fixed npe in UnusedImport check (#507)

* fixed npe in UnusedImport check

Author: AlexHaxe

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Added related messages to reporters for `CodeSimilarity` check ([#506](https://github.com/HaxeCheckstyle/haxe-checkstyle/issues/506))
 - Fixed Haxe nightly compilation ([#505](https://github.com/HaxeCheckstyle/haxe-checkstyle/issues/505))
+- Fixed null pointer exception in `UnusedImport` check ([#507](https://github.com/HaxeCheckstyle/haxe-checkstyle/issues/507))
 - Updated to Haxe 4.1.5 ([#505](https://github.com/HaxeCheckstyle/haxe-checkstyle/issues/505))
 
 ## version 2.7.0 (2020-12-23)

src/checkstyle/checks/imports/UnusedImportCheck.hx

@@ -81,6 +81,9 @@ class UnusedImportCheck extends Check {
 		return root.filterCallback(function(token:TokenTree, depth:Int):FilterResult {
 			return switch (token.tok) {
 				case Kwd(KwdImport):
+					if (TokenTreeCheckUtils.isMetadata(token)) {
+						return SkipSubtree;
+					}
 					FoundGoDeeper;
 				default:
 					GoDeeper;
@@ -116,6 +119,7 @@ class UnusedImportCheck extends Check {
 		var moduleName:StringBuf = new StringBuf();
 
 		while (true) {
+			if (token == null) return moduleName.toString();
 			switch (token.tok) {
 				case Binop(OpMult):
 					return null;
@@ -140,6 +144,7 @@ class UnusedImportCheck extends Check {
 	function detectTypeName(token:TokenTree):String {
 		var lastName:String = null;
 		while (true) {
+			if (token == null) return lastName;
 			switch (token.tok) {
 				case Binop(OpMult):
 					return null;

test/checkstyle/checks/imports/UnusedImportCheckTest.hx

@@ -18,6 +18,7 @@ class UnusedImportCheckTest extends CheckTestCase<UnusedImportCheckTests> {
 		assertNoMsg(check, IMPORT_BASE_CLASS);
 		assertNoMsg(check, IMPORT_AS);
 		assertNoMsg(check, IMPORT_IN_STATIC_FUNC);
+		assertNoMsg(check, METADATA_IMPORT);
 	}
 
 	@Test
@@ -258,4 +259,11 @@ enum abstract UnusedImportCheckTests(String) to String {
 			trace ('${Check3}');
 		}
 	}";
+	var METADATA_IMPORT = "
+	abstractAndClass Test {
+		private static var SRC =
+        {
+            @:import h3d.shader.BaseMesh;
+        };
+	}";
 }