Restore original settings after disabling ISE mode (#4308)

We were previously setting them to `undefined` which mostly worked,
unless the user had customized the setting. This was most apparent and
commonly done with `colorTheme`. Now we save when we enable, and restore
to that value. Note that will only work for the original session, but it
does allow the user to test ISE mode out without repercussions.

We could probably save the settings into the global storage context, but
that might get hairy!

Author: andyleejordan

src/features/ISECompatibility.ts

@@ -28,6 +28,7 @@ export class ISECompatibilityFeature implements vscode.Disposable {
 
     private _commandRegistrations: vscode.Disposable[] = [];
     private _iseModeEnabled: boolean;
+    private _originalSettings: Record<string, boolean | string | undefined> = {};
 
     constructor() {
         // TODO: This test isn't great.
@@ -50,7 +51,9 @@ export class ISECompatibilityFeature implements vscode.Disposable {
         this._iseModeEnabled = true;
         for (const iseSetting of ISECompatibilityFeature.settings) {
             try {
-                await vscode.workspace.getConfiguration(iseSetting.path).update(iseSetting.name, iseSetting.value, true);
+                const config = vscode.workspace.getConfiguration(iseSetting.path);
+                this._originalSettings[iseSetting.path + iseSetting.name] = config.get(iseSetting.name);
+                await config.update(iseSetting.name, iseSetting.value, true);
             } catch {
                 // The `update` call can fail if the setting doesn't exist. This
                 // happens when the extension runs in Azure Data Studio, which
@@ -72,9 +75,10 @@ export class ISECompatibilityFeature implements vscode.Disposable {
     private async DisableISEMode() {
         this._iseModeEnabled = false;
         for (const iseSetting of ISECompatibilityFeature.settings) {
-            const currently = vscode.workspace.getConfiguration(iseSetting.path).get<string | boolean>(iseSetting.name);
+            const config = vscode.workspace.getConfiguration(iseSetting.path);
+            const currently = config.get(iseSetting.name);
             if (currently === iseSetting.value) {
-                await vscode.workspace.getConfiguration(iseSetting.path).update(iseSetting.name, undefined, true);
+                await config.update(iseSetting.name, this._originalSettings[iseSetting.path + iseSetting.name], true);
             }
         }
     }