From ade75eceb9f62bbdb9d1e75b20d902e09ad7c034 Mon Sep 17 00:00:00 2001
From: "Josef M. Gallmetzer" <64498081+galjos@users.noreply.github.com>
Date: Mon, 13 Jul 2026 18:15:48 +0200
Subject: [PATCH] Harden _parse_fukui's table-end detection

xtb writes Fukui data only to stdout (verified: a clean-directory
--vfukui run writes no dedicated file for it), so this parser is
unavoidably stdout-scraping -- but it was only checking token count
to detect the end of the table, so a coincidental 4-token line right
after it would get silently misparsed as a data row. Now also checks
the label matches "digits then letters" and the last 3 tokens parse
as floats before accepting a row.
---
 ThermoScreening/calculator/xtb_cli.py | 12 ++++++--
 tests/calculator/test_xtb_cli.py      | 42 +++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/ThermoScreening/calculator/xtb_cli.py b/ThermoScreening/calculator/xtb_cli.py
index fad9e0b..cc70b45 100644
--- a/ThermoScreening/calculator/xtb_cli.py
+++ b/ThermoScreening/calculator/xtb_cli.py
@@ -9,6 +9,7 @@
 """
 
 import os
+import re
 import shutil
 import subprocess
 
@@ -184,9 +185,14 @@ def _parse_fukui(output):
         tokens = line.split()
         if len(tokens) != 4:
             break
-        label, f_plus, f_minus, f_zero = tokens
-        symbol = label.lstrip("0123456789")
-        rows.append((symbol, float(f_plus), float(f_minus), float(f_zero)))
+        label_match = re.match(r"^(\d+)([A-Za-z]+)$", tokens[0])
+        if label_match is None:
+            break
+        try:
+            f_plus, f_minus, f_zero = (float(token) for token in tokens[1:])
+        except ValueError:
+            break
+        rows.append((label_match.group(2), f_plus, f_minus, f_zero))
     return rows
 
 
diff --git a/tests/calculator/test_xtb_cli.py b/tests/calculator/test_xtb_cli.py
index 04b29a9..86dae65 100644
--- a/tests/calculator/test_xtb_cli.py
+++ b/tests/calculator/test_xtb_cli.py
@@ -110,6 +110,48 @@ def test_parse_fukui_raises_without_table():
         xtb_cli._parse_fukui("no such table here")
 
 
+def test_parse_fukui_stops_at_coincidental_four_token_line_with_bad_label():
+    # a line right after the table with 4 tokens but a label that isn't
+    # "digits then letters" must not be misparsed as data -- token count
+    # alone isn't enough to detect the end of the table
+    output = (
+        "Fukui functions:\n"
+        "     #        f(+)     f(-)     f(0)\n"
+        "     1C       0.024    0.024    0.024\n"
+        "     abc      0.1      0.2      0.3\n"
+        "     8O       0.131    0.129    0.130\n"
+    )
+    rows = xtb_cli._parse_fukui(output)
+
+    assert rows == [("C", 0.024, 0.024, 0.024)]
+
+
+def test_parse_fukui_stops_at_coincidental_four_token_line_with_bad_values():
+    # a line with a valid-looking label but non-numeric values must also
+    # not be misparsed as data
+    output = (
+        "Fukui functions:\n"
+        "     #        f(+)     f(-)     f(0)\n"
+        "     1C       0.024    0.024    0.024\n"
+        "     2C       n/a      n/a      n/a\n"
+        "     8O       0.131    0.129    0.130\n"
+    )
+    rows = xtb_cli._parse_fukui(output)
+
+    assert rows == [("C", 0.024, 0.024, 0.024)]
+
+
+def test_parse_fukui_handles_multi_digit_index_and_multi_letter_symbol():
+    output = (
+        "Fukui functions:\n"
+        "     #        f(+)     f(-)     f(0)\n"
+        "    14Cl      0.010    0.020    0.015\n"
+    )
+    rows = xtb_cli._parse_fukui(output)
+
+    assert rows == [("Cl", 0.010, 0.020, 0.015)]
+
+
 def test_run_xtb_fukui_builds_command_and_parses(monkeypatch, tmp_path):
     monkeypatch.chdir(tmp_path)
     monkeypatch.setenv("XTB_COMMAND", "/fake/xtb")