From 8bd65041f2e22bf4c37219c7008a7e4e2bda2799 Mon Sep 17 00:00:00 2001
From: Juergen Spitzmueller <spitz@lyx.org>
Date: Sun, 27 May 2018 11:54:07 +0200
Subject: [PATCH] Fix encoding problems in \input@path

As of LaTeX2e 2018, characters are made active earlier, which results
in new expansion problems.

Following a suggestion of Markus Kohm (pc) and the TL mailing list [1],
we embrace non-ASCII input paths in \detokenize. This relies on e-tex,
but I think we can assume this is nowadays available everywhere.

[1] http://tug.org/pipermail/tex-live/2018-May/041691.html

Fixes: #11146
---
 src/Buffer.cpp | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index b436a0f8a5..e05c4d07bb 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -1898,8 +1898,7 @@ Buffer::ExportStatus Buffer::writeLaTeXSource(otexstream & os,
 					    "file path name."),
 					  inputpath, uncodable_glyphs));
 			} else {
-				string docdir =
-					latex_path(original_path);
+				string docdir = os::latex_path(original_path);
 				if (contains(docdir, '#')) {
 					docdir = subst(docdir, "#", "\\#");
 					os << "\\catcode`\\#=11"
@@ -1910,9 +1909,20 @@ Buffer::ExportStatus Buffer::writeLaTeXSource(otexstream & os,
 					os << "\\catcode`\\%=11"
 					      "\\def\\%{%}\\catcode`\\%=14\n";
 				}
+				bool const detokenize = !isAscii(from_utf8(docdir));
+				bool const quote = contains(docdir, ' ');
 				os << "\\makeatletter\n"
-				   << "\\def\\input@path{{"
-				   << docdir << "}}\n"
+				   << "\\def\\input@path{{";
+				if (detokenize)
+					os << "\\detokenize{";
+				if (quote)
+					os << "\"";
+				os << docdir;
+				if (quote)
+					os << "\"";
+				if (detokenize)
+					os << "}";
+				os << "}}\n"
 				   << "\\makeatother\n";
 			}
 		}