JS: don't treat library without JS metadata as error, report warning and continue instead. See KT-16158

Author: Alexey Andreev

compiler/cli/src/org/jetbrains/kotlin/cli/js/K2JSCompiler.java

@@ -146,7 +146,7 @@ public void error(@NotNull String message) {
 
             @Override
             public void warning(@NotNull String message) {
-                messageCollector.report(CompilerMessageSeverity.WARNING, message, CompilerMessageLocation.NO_LOCATION);
+                messageCollector.report(CompilerMessageSeverity.STRONG_WARNING, message, CompilerMessageLocation.NO_LOCATION);
             }
         })) {
             return COMPILATION_ERROR;

compiler/testData/cli/js/notValidLibraryDir.out

@@ -1,2 +1,8 @@
-error: 'compiler/testData/integration/ant/js/simpleWithStdlibAndFolderAsAnotherLib' is not a valid Kotlin Javascript library
-COMPILATION_ERROR
+warning: 'compiler/testData/integration/ant/js/simpleWithStdlibAndFolderAsAnotherLib' is not a valid Kotlin Javascript library
+compiler/testData/cli/js/withLib.kt:2:8: error: unresolved reference: library
+import library.sample.*
+       ^
+compiler/testData/cli/js/withLib.kt:6:13: error: unresolved reference: pairAdd
+    val x = pairAdd(p)
+            ^
+COMPILATION_ERROR

js/js.frontend/src/org/jetbrains/kotlin/js/config/LibrarySourcesConfig.java

@@ -146,8 +146,8 @@ private boolean checkLibFilesAndReportErrors(@NotNull JsConfig.Reporter report,
             else {
                 List<KotlinJavascriptMetadata> metadataList = KotlinJavascriptMetadataUtils.loadMetadata(filePath);
                 if (metadataList.isEmpty()) {
-                    report.error("'" + path + "' is not a valid Kotlin Javascript library");
-                    return true;
+                    report.warning("'" + path + "' is not a valid Kotlin Javascript library");
+                    continue;
                 }
 
                 for (KotlinJavascriptMetadata metadata : metadataList) {