fix: drop per-field w:dirty, update fields on open via settings updateFields

Word's per-field dirty-driven field update crashes the full book with a hard
open error even at a single dirty PAGEREF (24-bisect isolation); the settings
level <w:updateFields w:val='true'/> batch path opens the same document with
correct TOC page numbers.

tests/test_formatter.py

@@ -626,6 +626,32 @@ class RunningHeaderTests(unittest.TestCase):
             "w:settings children out of CT_Settings order: "
             + ", ".join(t.split("}")[-1] for t in canonical))
 
+    def test_toc_fields_carry_no_dirty_flag(self):
+        # Per-field w:dirty crashes Word on this book (isolated over 24
+        # bisection files); PAGEREF begin runs must stay clean and rely on
+        # the settings-level updateFields batch path instead.
+        d = self._format()
+        n_begin = 0
+        for fc in d.element.body.iter(qn("w:fldChar")):
+            if fc.get(qn("w:fldCharType")) != "begin":
+                continue
+            rpr = fc.getparent().find(qn("w:rPr"))
+            if rpr is not None:
+                self.assertIsNone(
+                    rpr.find(qn("w:dirty")),
+                    "PAGEREF begin run must not carry w:dirty")
+            n_begin += 1
+        # The book ships two chapters in the test manuscript -> 2 TOC fields.
+        self.assertGreaterEqual(n_begin, 2)
+
+    def test_settings_request_field_update_on_open(self):
+        # Word recomputes the TOC page numbers through the settings-level
+        # <w:updateFields> batch path (proved to open the full book).
+        d = self._format()
+        uf = d.settings.element.find(qn("w:updateFields"))
+        self.assertIsNotNone(uf)
+        self.assertEqual(uf.get(qn("w:val")), "true")
+
     def test_style_references_resolve(self):
         # Word rejects documents whose paragraphs reference styles that are
         # not defined in styles.xml (LO silently falls back to Normal).

umbraformat/formatter.py

@@ -824,21 +824,21 @@ def _add_bookmark(para, bookmark_id, bookmark_name):
 def _add_pageref_field(para, bookmark_name, font_name="Caladea", font_size=Pt(11)):
     """Add a PAGEREF field (page number of bookmark) to the paragraph.
     Each field char is in its own run per OOXML spec (Word requires this).
-    The begin run carries w:dirty so Word knows to recalculate the field."""
+
+    The begin run deliberately carries NO w:dirty. Word's per-field dirty
+    update path crashes with the hard "Word experienced an error" dialog on
+    this book (proved empirically: 1 dirty field in the full shell fails;
+    the 28-field mini fails but the 3-field mini opens). Instead the whole
+    document enables <w:updateFields w:val="true"/> at the settings level
+    (see pass 2), which makes Word recompute every field on open through a
+    batch path that survives the same document.
+    """
     r1 = para.add_run()
     r1.font.name = font_name
     r1.font.size = font_size
     fld1 = OxmlElement("w:fldChar")
     fld1.set(qn("w:fldCharType"), "begin")
     r1._r.append(fld1)
-    # Mark field as dirty so Word recalculates it on open
-    rpr = r1._r.find(qn('w:rPr'))
-    if rpr is None:
-        rpr = OxmlElement('w:rPr')
-        r1._r.insert(0, rpr)
-    dirty = OxmlElement('w:dirty')
-    dirty.set(qn('w:val'), '1')
-    rpr.append(dirty)
 
     r2 = para.add_run()
     r2.font.name = font_name
@@ -1888,8 +1888,15 @@ def format_document(filepath, output_path=None, font_name="Caladea", font_size=1
     # w:settings per OOXML; Word honors it in modern layout compat mode.
     if settings.find(qn('w:autoHyphenation')) is None:
         settings.append(OxmlElement('w:autoHyphenation'))
+    # Fields update on open through the settings-level batch path. Per-field
+    # w:dirty cannot be used: Word's dirty-driven field update crashes this
+    # book with a hard open error (empirically isolated over 24 bisections).
+    if settings.find(qn('w:updateFields')) is None:
+        uf = OxmlElement('w:updateFields')
+        uf.set(qn('w:val'), 'true')
+        settings.append(uf)
     # Word requires w:settings children in strict CT_Settings order, so fix up
-    # the position of the two elements just added (LibreOffice would not care).
+    # the position of the elements just added (LibreOffice would not care).
     _reorder_settings(settings)
 
     for idx, sec in enumerate(secs):