editor: Don't treat scheme-prefixed text as a URL when pasting in Markdown (#59071)

Pasting text that merely starts with a scheme-like prefix (for example a
commit message like `editor: Fix crash in project panel`) over a
selection in a Markdown buffer would wrap the selection in a Markdown
link, because `url::Url::parse` accepts `editor:` as a valid URL scheme.

Paste now only treats clipboard text as a URL when the whole text is a
single standalone URL, using `linkify` (already a workspace dependency)
instead of `url::Url::parse`. Added a regression test covering the
scheme-like prefix case.

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 adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #59070

Release Notes:

- Fixed pasting text starting with a scheme-like prefix (such as
`editor: ...`) over a selection in a Markdown buffer incorrectly
creating a Markdown link.

crates/editor/src/clipboard.rs

@@ -139,7 +139,7 @@ impl Editor {
                                         &snapshot,
                                         range,
                                         to_insert,
-                                        url::Url::parse(to_insert).ok(),
+                                        is_standalone_url(to_insert),
                                     )
                                 } else {
                                     (range, Cow::Borrowed(to_insert))
@@ -169,7 +169,7 @@ impl Editor {
                     .all::<MultiBufferOffset>(&this.display_snapshot(cx));
                 this.change_selections(Default::default(), window, cx, |s| s.select(selections));
             } else {
-                let url = url::Url::parse(&clipboard_text).ok();
+                let clipboard_is_url = is_standalone_url(&clipboard_text);
 
                 let auto_indent_mode = if !clipboard_text.is_empty() {
                     Some(AutoindentMode::Block {
@@ -213,7 +213,12 @@ impl Editor {
                         let (edit_range, edit_text) = if let Some(language) = language
                             && language.name() == "Markdown"
                         {
-                            edit_for_markdown_paste(&snapshot, range, text_for_cursor, url.clone())
+                            edit_for_markdown_paste(
+                                &snapshot,
+                                range,
+                                text_for_cursor,
+                                clipboard_is_url,
+                            )
                         } else {
                             (range, Cow::Borrowed(text_for_cursor))
                         };
@@ -538,18 +543,30 @@ fn edit_for_markdown_paste<'a>(
     buffer: &MultiBufferSnapshot,
     range: Range<MultiBufferOffset>,
     to_insert: &'a str,
-    url: Option<url::Url>,
+    to_insert_is_url: bool,
 ) -> (Range<MultiBufferOffset>, Cow<'a, str>) {
-    if url.is_none() {
+    if !to_insert_is_url {
         return (range, Cow::Borrowed(to_insert));
     };
 
     let old_text = buffer.text_for_range(range.clone()).collect::<String>();
 
-    let new_text = if range.is_empty() || url::Url::parse(&old_text).is_ok() {
+    let new_text = if range.is_empty() || is_standalone_url(&old_text) {
         Cow::Borrowed(to_insert)
     } else {
         Cow::Owned(format!("[{old_text}]({to_insert})"))
     };
     (range, new_text)
 }
+
+/// Whether `text` consists solely of a single URL, as opposed to merely
+/// starting with a scheme-like prefix (e.g. a commit message like
+/// `editor: Fix ...`, which `url::Url::parse` would accept).
+fn is_standalone_url(text: &str) -> bool {
+    let mut finder = linkify::LinkFinder::new();
+    finder.kinds(&[linkify::LinkKind::Url]);
+    finder
+        .links(text)
+        .next()
+        .is_some_and(|link| link.start() == 0 && link.end() == text.len())
+}

crates/editor/src/editor_tests.rs

@@ -33268,6 +33268,36 @@ async fn test_paste_plain_text_from_other_app_replaces_selection_without_creatin
     cx.assert_editor_state(&format!("Hello, {text}ˇ.\nZed is {text}ˇ"));
 }
 
+#[gpui::test]
+async fn test_paste_text_with_scheme_like_prefix_replaces_selection_without_creating_markdown_link(
+    cx: &mut gpui::TestAppContext,
+) {
+    init_test(cx, |_| {});
+
+    // `url::Url::parse` accepts this as a URL with the scheme `editor`, but it
+    // should not be treated as one when pasting.
+    let text = "editor: Fix double-click bracket selection for large spans";
+
+    let markdown_language = Arc::new(Language::new(
+        LanguageConfig {
+            name: "Markdown".into(),
+            ..LanguageConfig::default()
+        },
+        None,
+    ));
+
+    let mut cx = EditorTestContext::new(cx).await;
+    cx.update_buffer(|buffer, cx| buffer.set_language(Some(markdown_language), cx));
+    cx.set_state("«(feat on git-ui-add-info-exclude-to-context-menus) Fmtˇ»");
+
+    cx.update_editor(|editor, window, cx| {
+        cx.write_to_clipboard(ClipboardItem::new_string(text.to_string()));
+        editor.paste(&Paste, window, cx);
+    });
+
+    cx.assert_editor_state(&format!("{text}ˇ"));
+}
+
 #[gpui::test]
 async fn test_paste_url_from_other_app_without_creating_markdown_link_in_non_markdown_language(
     cx: &mut gpui::TestAppContext,