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1 files changed, 831 insertions, 0 deletions

diff --git a/src/luarocks/deps.lua b/src/luarocks/deps.lua
new file mode 100644
index 0000000..1cd500c
--- /dev/null
+++ b/src/luarocks/deps.lua
@@ -0,0 +1,831 @@
+
+--- High-level dependency related functions.
+local deps = {}
+
+local cfg = require("luarocks.core.cfg")
+local manif = require("luarocks.manif")
+local path = require("luarocks.path")
+local dir = require("luarocks.dir")
+local fun = require("luarocks.fun")
+local util = require("luarocks.util")
+local vers = require("luarocks.core.vers")
+local queries = require("luarocks.queries")
+local deplocks = require("luarocks.deplocks")
+
+--- Generate a function that matches dep queries against the manifest,
+-- taking into account rocks_provided, the list of versions to skip,
+-- and the lockfile.
+-- @param deps_mode "one", "none", "all" or "order"
+-- @param rocks_provided a one-level table mapping names to versions,
+-- listing rocks to consider provided by the VM
+-- @param rocks_provided table: A table of auto-provided dependencies.
+-- by this Lua implementation for the given dependency.
+-- @param depskey key to use when matching the lockfile ("dependencies",
+-- "build_dependencies", etc.)
+-- @param skip_set a two-level table mapping names to versions to
+-- boolean, listing rocks that should not be matched
+-- @return function(dep): {string}, {string:string}, string, boolean
+-- * array of matching versions
+-- * map of versions to locations
+-- * version matched via lockfile if any
+-- * true if rock matched via rocks_provided
+local function prepare_get_versions(deps_mode, rocks_provided, depskey, skip_set)
+   assert(type(deps_mode) == "string")
+   assert(type(rocks_provided) == "table")
+   assert(type(depskey) == "string")
+   assert(type(skip_set) == "table" or skip_set == nil)
+
+   return function(dep)
+      local versions, locations
+      local provided = rocks_provided[dep.name]
+      if provided then
+         -- Provided rocks have higher priority than manifest's rocks.
+         versions, locations = { provided }, {}
+      else
+         if deps_mode == "none" then
+            deps_mode = "one"
+         end
+         versions, locations = manif.get_versions(dep, deps_mode)
+      end
+
+      if skip_set and skip_set[dep.name] then
+         for i = #versions, 1, -1 do
+            local v = versions[i]
+            if skip_set[dep.name][v] then
+               table.remove(versions, i)
+            end
+         end
+      end
+
+      local lockversion = deplocks.get(depskey, dep.name)
+
+      return versions, locations, lockversion, provided ~= nil
+   end
+end
+
+--- Attempt to match a dependency to an installed rock.
+-- @param get_versions a getter function obtained via prepare_get_versions
+-- @return (string, string, table) or (nil, nil, table):
+-- 1. latest installed version of the rock matching the dependency
+-- 2. location where the installed version is installed
+-- 3. the 'dep' query table
+-- 4. true if provided via VM
+-- or
+-- 1. nil
+-- 2. nil
+-- 3. either 'dep' or an alternative query to be used
+-- 4. false
+local function match_dep(dep, get_versions)
+   assert(type(dep) == "table")
+   assert(type(get_versions) == "function")
+
+   local versions, locations, lockversion, provided = get_versions(dep)
+
+   local latest_version
+   local latest_vstring
+   for _, vstring in ipairs(versions) do
+      local version = vers.parse_version(vstring)
+      if vers.match_constraints(version, dep.constraints) then
+         if not latest_version or version > latest_version then
+            latest_version = version
+            latest_vstring = vstring
+         end
+      end
+   end
+
+   if lockversion and not locations[lockversion] then
+      local latest_matching_msg = ""
+      if latest_vstring and latest_vstring ~= lockversion then
+         latest_matching_msg = " (latest matching is " .. latest_vstring .. ")"
+      end
+      util.printout("Forcing " .. dep.name .. " to pinned version " .. lockversion .. latest_matching_msg)
+      return nil, nil, queries.new(dep.name, dep.namespace, lockversion)
+   end
+
+   return latest_vstring, locations[latest_vstring], dep, provided
+end
+
+local function match_all_deps(dependencies, get_versions)
+   assert(type(dependencies) == "table")
+   assert(type(get_versions) == "function")
+
+   local matched, missing, no_upgrade = {}, {}, {}
+
+   for _, dep in ipairs(dependencies) do
+      local found, _, provided
+      found, _, dep, provided = match_dep(dep, get_versions)
+      if found then
+         if not provided then
+            matched[dep] = {name = dep.name, version = found}
+         end
+      else
+         if dep.constraints[1] and dep.constraints[1].no_upgrade then
+            no_upgrade[dep.name] = dep
+         else
+            missing[dep.name] = dep
+         end
+      end
+   end
+   return matched, missing, no_upgrade
+end
+
+--- Attempt to match dependencies of a rockspec to installed rocks.
