Restructure workflow step resolution and fix inserting newlines (#15720)

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/language/src/buffer_tests.rs

@@ -1822,6 +1822,92 @@ fn test_autoindent_query_with_outdent_captures(cx: &mut AppContext) {
     });
 }
 
+#[gpui::test]
+fn test_insert_empty_line(cx: &mut AppContext) {
+    init_settings(cx, |_| {});
+
+    // Insert empty line at the beginning, requesting an empty line above
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(0, 0), true, false, cx);
+        assert_eq!(buffer.text(), "\nabc\ndef\nghi");
+        assert_eq!(point, Point::new(0, 0));
+        buffer
+    });
+
+    // Insert empty line at the beginning, requesting an empty line above and below
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(0, 0), true, true, cx);
+        assert_eq!(buffer.text(), "\n\nabc\ndef\nghi");
+        assert_eq!(point, Point::new(0, 0));
+        buffer
+    });
+
+    // Insert empty line at the start of a line, requesting empty lines above and below
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(2, 0), true, true, cx);
+        assert_eq!(buffer.text(), "abc\ndef\n\n\n\nghi");
+        assert_eq!(point, Point::new(3, 0));
+        buffer
+    });
+
+    // Insert empty line in the middle of a line, requesting empty lines above and below
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndefghi\njkl", cx);
+        let point = buffer.insert_empty_line(Point::new(1, 3), true, true, cx);
+        assert_eq!(buffer.text(), "abc\ndef\n\n\n\nghi\njkl");
+        assert_eq!(point, Point::new(3, 0));
+        buffer
+    });
+
+    // Insert empty line in the middle of a line, requesting empty line above only
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndefghi\njkl", cx);
+        let point = buffer.insert_empty_line(Point::new(1, 3), true, false, cx);
+        assert_eq!(buffer.text(), "abc\ndef\n\n\nghi\njkl");
+        assert_eq!(point, Point::new(3, 0));
+        buffer
+    });
+
+    // Insert empty line in the middle of a line, requesting empty line below only
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndefghi\njkl", cx);
+        let point = buffer.insert_empty_line(Point::new(1, 3), false, true, cx);
+        assert_eq!(buffer.text(), "abc\ndef\n\n\nghi\njkl");
+        assert_eq!(point, Point::new(2, 0));
+        buffer
+    });
+
+    // Insert empty line at the end, requesting empty lines above and below
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(2, 3), true, true, cx);
+        assert_eq!(buffer.text(), "abc\ndef\nghi\n\n\n");
+        assert_eq!(point, Point::new(4, 0));
+        buffer
+    });
+
+    // Insert empty line at the end, requesting empty line above only
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(2, 3), true, false, cx);
+        assert_eq!(buffer.text(), "abc\ndef\nghi\n\n");
+        assert_eq!(point, Point::new(4, 0));
+        buffer
+    });
+
+    // Insert empty line at the end, requesting empty line below only
+    cx.new_model(|cx| {
+        let mut buffer = Buffer::local("abc\ndef\nghi", cx);
+        let point = buffer.insert_empty_line(Point::new(2, 3), false, true, cx);
+        assert_eq!(buffer.text(), "abc\ndef\nghi\n\n");
+        assert_eq!(point, Point::new(3, 0));
+        buffer
+    });
+}
+
 #[gpui::test]
 fn test_language_scope_at_with_javascript(cx: &mut AppContext) {
     init_settings(cx, |_| {});