From 5c775ced3933879dfcddb139bf7fc534ea6c6000 Mon Sep 17 00:00:00 2001
From: Giacomo Cavalieri <giacomo.cavalieri@icloud.com>
Date: Tue, 14 Jul 2026 14:27:15 +0200
Subject: [PATCH] nice thousands separator

---
 language-server/src/code_action.rs            | 23 ++++++++++++++++++-
 language-server/src/tests/action.rs           |  9 ++++++++
 ...rt_to_int_has_nicely_separated_digits.snap | 11 +++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 language-server/src/tests/snapshots/gleam_language_server__tests__action__convert_to_int_has_nicely_separated_digits.snap

diff --git a/language-server/src/code_action.rs b/language-server/src/code_action.rs
index b05e1f2f3..94de66895 100644
--- a/language-server/src/code_action.rs
+++ b/language-server/src/code_action.rs
@@ -13156,8 +13156,10 @@ impl<'a> ConvertIntToDifferentBase<'a> {
             let converted_number = match base {
                 Base::Binary => format!("{minus}0b{:b}", int),
                 Base::Octal => format!("{minus}0o{:o}", int),
-                Base::Decimal => format!("{minus}{}", int),
                 Base::Hexadecimal => format!("{minus}0x{:x}", int),
+                Base::Decimal => {
+                    format!("{minus}{}", format_int_with_thousands_separator(&int))
+                }
             };
             let title = format!("Convert to `{converted_number}`");
             self.edits.replace(location, converted_number);
@@ -13175,6 +13177,25 @@ impl<'a> ConvertIntToDifferentBase<'a> {
     }
 }
 
+fn format_int_with_thousands_separator(int: &BigInt) -> String {
+    if int <= &BigInt::from(9999) {
+        return int.to_string();
+    }
+
+    // We get chunks of three digits. If we start from 1234567
+    // we will have `765`, `432`, `1`
+    (int.to_string().chars().rev().chunks(3).into_iter())
+        // Each chunk is turned into a string and those are joined with a
+        // separator.
+        .map(|chunk| chunk.collect::<EcoString>())
+        .join("_")
+        // And finally reverse everything to bring it back to normal, the number
+        // is spelled in reverse right now!
+        .chars()
+        .rev()
+        .collect()
+}
+
 impl<'ast> ast::visit::Visit<'ast> for ConvertIntToDifferentBase<'ast> {
     fn visit_typed_function(&mut self, fun: &'ast TypedFunction) {
         // We skip all the functions the cursor is not inside of.
diff --git a/language-server/src/tests/action.rs b/language-server/src/tests/action.rs
index 56c731f04..be60d4a8d 100644
--- a/language-server/src/tests/action.rs
+++ b/language-server/src/tests/action.rs
@@ -15817,3 +15817,12 @@ fn convert_negative_int_hexadecimal_to_decimal() {
         find_position_of("0x6f").to_selection()
     );
 }
+
+#[test]
+fn convert_to_int_has_nicely_separated_digits() {
+    assert_code_action!(
+        "Convert to `1_234_567`",
+        "pub fn main() { 0b100101101011010000111 }",
+        find_position_of("0b100101101011010000111").to_selection()
+    );
+}
diff --git a/language-server/src/tests/snapshots/gleam_language_server__tests__action__convert_to_int_has_nicely_separated_digits.snap b/language-server/src/tests/snapshots/gleam_language_server__tests__action__convert_to_int_has_nicely_separated_digits.snap
new file mode 100644
index 000000000..c0dadc0a7
--- /dev/null
+++ b/language-server/src/tests/snapshots/gleam_language_server__tests__action__convert_to_int_has_nicely_separated_digits.snap
@@ -0,0 +1,11 @@
+---
+source: language-server/src/tests/action.rs
+expression: "pub fn main() { 0b100101101011010000111 }"
+---
+----- BEFORE ACTION
+pub fn main() { 0b100101101011010000111 }
+                ↑                        
+
+
+----- AFTER ACTION
+pub fn main() { 1_234_567 }
-- 
2.51.2