[FIR IDE] Add basic compiler-side Import Optimizer tests

These tests are not complete, but it is intentional - it is just a basic
setup, so when the need arise, the tests can be added right away

generators/frontend-api-generator/tests/org/jetbrains/kotlin/generators/tests/frontend/api/GenerateTests.kt

@@ -7,10 +7,7 @@ package org.jetbrains.kotlin.generators.tests.frontend.api
 
 import org.jetbrains.kotlin.generators.util.TestGeneratorUtil
 import org.jetbrains.kotlin.idea.fir.frontend.api.AbstractReferenceResolveTest
-import org.jetbrains.kotlin.idea.fir.frontend.api.components.AbstractExpectedExpressionTypeTest
-import org.jetbrains.kotlin.idea.fir.frontend.api.components.AbstractHLExpressionTypeTest
-import org.jetbrains.kotlin.idea.fir.frontend.api.components.AbstractOverriddenDeclarationProviderTest
-import org.jetbrains.kotlin.idea.fir.frontend.api.components.AbstractRendererTest
+import org.jetbrains.kotlin.idea.fir.frontend.api.components.*
 import org.jetbrains.kotlin.idea.fir.frontend.api.fir.AbstractResolveCallTest
 import org.jetbrains.kotlin.idea.fir.frontend.api.scopes.AbstractFileScopeTest
 import org.jetbrains.kotlin.idea.fir.frontend.api.scopes.AbstractMemberScopeByFqNameTest
@@ -81,6 +78,10 @@ fun main(args: Array<String>) {
             testClass<AbstractReferenceResolveTest> {
                 model("referenceResolve", pattern = TestGeneratorUtil.KT_WITHOUT_DOTS_IN_NAME)
             }
+
+            testClass<AbstractHLImportOptimizerTest> {
+                model("components/importOptimizer", pattern = TestGeneratorUtil.KT_WITHOUT_DOTS_IN_NAME)
+            }
         }
 
         testGroup("idea/idea-frontend-fir/idea-fir-low-level-api/tests", "compiler/fir/raw-fir/psi2fir/testData") {

idea/idea-frontend-fir/testData/components/importOptimizer/unusedFunctionImports.imports

@@ -0,0 +1,2 @@
+dependency.bar
+dependency.foo

idea/idea-frontend-fir/testData/components/importOptimizer/unusedFunctionImports.kt

@@ -0,0 +1,14 @@
+// FILE: main.kt
+package test
+
+import dependency.foo
+import dependency.bar
+
+fun usage() {}
+
+// FILE: dependency.kt
+package dependency
+
+fun foo() {}
+
+fun bar() {}

idea/idea-frontend-fir/testData/components/importOptimizer/usedFunctionImport.kt

@@ -0,0 +1,13 @@
+// FILE: main.kt
+package test
+
+import dependency.foo
+
+fun usage() {
+    foo()
+}
+
+// FILE: dependency.kt
+package dependency
+
+fun foo() {}

idea/idea-frontend-fir/tests/org/jetbrains/kotlin/idea/fir/frontend/api/components/AbstractHLImportOptimizerTest.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.fir.frontend.api.components
+
+import org.jetbrains.kotlin.idea.fir.frontend.api.test.framework.AbstractHLApiSingleModuleTest
+import org.jetbrains.kotlin.idea.frontend.api.analyse
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.test.model.TestModule
+import org.jetbrains.kotlin.test.services.TestServices
+import org.jetbrains.kotlin.test.services.assertions
+
+abstract class AbstractHLImportOptimizerTest : AbstractHLApiSingleModuleTest() {
+    override fun doTestByFileStructure(ktFiles: List<KtFile>, module: TestModule, testServices: TestServices) {
+        val mainKtFile = ktFiles.singleOrNull() ?: ktFiles.first { it.name == "main.kt" }
+        val unusedImports = analyse(mainKtFile) { analyseImports(mainKtFile).unusedImports }
+
+        val unusedImportPaths = unusedImports
+            .map { it.importPath ?: error("Import $it should have an import path, instead was ${it.text}") }
+            .sortedBy { it.toString() } // for stable results
+
+        val actualUnusedImports = buildString {
+            unusedImportPaths.forEach(::appendLine)
+        }
+
+        val expectedUnusedImports = testDataFileSibling(".imports")
+
+        testServices.assertions.assertEqualsToFile(expectedUnusedImports, actualUnusedImports)
+    }
+}

idea/idea-frontend-fir/tests/org/jetbrains/kotlin/idea/fir/frontend/api/components/HLImportOptimizerTestGenerated.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.fir.frontend.api.components;
+
+import com.intellij.testFramework.TestDataPath;
+import org.jetbrains.kotlin.test.util.KtTestUtil;
+import org.jetbrains.kotlin.test.TestMetadata;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.util.regex.Pattern;
+
+/** This class is generated by {@link GenerateNewCompilerTests.kt}. DO NOT MODIFY MANUALLY */
+@SuppressWarnings("all")
+@TestMetadata("idea/idea-frontend-fir/testData/components/importOptimizer")
+@TestDataPath("$PROJECT_ROOT")
+public class HLImportOptimizerTestGenerated extends AbstractHLImportOptimizerTest {
+    @Test
+    public void testAllFilesPresentInImportOptimizer() throws Exception {
+        KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("idea/idea-frontend-fir/testData/components/importOptimizer"), Pattern.compile("^([^.]+)\\.kt$"), null, true);
+    }
+
+    @Test
+    @TestMetadata("unusedFunctionImports.kt")
+    public void testUnusedFunctionImports() throws Exception {
+        runTest("idea/idea-frontend-fir/testData/components/importOptimizer/unusedFunctionImports.kt");
+    }
+
+    @Test
+    @TestMetadata("usedFunctionImport.kt")
+    public void testUsedFunctionImport() throws Exception {
+        runTest("idea/idea-frontend-fir/testData/components/importOptimizer/usedFunctionImport.kt");
+    }
+}