Fix vt100 6x6x6 color cube range and missing grayscale shades (232, 254-255) (#2055)

Author: kmvanbrunt

src/prompt_toolkit/output/vt100.py

@@ -210,17 +210,17 @@ def __init__(self) -> None:
         colors.append((0x00, 0xFF, 0xFF))  # 14
         colors.append((0xFF, 0xFF, 0xFF))  # 15
 
-        # colors 16..232: the 6x6x6 color cube
+        # colors 16..231: the 6x6x6 color cube
         valuerange = (0x00, 0x5F, 0x87, 0xAF, 0xD7, 0xFF)
 
-        for i in range(217):
+        for i in range(216):
             r = valuerange[(i // 36) % 6]
             g = valuerange[(i // 6) % 6]
             b = valuerange[i % 6]
             colors.append((r, g, b))
 
-        # colors 233..253: grayscale
-        for i in range(1, 22):
+        # colors 232..255: grayscale
+        for i in range(24):
             v = 8 + i * 10
             colors.append((v, v, v))
 

tests/test_vt100_output.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from prompt_toolkit.output.vt100 import _get_closest_ansi_color
+from prompt_toolkit.output.vt100 import _256_colors, _get_closest_ansi_color
 
 
 def test_get_closest_ansi_color():
@@ -18,3 +18,14 @@ def test_get_closest_ansi_color():
     assert _get_closest_ansi_color(0, 255, 10) == "ansibrightgreen"
 
     assert _get_closest_ansi_color(220, 220, 100) == "ansiyellow"
+
+
+def test_256_colors():
+    # 6x6x6 cube
+    assert _256_colors[(0, 0, 0)] == 16  # First color in cube
+    assert _256_colors[(255, 255, 255)] == 231  # Last color in cube
+    assert _256_colors[(95, 95, 95)] == 59  # Verifies a color between the boundaries
+
+    # Grayscale
+    assert _256_colors[(8, 8, 8)] == 232  # First grayscale level
+    assert _256_colors[(238, 238, 238)] == 255  # Last grayscale level