Fix for escaping backslashes in interpolated strings (fixes #6737) (#7020)

Co-authored-by: Gavin Foley <gavinmfoley@gmail.com>

crates/nu-parser/src/parser.rs

@@ -1604,14 +1604,24 @@ pub fn parse_string_interpolation(
 
     let mut b = start;
 
+    let mut consecutive_backslashes: usize = 0;
+
     while b != end {
-        if contents[b - start] == b'('
-            && (if double_quote && (b - start) > 0 {
-                contents[b - start - 1] != b'\\'
+        let current_byte = contents[b - start];
+
+        match mode {
+            InterpolationMode::String => {
+                let preceding_consecutive_backslashes = consecutive_backslashes;
+
+                let is_backslash = current_byte == b'\\';
+                consecutive_backslashes = if is_backslash {
+                    preceding_consecutive_backslashes + 1
                 } else {
-                true
-            })
-            && mode == InterpolationMode::String
+                    0
+                };
+
+                if current_byte == b'('
+                    && (!double_quote || preceding_consecutive_backslashes % 2 == 0)
                 {
                     mode = InterpolationMode::Expression;
                     if token_start < b {
@@ -1639,8 +1649,9 @@ pub fn parse_string_interpolation(
                         token_start = b;
                     }
                 }
-        if mode == InterpolationMode::Expression {
-            let byte = contents[b - start];
+            }
+            InterpolationMode::Expression => {
+                let byte = current_byte;
                 if let Some(b'\'') = delimiter_stack.last() {
                     if byte == b'\'' {
                         delimiter_stack.pop();
@@ -1674,8 +1685,12 @@ pub fn parse_string_interpolation(
                                 end: b + 1,
                             };
 
-                        let (expr, err) =
-                            parse_full_cell_path(working_set, None, span, expand_aliases_denylist);
+                            let (expr, err) = parse_full_cell_path(
+                                working_set,
+                                None,
+                                span,
+                                expand_aliases_denylist,
+                            );
                             error = error.or(err);
                             output.push(expr);
                         }
@@ -1685,6 +1700,8 @@ pub fn parse_string_interpolation(
                     }
                 }
             }
+        }
+
         b += 1;
     }
 

crates/nu-parser/tests/test_parser.rs

@@ -175,46 +175,6 @@ pub fn parse_binary_with_multi_byte_char() {
     assert!(!matches!(&expressions[0].expr, Expr::Binary(_)))
 }
 
-#[test]
-pub fn parse_string() {
-    let engine_state = EngineState::new();
-    let mut working_set = StateWorkingSet::new(&engine_state);
-
-    let (block, err) = parse(&mut working_set, None, b"\"hello nushell\"", true, &[]);
-
-    assert!(err.is_none());
-    assert!(block.len() == 1);
-    let expressions = &block[0];
-    assert!(expressions.len() == 1);
-    assert_eq!(
-        expressions[0].expr,
-        Expr::String("hello nushell".to_string())
-    )
-}
-
-#[test]
-pub fn parse_escaped_string() {
-    let engine_state = EngineState::new();
-    let mut working_set = StateWorkingSet::new(&engine_state);
-
-    let (block, err) = parse(
-        &mut working_set,
-        None,
-        b"\"hello \\u006e\\u0075\\u0073hell\"",
-        true,
-        &[],
-    );
-
-    assert!(err.is_none());
-    assert!(block.len() == 1);
-    let expressions = &block[0];
-    assert!(expressions.len() == 1);
-    assert_eq!(
-        expressions[0].expr,
-        Expr::String("hello nushell".to_string())
-    )
-}
-
 #[test]
 pub fn parse_call() {
     let engine_state = EngineState::new();
@@ -364,6 +324,181 @@ fn test_nothing_comparisson_neq() {
     ))
 }
 
