Add experimental theming support for syntax highlighting and the prompt

Author: ambv

Doc/whatsnew/3.14.rst

@@ -485,6 +485,23 @@ For further information on how to build Python, see
 (Contributed by Ken Jin in :gh:`128563`, with ideas on how to implement this
 in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh Haberman.)
 
+Syntax highlighting in PyREPL
+-----------------------------
+
+The default :term:`interactive` shell now highlights Python syntax as you
+type.  The feature is enabled by default unless the
+:envvar:`PYTHON_BASIC_REPL` environment is set or any color-disabling
+environment variables are used. See :ref:`using-on-controlling-color` for
+details.
+
+The default color theme for syntax highlighting strives for good contrast
+and uses exclusively the 4-bit VGA standard ANSI color codes for maximum
+compatibility. The theme can be customized using an experimental API
+``_colorize.set_theme()``.  This can be called interactively, as well as
+in the :envvar:`PYTHONSTARTUP` script.
+
+(Contributed by Łukasz Langa in :gh:`131507`.)
+
 
 Other language changes
 ======================

Lib/_colorize.py

@@ -7,7 +7,22 @@
 
 # types
 if False:
-    from typing import IO
+    from typing import IO, Literal
+
+    type ColorTag = (
+        Literal["PROMPT"]
+        | Literal["KEYWORD"]
+        | Literal["BUILTIN"]
+        | Literal["COMMENT"]
+        | Literal["STRING"]
+        | Literal["NUMBER"]
+        | Literal["OP"]
+        | Literal["DEFINITION"]
+        | Literal["SOFT_KEYWORD"]
+        | Literal["RESET"]
+    )
+
+    theme: dict[ColorTag, str]
 
 
 class ANSIColors:
@@ -110,3 +125,28 @@ def can_colorize(*, file: IO[str] | IO[bytes] | None = None) -> bool:
         return os.isatty(file.fileno())
     except io.UnsupportedOperation:
         return hasattr(file, "isatty") and file.isatty()
+
+
+def set_theme(t: dict[ColorTag, str] | None = None) -> None:
+    global theme
+
+    if t:
+        theme = t
+        return
+
+    colors = get_colors()
+    theme = {
+        "PROMPT": colors.BOLD_MAGENTA,
+        "KEYWORD": colors.BOLD_BLUE,
+        "BUILTIN": colors.CYAN,
+        "COMMENT": colors.RED,
+        "STRING": colors.GREEN,
+        "NUMBER": colors.YELLOW,
+        "OP": colors.RESET,
+        "DEFINITION": colors.BOLD_WHITE,
+        "SOFT_KEYWORD": colors.BOLD_BLUE,
+        "RESET": colors.RESET,
+    }
+
+
+set_theme()

Lib/_pyrepl/reader.py

@@ -22,10 +22,10 @@
 from __future__ import annotations
 
 import sys
+import _colorize
 
 from contextlib import contextmanager
 from dataclasses import dataclass, field, fields
-from _colorize import can_colorize, ANSIColors
 
 from . import commands, console, input
 from .utils import wlen, unbracket, disp_str, gen_colors
@@ -273,7 +273,7 @@ def __post_init__(self) -> None:
         self.screeninfo = [(0, [])]
         self.cxy = self.pos2xy()
         self.lxy = (self.pos, 0)
-        self.can_colorize = can_colorize()
+        self.can_colorize = _colorize.can_colorize()
 
         self.last_refresh_cache.screeninfo = self.screeninfo
         self.last_refresh_cache.pos = self.pos
@@ -492,7 +492,11 @@ def get_prompt(self, lineno: int, cursor_on_line: bool) -> str:
             prompt = self.ps1
 
         if self.can_colorize:
-            prompt = f"{ANSIColors.BOLD_MAGENTA}{prompt}{ANSIColors.RESET}"
+            prompt = (
+                f"{_colorize.theme["PROMPT"]}"
+                f"{prompt}"
+                f"{_colorize.theme["RESET"]}"
+            )
         return prompt
 
     def push_input_trans(self, itrans: input.KeymapTranslator) -> None:

