JS: remove unused imports from generated JS. Fix KT-14748

Author: Alexey Andreev

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/metadata/metadataProperties.kt

@@ -105,6 +105,8 @@ var JsNameRef.coroutineController by MetadataProperty(default = false)
 
 var JsFunction.continuationInterfaceRef: JsExpression? by MetadataProperty(default = null)
 
+var JsName.imported by MetadataProperty(default = false)
+
 enum class TypeCheck {
     TYPEOF,
     INSTANCEOF,

js/js.inliner/src/org/jetbrains/kotlin/js/inline/clean/removeUnusedImports.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * 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 org.jetbrains.kotlin.js.inline.clean
+
+import com.google.dart.compiler.backend.js.ast.*
+import com.google.dart.compiler.backend.js.ast.metadata.imported
+
+fun removeUnusedImports(root: JsNode) {
+    val collector = UsedImportsCollector()
+    root.accept(collector)
+    NodeRemover(JsVars::class.java) { statement ->
+        if (statement.vars.size == 1) {
+            val name = statement.vars[0].name
+            name.imported && name !in collector.usedImports
+        }
+        else {
+            false
+        }
+    }.accept(root)
+}
+
+private class UsedImportsCollector : RecursiveJsVisitor() {
+    val usedImports = mutableSetOf<JsName>()
+
+    override fun visitNameRef(nameRef: JsNameRef) {
+        val name = nameRef.name
+        if (name != null && name.imported) {
+            usedImports += name
+        }
+        super.visitNameRef(nameRef)
+    }
+}

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -4562,6 +4562,12 @@ public void testAllFilesPresentInInlineSizeReduction() throws Exception {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("js/js.translator/testData/box/inlineSizeReduction"), Pattern.compile("^([^_](.+))\\.kt$"), TargetBackend.ANY, true);
         }
 
+        @TestMetadata("inlineImportCleanup.kt")
+        public void testInlineImportCleanup() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/inlineSizeReduction/inlineImportCleanup.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("inlineLambdaCleanup.kt")
         public void testInlineLambdaCleanup() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/inlineSizeReduction/inlineLambdaCleanup.kt");

js/js.translator/src/org/jetbrains/kotlin/js/facade/K2JSTranslator.java

@@ -26,6 +26,7 @@
 import org.jetbrains.kotlin.js.coroutine.CoroutineTransformer;
 import org.jetbrains.kotlin.js.facade.exceptions.TranslationException;
 import org.jetbrains.kotlin.js.inline.JsInliner;
+import org.jetbrains.kotlin.js.inline.clean.RemoveUnusedImportsKt;
 import org.jetbrains.kotlin.js.translate.context.TranslationContext;
 import org.jetbrains.kotlin.js.translate.general.Translation;
 import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStatus;
@@ -88,6 +89,7 @@ public TranslationResult translate(
 
         CoroutineTransformer coroutineTransformer = new CoroutineTransformer(program);
         coroutineTransformer.accept(program);
+        RemoveUnusedImportsKt.removeUnusedImports(program);
         ProgressIndicatorAndCompilationCanceledStatus.checkCanceled();
         if (hasError(diagnostics)) return new TranslationResult.Fail(diagnostics);
 

js/js.translator/src/org/jetbrains/kotlin/js/translate/context/StaticContext.java

@@ -48,7 +48,6 @@
 import java.util.*;
 
 import static org.jetbrains.kotlin.js.config.LibrarySourcesConfig.UNKNOWN_EXTERNAL_MODULE_NAME;
-import static org.jetbrains.kotlin.js.translate.utils.AnnotationsUtils.getNameForAnnotatedObject;
 import static org.jetbrains.kotlin.js.translate.utils.AnnotationsUtils.isLibraryObject;
 import static org.jetbrains.kotlin.js.translate.utils.AnnotationsUtils.isNativeObject;
 import static org.jetbrains.kotlin.js.translate.utils.JsAstUtils.pureFqn;
@@ -403,6 +402,7 @@ public JsName importDeclaration(@NotNull String suggestedName, @NotNull JsExpres
         // TODO: remove prefix when problem with scopes is solved
 
         JsName result = rootFunction.getScope().declareFreshName("imported$" + suggestedName);
+        MetadataProperties.setImported(result, true);
         importStatements.add(JsAstUtils.newVar(result, declaration));
         return result;
     }

js/js.translator/testData/box/inlineSizeReduction/inlineImportCleanup.kt

@@ -0,0 +1,10 @@
+// MODULE: lib
+// FILE: lib.kt
+package lib
+
+inline fun foo(f: () -> String) = f()
+
+// MODULE: main(lib)
+// FILE: main.kt
+// PROPERTY_NOT_READ_FROM: foo_6r51u9$
+fun box() = lib.foo { "OK" }