Misplaced alignment tab character & when equations contain split/align

[MBradbury]

Running latexdiff when changing two equations each with a split in it to a single align with both the splits in it leads to a pdflatex compile error. Removing the \DIFadd{ } around the split environment allows the produced file to compile. This is likely to be a duplicate of #109.

latexdiff a.tex b.tex > c.tex

Trying the following does not prevent the \DIFadd{ } from being added around split.

latexdiff --exclude-safecmd "split" a.tex b.tex > c.tex

However, adding the align environment to ARRENV does prevent \DIFadd being added.

~/bin/latexdiff/latexdiff --config ARRENV="(?:(?:aligned)|(?:gathered)|(?:multlined)|(?:array)|(?:[pbvBV]?matrix)|(?:smallmatrix)|(?:cases)|(?:split)|(?:align))" a.tex b.tex > c.tex

a.tex:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}\label{eq:1}
\begin{split}
x &= y \\
& z
\end{split}
\end{equation}

\begin{equation}\label{eq:2}
\begin{split}
a &= b \\
& q
\end{split}
\end{equation}
\end{document}

b.tex:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\begin{split}
x &= y \\
& z
\end{split} \label{eq:1} \\
\begin{split}
a &= b \\
& q
\end{split} \label{eq:2}
\end{align}
\end{document}

c.tex:

\begin{document}
\DIFdelbegin \begin{displaymath}\DIFdel{%DIFDELCMD < \label{eq:1}%%%
\begin{split}
x &= y \\
& z
\end{split}
}\end{displaymath}%DIFAUXCMD
%DIFDELCMD < 

%DIFDELCMD < %%%
\begin{displaymath}\DIFdel{%DIFDELCMD < \label{eq:2}%%%
\begin{split}
a &= b \\
& q
\end{split}
}\end{displaymath}%DIFAUXCMD
\DIFdelend \DIFaddbegin \begin{align}
\DIFadd{\begin{split}
x &= y \\
& z
\end{split} \label{eq:1} }\\
\DIFadd{\begin{split}
a &= b \\
& q
\end{split} \label{eq:2}
}\end{align}\DIFaddend 
\end{document}

Package amsmath Warning: Cannot use `split' here;
(amsmath)                trying to recover with `aligned' on input line 50.


Package amsmath Warning: Cannot use `split' here;
(amsmath)                trying to recover with `aligned' on input line 59.

! Misplaced alignment tab character &.
\split@ ->\hbox to\wd \thr@@ {}&
                                \vcenter {\vbox {\moveleft \wd \thr@@ \boxz@ }}
l.69 }\end{align}
                 \DIFaddend

Version information (I'm using 6aef2ad off master):

latexdiff --version
This is LATEXDIFF 1.3.3a (Algorithm::Diff 1.1903, Perl v5.30.0)
  (c) 2004-2022 F J Tilmann

[ftilmann]

Thanks for preparing MWE. This is working now.

[AguirreNicolas]

It's seems to not be working for latexdiff-vc.
Similar example as above:

\begin{align}
  \begin{split}\label{chap3:eq:r2}
      \mathrm{R^2} ={}& 1 - \bigg\lbrack\sum_{i=1}^{N}(z_i - \widehat{z}_i) \bigg/ \sum_{i=1}^{N}(z_i - \overline{z}_i)\bigg\rbrack 
  \end{split}\\
  \begin{split}\label{chap3:eq:mse}
    \mathrm{MSE} ={}& \frac{1}{N}\sum_{i=1}^{N}(z_i - \widehat{z}_i)^{2}
  \end{split}\\
  \begin{split}\label{chap3:eq:mae}
  \mathrm{MAE} ={}&\frac{1}{N}\sum_{i=1}^{N}\lvert(z_i - \widehat{z}_i)\rvert
\end{split}
\end{align}

producing diff such:

\begin{align}
  \DIFadd{\begin{split}\label{chap3:eq:r2}
      \mathrm{R^2} ={}& 1 - \bigg\lbrack\sum_{i=1}^{N}(z_i - \widehat{z}_i) \bigg/ \sum_{i=1}^{N}(z_i - \overline{z}_i)\bigg\rbrack 
  \end{split}}\\
  \DIFadd{\begin{split}\label{chap3:eq:mse}
    \mathrm{MSE} ={}& \frac{1}{N}\sum_{i=1}^{N}(z_i - \widehat{z}_i)^{2}
  \end{split}}\\
  \DIFadd{\begin{split}\label{chap3:eq:mae}
  \mathrm{MAE} ={}&\frac{1}{N}\sum_{i=1}^{N}\lvert(z_i - \widehat{z}_i)\rvert
\end{split}
}\end{align}

using

This is LATEXDIFF 1.3.2 (Algorithm::Diff 1.15 so, Perl v5.26.1)
  (c) 2004-2021 F J Tilmann

[ftilmann]

@AguirreNicolas I tested the example of MBradybury, so your case must be subtly different. Would you mind providing old and new file for your example as it's otherwise ambiguous.

[MBradbury]

Hi both, looks like @AguirreNicolas is using an older version before the fix was included.

