Fix realpath exception (#1641)

Co-authored-by: Dirk Bäumer <dirkb@microsoft.com>

server/src/paths.ts

@@ -85,10 +85,16 @@ export function getFileSystemPath(uri: URI): string {
 		result = result[0].toUpperCase() + result.substr(1);
 	}
 	if (process.platform === 'win32' || process.platform === 'darwin') {
-		const realpath = fs.realpathSync.native(result);
-		// Only use the real path if only the casing has changed.
-		if (realpath.toLowerCase() === result.toLowerCase()) {
-			result = realpath;
+		try {
+      const realpath = fs.realpathSync.native(result);
+      // Only use the real path if only the casing has changed.
+      if (realpath.toLowerCase() === result.toLowerCase()) {
+        result = realpath;
+      }
+		} catch {
+			// Silently ignore errors from `fs.realpathSync` to handle scenarios where
+			// the file being linted is not yet written to disk. This occurs in editors
+			// such as Neovim for non-written buffers.
 		}
 	}
 	return result;
@@ -112,4 +118,4 @@ export function getUri(documentOrUri: string | TextDocument | URI): URI {
 		: documentOrUri instanceof URI
 			? documentOrUri
 			: URI.parse(documentOrUri.uri);
-}
+}