+-- @param dependencies table: The table of dependencies.
+-- @param rocks_provided table: The table of auto-provided dependencies.
+-- @param skip_set table or nil: Program versions to not use as valid matches.
+-- Table where keys are program names and values are tables where keys
+-- are program versions and values are 'true'.
+-- @param deps_mode string: Which trees to check dependencies for
+-- @return table, table, table: A table where keys are dependencies parsed
+-- in table format and values are tables containing fields 'name' and
+-- version' representing matches; a table of missing dependencies
+-- parsed as tables; and a table of "no-upgrade" missing dependencies
+-- (to be used in plugin modules so that a plugin does not force upgrade of
+-- its parent application).
+function deps.match_deps(dependencies, rocks_provided, skip_set, deps_mode)
+   assert(type(dependencies) == "table")
+   assert(type(rocks_provided) == "table")
+   assert(type(skip_set) == "table" or skip_set == nil)
+   assert(type(deps_mode) == "string")
+
+   local get_versions = prepare_get_versions(deps_mode, rocks_provided, "dependencies", skip_set)
+   return match_all_deps(dependencies, get_versions)
+end
+
+local function rock_status(dep, get_versions)
+   assert(dep:type() == "query")
+   assert(type(get_versions) == "function")
+
+   local installed, _, _, provided = match_dep(dep, get_versions)
+   local installation_type = provided and "provided by VM" or "installed"
+   return installed and installed.." "..installation_type..": success" or "not installed"
+end
+
+--- Check depenendencies of a package and report any missing ones.
+-- @param name string: package name.
+-- @param version string: package version.
+-- @param dependencies table: array of dependencies.
+-- @param deps_mode string: Which trees to check dependencies for
+-- @param rocks_provided table: A table of auto-dependencies provided
+-- by this Lua implementation for the given dependency.
+-- "one" for the current default tree, "all" for all trees,
+-- "order" for all trees with priority >= the current default, "none" for no trees.
+function deps.report_missing_dependencies(name, version, dependencies, deps_mode, rocks_provided)
+   assert(type(name) == "string")
+   assert(type(version) == "string")
+   assert(type(dependencies) == "table")
+   assert(type(deps_mode) == "string")
+   assert(type(rocks_provided) == "table")
+
+   if deps_mode == "none" then
+      return
+   end
+
+   local get_versions = prepare_get_versions(deps_mode, rocks_provided, "dependencies")
+
+   local first_missing_dep = true
+
+   for _, dep in ipairs(dependencies) do
+      local found, _
+      found, _, dep = match_dep(dep, get_versions)
+      if not found then
+         if first_missing_dep then
+            util.printout(("Missing dependencies for %s %s:"):format(name, version))
+            first_missing_dep = false
+         end
+
+         util.printout(("   %s (%s)"):format(tostring(dep), rock_status(dep, get_versions)))
+      end
+   end
+end
+
+function deps.fulfill_dependency(dep, deps_mode, rocks_provided, verify, depskey)
+   assert(dep:type() == "query")
+   assert(type(deps_mode) == "string" or deps_mode == nil)
+   assert(type(rocks_provided) == "table" or rocks_provided == nil)
+   assert(type(verify) == "boolean" or verify == nil)
+   assert(type(depskey) == "string")
+
+   deps_mode = deps_mode or "all"
+   rocks_provided = rocks_provided or {}
+
+   local get_versions = prepare_get_versions(deps_mode, rocks_provided, depskey)
+
+   local found, where
+   found, where, dep = match_dep(dep, get_versions)
+   if found then
+      local tree_manifests = manif.load_rocks_tree_manifests(deps_mode)
+      manif.scan_dependencies(dep.name, found, tree_manifests, deplocks.proxy(depskey))
+      return true, found, where
+   end
+
+   local search = require("luarocks.search")
+   local install = require("luarocks.cmd.install")
+
+   local url, search_err = search.find_suitable_rock(dep)
+   if not url then
+      return nil, "Could not satisfy dependency "..tostring(dep)..": "..search_err
+   end
+   util.printout("Installing "..url)
+   local install_args = {
+      rock = url,
+      deps_mode = deps_mode,
+      namespace = dep.namespace,
+      verify = verify,
+   }
+   local ok, install_err, errcode = install.command(install_args)
+   if not ok then
+      return nil, "Failed installing dependency: "..url.." - "..install_err, errcode
+   end
+
+   found, where = match_dep(dep, get_versions)
+   assert(found)
+   return true, found, where
+end
+
+local function check_supported_platforms(rockspec)
+   if rockspec.supported_platforms and next(rockspec.supported_platforms) then
+      local all_negative = true
+      local supported = false
+      for _, plat in pairs(rockspec.supported_platforms) do
+         local neg
+         neg, plat = plat:match("^(!?)(.*)")
+         if neg == "!" then
+            if cfg.is_platform(plat) then
+               return nil, "This rockspec for "..rockspec.package.." does not support "..plat.." platforms."
