Fix \title, \author and \date with an optional short argument

\title[short]{full} (and the same for \author and \date) was parsed with
the optional argument missing from the macro spec, so the leading "[" and
the short text were left as ordinary character nodes and the mandatory
argument was never recognised.  latex_to_text() then emitted the raw
"short]full" text, and \maketitle rendered a stray "[".

The optional argument is not a LaTeX kernel feature: the standard classes
(article, report, book) declare these three commands with a single
mandatory argument.  Several widely used classes do add a leading optional
argument holding a short form of the field, meant for running heads --
beamer for all three commands, and the AMS classes (amsart, amsbook,
amsproc, and acmart, which is built on amsart) for \title and \author.
Since documents using the standard classes simply never have the optional
argument present, declaring it costs them nothing.

Declare it in the latexwalker specs ('[{' instead of '{'), and have the
latex2text specs read the *last* argument rather than a fixed position, so
that they also keep working with a latex context in which these macros
were declared with the mandatory argument alone.

Adds regression tests at the latexwalker level, for the rendered title
block with the short form, and for a context declaring the mandatory
argument alone.

Closes #114.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NbTg7TMbpkWihLzotNLPdu

Author: 2 people

pylatexenc/latex2text/_defaultspecs.py

@@ -579,12 +579,20 @@ def _format_frac(n, l2tobj):
         # later, by '\maketitle', so what is stored has to be a string; in math
         # mode the 'fancy' math mode renders a node list to a math
         # piece rather than to a string
+        #
+        # the argnlist[-1:] slices: the default specs declare these macros with
+        # a leading optional argument, the "short" form of the field that
+        # beamer and the AMS classes accept (see the macro specs in
+        # pylatexenc/latexwalker/_defaultspecs.py), so the field itself is the
+        # *last* argument.  Taking the last one rather than a fixed position
+        # also keeps these formatters working with a latex context in which the
+        # macros were declared with the mandatory argument alone.
         ('title', lambda n, l2tobj: \
-         setattr(l2tobj, '_doc_title', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[0:1])))),
+         setattr(l2tobj, '_doc_title', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[-1:])))),
         ('author', lambda n, l2tobj: \
-         setattr(l2tobj, '_doc_author', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[0:1])))),
+         setattr(l2tobj, '_doc_author', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[-1:])))),
         ('date', lambda n, l2tobj: \
-         setattr(l2tobj, '_doc_date', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[0:1])))),
+         setattr(l2tobj, '_doc_date', str(l2tobj.nodelist_to_text(n.nodeargd.argnlist[-1:])))),
         ('maketitle', lambda n, l2tobj: \
          _format_maketitle(getattr(l2tobj, '_doc_title', r'[NO \title GIVEN]'),
                            getattr(l2tobj, '_doc_author', r'[NO \author GIVEN]'),

pylatexenc/latexwalker/_defaultspecs.py

@@ -206,10 +206,24 @@ def _finalize_lstlisting_environment_node(node):
 
             MacroSpec('mbox', arguments_spec_list=[ _arg_textmode('{') ]),
 
-            # \title, \author, \date
-            MacroSpec('title', '{'),
-            MacroSpec('author', '{'),
-            MacroSpec('date', '{'),
+            # \title, \author, \date.
+            #
+            # The standard classes (article, report, book) declare these with a
+            # single mandatory argument.  A number of widely used classes add a
+            # leading optional argument that holds a short form of the field,
+            # meant for running heads and similar places:
+            #
+            #     \title[Short title]{The full and rather long title}
+            #
+            # beamer does this for all three commands; the AMS classes (amsart,
+            # amsbook, amsproc — and acmart, which is built on amsart) do it for
+            # \title and \author.  Documents that use the standard classes
+            # simply never have the optional argument present, so declaring it
+            # here costs them nothing while letting the common non-standard
+            # forms parse correctly.
+            MacroSpec('title', '[{'),
+            MacroSpec('author', '[{'),
+            MacroSpec('date', '[{'),
 
