Do not generate violation for empty SuppressWarnings. #1187

pom.xml

@@ -685,7 +685,7 @@
           <regex><pattern>.*.checks.DescendantTokenCheck</pattern><branchRate>91</branchRate><lineRate>96</lineRate></regex>
           <regex><pattern>.*.checks.NewlineAtEndOfFileCheck</pattern><branchRate>83</branchRate><lineRate>88</lineRate></regex>
           <regex><pattern>.*.checks.OuterTypeFilenameCheck</pattern><branchRate>71</branchRate><lineRate>92</lineRate></regex>
-          <regex><pattern>.*.checks.SuppressWarningsHolder</pattern><branchRate>70</branchRate><lineRate>90</lineRate></regex>
+          <regex><pattern>.*.checks.SuppressWarningsHolder</pattern><branchRate>75</branchRate><lineRate>93</lineRate></regex>
           <regex><pattern>.*.checks.TodoCommentCheck</pattern><branchRate>100</branchRate><lineRate>92</lineRate></regex>
           <regex><pattern>.*.checks.TrailingCommentCheck</pattern><branchRate>90</branchRate><lineRate>93</lineRate></regex>
           <regex><pattern>.*.checks.TranslationCheck</pattern><branchRate>81</branchRate><lineRate>83</lineRate></regex>

src/main/java/com/puppycrawl/tools/checkstyle/checks/SuppressWarningsHolder.java

@@ -263,8 +263,7 @@ public class SuppressWarningsHolder
                     }
                 }
             }
-            if (values == null) {
-                log(ast, "suppress.warnings.missing.value");
+            if (isAnnotationEmpty(values)) {
                 return;
             }
 
@@ -306,6 +305,14 @@ public class SuppressWarningsHolder
         }
     }
 
+    /**
+     * @param values list of values in the annotation
+     * @return whether annotation is empty or contains some values
+     */
+    private boolean isAnnotationEmpty(List<String> values) {
+        return values == null;
+    }
+
     /**
      * get target of annotation
      * @param ast the AST node to get the child of

src/test/resources/com/puppycrawl/tools/checkstyle/InputSuppressWarningsHolder.java

@@ -28,3 +28,9 @@ public class InputSuppressWarningsHolder {
     @SuppressWarnings({"unused", true ? "unused" : ""})
     int l;
 }
+
+class CustomSuppressWarnings {
+    @SuppressWarnings
+    private @interface SuppressWarnings {
+    }
+}