preferences: fix regex incompatible with Firefox

Firefox doesn't handle lookahead/lookbehind patterns in regexes, leading
to Theia applications not starting when ran inside Firefox.

This commit replaces the problematic regex with a method that produces
the same result.

Signed-off-by: Paul Maréchal <paul.marechal@ericsson.com>

packages/preferences/src/browser/util/preference-tree-generator.spec.ts

@@ -0,0 +1,48 @@
+/********************************************************************************
+ * Copyright (C) 2020 Ericsson and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the Eclipse
+ * Public License v. 2.0 are satisfied: GNU General Public License, version 2
+ * with the GNU Classpath Exception which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ ********************************************************************************/
+
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+import { enableJSDOM } from '@theia/core/lib/browser/test/jsdom';
+const disableJSDOM = enableJSDOM();
+
+import { expect } from 'chai';
+import { Container } from 'inversify';
+import { PreferenceTreeGenerator } from './preference-tree-generator';
+import { PreferenceSchemaProvider } from '@theia/core/lib/browser';
+import { PreferenceConfigurations } from '@theia/core/lib/browser/preferences/preference-configurations';
+
+disableJSDOM();
+
+describe('preference-tree-generator', () => {
+
+    let preferenceTreeGenerator: PreferenceTreeGenerator;
+
+    beforeEach(() => {
+        const container = new Container();
+        container.bind<any>(PreferenceSchemaProvider).toConstantValue(undefined);
+        container.bind<any>(PreferenceConfigurations).toConstantValue(undefined);
+        preferenceTreeGenerator = container.resolve(PreferenceTreeGenerator);
+    });
+
+    it('PreferenceTreeGenerator.split', () => {
+        // We want to ensure that our `split` function emulates the following regex properly:
+        const splitter = /[\W_]|(?<=[^A-Z])(?=[A-Z])/;
+        const testString = 'aaaBbb.Ccc d E fff GGGgg_iiiJ0a';
+        expect(preferenceTreeGenerator['split'](testString)).deep.eq(testString.split(splitter));
+    });
+
+});

packages/preferences/src/browser/util/preference-tree-generator.ts

@@ -69,8 +69,7 @@ export class PreferenceTreeGenerator {
     });
 
     protected createLeafNode = (property: string, preferencesGroup: Preference.Branch): SelectableTreeNode => {
-        const splitter = /[\W_]|(?<=[^A-Z])(?=[A-Z])/; // Any non-word character or the 0-length space between a non-upper-case character and an upper-case character
-        const propertySpecifier = property.split(splitter).slice(1);
+        const propertySpecifier = this.split(property).slice(1);
         const name = propertySpecifier.map(word => word.slice(0, 1).toLocaleUpperCase() + word.slice(1)).join(' ').trim();
         return {
             id: property,
@@ -100,11 +99,24 @@ export class PreferenceTreeGenerator {
 
     protected toTitleCase(nonTitle: string): string {
         // Any non-word character or the 0-length space between a non-upper-case character and an upper-case character
-        const splitter = /[\W_]|(?<=[^A-Z])(?=[A-Z])/;
-        return nonTitle.split(splitter).map(word => this.capitalizeFirst(word)).join(' ').trim();
+        return this.split(nonTitle).map(word => this.capitalizeFirst(word)).join(' ').trim();
     }
 
     protected capitalizeFirst(maybeLowerCase: string): string {
         return maybeLowerCase.slice(0, 1).toLocaleUpperCase() + maybeLowerCase.slice(1);
     }
+
+    /**
+     * Split based on any non-word character or the 0-length space between a non-upper-case character and an upper-case character
+     */
+    private split(string: string): string[] {
+        const split: string[] = [];
+        const regex = /[A-Z]+[a-z0-9]*|[A-Z]*[a-z0-9]+/g;
+        // eslint-disable-next-line no-null/no-null
+        let match; while ((match = regex.exec(string)) !== null) {
+            split.push(match[0]);
+        }
+        return split;
+    }
+
 }