From 8a42066ec571b46891ca5165840779a3b7345c96 Mon Sep 17 00:00:00 2001
From: WyattAu <wyatt_au@protonmail.com>
Date: Mon, 31 Aug 2026 19:46:31 +0100
Subject: [PATCH] Add nil guards for kpse.find_file in unicode data loading

io.open(kpse.find_file"...") crashes with a cryptic error when
kpse.find_file returns nil (e.g. when the unicode-data package is
not installed, or when the font cache is empty/corrupted).

Add nil guards with a clear error message directing users to install
the 'unicode-data' TeX package.

Fixes #264
Closes #335
---
 src/luaotfload-multiscript.lua | 14 ++++++++++++--
 src/luaotfload-notdef.lua      | 14 ++++++++++++--
 src/luaotfload-unicode.lua     | 35 +++++++++++++++++++++++++++++-----
 3 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/src/luaotfload-multiscript.lua b/src/luaotfload-multiscript.lua
index bcf9edde..cc24873f 100644
--- a/src/luaotfload-multiscript.lua
+++ b/src/luaotfload-multiscript.lua
@@ -66,7 +66,12 @@ local script_extensions do
     * entry^0
   , multirawset)
 
-  local f = io.open(kpse.find_file"ScriptExtensions.txt")
+  local script_extensions_file = kpse.find_file"ScriptExtensions.txt"
+  if not script_extensions_file then
+    error("luaotfload: Cannot find ScriptExtensions.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(script_extensions_file)
   script_extensions = file:match(f:read'*a')
   f:close()
   for cp,t in next, script_extensions do
@@ -131,7 +136,12 @@ local script_mapping do
     * entry^0
   , multirawset)
 
-  local f = io.open(kpse.find_file"Scripts.txt")
+  local scripts_file = kpse.find_file"Scripts.txt"
+  if not scripts_file then
+    error("luaotfload: Cannot find Scripts.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(scripts_file)
   script_mapping = file:match(f:read'*a')
   f:close()
 
diff --git a/src/luaotfload-notdef.lua b/src/luaotfload-notdef.lua
index 13b5d51a..765cdc35 100644
--- a/src/luaotfload-notdef.lua
+++ b/src/luaotfload-notdef.lua
@@ -65,7 +65,12 @@ local ignorable_codepoints do
       lpeg.Ct''
     * entry^0
   , rawset)
-  local f = io.open(kpse.find_file"UnicodeData.txt")
+  local unicode_data_file = kpse.find_file"UnicodeData.txt"
+  if not unicode_data_file then
+    error("luaotfload: Cannot find UnicodeData.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(unicode_data_file)
   ignorable_codepoints = file:match(f:read'*a')
   f:close()
   entry = lpeg.Cg(codepoint_range * sep * ('Other_Default_Ignorable_Code_Point' * lpeg.Cc(true)
@@ -77,7 +82,12 @@ local ignorable_codepoints do
       lpeg.Carg(1)
     * entry^0
   , multirawset)
-  f = io.open(kpse.find_file"PropList.txt")
+  local proplist_file = kpse.find_file"PropList.txt"
+  if not proplist_file then
+    error("luaotfload: Cannot find PropList.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  f = io.open(proplist_file)
   ignorable_codepoints = file:match(f:read'*a', 1, ignorable_codepoints)
   f:close()
   for i = 0xFFF9,0xFFFB do
diff --git a/src/luaotfload-unicode.lua b/src/luaotfload-unicode.lua
index 715d4d98..078292ea 100644
--- a/src/luaotfload-unicode.lua
+++ b/src/luaotfload-unicode.lua
@@ -31,7 +31,12 @@ local alphnum_only do
     * entry^0
   , rawset)
 
-  local f = io.open(kpse.find_file"UnicodeData.txt")
+  local unicode_data_file = kpse.find_file"UnicodeData.txt"
+  if not unicode_data_file then
+    error("luaotfload: Cannot find UnicodeData.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(unicode_data_file)
   local data = file:match(f:read'*a')
   f:close()
   function alphnum_only(s)
@@ -104,7 +109,12 @@ local uppercase, lowercase, ccc, cased, case_ignorable, titlecase = {}, {}, {},
     end
   local file = entry^0 * -1
 
-  local f = io.open(kpse.find_file"UnicodeData.txt")
+  local unicode_data_file2 = kpse.find_file"UnicodeData.txt"
+  if not unicode_data_file2 then
+    error("luaotfload: Cannot find UnicodeData.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(unicode_data_file2)
   assert(file:match(f:read'*a'))
   f:close()
 end
@@ -129,7 +139,12 @@ local props do
     return t
   end) * -1
 
-  local f = io.open(kpse.find_file"PropList.txt")
+  local proplist_file = kpse.find_file"PropList.txt"
+  if not proplist_file then
+    error("luaotfload: Cannot find PropList.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(proplist_file)
   props = file:match(f:read'*a')
   f:close()
 end
@@ -143,7 +158,12 @@ do
     end
   end + (1-lpeg.P'\n')^0 * '\n')^0 * -1
 
-  local f = io.open(kpse.find_file"WordBreakProperty.txt")
+  local wbp_file = kpse.find_file"WordBreakProperty.txt"
+  if not wbp_file then
+    error("luaotfload: Cannot find WordBreakProperty.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(wbp_file)
   assert(file:match(f:read'*a'))
   f:close()
 end
@@ -187,7 +207,12 @@ do
               end
   local file = (entry + nl)^0 * -1
 
-  local f = io.open(kpse.find_file"SpecialCasing.txt")
+  local special_casing_file = kpse.find_file"SpecialCasing.txt"
+  if not special_casing_file then
+    error("luaotfload: Cannot find SpecialCasing.txt. "
+      .. "Install the 'unicode-data' TeX package (tlmgr install unicode-data).")
+  end
+  local f = io.open(special_casing_file)
   assert(file:match(f:read'*a'))
   f:close()
 end