+mod string {
+    use super::*;
+
+    #[test]
+    pub fn parse_string() {
+        let engine_state = EngineState::new();
+        let mut working_set = StateWorkingSet::new(&engine_state);
+
+        let (block, err) = parse(&mut working_set, None, b"\"hello nushell\"", true, &[]);
+
+        assert!(err.is_none());
+        assert!(block.len() == 1);
+        let expressions = &block[0];
+        assert!(expressions.len() == 1);
+        assert_eq!(
+            expressions[0].expr,
+            Expr::String("hello nushell".to_string())
+        )
+    }
+
+    #[test]
+    pub fn parse_escaped_string() {
+        let engine_state = EngineState::new();
+        let mut working_set = StateWorkingSet::new(&engine_state);
+
+        let (block, err) = parse(
+            &mut working_set,
+            None,
+            b"\"hello \\u006e\\u0075\\u0073hell\"",
+            true,
+            &[],
+        );
+
+        assert!(err.is_none());
+        assert!(block.len() == 1);
+        let expressions = &block[0];
+        assert!(expressions.len() == 1);
+        assert_eq!(
+            expressions[0].expr,
+            Expr::String("hello nushell".to_string())
+        )
+    }
+
+    mod interpolation {
+        use super::*;
+
+        #[test]
+        pub fn parse_string_interpolation() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(&mut working_set, None, b"$\"hello (39 + 3)\"", true, &[]);
+
+            assert!(err.is_none());
+            assert!(block.len() == 1);
+
+            let expressions = &block[0];
+            assert!(expressions.len() == 1);
+
+            let expr = &expressions[0].expr;
+
+            let subexprs: Vec<&Expr>;
+            match expr {
+                Expr::StringInterpolation(expressions) => {
+                    subexprs = expressions.iter().map(|e| &e.expr).collect();
+                }
+                _ => panic!("Expected an `Expr::StringInterpolation`"),
+            }
+
+            assert_eq!(subexprs.len(), 2);
+
+            assert_eq!(subexprs[0], &Expr::String("hello ".to_string()));
+
+            assert!(matches!(subexprs[1], &Expr::FullCellPath(..)));
+        }
+
+        #[test]
+        pub fn parse_string_interpolation_escaped_parenthesis() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(&mut working_set, None, b"$\"hello \\(39 + 3)\"", true, &[]);
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+            let expr = &expressions[0].expr;
+
+            let subexprs: Vec<&Expr>;
+            match expr {
+                Expr::StringInterpolation(expressions) => {
+                    subexprs = expressions.iter().map(|e| &e.expr).collect();
+                }
+                _ => panic!("Expected an `Expr::StringInterpolation`"),
+            }
+
+            assert_eq!(subexprs.len(), 1);
+
+            assert_eq!(subexprs[0], &Expr::String("hello (39 + 3)".to_string()));
+        }
+
+        #[test]
+        pub fn parse_string_interpolation_escaped_backslash_before_parenthesis() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(
+                &mut working_set,
+                None,
+                b"$\"hello \\\\(39 + 3)\"",
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+            let expr = &expressions[0].expr;
+
+            let subexprs: Vec<&Expr>;
+            match expr {
+                Expr::StringInterpolation(expressions) => {
+                    subexprs = expressions.iter().map(|e| &e.expr).collect();
+                }
+                _ => panic!("Expected an `Expr::StringInterpolation`"),
+            }
+
+            assert_eq!(subexprs.len(), 2);
+
+            assert_eq!(subexprs[0], &Expr::String("hello \\".to_string()));
+
+            assert!(matches!(subexprs[1], &Expr::FullCellPath(..)));
+        }
+
+        #[test]
+        pub fn parse_string_interpolation_backslash_count_reset_by_expression() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(
+                &mut working_set,
+                None,
+                b"$\"\\(1 + 3)\\(7 - 5)\"",
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+            let expr = &expressions[0].expr;
+
+            let subexprs: Vec<&Expr>;
+            match expr {
+                Expr::StringInterpolation(expressions) => {
+                    subexprs = expressions.iter().map(|e| &e.expr).collect();
+                }
+                _ => panic!("Expected an `Expr::StringInterpolation`"),
+            }
+
+            assert_eq!(subexprs.len(), 1);
+            assert_eq!(subexprs[0], &Expr::String("(1 + 3)(7 - 5)".to_string()));
+        }
+    }
+}
+
 mod range {
     use super::*;
     use nu_protocol::ast::{RangeInclusion, RangeOperator};