             # (Note: single backslash) end of line with optional no-break ('*') and
             # additional vertical spacing, e.g. \\*[2mm]

test/test_2_latex2text.py

@@ -16,6 +16,7 @@
 import pytest
 
 from pylatexenc.latexwalker import LatexWalker
+from pylatexenc import macrospec
 from pylatexenc import latex2text
 from pylatexenc.latex2text import LatexNodes2Text
 
@@ -1831,6 +1832,67 @@ def test_repl_doc_title(self):
 """ % { 'today': today, 'eqhrule': eqhrule }
         )
 
+    def test_repl_doc_title_optional_short_arg(self):
+
+        # \title[short]{full}, \author[short]{full} and \date[short]{full}, as
+        # accepted by beamer and by the AMS classes: the optional "short"
+        # argument must be consumed as an argument, and the mandatory argument
+        # is the one that goes into the rendered title block.
+
+        self.assertEqualUpToWhitespace(
+                LatexNodes2Text().latex_to_text(
+                    r"""
+\title[Short Title]{The Title}
+\author[T. A.]{The Author(s)}
+\date[2020]{July 4, 2020}
+\maketitle
+"""
+                ),
+            r"""
+The Title
+    The Author(s)
+    July 4, 2020
+=================
+"""
+        )
+
+    def test_repl_doc_title_macros_declared_without_optional_arg(self):
+
+        # the \title/\author/\date text specs pick the *last* argument, so they
+        # keep working with a latex context in which these macros were declared
+        # with the mandatory argument alone (as pylatexenc 2 did)
+
+        latex_context = macrospec.LatexContextDb()
+        latex_context.add_context_category(
+            'my-title-macros',
+            macros=[
+                macrospec.MacroSpec('title', '{'),
+                macrospec.MacroSpec('author', '{'),
+                macrospec.MacroSpec('date', '{'),
+                macrospec.MacroSpec('maketitle', ''),
+            ]
+        )
+        lw = LatexWalker(
+            r"""
+\title{The Title}
+\author{The Author(s)}
+\date{July 4, 2020}
+\maketitle
+""",
+            latex_context=latex_context
+        )
+        (nodelist, npos, nlen) = lw.get_latex_nodes()
+
+        self.assertEqualUpToWhitespace(
+            LatexNodes2Text().nodelist_to_text(nodelist),
+            r"""
+The Title
+    The Author(s)
+    July 4, 2020
+=================
+"""
+        )
+
 
     def test_math_alphabets(self):
 

test/test_2_latexwalker.py

@@ -2170,6 +2170,33 @@ def test_bug_issueno57(self):
         self.assertEqual(len(node.nodeargd.argnlist), 3)
 
 
+    def test_title_author_date_optional_short_argument(self):
+        # see issue #114.  The default specs declare \title, \author and \date
+        # with the optional "short form" argument that beamer and the AMS
+        # classes accept, in addition to the mandatory argument.
+
+        for macroname in ('title', 'author', 'date'):
+
+            lw = LatexWalker('\\'+macroname+r'[Short]{The Full Form}',
+                             tolerant_parsing=False)
+            (nodelist, npos, nlen) = lw.get_latex_nodes()
+            self.assertEqual(len(nodelist), 1)
+            argnlist = nodelist[0].nodeargd.argnlist
+            self.assertEqual(len(argnlist), 2)
+            self.assertEqual(argnlist[0].nodelist[0].chars, 'Short')
+            self.assertEqual(argnlist[1].nodelist[0].chars, 'The Full Form')
+
+            # the standard classes' form, with the optional argument absent
+            lw = LatexWalker('\\'+macroname+r'{The Full Form}',
+                             tolerant_parsing=False)
+            (nodelist, npos, nlen) = lw.get_latex_nodes()
+            self.assertEqual(len(nodelist), 1)
+            argnlist = nodelist[0].nodeargd.argnlist
+            self.assertEqual(len(argnlist), 2)
+            self.assertTrue(argnlist[0] is None)
+            self.assertEqual(argnlist[1].nodelist[0].chars, 'The Full Form')
+
+
     def test_href_url_argument_is_verbatim(self):
         # the target of \href is read verbatim, because a URL may well contain
         # characters that are special to LaTeX.  A percent sign in particular