editor: Add base64 encode/decode commands (#55361)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Adds `editor: convert to base64` and `editor: convert from base64` to
the command palette. Both commands operate on the current selection, or
the word under the cursor when nothing is selected. The decode command
silently no-ops on invalid base64 input or non-UTF-8 decoded bytes,
consistent with how other convert commands handle untransformable input.

Release Notes:

- Added `editor: convert to base64` and `editor: convert from base64`
commands to the command palette

---------

Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>

Cargo.lock

@@ -5467,6 +5467,7 @@ dependencies = [
  "aho-corasick",
  "anyhow",
  "assets",
+ "base64 0.22.1",
  "breadcrumbs",
  "buffer_diff",
  "client",

crates/editor/Cargo.toml

@@ -34,6 +34,7 @@ test-support = [
 aho-corasick.workspace = true
 anyhow.workspace = true
 assets.workspace = true
+base64.workspace = true
 breadcrumbs.workspace = true
 client.workspace = true
 clock.workspace = true

crates/editor/src/actions.rs

@@ -460,6 +460,10 @@ actions!(
         ConvertToRot13,
         /// Applies ROT47 cipher to selected text.
         ConvertToRot47,
+        /// Base64-encodes the selected text or word under cursor.
+        ConvertToBase64,
+        /// Base64-decodes the selected text or word under cursor.
+        ConvertFromBase64,
         /// Copies selected text to the clipboard.
         Copy,
         /// Copies selected text to the clipboard with leading/trailing whitespace trimmed.

crates/editor/src/editor.rs

@@ -13362,6 +13362,35 @@ impl Editor {
         })
     }
 
+    pub fn convert_to_base64(
+        &mut self,
+        _: &ConvertToBase64,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        use base64::Engine as _;
+        self.manipulate_text(window, cx, |text| {
+            base64::engine::general_purpose::STANDARD.encode(text)
+        })
+    }
+
+    pub fn convert_from_base64(
+        &mut self,
+        _: &ConvertFromBase64,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        use base64::Engine as _;
+        self.manipulate_text(
+            window,
+            cx,
+            |text| match base64::engine::general_purpose::STANDARD.decode(text) {
+                Ok(bytes) => String::from_utf8(bytes).unwrap_or_else(|_| text.to_string()),
+                Err(_) => text.to_string(),
+            },
+        )
+    }
+
     fn manipulate_text<Fn>(&mut self, window: &mut Window, cx: &mut Context<Self>, mut callback: Fn)
     where
         Fn: FnMut(&str) -> String,

crates/editor/src/editor_tests.rs

@@ -6864,6 +6864,40 @@ async fn test_convert_to_sentence_case(cx: &mut TestAppContext) {
     "});
 }
 
+#[gpui::test]
+async fn test_convert_to_base64(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+
+    let mut cx = EditorTestContext::new(cx).await;
+
+    // Encode a plain text selection
+    cx.set_state(indoc! {"
+        «helloˇ»
+    "});
+    cx.update_editor(|e, window, cx| e.convert_to_base64(&ConvertToBase64, window, cx));
+    cx.assert_editor_state(indoc! {"
+        «aGVsbG8=ˇ»
+    "});
+
+    // Decode a valid base64 selection
+    cx.set_state(indoc! {"
+        «aGVsbG8=ˇ»
+    "});
+    cx.update_editor(|e, window, cx| e.convert_from_base64(&ConvertFromBase64, window, cx));
+    cx.assert_editor_state(indoc! {"
+        «helloˇ»
+    "});
+
+    // Decode invalid base64 — should leave text unchanged
+    cx.set_state(indoc! {"
+        «not!!!ˇ»
+    "});
+    cx.update_editor(|e, window, cx| e.convert_from_base64(&ConvertFromBase64, window, cx));
+    cx.assert_editor_state(indoc! {"
+        «not!!!ˇ»
+    "});
+}
+
 #[gpui::test]
 async fn test_manipulate_text(cx: &mut TestAppContext) {
     init_test(cx, |_| {});

crates/editor/src/element.rs

@@ -555,6 +555,8 @@ impl EditorElement {
             register_action(editor, window, Editor::toggle_case);
             register_action(editor, window, Editor::convert_to_rot13);
             register_action(editor, window, Editor::convert_to_rot47);
+            register_action(editor, window, Editor::convert_to_base64);
+            register_action(editor, window, Editor::convert_from_base64);
             register_action(editor, window, Editor::delete_to_previous_word_start);
             register_action(editor, window, Editor::delete_to_previous_subword_start);
             register_action(editor, window, Editor::delete_to_next_word_end);