JS: add DCE devmode. Fix mapping paths in source maps

See KT-20210, KT-21307

js/js.translator/src/org/jetbrains/kotlin/js/facade/SourceMapBuilderConsumer.java

@@ -34,6 +34,9 @@ import java.util.List;
 import java.util.function.Supplier;
 
 public class SourceMapBuilderConsumer implements SourceLocationConsumer {
+    @NotNull
+    private final File sourceBaseDir;
+
     @NotNull
     private final SourceMapMappingConsumer mappingConsumer;
 
@@ -48,10 +51,12 @@ public class SourceMapBuilderConsumer implements SourceLocationConsumer {
     private final List<Object> sourceStack = new ArrayList<>();
 
     public SourceMapBuilderConsumer(
+            @NotNull File sourceBaseDir,
             @NotNull SourceMapMappingConsumer mappingConsumer,
             @NotNull SourceFilePathResolver pathResolver,
             boolean provideCurrentModuleContent, boolean provideExternalModuleContent
     ) {
+        this.sourceBaseDir = sourceBaseDir;
         this.mappingConsumer = mappingConsumer;
         this.pathResolver = pathResolver;
         this.provideCurrentModuleContent = provideCurrentModuleContent;
@@ -109,7 +114,23 @@ public class SourceMapBuilderConsumer implements SourceLocationConsumer {
         else if (sourceInfo instanceof JsLocationWithSource) {
             JsLocationWithSource location = (JsLocationWithSource) sourceInfo;
             Supplier<Reader> contentSupplier = provideExternalModuleContent ? location.getSourceProvider()::invoke : () -> null;
-            mappingConsumer.addMapping(location.getFile(), location.getIdentityObject(), contentSupplier,
+            String path;
+
+            File absFile = new File(location.getFile()).isAbsolute() ?
+                           new File(location.getFile()) :
+                           new File(sourceBaseDir, location.getFile());
+            if (absFile.isAbsolute()) {
+                try {
+                    path = pathResolver.getPathRelativeToSourceRoots(absFile);
+                }
+                catch (IOException e) {
+                    path = location.getFile();
+                }
+            }
+            else {
+                path = location.getFile();
+            }
+            mappingConsumer.addMapping(path, location.getIdentityObject(), contentSupplier,
                                location.getStartLine(), location.getStartChar());
         }
     }

js/js.translator/src/org/jetbrains/kotlin/js/facade/TranslationResult.kt

@@ -69,6 +69,7 @@ abstract class TranslationResult protected constructor(val diagnostics: Diagnost
                         val sourceMapContentEmbedding = config.sourceMapContentEmbedding
                         val pathResolver = SourceFilePathResolver.create(config)
                         SourceMapBuilderConsumer(
+                                File("."),
                                 sourceMapBuilder,
                                 pathResolver,
                                 sourceMapContentEmbedding == SourceMapSourceEmbedding.ALWAYS,