Preserve completion styles after common-prefix insertion

src/prompt_toolkit/completion/base.py

@@ -117,6 +117,8 @@ def new_completion_from_position(self, position: int) -> Completion:
             text=self.text[position - self.start_position :],
             display=self.display,
             display_meta=self._display_meta,
+            style=self.style,
+            selected_style=self.selected_style,
         )
 
 

tests/test_buffer.py

@@ -1,8 +1,12 @@
 from __future__ import annotations
 
+import asyncio
+
 import pytest
 
 from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.completion import Completer, Completion
+from prompt_toolkit.document import Document
 
 
 @pytest.fixture
@@ -110,3 +114,33 @@ def test_swap_characters_before_cursor(_buffer):
     _buffer.swap_characters_before_cursor()
 
     assert _buffer.text == "hello wrold"
+
+
+def test_common_completion_preserves_styles():
+    class StyledCompleter(Completer):
+        def get_completions(self, document, complete_event):
+            for text, style, selected_style in (
+                ("hello", "fg:ansired", "bg:ansigreen"),
+                ("help", "fg:ansiblue", "bg:ansiyellow"),
+            ):
+                yield Completion(
+                    text,
+                    start_position=-2,
+                    style=style,
+                    selected_style=selected_style,
+                )
+
+    buffer = Buffer(completer=StyledCompleter(), document=Document("he", 2))
+    asyncio.run(buffer._async_completer(insert_common_part=True))
+
+    assert buffer.text == "hel"
+    assert buffer.complete_state is not None
+    completions = buffer.complete_state.completions
+    assert [(c.text, c.style, c.selected_style) for c in completions] == [
+        ("lo", "fg:ansired", "bg:ansigreen"),
+        ("p", "fg:ansiblue", "bg:ansiyellow"),
+    ]
+    buffer.go_to_completion(0)
+    assert buffer.text == "hello"
+    buffer.go_to_completion(1)
+    assert buffer.text == "help"

tests/test_completion.py

@@ -8,6 +8,7 @@
 
 from prompt_toolkit.completion import (
     CompleteEvent,
+    Completion,
     FuzzyWordCompleter,
     NestedCompleter,
     PathCompleter,
@@ -467,3 +468,23 @@ def create_completer(deduplicate: bool):
         )
     )
     assert len(completions) == 5
+
+
+def test_completion_from_position_preserves_styles():
+    completion = Completion(
+        "hello",
+        start_position=-2,
+        display=[("bold", "Hello")],
+        display_meta=lambda: "greeting",
+        style="fg:ansired",
+        selected_style="bg:ansigreen",
+    )
+
+    suffix = completion.new_completion_from_position(1)
+
+    assert suffix.text == "lo"
+    assert suffix.start_position == 0
+    assert suffix.display == completion.display
+    assert suffix._display_meta is completion._display_meta
+    assert suffix.style == completion.style
+    assert suffix.selected_style == completion.selected_style