Report error on non-existent classpath in -Xplugin

#KT-52380 Fixed

compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.kt

@@ -24,6 +24,7 @@ import org.jetbrains.kotlin.cli.common.ExitCode.*
 import org.jetbrains.kotlin.cli.common.arguments.CommonCompilerArguments
 import org.jetbrains.kotlin.cli.common.environment.setIdeaIoUseFallback
 import org.jetbrains.kotlin.cli.common.messages.*
+import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity.ERROR
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity.INFO
 import org.jetbrains.kotlin.cli.jvm.plugins.PluginCliParser
 import org.jetbrains.kotlin.compiler.plugin.ComponentRegistrar
@@ -161,8 +162,15 @@ abstract class CLICompiler<A : CommonCompilerArguments> : CLITool<A>() {
     protected abstract fun MutableList<String>.addPlatformOptions(arguments: A)
 
     protected fun loadPlugins(paths: KotlinPaths?, arguments: A, configuration: CompilerConfiguration): ExitCode {
-        var pluginClasspaths: Iterable<String> = arguments.pluginClasspaths?.asIterable() ?: emptyList()
-        val pluginOptions = arguments.pluginOptions?.toMutableList() ?: ArrayList()
+        val pluginClasspaths = arguments.pluginClasspaths.orEmpty().toMutableList()
+        val pluginOptions = arguments.pluginOptions.orEmpty().toMutableList()
+        val messageCollector = configuration.getNotNull(MESSAGE_COLLECTOR_KEY)
+
+        for (classpath in pluginClasspaths) {
+            if (!File(classpath).exists()) {
+                messageCollector.report(ERROR, "Plugin classpath entry points to a non-existent location: $classpath")
+            }
+        }
 
         if (!arguments.disableDefaultScriptingPlugin) {
             val explicitOrLoadedScriptingPlugin =
@@ -174,9 +182,8 @@ abstract class CLICompiler<A : CommonCompilerArguments> : CLITool<A>() {
                 val (jars, missingJars) =
                     PathUtil.KOTLIN_SCRIPTING_PLUGIN_CLASSPATH_JARS.map { File(libPath, it) }.partition { it.exists() }
                 if (missingJars.isEmpty()) {
-                    pluginClasspaths = jars.map { it.canonicalPath } + pluginClasspaths
+                    pluginClasspaths.addAll(0, jars.map { it.canonicalPath })
                 } else {
-                    val messageCollector = configuration.getNotNull(MESSAGE_COLLECTOR_KEY)
                     messageCollector.report(
                         CompilerMessageSeverity.LOGGING,
                         "Scripting plugin will not be loaded: not all required jars are present in the classpath (missing files: $missingJars)"

compiler/testData/cli/jvm/extraArgumentPassedInObsoleteForm.args

@@ -1,5 +1,5 @@
--Xplugin
-non-existing-file.jar
+-Xjsr305
+strict
 $TESTDATA_DIR$/simple.kt
 -d
 $TEMP_DIR$

compiler/testData/cli/jvm/extraArgumentPassedInObsoleteForm.out

@@ -1,2 +1,2 @@
-warning: advanced option value is passed in an obsolete form. Please use the '=' character to specify the value: -Xplugin=...
+warning: advanced option value is passed in an obsolete form. Please use the '=' character to specify the value: -Xjsr305=...
 OK

compiler/testData/cli/jvm/nonExistingPluginClassPath.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/simple.kt
+-d
+$TEMP_DIR$
+-Xplugin=/non-existing-path

compiler/testData/cli/jvm/nonExistingPluginClassPath.out

@@ -0,0 +1,2 @@
+error: plugin classpath entry points to a non-existent location: /non-existing-path
+COMPILATION_ERROR

compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java

@@ -784,6 +784,11 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/nonExistingPhaseName.args");
         }
 
+        @TestMetadata("nonExistingPluginClassPath.args")
+        public void testNonExistingPluginClassPath() throws Exception {
+            runTest("compiler/testData/cli/jvm/nonExistingPluginClassPath.args");
+        }
+
         @TestMetadata("nonExistingSourcePath.args")
         public void testNonExistingSourcePath() throws Exception {
             runTest("compiler/testData/cli/jvm/nonExistingSourcePath.args");