Add paths to Lua package.path so require works for user scripts

This adds the global and personal plugins directories to the
package.path setting in Lua, so doing 'require' will work
properly.

Change-Id: Iec33bc60cd7d41aa122da456db91d4ccc3085f82
Reviewed-on: https://code.wireshark.org/review/841
Reviewed-by: Hadriel Kaplan <hadrielk@yahoo.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 42 insertions, 1 deletions

diff --git a/epan/wslua/template-init.lua b/epan/wslua/template-init.lua
index 2f99159b07..806593739e 100644
--- a/epan/wslua/template-init.lua
+++ b/epan/wslua/template-init.lua
@@ -64,12 +64,53 @@ function typeof(obj)
     return mt and mt.__typeof or obj.__typeof or type(obj)
 end
 
--- the following function is since 1.11.3
+-- the following function checks if a file exists
+-- since 1.11.3
 function file_exists(name)
    local f = io.open(name,"r")
    if f ~= nil then io.close(f) return true else return false end
 end
 
+-- the following function prepends the given directory name to
+-- the package.path, so that a 'require "foo"' will work if 'foo'
+-- is in the directory name given to this function. For example,
+-- if your Lua file will do a 'require "foo"' and the foo.lua
+-- file is in a local directory (local to your script) named 'bar',
+-- then call this function before doing your 'require', by doing
+--     package.prepend_path("bar")
+-- and that will let Wireshark's Lua find the file "bar/foo.lua"
+-- when you later do 'require "foo"'
+--
+-- Because this function resides here in init.lua, it does not
+-- have the same environment as your script, so it has to get it
+-- using the debug library, which is why the code appears so
+-- cumbersome.
+--
+-- since 1.11.3
+function package.prepend_path(name)
+    local debug = require "debug"
+    -- get the function calling this package.prepend_path function
+    local dt = debug.getinfo(2, "f")
+    if not dt then
+        error("could not retrieve debug info table")
+    end
+    -- get its upvalue
+    local _, val = debug.getupvalue(dt.func, 1)
+    if not val or type(val) ~= 'table' then
+        error("No calling function upvalue or it is not a table")
+    end
+    -- get the __DIR__ field in its upvalue table
+    local dir = val["__DIR__"]
+    -- get the platform-specific directory separator character
+    local sep = package.config:sub(1,1)
+    -- prepend the dir and given name to path
+    if dir and dir:len() > 0 then
+        package.path = dir .. sep .. name .. sep .. "?.lua;" .. package.path
+    end
+    -- also prepend just the name as a directory
+    package.path = name .. sep .. "?.lua;" .. package.path
+end
+
 -- %WTAP_ENCAPS%
 
 -- %WTAP_FILETYPES%