parser: add \u{} escape sequence for Unicode characters

CHANGELOG.md

@@ -3,6 +3,7 @@
 **Improvements**
 
 * Add `\x` escape sequence for hex bytes.
+* Add `\u{}` escape sequence for Unicode characters.
 * Allow empty commands, keys, and prefixes.
 
 # 0.5.0 (2024-05-31)

src/lib.rs

@@ -295,8 +295,9 @@
 //! Strings can be quoted using `"` or `'`, in which case they can contain
 //! arbitrary Unicode characters. `\` is used as an escape character, both to
 //! escape quotes `\"` and `\'` as well as itself `\\`, and also `\0` (null),
-//! `\n` (newline), `\r` (carriage return), and `\t` (tab). `\x` can be used
-//! to represent arbitrary hexadecimal characters, e.g. `\x7a`.
+//! `\n` (newline), `\r` (carriage return), and `\t` (tab). `\x` can be used to
+//! represent arbitrary hexadecimal bytes (e.g. `\x7a`) and `\u{}` can be used
+//! to represent arbitrary Unicode characters (e.g. `\u{1f44b}`)
 //!
 //! ```text
 //! string

src/parser.rs

@@ -1,7 +1,7 @@
 use crate::command::{Argument, Block, Command};
 
 use nom::branch::alt;
-use nom::bytes::complete::{escaped_transform, is_not, tag, take};
+use nom::bytes::complete::{escaped_transform, is_not, tag, take, take_while_m_n};
 use nom::character::complete::{
     alphanumeric1, anychar, char, line_ending, not_line_ending, space0, space1,
 };
@@ -201,6 +201,18 @@ fn quoted_string(quote: char) -> impl FnMut(Span) -> IResult<String> {
                             Err(_) => Err(Error::new(input, ErrorKind::HexDigit)),
                         },
                     ),
+                    map_res(
+                        delimited(
+                            tag("u{"),
+                            take_while_m_n(1, 6, |c: char| c.is_ascii_hexdigit()),
+                            tag("}"),
+                        ),
+                        |input: Span| {
+                            let codepoint = u32::from_str_radix(input.fragment(), 16)
+                                .or(Err(Error::new(input, ErrorKind::HexDigit)))?;
+                            char::from_u32(codepoint).ok_or(Error::new(input, ErrorKind::Char))
+                        },
+                    ),
                 )),
             ),
             tag(q),

tests/errors/string_escape_unicode_char.error

@@ -0,0 +1,3 @@
+parse error at line 2 column 1 for Tag:
+'\u{fg}'
+^

tests/errors/string_escape_unicode_char.in

@@ -0,0 +1,3 @@
+# A Unicode escape with a non-hex character errors.
+'\u{fg}'
+---

tests/errors/string_escape_unicode_empty.error

@@ -0,0 +1,3 @@
+parse error at line 2 column 1 for Tag:
+'\u{}'
+^

tests/errors/string_escape_unicode_empty.in

@@ -0,0 +1,3 @@
+# A Unicode escape with no digits errors.
+'\u{}'
+---

tests/errors/string_escape_unicode_long.error

@@ -0,0 +1,3 @@
+parse error at line 2 column 1 for Tag:
+'\u{1234567}'
+^

tests/errors/string_escape_unicode_long.in

@@ -0,0 +1,3 @@
+# A Unicode escape with 7 digits errors.
+'\u{1234567}'
+---

tests/scripts/strings

@@ -40,13 +40,13 @@ command foo="" bar=''
 ---
 Command { name: "command", args: [Argument { key: Some("foo"), value: "" }, Argument { key: Some("bar"), value: "" }], prefix: None, silent: false, fail: false, line_number: 39 }
 
-# Escape sequences are respected both in single- and double-quotes, including
+# Escape sequences are respected both in single and double quotes, including
 # both quote types.
-'\\ \' \" \0 \n \r \t \\ \x00 \x7A \xff'
-"\\ \' \" \0 \n \r \t \\ \x00 \x7A \xff"
+'\\ \' \" \0 \n \r \t \\ \x00 \x7A \xff \u{1F44b}'
+"\\ \' \" \0 \n \r \t \\ \x00 \x7A \xff \u{1F44b}"
 ---
-Command { name: "\\ ' \" \0 \n \r \t \\ \0 z ÿ", args: [], prefix: None, silent: false, fail: false, line_number: 45 }
-Command { name: "\\ ' \" \0 \n \r \t \\ \0 z ÿ", args: [], prefix: None, silent: false, fail: false, line_number: 46 }
+Command { name: "\\ ' \" \0 \n \r \t \\ \0 z ÿ 👋", args: [], prefix: None, silent: false, fail: false, line_number: 45 }
+Command { name: "\\ ' \" \0 \n \r \t \\ \0 z ÿ 👋", args: [], prefix: None, silent: false, fail: false, line_number: 46 }
 
 # Quoted strings can contain the other, unescaped quote kind.
 '"'