From d4798d6ee19ddd1fc4cd08093adf022f3797420b Mon Sep 17 00:00:00 2001
From: Gavin Foley <6389719+gavinfoley@users.noreply.github.com>
Date: Sun, 6 Nov 2022 14:57:28 -0500
Subject: [PATCH] Fix for escaping backslashes in interpolated strings (fixes
 #6737) (#7020)

Co-authored-by: Gavin Foley <gavinmfoley@gmail.com>
---
 crates/nu-parser/src/parser.rs        | 147 ++++++++++--------
 crates/nu-parser/tests/test_parser.rs | 215 +++++++++++++++++++++-----
 2 files changed, 257 insertions(+), 105 deletions(-)

diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index 9cd521cf47..5260e9c194 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -1604,87 +1604,104 @@ 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'\\'
-            } else {
-                true
-            })
-            && mode == InterpolationMode::String
-        {
-            mode = InterpolationMode::Expression;
-            if token_start < b {
-                let span = Span {
-                    start: token_start,
-                    end: b,
-                };
-                let str_contents = working_set.get_span_contents(span);
+        let current_byte = contents[b - start];
 
-                let str_contents = if double_quote {
-                    let (str_contents, err) = unescape_string(str_contents, span);
-                    error = error.or(err);
+        match mode {
+            InterpolationMode::String => {
+                let preceding_consecutive_backslashes = consecutive_backslashes;
 
-                    str_contents
+                let is_backslash = current_byte == b'\\';
+                consecutive_backslashes = if is_backslash {
+                    preceding_consecutive_backslashes + 1
                 } else {
-                    str_contents.to_vec()
+                    0
                 };
 
-                output.push(Expression {
-                    expr: Expr::String(String::from_utf8_lossy(&str_contents).to_string()),
-                    span,
-                    ty: Type::String,
-                    custom_completion: None,
-                });
-                token_start = b;
-            }
-        }
-        if mode == InterpolationMode::Expression {
-            let byte = contents[b - start];
-            if let Some(b'\'') = delimiter_stack.last() {
-                if byte == b'\'' {
-                    delimiter_stack.pop();
-                }
-            } else if let Some(b'"') = delimiter_stack.last() {
-                if byte == b'"' {
-                    delimiter_stack.pop();
-                }
-            } else if let Some(b'`') = delimiter_stack.last() {
-                if byte == b'`' {
-                    delimiter_stack.pop();
-                }
-            } else if byte == b'\'' {
-                delimiter_stack.push(b'\'')
-            } else if byte == b'"' {
-                delimiter_stack.push(b'"');
-            } else if byte == b'`' {
-                delimiter_stack.push(b'`')
-            } else if byte == b'(' {
-                delimiter_stack.push(b')');
-            } else if byte == b')' {
-                if let Some(b')') = delimiter_stack.last() {
-                    delimiter_stack.pop();
-                }
-                if delimiter_stack.is_empty() {
-                    mode = InterpolationMode::String;
-
+                if current_byte == b'('
+                    && (!double_quote || preceding_consecutive_backslashes % 2 == 0)
+                {
+                    mode = InterpolationMode::Expression;
                     if token_start < b {
                         let span = Span {
                             start: token_start,
-                            end: b + 1,
+                            end: b,
+                        };
+                        let str_contents = working_set.get_span_contents(span);
+
+                        let str_contents = if double_quote {
+                            let (str_contents, err) = unescape_string(str_contents, span);
+                            error = error.or(err);
+
+                            str_contents
+                        } else {
+                            str_contents.to_vec()
                         };
 
-                        let (expr, err) =
-                            parse_full_cell_path(working_set, None, span, expand_aliases_denylist);
-                        error = error.or(err);
-                        output.push(expr);
+                        output.push(Expression {
+                            expr: Expr::String(String::from_utf8_lossy(&str_contents).to_string()),
+                            span,
+                            ty: Type::String,
+                            custom_completion: None,
+                        });
+                        token_start = b;
                     }
+                }
+            }
+            InterpolationMode::Expression => {
+                let byte = current_byte;
+                if let Some(b'\'') = delimiter_stack.last() {
+                    if byte == b'\'' {
+                        delimiter_stack.pop();
+                    }
+                } else if let Some(b'"') = delimiter_stack.last() {
+                    if byte == b'"' {
+                        delimiter_stack.pop();
+                    }
+                } else if let Some(b'`') = delimiter_stack.last() {
+                    if byte == b'`' {
+                        delimiter_stack.pop();
+                    }
+                } else if byte == b'\'' {
+                    delimiter_stack.push(b'\'')
+                } else if byte == b'"' {
+                    delimiter_stack.push(b'"');
+                } else if byte == b'`' {
+                    delimiter_stack.push(b'`')
+                } else if byte == b'(' {
+                    delimiter_stack.push(b')');
+                } else if byte == b')' {
+                    if let Some(b')') = delimiter_stack.last() {
+                        delimiter_stack.pop();
+                    }
+                    if delimiter_stack.is_empty() {
+                        mode = InterpolationMode::String;
 
-                    token_start = b + 1;
-                    continue;
+                        if token_start < b {
+                            let span = Span {
+                                start: token_start,
+                                end: b + 1,
+                            };
+
+                            let (expr, err) = parse_full_cell_path(
+                                working_set,
+                                None,
+                                span,
+                                expand_aliases_denylist,
+                            );
+                            error = error.or(err);
+                            output.push(expr);
+                        }
+
+                        token_start = b + 1;
+                        continue;
+                    }
                 }
             }
         }
+
         b += 1;
     }
 
diff --git a/crates/nu-parser/tests/test_parser.rs b/crates/nu-parser/tests/test_parser.rs
index c75a74c39e..500376059c 100644
--- a/crates/nu-parser/tests/test_parser.rs
+++ b/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};