Wizard: validate project path for emptiness

#KT-38567 fixed

libraries/tools/new-project-wizard/resources/messages/KotlinNewProjectWizardBundle.properties

@@ -40,6 +40,7 @@ project.kind.singleplatform=Singleplatform project
 project=Project
 
 plugin.structure.setting.location=Location
+plugin.structure.setting.location.error.is.not.empty=Directory is not empty
 plugin.structure.setting.name=Name
 plugin.structure.setting.group.id=Group ID
 plugin.structure.setting.artifact.id=Artifact ID

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/core/entity/settings/Setting.kt

@@ -23,7 +23,8 @@ interface Setting<out V : Any, out T : SettingType<V>> : Entity, ActivityChecker
     val defaultValue: SettingDefaultValue<V>?
     val isRequired: Boolean
     val isSavable: Boolean
-    var neededAtPhase: GenerationPhase
+    val neededAtPhase: GenerationPhase
+    val validateOnProjectCreation: Boolean
     val type: T
 }
 
@@ -34,8 +35,9 @@ data class InternalSetting<out V : Any, out T : SettingType<V>>(
     override val isAvailable: Checker,
     override val isRequired: Boolean,
     override val isSavable: Boolean,
-    override var neededAtPhase: GenerationPhase,
+    override val neededAtPhase: GenerationPhase,
     override val validator: SettingValidator<@UnsafeVariance V>,
+    override val validateOnProjectCreation: Boolean,
     override val type: T
 ) : Setting<V, T>, EntityWithValue<V>()
 

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/core/entity/settings/SettingBuilder.kt

@@ -19,6 +19,8 @@ abstract class SettingBuilder<V : Any, T : SettingType<V>>(
 ) {
     var isAvailable: Reader.() -> Boolean = { true }
     open var defaultValue: SettingDefaultValue<V>? = null
+
+    var validateOnProjectCreation = true
     var isSavable: Boolean = false
     var isRequired: Boolean? = null
 
@@ -51,6 +53,7 @@ abstract class SettingBuilder<V : Any, T : SettingType<V>>(
         isSavable = isSavable,
         neededAtPhase = neededAtPhase,
         validator = validator,
+        validateOnProjectCreation = validateOnProjectCreation,
         type = type
     )
 }

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/plugins/StructurePlugin.kt

@@ -4,12 +4,14 @@ package org.jetbrains.kotlin.tools.projectWizard.plugins
 import org.jetbrains.kotlin.tools.projectWizard.KotlinNewProjectWizardBundle
 import org.jetbrains.kotlin.tools.projectWizard.core.*
 import org.jetbrains.kotlin.tools.projectWizard.core.entity.StringValidators
+import org.jetbrains.kotlin.tools.projectWizard.core.entity.ValidationResult
 import org.jetbrains.kotlin.tools.projectWizard.core.entity.settings.reference
 import org.jetbrains.kotlin.tools.projectWizard.core.service.FileSystemWizardService
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.PomIR
 import org.jetbrains.kotlin.tools.projectWizard.phases.GenerationPhase
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Module
 import org.jetbrains.kotlin.tools.projectWizard.settings.version.Version
+import java.nio.file.Files
 import java.nio.file.Paths
 
 class StructurePlugin(context: Context) : Plugin(context) {
@@ -18,6 +20,15 @@ class StructurePlugin(context: Context) : Plugin(context) {
         GenerationPhase.FIRST_STEP
     ) {
         defaultValue = value(Paths.get("."))
+
+        validateOnProjectCreation = false
+
+        validate { path ->
+            if (!Files.exists(path)) return@validate ValidationResult.OK
+            ValidationResult.create(Files.list(path).noneMatch { true }) {
+                KotlinNewProjectWizardBundle.message("plugin.structure.setting.location.error.is.not.empty")
+            }
+        }
     }
     val name by stringSetting(
         KotlinNewProjectWizardBundle.message("plugin.structure.setting.name"),

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/wizard/Wizard.kt

@@ -42,7 +42,7 @@ abstract class Wizard(createPlugins: PluginsCreator, servicesManager: ServicesMa
     fun validate(phases: Set<GenerationPhase>): ValidationResult = context.read {
         pluginSettings.map { setting ->
             val value = setting.reference.notRequiredSettingValue ?: return@map ValidationResult.OK
-            if (setting.neededAtPhase in phases && setting.isActive(this))
+            if (setting.validateOnProjectCreation && setting.neededAtPhase in phases && setting.isActive(this))
                 (setting.validator as SettingValidator<Any>).validate(this, value)
             else ValidationResult.OK
         }.fold()