+            end
+         else
+            all_negative = false
+            if cfg.is_platform(plat) then
+               supported = true
+               break
+            end
+         end
+      end
+      if supported == false and not all_negative then
+         local plats = cfg.print_platforms()
+         return nil, "This rockspec for "..rockspec.package.." does not support "..plats.." platforms."
+      end
+   end
+
+   return true
+end
+
+--- Check dependencies of a rock and attempt to install any missing ones.
+-- Packages are installed using the LuaRocks "install" command.
+-- Aborts the program if a dependency could not be fulfilled.
+-- @param rockspec table: A rockspec in table format.
+-- @param depskey string: Rockspec key to fetch to get dependency table
+-- ("dependencies", "build_dependencies", etc.).
+-- @param deps_mode string
+-- @param verify boolean
+-- @param deplock_dir string: dirname of the deplock file
+-- @return boolean or (nil, string, [string]): True if no errors occurred, or
+-- nil and an error message if any test failed, followed by an optional
+-- error code.
+function deps.fulfill_dependencies(rockspec, depskey, deps_mode, verify, deplock_dir)
+   assert(type(rockspec) == "table")
+   assert(type(depskey) == "string")
+   assert(type(deps_mode) == "string")
+   assert(type(verify) == "boolean" or verify == nil)
+   assert(type(deplock_dir) == "string" or deplock_dir == nil)
+
+   local name = rockspec.name
+   local version = rockspec.version
+   local rocks_provided = rockspec.rocks_provided
+
+   local ok, filename, err = deplocks.load(name, deplock_dir or ".")
+   if filename then
+      util.printout("Using dependencies pinned in lockfile: " .. filename)
+
+      local get_versions = prepare_get_versions("none", rocks_provided, depskey)
+      for dnsname, dversion in deplocks.each(depskey) do
+         local dname, dnamespace = util.split_namespace(dnsname)
+         local dep = queries.new(dname, dnamespace, dversion)
+
+         util.printout(("%s %s is pinned to %s (%s)"):format(
+            name, version, tostring(dep), rock_status(dep, get_versions)))
+
+         local ok, err = deps.fulfill_dependency(dep, "none", rocks_provided, verify, depskey)
+         if not ok then
+            return nil, err
+         end
+      end
+      util.printout()
+      return true
+   elseif err then
+      util.warning(err)
+   end
+
+   ok, err = check_supported_platforms(rockspec)
+   if not ok then
+      return nil, err
+   end
+
+   deps.report_missing_dependencies(name, version, rockspec[depskey], deps_mode, rocks_provided)
+
+   util.printout()
+
+   local get_versions = prepare_get_versions(deps_mode, rocks_provided, depskey)
+   for _, dep in ipairs(rockspec[depskey]) do
+
+      util.printout(("%s %s depends on %s (%s)"):format(
+         name, version, tostring(dep), rock_status(dep, get_versions)))
+
+      local ok, found_or_err, _, no_upgrade = deps.fulfill_dependency(dep, deps_mode, rocks_provided, verify, depskey)
+      if ok then
+         deplocks.add(depskey, dep.name, found_or_err)
+      else
+         if no_upgrade then
+            util.printerr("This version of "..name.." is designed for use with")
+            util.printerr(tostring(dep)..", but is configured to avoid upgrading it")
+            util.printerr("automatically. Please upgrade "..dep.name.." with")
+            util.printerr("   luarocks install "..dep.name)
+            util.printerr("or look for a suitable version of "..name.." with")
+            util.printerr("   luarocks search "..name)
+         end
+         return nil, found_or_err
+      end
+   end
+
+   return true
+end
+
+--- If filename matches a pattern, return the capture.
