Add 'printed_strlen' utility function

colcon_core/output_style/__init__.py

@@ -3,6 +3,7 @@
 
 from collections import namedtuple
 import os
+import re
 from types import SimpleNamespace
 
 from colcon_core.environment_variable import EnvironmentVariable
@@ -14,6 +15,22 @@
 DEFAULT_OUTPUT_STYLE_ENVIRONMENT_VARIABLE = EnvironmentVariable(
     'COLCON_DEFAULT_OUTPUT_STYLE', 'Select the default output style extension')
 
+# Match CSI (Control Sequence Introducer) and basic G0/G1 sequences.
+_ANSI_ESCAPE_RE = re.compile(r'\x1b(?:\[[0-9;]*[a-zA-Z]|[()][a-zA-Z])')
+
+
+def printed_strlen(s):
+    """
+    Get the printed length of a string by skipping over ANSI escape sequences.
+
+    :param s: The string to measure
+    :returns: The number of printable characters in the string
+    :rtype: int
+    """
+    if '\x1b' not in s:
+        return len(s)
+    return len(_ANSI_ESCAPE_RE.sub('', s))
+
 
 class Stylizer(namedtuple('Stylizer', ('start', 'end'))):
     """A text style modifier."""

test/spell_check.words

@@ -1,5 +1,6 @@
 addfinalizer
 addopts
+ansi
 apache
 argparse
 asyncio
@@ -63,6 +64,7 @@ hookwrapper
 https
 importlib
 importorskip
+introducer
 isatty
 isdigit
 iterdir

test/test_output_style.py

@@ -12,6 +12,7 @@
 from colcon_core.output_style import apply_output_style
 from colcon_core.output_style import DEFAULT_OUTPUT_STYLE_ENVIRONMENT_VARIABLE
 from colcon_core.output_style import OutputStyleExtensionPoint
+from colcon_core.output_style import printed_strlen
 from colcon_core.output_style import StyleCollection
 from colcon_core.output_style import Stylizer
 import pytest
@@ -127,3 +128,20 @@ def test_style_dump(mock_stdout):
     stdout = mock_stdout.getvalue()
     assert 'loud_errors' in stdout
     assert 'soft_warnings' in stdout
+
+
+@pytest.mark.parametrize(
+    'test_string, expected_length',
+    [
+        ('hello', 5),
+        ('\x1b[31m' + 'hello' + '\x1b[0m', 5),
+        ('\x1b[1m' + 'bold' + '\x1b[0m', 4),
+        ('\x1b[1;31m' + 'red bold' + '\x1b[0m', 8),
+        ('\x1b[31m' + 'omelet' + '\x1b[0m', 6),
+        ('\x1b[2K' + 'hello', 5),
+        ('\x1b[2K' + 'omelet', 6),
+        ('\x1b(B' + 'hello', 5),
+    ]
+)
+def test_printed_strlen(test_string, expected_length):
+    assert printed_strlen(test_string) == expected_length