From 5f5926e0bad3d2cc0d3426c1028f79a4db33bbe1 Mon Sep 17 00:00:00 2001
From: Cameron <cameron.clark@hey.com>
Date: Fri, 17 Nov 2023 12:44:17 +0000
Subject: [PATCH] feat(prettier) Use minimum amount of escapes in strings
 (#1376)

```ts
[
    "foo",
    'bar',
    "bar'",
    'bar\'',
    'bar"',
    "bar\"",
    "bar\"\"\"''",
    "bar\"\"\"'''",
]

```

Becomes:
```ts
["foo", "bar", "bar'", "bar'", 'bar"', 'bar"', 'bar"""\'\'', "bar\"\"\"'''"];
```
---
 crates/oxc_prettier/src/format/mod.rs    |  4 +-
 crates/oxc_prettier/src/format/string.rs | 57 ++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 crates/oxc_prettier/src/format/string.rs

diff --git a/crates/oxc_prettier/src/format/mod.rs b/crates/oxc_prettier/src/format/mod.rs
index 0abbb2bd3..8bdcd5b93 100644
--- a/crates/oxc_prettier/src/format/mod.rs
+++ b/crates/oxc_prettier/src/format/mod.rs
@@ -21,6 +21,7 @@ mod function_parameters;
 mod module;
 mod object;
 mod statement;
+mod string;
 mod ternary;
 
 use crate::{
@@ -720,8 +721,7 @@ impl<'a> Format<'a> for RegExpLiteral {
 
 impl<'a> Format<'a> for StringLiteral {
     fn format(&self, p: &mut Prettier<'a>) -> Doc<'a> {
-        let quote = if p.options.single_quote { "'" } else { "\"" };
-        array!(p, ss!(quote), p.str(&self.value), ss!(quote))
+        array!(p, p.str(&string::print_string(self.value.as_str(), p.options.single_quote)))
     }
 }
 
diff --git a/crates/oxc_prettier/src/format/string.rs b/crates/oxc_prettier/src/format/string.rs
new file mode 100644
index 000000000..4c3c80a56
--- /dev/null
+++ b/crates/oxc_prettier/src/format/string.rs
@@ -0,0 +1,57 @@
+fn get_preferred_quote(raw: &str, prefer_single_quote: bool) -> char {
+    let (preferred_quote_char, alternate_quote_char) =
+        if prefer_single_quote { ('\'', '"') } else { ('"', '\'') };
+
+    let mut preferred_quote_count = 0;
+    let mut alternate_quote_count = 0;
+
+    for character in raw.chars() {
+        if character == preferred_quote_char {
+            preferred_quote_count += 1;
+        } else if character == alternate_quote_char {
+            alternate_quote_count += 1;
+        }
+    }
+
+    if preferred_quote_count > alternate_quote_count {
+        alternate_quote_char
+    } else {
+        preferred_quote_char
+    }
+}
+
+fn make_string(raw_text: &str, enclosing_quote: char) -> String {
+    let other_quote = if enclosing_quote == '"' { '\'' } else { '"' };
+    let mut result = String::new();
+    result.push(enclosing_quote);
+
+    let mut chars = raw_text.chars().peekable();
+    while let Some(c) = chars.next() {
+        match c {
+            '\\' => {
+                if let Some(&next_char) = chars.peek() {
+                    if next_char != other_quote {
+                        result.push('\\');
+                    }
+                    result.push(next_char);
+                    chars.next();
+                } else {
+                    result.push('\\');
+                }
+            }
+            _ if c == enclosing_quote => {
+                result.push('\\');
+                result.push(c);
+            }
+            _ => result.push(c),
+        }
+    }
+
+    result.push(enclosing_quote);
+    result
+}
+
+pub(super) fn print_string(raw_text: &str, prefer_single_quote: bool) -> String {
+    let enclosing_quote = get_preferred_quote(raw_text, prefer_single_quote);
+    make_string(raw_text, enclosing_quote)
+}