core: refine typing of isObject<T>

packages/core/src/browser/shell/shell-layout-restorer.ts

@@ -278,12 +278,12 @@ export class ShellLayoutRestorer implements CommandContribution {
                     });
                 }
                 return widgets;
-            } else if (isObject<Record<string, WidgetDescription>>(value) && !Array.isArray(value)) {
+            } else if (isObject(value) && !Array.isArray(value)) {
                 const copy: Record<string, unknown> = {};
                 for (const p in value) {
                     if (this.isWidgetProperty(p)) {
                         parseContext.push(async context => {
-                            copy[p] = await this.convertToWidget(value[p], context);
+                            copy[p] = await this.convertToWidget(value[p] as WidgetDescription, context);
                         });
                     } else {
                         copy[p] = value[p];

packages/core/src/common/types.ts

@@ -17,6 +17,8 @@
 export { ArrayUtils } from './array-utils';
 export { Prioritizeable } from './prioritizeable';
 
+type UnknownObject = Record<string | number | symbol, unknown>;
+
 export type Deferred<T> = { [P in keyof T]: Promise<T[P]> };
 export type MaybeArray<T> = T | T[];
 export type MaybeNull<T> = { [P in keyof T]: T[P] | null };
@@ -54,7 +56,7 @@ export function isFunction<T extends (...args: unknown[]) => unknown>(value: unk
     return typeof value === 'function';
 }
 
-export function isObject<T = Record<string | number | symbol, unknown>>(value: unknown): value is T {
+export function isObject<T extends object = UnknownObject>(value: unknown): value is UnknownObject & { [K in keyof T]: unknown } {
     // eslint-disable-next-line no-null/no-null
     return typeof value === 'object' && value !== null;
 }

packages/markers/src/browser/problem/problem-selection.ts

@@ -25,7 +25,7 @@ export interface ProblemSelection {
 }
 export namespace ProblemSelection {
     export function is(arg: unknown): arg is ProblemSelection {
-        return isObject<ProblemSelection>(arg) && ProblemMarker.is(arg.marker);
+        return isObject<ProblemSelection>(arg) && Marker.is(arg.marker) && ProblemMarker.is(arg.marker);
     }
 
     export class CommandHandler extends SelectionCommandHandler<ProblemSelection> {

packages/markers/src/common/marker.ts

@@ -14,6 +14,8 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 // *****************************************************************************
 
+import { isObject, isString } from '@theia/core/lib/common/types';
+
 /*
 * A marker represents meta information for a given uri
 */
@@ -37,3 +39,15 @@ export interface Marker<T> {
      */
     data: T;
 }
+export namespace Marker {
+    export function is(value: unknown): value is Marker<object>;
+    export function is<T>(value: unknown, subTypeCheck: (value: unknown) => value is T): value is Marker<T>;
+    export function is(value: unknown, subTypeCheck?: (value: unknown) => boolean): boolean {
+        subTypeCheck ??= isObject;
+        return isObject<Marker<object>>(value)
+            && !Array.isArray(value)
+            && subTypeCheck(value.data)
+            && isString(value.uri)
+            && isString(value.owner);
+    }
+}

packages/plugin-ext/src/plugin/types-impl.ts

@@ -546,6 +546,8 @@ export class Range {
             return true;
         }
         return isObject<theia.Range>(arg)
+            && isObject(arg.start)
+            && isObject(arg.end)
             && Position.isPosition(arg.start)
             && Position.isPosition(arg.end);
     }