From 15a242e822827288e2c2e4c0c92331087b40f581 Mon Sep 17 00:00:00 2001
From: Julio B <julio.bacel@gmail.com>
Date: Mon, 27 Dec 2021 07:51:49 +0200
Subject: [PATCH 1/2] fix: highlight of \iffalse

The contents after \else should not be highlighted as a comment
ref: #1988
---
 autoload/vimtex/syntax/core.vim   |  2 +-
 test/test-syntax/test-iffalse.tex | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/autoload/vimtex/syntax/core.vim b/autoload/vimtex/syntax/core.vim
index 83406755e8..e7d9b2e7af 100644
--- a/autoload/vimtex/syntax/core.vim
+++ b/autoload/vimtex/syntax/core.vim
@@ -434,7 +434,7 @@ function! vimtex#syntax#core#init() abort " {{{1
 
   " Highlight \iffalse ... \fi blocks as comments
   syntax region texComment matchgroup=texCmd
-        \ start="^\s*\\iffalse\>" end="\\fi\>"
+        \ start="^\s*\\iffalse\>" end="\\\(fi\|else\)\>"
         \ contains=texCommentConditionals
   syntax region texCommentConditionals matchgroup=texComment
         \ start="\\if\w\+" end="\\fi\>"
diff --git a/test/test-syntax/test-iffalse.tex b/test/test-syntax/test-iffalse.tex
index 57781e9da9..a20be7ffcf 100644
--- a/test/test-syntax/test-iffalse.tex
+++ b/test/test-syntax/test-iffalse.tex
@@ -11,6 +11,7 @@
 \iffalse
 Commented stuff
 Another \ifstuff here \fi
+\ifaa \else \fi
 \ifasd \fi \f \fii
 
 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
@@ -19,4 +20,16 @@
 gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
 \fi
 
+\iffalse
+Commented stuff
+Another \ifstuff here \fi
+\ifaa \else \fi
+\ifasd \fi \f \fii
+\else
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
+tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
+\fi
+
 \end{document}

From 09ba976c4a9c528ad3baced824ffff3c788dcdd2 Mon Sep 17 00:00:00 2001
From: Julio B <julio.bacel@gmail.com>
Date: Tue, 1 Feb 2022 20:24:15 +0200
Subject: [PATCH 2/2] feat(syntax): support \iftrue command

Highlight the \else section of \iftrue command as a comment
ref: #1988
---
 autoload/vimtex/syntax/core.vim  | 19 ++++++++++++++++
 test/test-syntax/test-iftrue.tex | 38 ++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 test/test-syntax/test-iftrue.tex

diff --git a/autoload/vimtex/syntax/core.vim b/autoload/vimtex/syntax/core.vim
index e7d9b2e7af..28201f421c 100644
--- a/autoload/vimtex/syntax/core.vim
+++ b/autoload/vimtex/syntax/core.vim
@@ -436,6 +436,25 @@ function! vimtex#syntax#core#init() abort " {{{1
   syntax region texComment matchgroup=texCmd
         \ start="^\s*\\iffalse\>" end="\\\(fi\|else\)\>"
         \ contains=texCommentConditionals
+
+  syntax cluster texIftrueCluster contains=TOP
+  syntax cluster texIftrueClusterCommon contains=@texIftrueCluster,texIftrueConditionals
+
+  syntax region texIftrue matchgroup=texCmd
+        \ start="^\s*\\iftrue\>"  end="\(\\\(fi\|else\)\>\)\@="
+        \ transparent contains=@texIftrueClusterCommon
+        \ nextgroup=texIftrueElseComment
+
+  syntax region texIftrueElseComment matchgroup=texCmd
+        \ start="\(\(\\fi\>\)@=\|\\else\>\)"  end="\\fi\>"
+        \ contained contains=texCommentConditionals
+
+  highlight def link texIftrueElseComment texComment
+
+  syntax region texIftrueConditionals matchgroup=texCmd
+        \ start="\\if\w\+" end="\\fi\>"
+        \ contained contains=@texIftrueClusterCommon
+
   syntax region texCommentConditionals matchgroup=texComment
         \ start="\\if\w\+" end="\\fi\>"
         \ contained transparent
diff --git a/test/test-syntax/test-iftrue.tex b/test/test-syntax/test-iftrue.tex
new file mode 100644
index 0000000000..72099a57e0
--- /dev/null
+++ b/test/test-syntax/test-iftrue.tex
@@ -0,0 +1,38 @@
+\documentclass{article}
+\usepackage[utf8]{inputenc}
+\usepackage{graphicx}
+
+\begin{document}
+
+\iftrue
+\section{asd}
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
+tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
+\ifasd \fi
+\ifaa asd \else asd \fi
+\fi
+
+\section{qwe}
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
+tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
+
+\iftrue
+\section{asd}
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
+tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
+\ifasd \fi
+\ifaa asd \else asd \fi
+\else
+Commented stuff
+Another \ifstuff here \fi
+\ifaa \else \fi
+\ifasd \fi \f \fii
+\fi
+
+\end{document}