add support for SOURCE_MAP_BASE

src/de/inetsoftware/jwebassembly/JWebAssembly.java

@@ -62,6 +62,12 @@ public class JWebAssembly {
      */
     public static final String DEBUG_NAMES = "DebugNames";
 
+    /**
+     * Property for relative path between the final wasm file location and the source files location for the source map.
+     * If not empty it should end with a slash like "../../src/main/java/".
+     */
+    public static final String SOURCE_MAP_BASE = "SourceMapBase";
+
     /**
      * The name of the annotation for import functions.
      */

src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java

@@ -63,6 +63,8 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
 
     private final boolean               createSourceMap;
 
+    private final String                javaSourceMapBase;
+
     private WasmOutputStream            codeStream          = new WasmOutputStream();
 
     private List<TypeEntry>             functionTypes       = new ArrayList<>();
@@ -102,6 +104,7 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         this.target = target;
         // for now we build the source map together with debug names
         createSourceMap = options.debugNames();
+        javaSourceMapBase = options.getSourceMapBase();
     }
 
     /**
@@ -560,7 +563,7 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
     protected void writeMethodStart( FunctionName name, String sourceFile ) throws IOException {
         if( createSourceMap ) {
             int idx = name.className.lastIndexOf( '/' );
-            this.javaSourceFile = name.className.substring( 0, idx + 1 ) + sourceFile;
+            this.javaSourceFile = javaSourceMapBase + name.className.substring( 0, idx + 1 ) + sourceFile;
         }
         codeStream.reset();
     }

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

@@ -17,6 +17,8 @@ package de.inetsoftware.jwebassembly.wasm;
 
 import java.util.HashMap;
 
+import javax.annotation.Nonnull;
+
 import de.inetsoftware.jwebassembly.JWebAssembly;
 import de.inetsoftware.jwebassembly.module.FunctionName;
 
@@ -31,6 +33,9 @@ public class WasmOptions {
 
     private final boolean useGC;
 
+    @Nonnull
+    private final String  sourceMapBase;
+
     /**
      * NonGC function for ref_eq polyfill.
      */
@@ -45,6 +50,11 @@ public class WasmOptions {
     public WasmOptions( HashMap<String, String> properties ) {
         debugNames = Boolean.parseBoolean( properties.get( JWebAssembly.DEBUG_NAMES ) );
         useGC = Boolean.parseBoolean( properties.getOrDefault( JWebAssembly.WASM_USE_GC, "false" ) );
+        String base = properties.getOrDefault( JWebAssembly.SOURCE_MAP_BASE, "" );
+        if( !base.isEmpty() && !base.endsWith( "/" ) ) {
+            base += "/";
+        }
+        sourceMapBase = base;
     }
 
     /**
@@ -64,4 +74,14 @@ public class WasmOptions {
     public boolean useGC() {
         return useGC;
     }
+
+    /**
+     * 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/". 
+     * @return the path
+     */
+    @Nonnull
+    public String getSourceMapBase() {
+        return sourceMapBase;
+    }
 }