[vscode] support for 'pathSeparator' variable substitution

[alex-gilin]

Signed-off-by: Alexander Gilin alexander.gilin@sap.com

What it does

vscode alignment: allow using the predefined variable ${pathSeparator} (the character used by the operating system to separate components in file paths) in Debugging and Task configuration files

How to test

Variable substitution is supported inside key and value strings in launch.json and tasks.json files.
Expecting result: ${pathSeparator} - / on macOS or linux, \ on Windows

• create simple "Hello World" TypeScript project like follows:
  create an empty folder "myProject", generate a tsconfig.json file and open that folder in theia:
  mkdir myProject
cd myProject
tsc --init
  Now create a 'HelloWorld.ts' file with the following content:
  function sayHello(name: string): void {
console.log('Hello ' + name + '!');
}

  sayHello('Dave');

• compile the code : tsc -p .

• open debug view -> Add configuration -> Node.js Launch Program
  In the created configuration change a path to the program like next:
  "program": "${workspaceFolder}${pathSeparator}helloworld.js"

• run this configuration and verify the program path is resolved correctly.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to review in accordance with the review guidelines

[amiramw]

@alex-gilin please follow open PR template

[kittaakos]

Out of curiosity, what's the intention here? So if the backend is a Linux machine and the frontend is running on a Windows node, what do you want to see: \\ or /?

If you need the backend OS, you have to use:

theia/packages/core/src/node/application-server.ts

Lines 45 to 47 in f1d4690

	async getBackendOS(): Promise<OS.Type> {
	return OS.type();
	}

If you were aware of all these 👆 , just ignore my comment. 😊

[alex-gilin]

@kittaakos
I agree, good point. Updated.

[kittaakos]

I would do like this, to make sure the backend OS is resolved by the time you register the variables. I did not debug into your code, but your isWindowsBackend variable could give a false-negative result because it is not yet resolved by the time you're doing the variable registration.

diff --git a/packages/variable-resolver/src/browser/common-variable-contribution.ts b/packages/variable-resolver/src/browser/common-variable-contribution.ts
index 318f87d3c..b755f9a81 100644
--- a/packages/variable-resolver/src/browser/common-variable-contribution.ts
+++ b/packages/variable-resolver/src/browser/common-variable-contribution.ts
@@ -24,6 +24,8 @@ import { VariableInput } from './variable-input';
 import { QuickInputService } from '@theia/core/lib/browser/quick-open/quick-input-service';
 import { QuickPickService, QuickPickItem } from '@theia/core/lib/common/quick-pick-service';
 import { MaybeArray, RecursivePartial } from '@theia/core/lib/common/types';
+import { ApplicationServer } from '@theia/core/lib/common/application-protocol';
+import { OS } from '@theia/core/lib/common/os';
 
 @injectable()
 export class CommonVariableContribution implements VariableContribution {
@@ -46,8 +48,18 @@ export class CommonVariableContribution implements VariableContribution {
     @inject(QuickPickService)
     protected readonly quickPickService: QuickPickService;
 
+    @inject(ApplicationServer)
+    protected readonly appServer: ApplicationServer;
+
     async registerVariables(variables: VariableRegistry): Promise<void> {
-        const execPath = await this.env.getExecPath();
+        const [execPath, backendOS] = await Promise.all([
+            this.env.getExecPath(),
+            this.appServer.getBackendOS()
+        ]);
+        variables.registerVariable({
+            name: 'pathSeparator',
+            resolve: () => backendOS === OS.Type.Windows ? '\\' : '/'
+        });
         variables.registerVariable({
             name: 'execPath',
             resolve: () => execPath

[alex-gilin]

@kittaakos ,
in my approach I relied on 'postConstruct' invocation order. But anyhow, your proposal better :)

[kittaakos]

👍 Thank you for the patch, @alex-gilin