NEW_DEFAULT
+                            instructions.remove( i ); // SET temp from a dup of the instance reference
+                            instructions.remove( i ); // GET temp from a dup of the instance reference
+                            instructions.remove( i ); // GET temp from a dup of the instance reference
+                            break;
+                        }
+                    }
+                }
+                // The new signature need a return value. The <init> of Java has ever a void return value
+                String signature = name.signature;
+                signature = signature.substring( 0, signature.length() - 1 ) + "Ljava/lang/Object;";
+                FunctionName name2 = new ImportSyntheticFunctionName( "String", "init", signature, importAnannotation );
+                instruction = new WasmCallInstruction( name2, javaCodePos, lineNumber, types );
+            }
+        }
+
+        instructions.add( instruction );
     }
 
     /**