From 82aed82b8462ec1f083d9471edef2868692ded6a Mon Sep 17 00:00:00 2001
From: Derek Bailey <derekbailey@google.com>
Date: Wed, 5 May 2021 16:36:49 -0700
Subject: [PATCH] Added support for Lua 5.1, 5.2 and 5.4 (#6606)

This adds basic support for different Lua versions.

For Lua 5.2 and Lua 5.3, both the Bit32 and Compat53 Lua modules must be
installed for it to work. You can typically get these on Linux using

apt install lua-compat53 lua-bit32

For Lua 5.4, it should work as is, as it is a clean superset of Lua 5.3,
which is what the original Lua Flatbuffers supported.
---
 lua/flatbuffers/compat.lua     | 27 +++++++++++++++------------
 lua/flatbuffers/compat_5_1.lua | 21 +++++++++++++++++++++
 tests/LuaTest.sh               |  2 +-
 tests/luatest.lua              |  2 +-
 4 files changed, 38 insertions(+), 14 deletions(-)
 create mode 100644 lua/flatbuffers/compat_5_1.lua

diff --git a/lua/flatbuffers/compat.lua b/lua/flatbuffers/compat.lua
index fbce45785..1296c33fc 100644
--- a/lua/flatbuffers/compat.lua
+++ b/lua/flatbuffers/compat.lua
@@ -1,12 +1,15 @@
-local m
-if _VERSION == "Lua 5.3" then
-    m = require("flatbuffers.compat_5_3")
-else
-    local ok = pcall(require, "jit")
-    if not ok then
-        error("Only Lua 5.3 or LuaJIT is supported")
-    else
-        m = require("flatbuffers.compat_luajit")
-    end
-end
-return m
\ No newline at end of file
+local compats = {
+    ["Lua 5.1"] = function()  
+        -- Check if Lua JIT is installed first
+        local ok = pcall(require, "jit")
+        if not ok then
+            return require("flatbuffers.compat_5_1")
+        else
+            return require("flatbuffers.compat_luajit")
+        end
+    end,
+    ["Lua 5.2"] = function() return require("flatbuffers.compat_5_1") end,
+    ["Lua 5.3"] = function() return require("flatbuffers.compat_5_3") end,
+    ["Lua 5.4"] = function() return require("flatbuffers.compat_5_3") end,
+}
+return assert(compats[_VERSION], "Unsupported Lua Version: ".._VERSION)()
\ No newline at end of file
diff --git a/lua/flatbuffers/compat_5_1.lua b/lua/flatbuffers/compat_5_1.lua
new file mode 100644
index 000000000..8c5e43213
--- /dev/null
+++ b/lua/flatbuffers/compat_5_1.lua
@@ -0,0 +1,21 @@
+local m = {}
+local ok, bit = pcall(require, "bit32")
+assert(ok, "The Bit32 library must be installed")
+assert(pcall(require, "compat53"), "The Compat 5.3 library must be installed")
+
+m.GetAlignSize = function(k, size)
+    return bit.band(bit.bnot(k) + 1,(size - 1))
+end
+
+if not table.unpack then
+    table.unpack = unpack
+end
+
+if not table.pack then
+    table.pack = pack
+end
+
+m.string_pack = string.pack
+m.string_unpack = string.unpack
+
+return m
diff --git a/tests/LuaTest.sh b/tests/LuaTest.sh
index b6f17b541..d736a6b1e 100755
--- a/tests/LuaTest.sh
+++ b/tests/LuaTest.sh
@@ -19,7 +19,7 @@ test_dir="$(pwd)"
 
 ${test_dir}/../flatc --lua -I include_test monster_test.fbs
 
-declare -a versions=(luajit lua5.3)
+declare -a versions=(luajit lua5.1 lua5.2 lua5.3 lua5.4)
 
 for i in "${versions[@]}"
 do
diff --git a/tests/luatest.lua b/tests/luatest.lua
index 952c4faed..7380d7d2b 100644
--- a/tests/luatest.lua
+++ b/tests/luatest.lua
@@ -370,4 +370,4 @@ if not result then
     print("Unable to run tests due to test framework error: ",err)
 end
 
-os.exit(result or -1)
+os.exit(result and 0 or -1)