From 48fca1c151f6f734087b34d4656f91e1e239ad2c Mon Sep 17 00:00:00 2001
From: dj-sourbrough <56027726+dj-sourbrough@users.noreply.github.com>
Date: Thu, 7 Mar 2024 13:05:04 +0100
Subject: [PATCH] Fix: lex now throws error on unbalanced closing parentheses
 (issue #11982) (#12098)
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- Fixes issue #11982

# Description
Expressions with unbalanced parenthesis [excess closing ')' parenthesis]
will throw an error instead of interpreting ')' as a string.

Solved he same way as closing braces '}' are handled.

![Screenshot 2024-03-06 at 14 53
46](https://github.com/nushell/nushell/assets/56027726/86834e47-a1e5-484d-881d-0e3b80fecef8)

![Screenshot 2024-03-06 at 14 48
27](https://github.com/nushell/nushell/assets/56027726/bb27c969-6a3b-4735-8a1e-a5881d9096d3)

# User-Facing Changes
- Trailing closing parentheses ')' which do not match the number of
opening parentheses '(' will lead to a parse error.
- From what I have found in the documentation this is the intended
behavior, thus no documentation has been updated on my part

# Tests + Formatting
- Two tests added in src/tests/test_parser.rs
- All previous tests are still passing
- cargo fmt, clippy and test have been run

Unable to get the following command run
- `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"` to run the tests for the standard library
![Screenshot 2024-03-06 at 20 06
25](https://github.com/nushell/nushell/assets/56027726/91724fb9-d7d0-472b-bf14-bfa2a7618d09)

---------

Co-authored-by: Noak Jönsson <noakj@kth.se>
---
 crates/nu-parser/src/lex.rs | 17 +++++++++++++++++
 src/tests/test_parser.rs    | 10 ++++++++++
 2 files changed, 27 insertions(+)

diff --git a/crates/nu-parser/src/lex.rs b/crates/nu-parser/src/lex.rs
index 42f0fa85da..399afb428e 100644
--- a/crates/nu-parser/src/lex.rs
+++ b/crates/nu-parser/src/lex.rs
@@ -207,6 +207,23 @@ pub fn lex_item(
             // We encountered a closing `)` delimiter. Pop off the opening `(`.
             if let Some(BlockKind::Paren) = block_level.last() {
                 let _ = block_level.pop();
+            } else {
+                // We encountered a closing `)` delimiter, but the last opening
+                // delimiter was not a `(`. This is an error.
+                let span = Span::new(span_offset + token_start, span_offset + *curr_offset);
+
+                *curr_offset += 1;
+                return (
+                    Token {
+                        contents: TokenContents::Item,
+                        span,
+                    },
+                    Some(ParseError::Unbalanced(
+                        "(".to_string(),
+                        ")".to_string(),
+                        Span::new(span.end, span.end + 1),
+                    )),
+                );
             }
         } else if is_item_terminator(&block_level, c, additional_whitespace, special_tokens) {
             break;
diff --git a/src/tests/test_parser.rs b/src/tests/test_parser.rs
index 6f1224a031..83fc7aa339 100644
--- a/src/tests/test_parser.rs
+++ b/src/tests/test_parser.rs
@@ -550,6 +550,16 @@ fn unbalanced_delimiter4() -> TestResult {
     fail_test(r#"}"#, "unbalanced { and }")
 }
 
+#[test]
+fn unbalanced_parens1() -> TestResult {
+    fail_test(r#")"#, "unbalanced ( and )")
+}
+
+#[test]
+fn unbalanced_parens2() -> TestResult {
+    fail_test(r#"("("))"#, "unbalanced ( and )")
+}
+
 #[test]
 fn register_with_string_literal() -> TestResult {
     fail_test(r#"register 'nu-plugin-math'"#, "File not found")