Avoid class-name based contribution filtering

Update example to avoid class name based contribution filtering.
Class names are minified in production which breaks the contribution filter.

Use instance of check instead. 
Also mention this in the `FilterContribution` JS-Doc

examples/api-samples/src/browser/contribution-filter/sample-filtered-command-contribution.ts

@@ -14,7 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
-import { Command, CommandContribution, CommandRegistry, FilterContribution, ContributionFilterRegistry, bindContribution, Filter } from '@theia/core/lib/common';
+import { Command, CommandContribution, CommandRegistry, ContributionFilterRegistry, FilterContribution, bindContribution } from '@theia/core/lib/common';
 import { injectable, interfaces } from '@theia/core/shared/inversify';
 
 export namespace SampleFilteredCommand {
@@ -58,8 +58,8 @@ export class SampleFilterAndCommandContribution implements FilterContribution, C
             contrib => contrib.constructor !== this.constructor
         ]);
         registry.addFilters('*', [
-            // filter a contribution based on its class name
-            filterClassName(name => name !== 'SampleFilteredCommandContribution')
+            // filter a contribution based on its class type
+            contrib => !(contrib instanceof SampleFilteredCommandContribution)
         ]);
     }
 }
@@ -69,12 +69,3 @@ export function bindSampleFilteredCommandContribution(bind: interfaces.Bind): vo
     bind(SampleFilterAndCommandContribution).toSelf().inSingletonScope();
     bindContribution(bind, SampleFilterAndCommandContribution, [CommandContribution, FilterContribution]);
 }
-
-function filterClassName(filter: Filter<string>): Filter<Object> {
-    return object => {
-        const className = object?.constructor?.name;
-        return className
-            ? filter(className)
-            : false;
-    };
-}

packages/core/src/common/contribution-filter/contribution-filter.ts

@@ -50,6 +50,15 @@ export const FilterContribution = Symbol('FilterContribution');
 export interface FilterContribution {
     /**
      * Use the registry to register your contribution filters.
+     * * Note that filtering contributions based on their class (constructor) name is discouraged.
+     * Class names are minified in production builds and therefore not reliable.
+     * Use instance of checks or direct constructor comparison instead:
+     *
+     * ```ts
+     * registry.addFilters('*', [
+     *     contrib => !(contrib instanceof SampleFilteredCommandContribution)
+     * ]);
+     * ```
      */
     registerContributionFilters(registry: ContributionFilterRegistry): void;
 }