[vscode] support for 'pathSeparator' variable substitution,

where ${pathSeparator} - / on macOS or linux, \\ on Windows

Signed-off-by: Alex Gilin <alexander.gilin@sap.com>

packages/variable-resolver/src/browser/common-variable-contribution.ts

@@ -14,10 +14,12 @@
  * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
  ********************************************************************************/
 
-import { injectable, inject } from 'inversify';
+import { injectable, inject, postConstruct } from 'inversify';
 import { VariableContribution, VariableRegistry } from './variable';
+import { ApplicationServer } from '@theia/core/lib/common/application-protocol';
 import { EnvVariablesServer } from '@theia/core/lib/common/env-variables';
 import { CommandService } from '@theia/core/lib/common/command';
+import { OS } from '@theia/core/lib/common/os';
 import { PreferenceService } from '@theia/core/lib/browser/preferences/preference-service';
 import { ResourceContextKey } from '@theia/core/lib/browser/resource-context-key';
 import { VariableInput } from './variable-input';
@@ -46,6 +48,18 @@ export class CommonVariableContribution implements VariableContribution {
     @inject(QuickPickService)
     protected readonly quickPickService: QuickPickService;
 
+    @inject(ApplicationServer)
+    protected readonly applicationServer!: ApplicationServer;
+
+    private isWindowsBackend: boolean;
+
+    @postConstruct()
+    public init(): void {
+        this.applicationServer.getBackendOS().then(os => {
+            this.isWindowsBackend = os === OS.Type.Windows;
+        });
+    }
+
     async registerVariables(variables: VariableRegistry): Promise<void> {
         const execPath = await this.env.getExecPath();
         variables.registerVariable({
@@ -129,6 +143,10 @@ export class CommonVariableContribution implements VariableContribution {
                 return undefined;
             }
         });
+        variables.registerVariable({
+            name: 'pathSeparator',
+            resolve: () => this.isWindowsBackend ? '\\' : '/'
+        });
     }
 
 }