Respect the newly added Background analysis scope option in OmniSharp

Related to #5998
This ensures that the Background analysis scope option becomes the source of truth for both C# extension and OmniSharp

Author: mavasani

src/features/diagnosticsProvider.ts

@@ -135,7 +135,11 @@ class OmniSharpDiagnosticsProvider extends AbstractSupport {
     ) {
         super(server, languageMiddlewareFeature);
 
-        this._analyzersEnabled = vscode.workspace.getConfiguration('omnisharp').get('enableRoslynAnalyzers', false);
+        const scopeOption = vscode.workspace
+            .getConfiguration('dotnet')
+            .get<string>('backgroundAnalysis.analyzerDiagnosticsScope', 'openFiles');
+        this._analyzersEnabled =
+            vscode.workspace.getConfiguration('omnisharp').get('enableRoslynAnalyzers', false) && scopeOption != 'none';
         this._validationAdvisor = validationAdvisor;
         this._diagnostics = vscode.languages.createDiagnosticCollection('csharp');
         this._suppressHiddenDiagnostics = vscode.workspace

src/shared/options.ts

@@ -119,7 +119,14 @@ export class Options {
             'omnisharp.useEditorFormattingSettings',
             true
         );
-        const enableRoslynAnalyzers = Options.readOption<boolean>(config, 'omnisharp.enableRoslynAnalyzers', false);
+        const diagnosticAnalysisScope = Options.readOption<string>(
+            config,
+            'dotnet.backgroundAnalysis.analyzerDiagnosticsScope',
+            'openFiles'
+        );
+        const enableRoslynAnalyzers =
+            Options.readOption<boolean>(config, 'omnisharp.enableRoslynAnalyzers', false) &&
+            diagnosticAnalysisScope != 'none';
         const enableEditorConfigSupport = Options.readOption<boolean>(
             config,
             'omnisharp.enableEditorConfigSupport',
@@ -138,11 +145,9 @@ export class Options {
             'omnisharp.enableImportCompletion'
         );
         const enableAsyncCompletion = Options.readOption<boolean>(config, 'omnisharp.enableAsyncCompletion', false);
-        const analyzeOpenDocumentsOnly = Options.readOption<boolean>(
-            config,
-            'omnisharp.analyzeOpenDocumentsOnly',
-            false
-        );
+        const analyzeOpenDocumentsOnly =
+            Options.readOption<boolean>(config, 'omnisharp.analyzeOpenDocumentsOnly', false) ||
+            diagnosticAnalysisScope == 'openFiles';
         const organizeImportsOnFormat = Options.readOption<boolean>(config, 'omnisharp.organizeImportsOnFormat', false);
         const disableMSBuildDiagnosticWarning = Options.readOption<boolean>(
             config,