+-- For example, given "libfoo.so" and "lib?.so" is a pattern,
+-- returns "foo" (which can then be used to build names
+-- based on other patterns.
+-- @param file string: a filename
+-- @param pattern string: a pattern, where ? is to be matched by the filename.
+-- @return string The pattern, if found, or nil.
+local function deconstruct_pattern(file, pattern)
+   local depattern = "^"..(pattern:gsub("%.", "%%."):gsub("%*", ".*"):gsub("?", "(.*)")).."$"
+   return (file:match(depattern))
+end
+
+--- Construct all possible patterns for a name and add to the files array.
+-- Run through the patterns array replacing all occurrences of "?"
+-- with the given file name and store them in the files array.
+-- @param file string A raw name (e.g. "foo")
+-- @param array of string An array of patterns with "?" as the wildcard
+-- (e.g. {"?.so", "lib?.so"})
+-- @param files The array of constructed names
+local function add_all_patterns(file, patterns, files)
+   for _, pattern in ipairs(patterns) do
+      table.insert(files, {#files + 1, (pattern:gsub("?", file))})
+   end
+end
+
+local function get_external_deps_dirs(mode)
+   local patterns = cfg.external_deps_patterns
+   local subdirs = cfg.external_deps_subdirs
+   if mode == "install" then
+      patterns = cfg.runtime_external_deps_patterns
+      subdirs = cfg.runtime_external_deps_subdirs
+   end
+   local dirs = {
+      BINDIR = { subdir = subdirs.bin, testfile = "program", pattern = patterns.bin },
+      INCDIR = { subdir = subdirs.include, testfile = "header", pattern = patterns.include },
+      LIBDIR = { subdir = subdirs.lib, testfile = "library", pattern = patterns.lib }
+   }
+   if mode == "install" then
+      dirs.INCDIR = nil
+   end
+   return dirs
+end
+
+local function resolve_prefix(prefix, dirs)
+   if type(prefix) == "string" then
+      return prefix
+   elseif type(prefix) == "table" then
+      if prefix.bin then
+         dirs.BINDIR.subdir = prefix.bin
+      end
+      if prefix.include then
+         if dirs.INCDIR then
+            dirs.INCDIR.subdir = prefix.include
+         end
+      end
+      if prefix.lib then
+         dirs.LIBDIR.subdir = prefix.lib
+      end
+      return prefix.prefix
+   end
+end
+
+local function add_patterns_for_file(files, file, patterns)
+   -- If it doesn't look like it contains a filename extension
+   if not (file:match("%.[a-z]+$") or file:match("%.[a-z]+%.")) then
+      add_all_patterns(file, patterns, files)
+   else
+      for _, pattern in ipairs(patterns) do
+         local matched = deconstruct_pattern(file, pattern)
+         if matched then
+            add_all_patterns(matched, patterns, files)
+         end
+      end
+      table.insert(files, {#files + 1, file})
+   end
+end
+
+local function check_external_dependency_at(prefix, name, ext_files, vars, dirs, err_files, cache)
+   local fs = require("luarocks.fs")
+   cache = cache or {}
+
+   for dirname, dirdata in util.sortedpairs(dirs) do
+      local paths
+      local path_var_value = vars[name.."_"..dirname]
+      if path_var_value then
+         paths = { path_var_value }
+      elseif type(dirdata.subdir) == "table" then
+         paths = {}
+         for i,v in ipairs(dirdata.subdir) do
+            paths[i] = dir.path(prefix, v)
+         end
+      else
+         paths = { dir.path(prefix, dirdata.subdir) }
+      end
+      local file_or_files = ext_files[dirdata.testfile]
+      if file_or_files then
+         local files = {}
+         if type(file_or_files) == "string" then
+            add_patterns_for_file(files, file_or_files, dirdata.pattern)
+         elseif type(file_or_files) == "table" then
+            for _, f in ipairs(file_or_files) do
+               add_patterns_for_file(files, f, dirdata.pattern)
+            end
+         end
+
+         local found = false
+         table.sort(files, function(a, b)
+            if (not a[2]:match("%*")) and b[2]:match("%*") then
+               return true
