Re: require flow and relation between package.searchers and package.searchpath

I wrote a searcher to basically search for modules with sub modules properly in my installation directory structure. But I do not see the error message returned by my searcher in the final result.

I have the following directory structure:

Structure Root

|---- __Lua\Lua53\lua.exe - lua executable and dll

|---- moduleX

|---- src -- All module lua files

|---- moduleY

So suppose the moduleX has a submodule test. And when I do require("moduleX.test") it basically needs to load the file -> "Structure Root/moduleX/src/moduleX/test.lua" I added the path in package.path as "Structure Root/?/src/?.lua". This of course does not work since the default searcher translates it to "Structure Root/moduleX/test/src/moduleX/test.lua". So I wrote this searcher and added it to searchers:

-- Searcher for nested lua modules

package.searchers[#package.searchers + 1] = function(mod)

-- Check if this is a multi hierarchy module

if mod:find(".",1,true) then

-- Get the top most name

local totErr = ""

local top = mod:sub(1,mod:find(".",1,true)-1)

local sep = package.config:match("(.-)%s")

local delim = package.config:match(".-%s+(.-)%s")

local subst = mod:gsub("%.",sep)

-- Now loop through all the lua module paths

for path in package.path:gmatch("(.-)"..delim) do

if path:sub(-5,-1) == "?.lua" then

path = path:sub(1,-6)..subst..".lua"

end

path = path:gsub("%?",top)

--print("Search at..."..path)

-- try loading this file

local f,err = loadfile(path)

if not f then

totErr = totErr.."no file '"..path.."'\n"

else

--print("FOUND")

return f

end

return nil,totErr

end

Now when I do require("moduleX.test") it is successfully able to load that module. But if I do require("moduleX.tst") I see no error message returned by my searcher. Can anybody please help me figure out what am I doing wrong here.

Thanks,

Milind

On Mon, Aug 10, 2015 at 1:35 PM, Milind Gupta <milind.gupta@gmail.com> wrote:

Thank you very much for the detailed explanation.

Milind

On Mon, Aug 10, 2015 at 12:59 PM, Philipp Janda <siffiejoe@gmx.net> wrote:
Am 10.08.2015 um 21:37 schröbte Milind Gupta:

Hi,

Hi!

I am trying to understand how does the require function invoke
package.searchpath and package.searchers. Does a searcher called searchpath
function? If yes then that means the searcher is responsible for reading
the paths and deciding which one is a lua fie (for example the lua module
searcher) and then passing the paths one by one to package.searchpath?

`require` calls the functions in `package.searchers` one after the other passing the module name as an argument until one of the searchers returns a function (the loaded chunk) or raises an error (e.g. if the module was found but contained syntax errors). If the searchers return a string instead, those error messages are concatenated and printed at the end if all searchers were unsuccessful.

`require` does not call `package.searchpath` directly, but a searcher may of course. All standard searchers except the first (the `package.preload` searcher) use the equivalent C code.

`package.searchpath` takes a path template list (usually `package.path` or `package.cpath`) and a module name, and creates a list of actual paths. It then tries those paths one by one, searching for a file that exists (is readable). If it finds one, it returns the path to that file. Otherwise it returns `nil` plus a string that can be returned from a searcher as an error message.

Thanks,
Milind

Philipp