Lib/_pyrepl/utils.py

@@ -1,16 +1,17 @@
+from __future__ import annotations
 import builtins
 import functools
 import keyword
 import re
 import token as T
 import tokenize
 import unicodedata
+import _colorize
 
 from collections import deque
 from io import StringIO
 from tokenize import TokenInfo as TI
-from typing import Iterable, Iterator, Literal, Match, NamedTuple, Self
-from _colorize import ANSIColors
+from typing import Iterable, Iterator, Match, NamedTuple, Self
 
 from .types import CharBuffer, CharWidths
 from .trace import trace
@@ -21,18 +22,6 @@
 IDENTIFIERS_AFTER = {"def", "class"}
 BUILTINS = {str(name) for name in dir(builtins) if not name.startswith('_')}
 
-type ColorTag = (
-    Literal["KEYWORD"]
-    | Literal["BUILTIN"]
-    | Literal["COMMENT"]
-    | Literal["STRING"]
-    | Literal["NUMBER"]
-    | Literal["OP"]
-    | Literal["DEFINITION"]
-    | Literal["SOFT_KEYWORD"]
-    | Literal["SYNC"]
-)
-
 
 class Span(NamedTuple):
     """Span indexing that's inclusive on both ends."""
@@ -55,20 +44,7 @@ def from_token(cls, token: TI, line_len: list[int]) -> Self:
 
 class ColorSpan(NamedTuple):
     span: Span
-    tag: ColorTag
-
-
-TAG_TO_ANSI: dict[ColorTag, str] = {
-    "KEYWORD": ANSIColors.BOLD_BLUE,
-    "BUILTIN": ANSIColors.CYAN,
-    "COMMENT": ANSIColors.RED,
-    "STRING": ANSIColors.GREEN,
-    "NUMBER": ANSIColors.YELLOW,
-    "OP": ANSIColors.RESET,
-    "DEFINITION": ANSIColors.BOLD_WHITE,
-    "SOFT_KEYWORD": ANSIColors.BOLD_BLUE,
-    "SYNC": ANSIColors.RESET,
-}
+    tag: _colorize.ColorTag
 
 
 @functools.cache
@@ -305,11 +281,11 @@ def disp_str(
     post_color = ""
     if colors and colors[0].span.start < start_index:
         # looks like we're continuing a previous color (e.g. a multiline str)
-        pre_color = TAG_TO_ANSI[colors[0].tag]
+        pre_color = _colorize.theme[colors[0].tag]
 
     for i, c in enumerate(buffer, start_index):
         if colors and colors[0].span.start == i:  # new color starts now
-            pre_color = TAG_TO_ANSI[colors[0].tag]
+            pre_color = _colorize.theme[colors[0].tag]
 
         if c == "\x1a":  # CTRL-Z on Windows
             chars.append(c)
@@ -326,7 +302,7 @@ def disp_str(
             char_widths.append(str_width(c))
 
         if colors and colors[0].span.end == i:  # current color ends now
-            post_color = TAG_TO_ANSI["SYNC"]
+            post_color = _colorize.theme["RESET"]
             colors.pop(0)
 
         chars[-1] = pre_color + chars[-1] + post_color
@@ -336,7 +312,7 @@ def disp_str(
     if colors and colors[0].span.start < i and colors[0].span.end > i:
         # even though the current color should be continued, reset it for now.
         # the next call to `disp_str()` will revive it.
-        chars[-1] += TAG_TO_ANSI["SYNC"]
+        chars[-1] += _colorize.theme["RESET"]
 
     # trace("disp_str({buffer}) = {s}, {b}", buffer=repr(buffer), s=chars, b=char_widths)
     return chars, char_widths

Lib/test/test_pyrepl/test_reader.py

@@ -11,11 +11,11 @@
 from .support import reader_no_colors as prepare_reader
 from _pyrepl.console import Event
 from _pyrepl.reader import Reader
-from _pyrepl.utils import TAG_TO_ANSI
+from _colorize import theme
 
 
-overrides = {"SYNC": "z", "SOFT_KEYWORD": "K"}
-colors = {overrides.get(k, k[0].lower()): v for k, v in TAG_TO_ANSI.items()}
+overrides = {"RESET": "z", "SOFT_KEYWORD": "K"}
+colors = {overrides.get(k, k[0].lower()): v for k, v in theme.items()}
 
 
 class TestReader(ScreenEqualMixin, TestCase):