Fix for escaping backslashes in interpolated strings (fixes #6737) (#7119)

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

crates/nu-parser/src/parser.rs

@@ -1639,16 +1639,24 @@ pub fn parse_string_interpolation(
     let mut token_start = start;
     let mut delimiter_stack = vec![];
 
+    let mut consecutive_backslashes: usize = 0;
+
     let mut b = start;
 
     while b != end {
-        if contents[b - start] == b'('
+        let current_byte = contents[b - start];
-            && (if double_quote && (b - start) > 0 {
+
-                contents[b - start - 1] != b'\\'
+        if 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
+                0
-            })
+            };
-            && mode == InterpolationMode::String
+
+            if current_byte == b'(' && (!double_quote || preceding_consecutive_backslashes % 2 == 0)
             {
                 mode = InterpolationMode::Expression;
                 if token_start < b {
@@ -1673,8 +1681,10 @@ pub fn parse_string_interpolation(
                     token_start = b;
                 }
             }
+        }
+
         if mode == InterpolationMode::Expression {
-            let byte = contents[b - start];
+            let byte = current_byte;
             if let Some(b'\'') = delimiter_stack.last() {
                 if byte == b'\'' {
                     delimiter_stack.pop();

crates/nu-parser/tests/test_parser.rs

@@ -210,48 +210,6 @@ pub fn parse_binary_with_multi_byte_char() {
     }
 }
 
-#[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);
-    if let PipelineElement::Expression(_, expr) = &expressions[0] {
-        assert_eq!(expr.expr, Expr::String("hello nushell".to_string()))
-    } else {
-        panic!("Not an expression")
-    }
-}
-
-#[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);
-    if let PipelineElement::Expression(_, expr) = &expressions[0] {
-        assert_eq!(expr.expr, Expr::String("hello nushell".to_string()))
-    } else {
-        panic!("Not an expression")
-    }
-}
-
 #[test]
 pub fn parse_call() {
     let engine_state = EngineState::new();
@@ -410,6 +368,258 @@ 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);
+        if let PipelineElement::Expression(_, expr) = &expressions[0] {
+            assert_eq!(expr.expr, Expr::String("hello nushell".to_string()))
+        } else {
+            panic!("Not an expression")
+        }
+    }
+
+    #[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);
+        if let PipelineElement::Expression(_, expr) = &expressions[0] {
+            assert_eq!(expr.expr, Expr::String("hello nushell".to_string()))
+        } else {
+            panic!("Not an expression")
+        }
+    }
+
+    mod interpolation {
+        use nu_protocol::Span;
+
+        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"$\"hello (39 + 3)\"", true, &[]);
+
+            assert!(err.is_none());
+            assert!(block.len() == 1);
+
+            let expressions = &block[0];
+            assert!(expressions.len() == 1);
+
+            if let PipelineElement::Expression(_, expr) = &expressions[0] {
+                let subexprs: Vec<&Expr>;
+                match expr {
+                    Expression {
+                        expr: Expr::StringInterpolation(expressions),
+                        ..
+                    } => {
+                        subexprs = expressions.iter().map(|e| &e.expr).collect();
+                    }
+                    _ => panic!("Expected an `Expr::StringInterpolation`"),
+                }
+
+                assert_eq!(subexprs.len(), 2);
+
+                assert_eq!(subexprs[0], &Expr::String("hello ".to_string()));
+
+                assert!(matches!(subexprs[1], &Expr::FullCellPath(..)));
+            } else {
+                panic!("Not an expression")
+            }
+        }
+
+        #[test]
+        pub fn parse_string_interpolation_escaped_parenthesis() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(&mut working_set, None, b"$\"hello \\(39 + 3)\"", true, &[]);
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+
+            if let PipelineElement::Expression(_, expr) = &expressions[0] {
+                let subexprs: Vec<&Expr>;
+                match expr {
+                    Expression {
+                        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()));
+            } else {
+                panic!("Not an expression")
+            }
+        }
+
+        #[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"$\"hello \\\\(39 + 3)\"",
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+
+            if let PipelineElement::Expression(_, expr) = &expressions[0] {
+                let subexprs: Vec<&Expr>;
+                match expr {
+                    Expression {
+                        expr: Expr::StringInterpolation(expressions),
+                        ..
+                    } => {
+                        subexprs = expressions.iter().map(|e| &e.expr).collect();
+                    }
+                    _ => panic!("Expected an `Expr::StringInterpolation`"),
+                }
+
+                assert_eq!(subexprs.len(), 2);
+
+                assert_eq!(subexprs[0], &Expr::String("hello \\".to_string()));
+
+                assert!(matches!(subexprs[1], &Expr::FullCellPath(..)));
+            } else {
+                panic!("Not an expression")
+            }
+        }
+
+        #[test]
+        pub fn parse_string_interpolation_backslash_count_reset_by_expression() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            let (block, err) = parse(
+                &mut working_set,
+                None,
+                b"$\"\\(1 + 3)\\(7 - 5)\"",
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+
+            assert!(block.len() == 1);
+            let expressions = &block[0];
+
+            assert!(expressions.len() == 1);
+
+            if let PipelineElement::Expression(_, expr) = &expressions[0] {
+                let subexprs: Vec<&Expr>;
+                match expr {
+                    Expression {
+                        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()));
+            } else {
+                panic!("Not an expression")
+            }
+        }
+
+        #[test]
+        pub fn parse_nested_expressions() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_variable(
+                "foo".to_string().into_bytes(),
+                Span::new(0, 0),
+                nu_protocol::Type::CellPath,
+                false,
+            );
+
+            let (_block, err) = parse(
+                &mut working_set,
+                None,
+                br#"
+                $"(($foo))"
+                "#,
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+        }
+
+        #[test]
+        pub fn parse_path_expression() {
+            let engine_state = EngineState::new();
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_variable(
+                "foo".to_string().into_bytes(),
+                Span::new(0, 0),
+                nu_protocol::Type::CellPath,
+                false,
+            );
+
+            let (_block, err) = parse(
+                &mut working_set,
+                None,
+                br#"
+                $"Hello ($foo.bar)"
+                "#,
+                true,
+                &[],
+            );
+
+            assert!(err.is_none());
+        }
+    }
+}
+
 mod range {
     use super::*;
     use nu_protocol::ast::{RangeInclusion, RangeOperator};