From f7aabdd9fad7c67c0b6a691d401310ba8051417f Mon Sep 17 00:00:00 2001
From: Juergen Spitzmueller <spitz@lyx.org>
Date: Fri, 16 Jun 2017 10:05:12 +0200
Subject: [PATCH] Catch "! Incomplete \\if[x]" error

Fixes: #10666
---
 src/LaTeX.cpp | 6 ++++++
 status.22x    | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/src/LaTeX.cpp b/src/LaTeX.cpp
index 06add5bb6a..739a9926dd 100644
--- a/src/LaTeX.cpp
+++ b/src/LaTeX.cpp
@@ -778,6 +778,12 @@ int LaTeX::scanLogFile(TeXErrors & terr)
 				}
 			}
 
+			if (prefixIs(token, "! Incomplete \\if")) {
+				// bug 10666. At this point its not clear we finish with error.
+				wait_for_error = desc;
+				continue;
+			}
+
 			if (prefixIs(token, "! Paragraph ended before \\Hy@setref@link was complete.")){
 					// bug 7344. We must rerun LaTeX if hyperref has been toggled.
 					retval |= ERROR_RERUN;
diff --git a/status.22x b/status.22x
index abda25426b..4a56ac4565 100644
--- a/status.22x
+++ b/status.22x
@@ -47,6 +47,9 @@ What's new
 - Assure properly nested \begin{lang} and \end{lang} tags even when
   no language package is selected (bug 10685).
 
+- Catch "! Incomplete \if[x]" LaTeX error (bug 10666).
+
+
 * LYX2LYX
 
 
-- 
2.39.5