feat(config): add createDiagnosticsPlugin API (#61)

Author: johnsoncodehk

packages/config/index.ts

@@ -1,4 +1,5 @@
 export * from '@tsslint/types';
+export { create as createDiagnosticsPlugin } from './lib/plugins/diagnostics.js';
 export { create as createIgnorePlugin } from './lib/plugins/ignore.js';
 
 import type { Config, Plugin, Rule } from '@tsslint/types';

packages/config/lib/plugins/diagnostics.ts

@@ -0,0 +1,27 @@
+import type { Plugin } from '@tsslint/types';
+
+type CheckMode = 'syntactic' | 'semantic' | 'declaration';
+
+export function create(mode: CheckMode | CheckMode[] = 'semantic'): Plugin {
+	const modes = Array.isArray(mode) ? mode : [mode];
+	return ({ languageService }) => ({
+		resolveDiagnostics(sourceFile, diagnostics) {
+			const program = languageService.getProgram()!;
+			for (const mode of modes) {
+				const diags = mode === 'syntactic'
+					? program.getSyntacticDiagnostics(sourceFile)
+					: mode === 'semantic'
+						? program.getSemanticDiagnostics(sourceFile)
+						: mode === 'declaration'
+							? program.getDeclarationDiagnostics(sourceFile)
+							: [];
+				for (const diag of diags) {
+					diag.start ??= 0;
+					diag.length ??= 0;
+					diagnostics.push(diag as any);
+				}
+			}
+			return diagnostics;
+		},
+	});
+}