Add the compiler flag "IgnoreNative" to generate stubs for rall not replaced, referenced native methods. #43

src/de/inetsoftware/jwebassembly/JWebAssembly.java

@@ -103,6 +103,11 @@ public class JWebAssembly {
      */
     public static final String WASM_USE_EH = "wasm.use_eh";
 
+    /**
+     * Compiler property to ignore all referenced native methods without declared replacement in a library and replace them with a stub that throws an exception at runtime.
+     */
+    public static final String IGNORE_NATIVE = "IgnoreNative";
+
     /**
      * The logger instance
      */

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

@@ -1,5 +1,5 @@
 /*
-   Copyright 2019 Volker Berlin (i-net software)
+   Copyright 2019 - 2022 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.
@@ -66,6 +66,10 @@ public abstract class ArraySyntheticFunctionName extends SyntheticFunctionName {
      */
     @Override
     public Iterator<AnyType> getSignature( TypeManager types ) {
-        return Arrays.asList( signatureTypes ).iterator();
+        if( signatureTypes != null ) {
+            return Arrays.asList( signatureTypes ).iterator();
+        } else {
+            return super.getSignature( types );
+        }
     }
 }

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

@@ -602,7 +602,15 @@ public class ModuleGenerator {
                     strings.getStringConstantFunction();
                     return null;
                 }
-                throw new WasmException( "Abstract or native method can not be used: " + name.signatureName +"\nIf you want to use classes with native code, you must use a library that implements these native methods, such as 'de.inetsoftware:jwebassembly-api:+'.", -1 );
+
+                if( writer.options.ignoreNative() ) {
+                    JWebAssembly.LOGGER.severe( "Native method will throw an exception at runtime: " + name.signatureName );
+                    WatCodeSyntheticFunctionName nativeStub = new WatCodeSyntheticFunctionName( name.className, name.methodName, name.signature, "unreachable", (AnyType[])null );
+                    functions.markAsNeededAndReplaceIfExists( nativeStub );
+                    return null;
+                }
+
+                throw new WasmException( "Native methods cannot be compiled to WebAssembly: " + name.signatureName +"\nIf you want to use classes with native code, you must use a library that implements these native methods, such as 'de.inetsoftware:jwebassembly-api:+' or implements this native method self.", -1 );
             }
         } catch( Throwable ioex ) {
             int lineNumber = code == null ? -1 : code.getFirstLineNr();

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

@@ -48,6 +48,8 @@ public class WasmOptions {
 
     private final boolean         useEH;
 
+    private final boolean         ignoreNative;
+
     @Nonnull
     private final String          sourceMapBase;
 
@@ -76,6 +78,8 @@ public class WasmOptions {
         debugNames = Boolean.parseBoolean( properties.get( JWebAssembly.DEBUG_NAMES ) );
         useGC = Boolean.parseBoolean( properties.getOrDefault( JWebAssembly.WASM_USE_GC, "false" ) );
         useEH = Boolean.parseBoolean( properties.getOrDefault( JWebAssembly.WASM_USE_EH, "false" ) );
+        ignoreNative = Boolean.parseBoolean( properties.getOrDefault( JWebAssembly.IGNORE_NATIVE, "false" ) );
+
         String base = properties.getOrDefault( JWebAssembly.SOURCE_MAP_BASE, "" );
         if( !base.isEmpty() && !base.endsWith( "/" ) ) {
             base += "/";
@@ -110,6 +114,15 @@ public class WasmOptions {
         return useEH;
     }
 
+    /**
+     * Compiler property to add a stub for all referenced native methods that has no replacement.
+     * 
+     * @return true, if ignore missing native methods
+     */
+    public boolean ignoreNative() {
+        return ignoreNative;
+    }
+
     /**
      * Get the relative path between the final wasm file location and the source files location.
      * If not empty it should end with a slash like "../../src/main/java/". 

test/de/inetsoftware/jwebassembly/runtime/RuntimeErrors.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 - 2021 Volker Berlin (i-net software)
+ * Copyright 2017 - 2022 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.
@@ -88,7 +88,7 @@ public class RuntimeErrors {
 
     @Test
     public void nativeMethod() throws IOException {
-        compileErrorTest( "Abstract or native method can not be used:", NativeMethod.class );
+        compileErrorTest( "Native methods cannot be compiled to WebAssembly:", NativeMethod.class );
     }
 
     static class NativeMethod {