[JENKINS-64445] - Fix null safety for plugin categories (#5121)

* [JENKINS-64445] - Fix null safety for plugin categories

* Update core/src/main/java/hudson/model/UpdateSite.java

Co-authored-by: Ramon Leon <manuelramonleonjimenez@gmail.com>

* Update core/src/main/java/hudson/model/UpdateSite.java

Co-authored-by: Ramon Leon <manuelramonleonjimenez@gmail.com>

core/src/main/java/hudson/PluginManager.java

@@ -1363,8 +1363,8 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                     return StringUtils.containsIgnoreCase(plugin.name, query) ||
                         StringUtils.containsIgnoreCase(plugin.title, query) ||
                         StringUtils.containsIgnoreCase(plugin.excerpt, query) ||
-                        Arrays.asList(plugin.categories).contains(query) ||
-                        Arrays.stream(plugin.categories)
+                        plugin.hasCategory(query) ||
+                        plugin.getCategoriesStream()
                             .map(UpdateCenter::getCategoryDisplayName)
                             .anyMatch(category -> StringUtils.containsIgnoreCase(category, query)) ||
                         plugin.hasWarnings() && query.equalsIgnoreCase("warning:");
@@ -1396,7 +1396,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                     jsonObject.put("title", plugin.title);
                     jsonObject.put("displayName", plugin.getDisplayName());
                     jsonObject.put("wiki", plugin.wiki);
-                    jsonObject.put("categories", Arrays.stream(plugin.categories)
+                    jsonObject.put("categories", plugin.getCategoriesStream()
                         .filter(PluginManager::isNonMetaLabel)
                         .map(UpdateCenter::getCategoryDisplayName)
                         .collect(toList())
@@ -2406,11 +2406,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
 
     @Restricted(DoNotUse.class) // Used from table.jelly
     public boolean hasAdoptThisPluginLabel(UpdateSite.Plugin plugin) {
-        final String[] categories = plugin.categories;
-        if (categories == null) {
-            return false;
-        }
-        return Arrays.asList(categories).contains("adopt-this-plugin");
+        return plugin.hasCategory("adopt-this-plugin");
     }
 
     @Restricted(DoNotUse.class) // Used from table.jelly
@@ -2427,11 +2423,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
         if (pluginMeta == null) {
             return false;
         }
-        final String[] categories = pluginMeta.categories;
-        if (categories == null) {
-            return false;
-        }
-        return Arrays.asList(categories).contains("adopt-this-plugin");
+        return pluginMeta.hasCategory("adopt-this-plugin");
     }
 
     /**

core/src/main/java/hudson/model/UpdateSite.java

@@ -66,6 +66,8 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
+import java.util.stream.Stream;
+
 import edu.umd.cs.findbugs.annotations.CheckForNull;
 import edu.umd.cs.findbugs.annotations.NonNull;
 import edu.umd.cs.findbugs.annotations.Nullable;
@@ -626,11 +628,9 @@ public class UpdateSite {
 
                 // compatibility with update sites that have no separate 'deprecated' top-level entry.
                 // Also do this even if there are deprecations to potentially allow limiting the top-level entry to overridden URLs.
-                if (p.categories != null) {
-                    if (Arrays.asList(p.categories).contains("deprecated")) {
-                        if (!this.deprecations.containsKey(p.name)) {
-                            this.deprecations.put(p.name, new Deprecation(p.wiki));
-                        }
+                if (p.hasCategory("deprecated")) {
+                    if (!this.deprecations.containsKey(p.name)) {
+                        this.deprecations.put(p.name, new Deprecation(p.wiki));
                     }
                 }
             }
@@ -1091,9 +1091,10 @@ public class UpdateSite {
         public final String minimumJavaVersion;
         /**
          * Categories for grouping plugins, taken from labels assigned to wiki page.
-         * Can be null.
+         * Can be {@code null} if the update center does not return categories.
          */
         @Exported
+        @CheckForNull
         public final String[] categories;
 
         /**
@@ -1510,6 +1511,26 @@ public class UpdateSite {
             return warnings;
         }
 
+        /**
+         * Checks whether a plugin has a desired category
+         * @since TODO
+         */
+        public boolean hasCategory(String category) {
+            if (categories == null) {
+                return false;
+            }
+            // TODO: cache it in a hashset for performance improvements
+            return Arrays.asList(categories).contains(category);
+        }
+
+        /**
+         * Get categories stream for further search.
+         * @since TODO
+         */
+        public Stream<String> getCategoriesStream() {
+            return categories != null ? Arrays.stream(categories) : Stream.empty();
+        }
+
         /**
          * @since 2.40
          */