fix error message for extra close parenthesis #263

CHANGELOG.md

@@ -16,6 +16,7 @@
 * fix odd? even? on non integers
 * fix object literals with null value [#264](https://github.com/jcubic/lips/issues/264)
 * fix version and date in executable [#261](https://github.com/jcubic/lips/issues/261)
+* fix error on extra close parenthesis [#263](https://github.com/jcubic/lips/issues/263)
 
 ## 1.0.0-beta.17
 ### Breaking

README.md

@@ -8,7 +8,7 @@
 [![npm](https://img.shields.io/badge/npm-1.0.0%E2%80%93beta.17.3-blue.svg)](https://www.npmjs.com/package/@jcubic/lips)
 ![1.0.0 Complete](https://img.shields.io/github/milestones/progress-percent/jcubic/lips/1?label=1.0.0%20Complete)
 [![Build and test](https://github.com/jcubic/lips/actions/workflows/build.yaml/badge.svg?branch=devel&event=push)](https://github.com/jcubic/lips/actions/workflows/build.yaml)
-[![Coverage Status](https://coveralls.io/repos/github/jcubic/lips/badge.svg?branch=devel&915345bb7efef31d29f7c395edf02656)](https://coveralls.io/github/jcubic/lips?branch=devel)
+[![Coverage Status](https://coveralls.io/repos/github/jcubic/lips/badge.svg?branch=devel&588ba056f11c7ab86ecec631717742c3)](https://coveralls.io/github/jcubic/lips?branch=devel)
 [![Join Gitter Chat](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/jcubic/lips)
 ![NPM Download Count](https://img.shields.io/npm/dm/@jcubic/lips)
 ![JSDelivr Download count](https://img.shields.io/jsdelivr/npm/hm/@jcubic/lips)

src/lips.js

@@ -1531,11 +1531,17 @@ class Parser {
     balanced() {
         return this._state.parentheses === 0;
     }
-    ballancing_error(expr) {
+    ballancing_error(expr, prev) {
         const count = this._state.parentheses;
-        const e = new Error('Parser: expected parenthesis but eof found');
-        const re = new RegExp(`\\){${count}}$`);
-        e.__code__ = [expr.toString().replace(re, '')];
+        let e;
+        if (count < 0) {
+            e = new Error('Parser: unexpected parenthesis');
+            e.__code__ = [prev.toString() + ')'];
+        } else {
+            e = new Error('Parser: expected parenthesis but eof found');
+            const re = new RegExp(`\\){${count}}$`);
+            e.__code__ = [expr.toString().replace(re, '')];
+        }
         throw e;
     }
     // Cover This function (array and object branch)
@@ -1658,6 +1664,9 @@ class Parser {
             this.skip();
             this._refs[ref_label] = this._read_object();
             return this._refs[ref_label];
+        } else if (this.is_close(token)) {
+            this.skip();
+            // invalid state, we don't need to return anything
         } else if (this.is_open(token)) {
             this.skip();
             return this.read_list();
@@ -1698,14 +1707,16 @@ async function* parse(arg, env) {
     }
     const parser = new Parser(arg, { env });
     let i = 100000;
+    let prev;
     while (true) {
         const expr = await parser.read_object();
         if (!parser.balanced()) {
-            parser.ballancing_error(expr);
+            parser.ballancing_error(expr, prev);
         }
         if (expr === eof) {
             break;
         }
+        prev = expr;
         yield expr;
     }
 }

tests/parser.scm

@@ -181,6 +181,14 @@
         (let ((x '#3=(1 2 . #3#)))
           (t.is (eq? x (cddr x)) true))))
 
+(test "parser: should throw an error on extra close paren"
+      (lambda (t)
+        (t.is (try
+               (lips.exec "(define x 10))")
+               (catch (e)
+                      e.message))
+              "Parser: unexpected parenthesis")))
+
 (test "tokenizer: should create tokens for simple list"
       (lambda (t)
         (t.is (lips.tokenize "(foo bar baz)")