From 675ddb89f9d1ffa2f50d0dee04461300f013461e Mon Sep 17 00:00:00 2001
From: Stephen Chung <schungx@live.com>
Date: Thu, 9 Dec 2021 13:34:51 +0800
Subject: [PATCH] Add "" and `` in string literals.

---
 CHANGELOG.md     | 1 +
 src/tokenizer.rs | 9 +++++++++
 tests/string.rs  | 8 ++++++++
 3 files changed, 18 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b921acc..eacb2b1d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ New features
 Enhancements
 ------------
 
+* Two double quotes (`""`) in a string literal now maps to `"`; two back-ticks (``` `` ```) in a literal string now maps to `` ` ``.
 * Added `Engine::register_type_with_name_raw` to register a custom type based on a fully-qualified type path.
 * Added `into_array` and `into_typed_array` for `Dynamic`.
 * Added `FnPtr::call` and `FnPtr::call_within_context` to simplify calling a function pointer.
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 8bdcc508..79018371 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -1175,6 +1175,15 @@ pub fn parse_string_literal(
                 result.push(next_char)
             }
 
+            // Double wrapper
+            _ if termination_char == next_char
+                && escape.is_empty()
+                && stream.peek_next().map_or(false, |c| c == termination_char) =>
+            {
+                eat_next(stream, pos);
+                result.push(termination_char)
+            }
+
             // Close wrapper
             _ if termination_char == next_char && escape.is_empty() => {
                 state.is_within_text_terminated_by = None;
diff --git a/tests/string.rs b/tests/string.rs
index 62f00b86..ac7991f3 100644
--- a/tests/string.rs
+++ b/tests/string.rs
@@ -8,6 +8,10 @@ fn test_string() -> Result<(), Box<EvalAltResult>> {
         engine.eval::<String>(r#""Test string: \u2764""#)?,
         "Test string: ❤"
     );
+    assert_eq!(
+        engine.eval::<String>(r#""Test string: ""\u2764""""#)?,
+        r#"Test string: "❤""#
+    );
     assert_eq!(
         engine.eval::<String>("\"Test\rstring: \\u2764\"")?,
         "Test\rstring: ❤"
@@ -24,6 +28,10 @@ fn test_string() -> Result<(), Box<EvalAltResult>> {
         engine.eval::<String>("     `Test string: \\u2764\nhello,\\nworld!`")?,
         "Test string: \\u2764\nhello,\\nworld!"
     );
+    assert_eq!(
+        engine.eval::<String>(r#"     `Test string: \\u2764\n``hello``,\\n"world"!`"#)?,
+        r#"Test string: \\u2764\n`hello`,\\n"world"!"#
+    );
     assert_eq!(
         engine.eval::<String>("     `\nTest string: \\u2764\nhello,\\nworld!`")?,
         "Test string: \\u2764\nhello,\\nworld!"