Fix edge case in insert_text_at_position when inserting in line beyond actual content

(insertion coordinates were not adjusted to true end coordinates)

test/solidlsp/test_text_utils.py

@@ -32,3 +32,19 @@ class TestTextUtils:
         assert TextUtils.get_index_from_line_col(self.TEXT, 0, 1) == 1
         assert TextUtils.get_index_from_line_col(self.TEXT, 1, 1) == 3 + 1 + 1
         assert TextUtils.get_index_from_line_col(self.TEXT, 2, 1) == 3 + 1 + 3 + 2 + 1
+
+    def test_insert_text_at_index(self):
+        insertion = "XXX"
+        new_text, l, c = TextUtils.insert_text_at_position(self.TEXT, 0, 1, insertion)
+        assert (l, c) == (0, 1 + len(insertion))
+        assert new_text.startswith("0XXX12")
+
+    def test_insert_text_in_next_line_beyond_content(self):
+        """
+        Test inserting text at a line index 1 beyond the actual number of lines.
+        This case is specifically handled as an edge case in the implementation.
+        """
+        insertion = "XXX"
+        new_text, l, c = TextUtils.insert_text_at_position(self.TEXT, 4, 0, insertion)
+        assert (l, c) == (4, len(insertion))
+        assert new_text == self.TEXT + "\n" + insertion