Only expose event to subclasses, instead of event emitter

extensions/ql-vscode/src/common/vscode/file-path-discovery.ts

@@ -1,5 +1,6 @@
 import { Discovery } from "../discovery";
 import {
+  Event,
   EventEmitter,
   RelativePattern,
   Uri,
@@ -36,7 +37,7 @@ export abstract class FilePathDiscovery<T extends PathData> extends Discovery {
   private pathData: T[] = [];
 
   /** Event that fires whenever the contents of `pathData` changes */
-  protected readonly onDidChangePathDataEmitter: AppEventEmitter<void>;
+  private readonly onDidChangePathDataEmitter: AppEventEmitter<void>;
 
   /**
    * The set of file paths that may have changed on disk since the last time
@@ -75,6 +76,10 @@ export abstract class FilePathDiscovery<T extends PathData> extends Discovery {
     return this.pathData;
   }
 
+  protected get onDidChangePathData(): Event<void> {
+    return this.onDidChangePathDataEmitter.event;
+  }
+
   /**
    * Compute any extra data to be stored regarding the given path.
    */

extensions/ql-vscode/src/queries-panel/query-discovery.ts

@@ -48,7 +48,7 @@ export class QueryDiscovery
    * Event that fires when the set of queries in the workspace changes.
    */
   public get onDidChangeQueries(): Event<void> {
-    return this.onDidChangePathDataEmitter.event;
+    return this.onDidChangePathData;
   }
 
   /**

extensions/ql-vscode/src/queries-panel/query-pack-discovery.ts

@@ -27,7 +27,7 @@ export class QueryPackDiscovery extends FilePathDiscovery<QueryPack> {
    * Event that fires when the set of query packs in the workspace changes.
    */
   public get onDidChangeQueryPacks(): Event<void> {
-    return this.onDidChangePathDataEmitter.event;
+    return this.onDidChangePathData;
   }
 
   /**

extensions/ql-vscode/test/vscode-tests/minimal-workspace/common/vscode/file-path-discovery.test.ts

@@ -25,7 +25,7 @@ class TestFilePathDiscovery extends FilePathDiscovery<TestData> {
   }
 
   public get onDidChangePaths() {
-    return this.onDidChangePathDataEmitter.event;
+    return this.onDidChangePathData;
   }
 
   public getPathData(): readonly TestData[] {