fix: populate ... for required modules (#693)

* fix: populate `...` for required modules

Fixes #689.

* adjust code to more closely match documented semantics

Instead of hardcoding the arguments within the loader, pass them
through the searcher, as specified by the documented behavior:

#689 (comment)

> quoted from https://www.lua.org/manual/5.4/manual.html#pdf-require
>
>> Once a loader is found, require calls the loader with two arguments:
>> modname and an extra value, a loader data, also returned by the
>> searcher. The loader data can be any value useful to the module;
>> for the default searchers, it indicates where the loader was found.
>> (For instance, if the loader came from a file, this extra value is
>> the file path.)

Thanks @fperrad for the research!

* loader args: provide consistent behavior across Lua versions

This implements a compromise solution that allows Teal modules
to always get both arguments, even in Lua 5.1 based systems
(this should be harmless for modules which don't expect a second
argument there), without hardcoding `loader_data`, just in case
the user is on an environment that runs a patched `require` for
debug reasons or something.

spec/cli/run_spec.lua

@@ -93,6 +93,28 @@ describe("tl run", function()
          ]], output)
       end)
 
+      it("passes standard arguments to required chunks", function()
+         local dir_name = util.write_tmp_dir(finally, {
+            ["ld.tl"] = [[
+            require("foo")
+            print("Done")
+            ]],
+            ["foo.tl"] = [[
+            print(...)
+            ]]
+         })
+         local pd, output
+         util.do_in(dir_name, function()
+            pd = io.popen(util.tl_cmd("run", "ld.tl"), "r")
+            output = pd:read("*a")
+         end)
+         util.assert_popen_close(0, pd:close())
+         util.assert_line_by_line(util.os_path([[
+            foo ./foo.tl
+            Done
+         ]]), output)
+      end)
+
       describe("-l --require", function()
          it("can require a module from the CLI like Lua", function()
             local dir_name = util.write_tmp_dir(finally, {

tl.lua

@@ -5487,14 +5487,14 @@ local function init_globals(lax)
             }),
             ["loaders"] = a_type({
                typename = "array",
-               elements = a_type({ typename = "function", args = TUPLE({ STRING }), rets = TUPLE({ ANY }) }),
+               elements = a_type({ typename = "function", args = TUPLE({ STRING }), rets = TUPLE({ ANY, ANY }) }),
             }),
             ["loadlib"] = a_type({ typename = "function", args = TUPLE({ STRING, STRING }), rets = TUPLE({ FUNCTION }) }),
             ["path"] = STRING,
             ["preload"] = TABLE,
             ["searchers"] = a_type({
                typename = "array",
-               elements = a_type({ typename = "function", args = TUPLE({ STRING }), rets = TUPLE({ ANY }) }),
+               elements = a_type({ typename = "function", args = TUPLE({ STRING }), rets = TUPLE({ ANY, ANY }) }),
             }),
             ["searchpath"] = a_type({ typename = "function", args = TUPLE({ STRING, STRING, OPT(STRING), OPT(STRING) }), rets = TUPLE({ STRING, STRING }) }),
          },
@@ -10824,11 +10824,11 @@ local function tl_package_loader(module_name)
       local code = assert(tl.pretty_print_ast(program, env.gen_target, true))
       local chunk, err = load(code, "@" .. found_filename, "t")
       if chunk then
-         return function()
-            local ret = chunk()
+         return function(modname, loader_data)
+            local ret = chunk(modname, loader_data)
             package.loaded[module_name] = ret
             return ret
-         end
+         end, found_filename
       else
          error("Internal Compiler Error: Teal generator produced invalid Lua. Please report a bug at https://github.com/teal-language/tl\n\n" .. err)
       end

tl.tl

@@ -5487,14 +5487,14 @@ local function init_globals(lax: boolean): {string:Variable}, {string:Type}
             },
             ["loaders"] = a_type {
                typename = "array",
-               elements = a_type { typename = "function", args = TUPLE { STRING }, rets = TUPLE { ANY } }
+               elements = a_type { typename = "function", args = TUPLE { STRING }, rets = TUPLE { ANY, ANY } }
             },
             ["loadlib"] = a_type { typename = "function", args = TUPLE { STRING, STRING }, rets = TUPLE { FUNCTION } },
             ["path"] = STRING,
             ["preload"] = TABLE,
             ["searchers"] = a_type {
                typename = "array",
-               elements = a_type { typename = "function", args = TUPLE { STRING }, rets = TUPLE { ANY } }
+               elements = a_type { typename = "function", args = TUPLE { STRING }, rets = TUPLE { ANY, ANY } }
             },
             ["searchpath"] = a_type { typename = "function", args = TUPLE { STRING, STRING, OPT(STRING), OPT(STRING) }, rets = TUPLE { STRING, STRING } },
          },
@@ -10791,7 +10791,7 @@ tl.gen = function(input: string, env: Env): string, Result
    return code, result
 end
 
-local function tl_package_loader(module_name: string): any
+local function tl_package_loader(module_name: string): any, any
    local found_filename, fd, tried = tl.search_module(module_name, false)
    if found_filename then
       local input = read_full_file(fd)
@@ -10824,11 +10824,14 @@ local function tl_package_loader(module_name: string): any
       local code = assert(tl.pretty_print_ast(program, env.gen_target, true))
       local chunk, err = load(code, "@" .. found_filename, "t")
       if chunk then
-         return function(): any
-            local ret = chunk()
+         return function(modname: string, loader_data: string): any
+            if loader_data == nil then
+               loader_data = found_filename
+            end
+            local ret = chunk(modname, loader_data)
             package.loaded[module_name] = ret
             return ret
-         end
+         end, found_filename
       else
          error("Internal Compiler Error: Teal generator produced invalid Lua. Please report a bug at https://github.com/teal-language/tl\n\n" .. err)
       end