Fix creator ClassFqn suggestion and validation

This catches more invalid FQNs parts

src/main/kotlin/creator/custom/BuiltinValidations.kt

@@ -23,11 +23,13 @@ package com.demonwav.mcdev.creator.custom
 import com.demonwav.mcdev.asset.MCDevBundle
 import com.demonwav.mcdev.platform.fabric.util.FabricVersions
 import com.demonwav.mcdev.util.SemanticVersion
+import com.intellij.lang.java.lexer.JavaLexer
 import com.intellij.openapi.ui.ComboBox
 import com.intellij.openapi.ui.ValidationInfo
 import com.intellij.openapi.ui.validation.DialogValidation
 import com.intellij.openapi.ui.validation.validationErrorIf
 import com.intellij.openapi.util.text.StringUtil
+import com.intellij.pom.java.LanguageLevel
 import javax.swing.JComponent
 
 object BuiltinValidations {
@@ -58,7 +60,9 @@ object BuiltinValidations {
     }
 
     val validClassFqn = validationErrorIf<String>(MCDevBundle("creator.validation.class_fqn")) {
-        it.isBlank() || it.split('.').any { part -> !StringUtil.isJavaIdentifier(part) }
+        it.isBlank() || it.split('.').any { part ->
+            !StringUtil.isJavaIdentifier(part) || JavaLexer.isKeyword(part, LanguageLevel.HIGHEST)
+        }
     }
 
     fun byRegex(regex: Regex): DialogValidation.WithParameter<() -> String> =

src/main/kotlin/creator/custom/derivation/SuggestClassNamePropertyDerivation.kt

@@ -33,11 +33,14 @@ class SuggestClassNamePropertyDerivation : PreparedDerivation {
     override fun derive(parentValues: List<Any?>): Any? {
         val coords = parentValues[0] as BuildSystemCoordinates
         val name = parentValues[1] as String
-        return ClassFqn("${coords.groupId}.${name.decapitalize()}.${name.capitalize()}")
+        val sanitizedName = name.split(NOT_JAVA_IDENTIFIER).joinToString("", transform = String::capitalize)
+        return ClassFqn("${coords.groupId}.${sanitizedName.decapitalize()}.$sanitizedName")
     }
 
     companion object : PropertyDerivationFactory {
 
+        private val NOT_JAVA_IDENTIFIER = Regex("\\P{javaJavaIdentifierPart}+")
+
         override fun create(
             reporter: TemplateValidationReporter,
             parents: List<CreatorProperty<*>?>?,

src/test/kotlin/creator/ClassFqnCreatorPropertyTest.kt

@@ -0,0 +1,101 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2024 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.creator
+
+import com.demonwav.mcdev.creator.custom.BuiltinValidations
+import com.demonwav.mcdev.creator.custom.TemplateDescriptor
+import com.demonwav.mcdev.creator.custom.model.BuildSystemCoordinates
+import com.demonwav.mcdev.creator.custom.model.ClassFqn
+import com.intellij.openapi.ui.validation.invoke
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNotNull
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+
+@DisplayName("Class FQN Creator Property Tests")
+class ClassFqnCreatorPropertyTest : CreatorTemplateProcessorTestBase() {
+
+    private fun checkValidation(input: String, expectedMessage: String?) {
+        val validation = BuiltinValidations.validClassFqn { input }
+        val validationInfo = validation.validate()
+        if (expectedMessage == null) {
+            assertNull(validationInfo?.message) { "Expected input to be valid: '$input'" }
+        } else {
+            assertNotNull(validationInfo, "Expected input to be invalid: '$input'")
+            assertEquals(expectedMessage, validationInfo!!.message)
+        }
+    }
+
+    @Test
+    @DisplayName("Validation")
+    fun validation() {
+        checkValidation("test.TestName", null)
+        val invalidFqns = listOf(
+            "test.0InvalidName",
+            "test.Invalid-Name",
+            "test.package.InvalidPackage",
+            "test..InvalidPackage",
+            "test."
+        )
+        for (fqn in invalidFqns) {
+            checkValidation(fqn, "Must be a valid class fully qualified name")
+        }
+    }
+
+    @Test
+    @DisplayName("Class Name Suggestion")
+    fun classNameSuggestion() {
+        makeTemplate(
+            """
+            {
+              "version": ${TemplateDescriptor.FORMAT_VERSION},
+              "properties": [
+                {
+                  "name": "BUILD_COORDS",
+                  "type": "build_system_coordinates"
+                },
+                {
+                  "name": "NAME",
+                  "type": "string"
+                },
+                {
+                  "name": "FQN",
+                  "type": "class_fqn",
+                  "derives": {
+                    "method": "suggestClassName",
+                    "parents": ["BUILD_COORDS", "NAME"]
+                  }
+                }
+              ]
+            }
+            """.trimIndent()
+        )
+
+        val buildCoordsProperty = processor.context.property<BuildSystemCoordinates>("BUILD_COORDS")
+        val nameProperty = processor.context.property<String>("NAME")
+        val fqnProperty = processor.context.property<ClassFqn>("FQN")
+
+        buildCoordsProperty.graphProperty.set(BuildSystemCoordinates("com.example.project", "example-project", "1.0"))
+        nameProperty.graphProperty.set("My Project")
+        assertEquals(ClassFqn("com.example.project.myProject.MyProject"), fqnProperty.get())
+    }
+}