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gh-148228: Enable error overlays in the REPL #148229

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gh-148228: Enable error overlays in the REPL #148229

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86977f9
Enable error overlays
johnslavik Apr 7, 2026
9415f6b
Fix `down` command error reporting bug
johnslavik Apr 7, 2026
62b3577
Fix `test_down_arrow_end_of_input`
johnslavik Apr 7, 2026
50188d3
Fix `test_right_arrow_end_of_line` test
johnslavik Apr 7, 2026
c4b55f2
Merge branch 'main' into enable-error-overlays
johnslavik Apr 9, 2026
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1 change: 1 addition & 0 deletions Lib/_colorize.py
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,7 @@ class LiveProfiler(ThemeSection):
@dataclass(frozen=True, kw_only=True)
class Syntax(ThemeSection):
prompt: str = ANSIColors.BOLD_MAGENTA
error: str = ANSIColors.BOLD_RED
keyword: str = ANSIColors.BOLD_BLUE
keyword_constant: str = ANSIColors.BOLD_BLUE
builtin: str = ANSIColors.CYAN
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6 changes: 4 additions & 2 deletions Lib/_pyrepl/commands.py
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Original file line number Diff line number Diff line change
Expand Up @@ -296,8 +296,10 @@ def do(self) -> None:
r.select_item(r.historyi + 1)
r.pos = r.eol(0)
return
r.pos = len(b)
r.error("end of buffer")
if r.pos == len(b):
r.error("end of buffer")
else:
r.pos = len(b)
Comment on lines +299 to +302
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@pablogsal pablogsal Apr 24, 2026

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Do we have tests that cover both branches here?

return

if (
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9 changes: 7 additions & 2 deletions Lib/_pyrepl/reader.py
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Expand Up @@ -288,6 +288,7 @@ class Reader:
ps3: str = "|.. "
ps4: str = R"\__ "
kill_ring: list[list[str]] = field(default_factory=list)
error_prefix: str = "! "
msg: str = ""
arg: int | None = None
finished: bool = False
Expand Down Expand Up @@ -875,9 +876,13 @@ def finish(self) -> None:
pass

def error(self, msg: str = "none") -> None:
self.msg = "! " + msg + " "
self.invalidate_message()
error_prefix = self.error_prefix
if self.can_colorize:
t = THEME()
error_prefix = f"{t.error}{error_prefix}{t.reset}"
self.console.beep()
self.msg = error_prefix + msg
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@pablogsal pablogsal Apr 24, 2026

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Maybe I am misreading this flow but if I am not wrong, the error() now embeds the escape sequences into self.msg. The message renderer at _render_message_lines slices by string length, not visible width. Then, len(message_line) counts the ANSI bytes (\x1b[1;31m ... \x1b[0m), so on narrow terminals (or long error messages) the slice boundary can land mid-escape, producing a truncated \x1b[ on one line and stray m on the next leaving the whole line un-colored or visually corrupted.

self.invalidate_message()

def update_screen(self) -> None:
if self.invalidation.is_cursor_only:
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3 changes: 0 additions & 3 deletions Lib/_pyrepl/readline.py
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Expand Up @@ -124,9 +124,6 @@ def __post_init__(self) -> None:
self.commands["backspace_dedent"] = backspace_dedent
self.commands["backspace-dedent"] = backspace_dedent

def error(self, msg: str = "none") -> None:
pass # don't show error messages by default

def get_stem(self) -> str:
b = self.buffer
p = self.pos - 1
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8 changes: 6 additions & 2 deletions Lib/test/test_pyrepl/test_pyrepl.py
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Expand Up @@ -213,13 +213,15 @@ def test_down_arrow_end_of_input(self):
events = itertools.chain(
code_to_events(code),
[
# Go left first to avoid end of buffer error.
Event(evt="key", data="left", raw=bytearray(b"\x1bOD")),
Event(evt="key", data="down", raw=bytearray(b"\x1bOB")),
],
)

reader, console = handle_all_events(events)
self.assertEqual(reader.cxy, (0, 2))
console.move_cursor.assert_called_once_with(0, 2)
console.move_cursor.assert_called_with(0, 2)

def test_left_arrow_simple(self):
events = itertools.chain(
Expand All @@ -237,13 +239,15 @@ def test_right_arrow_end_of_line(self):
events = itertools.chain(
code_to_events("11+11"),
[
# Go left first to avoid end of buffer error.
Event(evt="key", data="left", raw=bytearray(b"\x1bOD")),
Event(evt="key", data="right", raw=bytearray(b"\x1bOC")),
],
)

reader, console = handle_all_events(events)
self.assertEqual(reader.cxy, (5, 0))
console.move_cursor.assert_called_once_with(5, 0)
console.move_cursor.assert_called_with(5, 0)

def test_cursor_position_simple_character(self):
events = itertools.chain(code_to_events("k"))
Expand Down
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