Fix regex-based version extraction in requirements.txt parsing (#1122)

* Initial plan

* Fix review comments: remove duplicate import, fix regex syntax, add tests

Co-authored-by: oscarlevin <6504596+oscarlevin@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: oscarlevin <6504596+oscarlevin@users.noreply.github.com>
Co-authored-by: Oscar Levin <oscar.levin@gmail.com>

Author: Copilot

pretext/utils.py

@@ -16,7 +16,6 @@
 import logging
 import logging.handlers
 import psutil
-import re
 import typing as t
 from . import types as pt  # PreTeXt types
 from lxml import etree as ET  # noqa: N812
@@ -134,7 +133,7 @@ def requirements_version(dirpath: Optional[Path] = None) -> Optional[str]:
         return None
     try:
         with open(pp / "requirements.txt", "r") as f:
-            REGEX = r"\s*pretext(book)?(\[.*\])?\s*==\s*(?P<version>[\d\.]+)\s*"gm
+            REGEX = r"\s*pretext(book)?(\[.*\])?\s*==\s*(?P<version>[\d\.]+)\s*"
             for line in f.readlines():
                 match = re.match(REGEX, line)
                 if match:

tests/test_utils.py

@@ -42,3 +42,32 @@ def test_is_unmodified() -> None:
         b"foo\n<!-- Managed automatically by PreTeXt authoring tools -->\nbar"
     )
     assert utils.is_unmodified("foo", magic_comment)
+
+
+def test_requirements_version(tmp_path: Path) -> None:
+    # Create a minimal project.ptx so project_path() can find the project root
+    (tmp_path / "project.ptx").write_text("")
+
+    cases = [
+        ("pretext == 2.36.0", "2.36.0"),
+        ("pretextbook == 1.2.3", "1.2.3"),
+        ("pretext[prefigure] == 2.36.0", "2.36.0"),
+        ("  pretext  ==  3.0.0  ", "3.0.0"),
+        ("pretext[prefigure,extra] == 0.9.1", "0.9.1"),
+    ]
+
+    for line, expected in cases:
+        req_file = tmp_path / "requirements.txt"
+        req_file.write_text(line + "\n")
+        assert utils.requirements_version(tmp_path) == expected, f"Failed for: {line!r}"
+
+    # Lines that should NOT match
+    non_matching = [
+        "numpy == 1.0.0",
+        "pretext ==",
+        "pretext",
+    ]
+    for line in non_matching:
+        req_file = tmp_path / "requirements.txt"
+        req_file.write_text(line + "\n")
+        assert utils.requirements_version(tmp_path) is None, f"Should not match: {line!r}"