[AguirreNicolas]

@ftilmann

main.tex

\documentclass[11pt,twoside]{book}
\usepackage{amsmath,amssymb,amsfonts,amsbsy,latexsym,mathtools,bm}%,bbm} 

\begin{document}

\include{A}

\end{document}

A.tex (pre-commit)

\chapter{Chap name}

Pre-align:

A.tex (commited)

\chapter{Chap name}

Pre-align:

Post-align/split:

\begin{align}
  \begin{split}\label{chap3:eq:r2}
      \mathrm{R^2} ={}& 1 - \bigg\lbrack\sum_{i=1}^{N}(z_i - \widehat{z}_i) \bigg/ \sum_{i=1}^{N}(z_i - \overline{z}_i)\bigg\rbrack 
  \end{split}\\
  \begin{split}\label{chap3:eq:mse}
    \mathrm{MSE} ={}& \frac{1}{N}\sum_{i=1}^{N}(z_i - \widehat{z}_i)^{2}
  \end{split}\\
  \begin{split}\label{chap3:eq:mae}
  \mathrm{MAE} ={}&\frac{1}{N}\sum_{i=1}^{N}\lvert(z_i - \widehat{z}_i)\rvert
\end{split}
\end{align}

bla bla bla

terminal cmd:

latexdiff-vc --flatten --git -r xxx_comit_hash_xxx main.tex > diff.tex

main-diff.tex

\documentclass[11pt,twoside]{book}
%DIF LATEXDIFF DIFFERENCE FILE
%DIF DEL /tmp/TRaKNRRQ2s/latexdiff-vc-8c1adf67796d252c21c57531ebed54c196968fbb/main.tex   Wed Nov  9 06:41:55 2022
%DIF ADD main.tex                                                                         Wed Nov  9 06:41:27 2022
\usepackage{amsmath,amssymb,amsfonts,amsbsy,latexsym,mathtools,bm}%,bbm} 
%DIF PREAMBLE EXTENSION ADDED BY LATEXDIFF
%DIF UNDERLINE PREAMBLE %DIF PREAMBLE
\RequirePackage[normalem]{ulem} %DIF PREAMBLE
\RequirePackage{color}\definecolor{RED}{rgb}{1,0,0}\definecolor{BLUE}{rgb}{0,0,1} %DIF PREAMBLE
\providecommand{\DIFadd}[1]{{\protect\color{blue}\uwave{#1}}} %DIF PREAMBLE
\providecommand{\DIFdel}[1]{{\protect\color{red}\sout{#1}}}                      %DIF PREAMBLE
%DIF SAFE PREAMBLE %DIF PREAMBLE
\providecommand{\DIFaddbegin}{} %DIF PREAMBLE
\providecommand{\DIFaddend}{} %DIF PREAMBLE
\providecommand{\DIFdelbegin}{} %DIF PREAMBLE
\providecommand{\DIFdelend}{} %DIF PREAMBLE
\providecommand{\DIFmodbegin}{} %DIF PREAMBLE
\providecommand{\DIFmodend}{} %DIF PREAMBLE
%DIF FLOATSAFE PREAMBLE %DIF PREAMBLE
\providecommand{\DIFaddFL}[1]{\DIFadd{#1}} %DIF PREAMBLE
\providecommand{\DIFdelFL}[1]{\DIFdel{#1}} %DIF PREAMBLE
\providecommand{\DIFaddbeginFL}{} %DIF PREAMBLE
\providecommand{\DIFaddendFL}{} %DIF PREAMBLE
\providecommand{\DIFdelbeginFL}{} %DIF PREAMBLE
\providecommand{\DIFdelendFL}{} %DIF PREAMBLE
%DIF COLORLISTINGS PREAMBLE %DIF PREAMBLE
\RequirePackage{listings} %DIF PREAMBLE
\RequirePackage{color} %DIF PREAMBLE
\lstdefinelanguage{DIFcode}{ %DIF PREAMBLE
%DIF DIFCODE_UNDERLINE %DIF PREAMBLE
  moredelim=[il][\color{red}\sout]{\%DIF\ <\ }, %DIF PREAMBLE
  moredelim=[il][\color{blue}\uwave]{\%DIF\ >\ } %DIF PREAMBLE
} %DIF PREAMBLE
\lstdefinestyle{DIFverbatimstyle}{ %DIF PREAMBLE
	language=DIFcode, %DIF PREAMBLE
	basicstyle=\ttfamily, %DIF PREAMBLE
	columns=fullflexible, %DIF PREAMBLE
	keepspaces=true %DIF PREAMBLE
} %DIF PREAMBLE
\lstnewenvironment{DIFverbatim}{\lstset{style=DIFverbatimstyle}}{} %DIF PREAMBLE
\lstnewenvironment{DIFverbatim*}{\lstset{style=DIFverbatimstyle,showspaces=true}}{} %DIF PREAMBLE
%DIF END PREAMBLE EXTENSION ADDED BY LATEXDIFF

\begin{document}

 \newpage \chapter{Chap name}

Pre-align:
\DIFaddbegin 

\DIFadd{Post-align/split:
}

\begin{align}
  \DIFadd{\begin{split}\label{chap3:eq:r2}
      \mathrm{R^2} ={}& 1 - \bigg\lbrack\sum_{i=1}^{N}(z_i - \widehat{z}_i) \bigg/ \sum_{i=1}^{N}(z_i - \overline{z}_i)\bigg\rbrack 
  \end{split}}\\
  \DIFadd{\begin{split}\label{chap3:eq:mse}
    \mathrm{MSE} ={}& \frac{1}{N}\sum_{i=1}^{N}(z_i - \widehat{z}_i)^{2}
  \end{split}}\\
  \DIFadd{\begin{split}\label{chap3:eq:mae}
  \mathrm{MAE} ={}&\frac{1}{N}\sum_{i=1}^{N}\lvert(z_i - \widehat{z}_i)\rvert
\end{split}
}\end{align}

\DIFadd{bla bla bla }\DIFaddend \newpage 

\end{document}

[AguirreNicolas]

@MBradbury @ftilmann
You are absolutly right.
I was in 1.3.2 (from CTAN)
Just update to 1.3.3., and work properly.

Thank you guys!

[ftilmann]

Great to hear this. Apologies for the delayed update of the CTAN version. I have initiated this now, and 1.3.3 should be distributed through CTAN in the next few days.