+            elseif a[2]:match("%*") and (not b[2]:match("%*")) then
+               return false
+            else
+               return a[1] < b[1]
+            end
+         end)
+         for _, fa in ipairs(files) do
+
+            local f = fa[2]
+            -- small convenience hack
+            if f:match("%.so$") or f:match("%.dylib$") or f:match("%.dll$") then
+               f = f:gsub("%.[^.]+$", "."..cfg.external_lib_extension)
+            end
+
+            local pattern
+            if f:match("%*") then
+               pattern = "^" .. f:gsub("([-.+])", "%%%1"):gsub("%*", ".*") .. "$"
+               f = "matching "..f
+            end
+
+            for _, d in ipairs(paths) do
+               if pattern then
+                  if not cache[d] then
+                     cache[d] = fs.list_dir(d)
+                  end
+                  local match = string.match
+                  for _, entry in ipairs(cache[d]) do
+                     if match(entry, pattern) then
+                        found = true
+                        break
+                     end
+                  end
+               else
+                  found = fs.is_file(dir.path(d, f))
+               end
+               if found then
+                  dirdata.dir = d
+                  dirdata.file = f
+                  break
+               else
+                  table.insert(err_files[dirdata.testfile], f.." in "..d)
+               end
+            end
+            if found then
+               break
+            end
+         end
+         if not found then
+            return nil, dirname, dirdata.testfile
+         end
+      else
+         -- When we have a set of subdir suffixes, look for one that exists.
+         -- For these reason, we now put "lib" ahead of "" on Windows in our
+         -- default set.
+         dirdata.dir = paths[1]
+         for _, p in ipairs(paths) do
+            if fs.exists(p) then
+               dirdata.dir = p
+               break
+            end
+         end
+      end
+   end
+
+   for dirname, dirdata in pairs(dirs) do
+      vars[name.."_"..dirname] = dirdata.dir
+      vars[name.."_"..dirname.."_FILE"] = dirdata.file
+   end
+   vars[name.."_DIR"] = prefix
+   return true
+end
+
+local function check_external_dependency(name, ext_files, vars, mode, cache)
+   local ok
+   local err_dirname
+   local err_testfile
+   local err_files = {program = {}, header = {}, library = {}}
+
+   local dirs = get_external_deps_dirs(mode)
+
+   local prefixes
+   if vars[name .. "_DIR"] then
+      prefixes = { vars[name .. "_DIR"] }
+   elseif vars.DEPS_DIR then
+      prefixes = { vars.DEPS_DIR }
+   else
+      prefixes = cfg.external_deps_dirs
+   end
+
+   for _, prefix in ipairs(prefixes) do
+      prefix = resolve_prefix(prefix, dirs)
+      if cfg.is_platform("mingw32") and name == "LUA" then
+         dirs.LIBDIR.pattern = fun.filter(util.deep_copy(dirs.LIBDIR.pattern), function(s)
+            return not s:match("%.a$")
+         end)
+      elseif cfg.is_platform("windows") and name == "LUA" then
+         dirs.LIBDIR.pattern = fun.filter(util.deep_copy(dirs.LIBDIR.pattern), function(s)
+            return not s:match("%.dll$")
+         end)
+      end
+      ok, err_dirname, err_testfile = check_external_dependency_at(prefix, name, ext_files, vars, dirs, err_files, cache)
+      if ok then
+         return true
+      end
+   end
+
+   return nil, err_dirname, err_testfile, err_files
+end
+
+function deps.autodetect_external_dependencies(build)
+   -- only applies to the 'builtin' build type
+   if not build or not build.modules then
+      return nil
+   end
+
+   local extdeps = {}
+   local any = false
+   for _, data in pairs(build.modules) do
+      if type(data) == "table" and data.libraries then
+         local libraries = data.libraries
+         if type(libraries) == "string" then
+            libraries = { libraries }
+         end
+         local incdirs = {}
+         local libdirs = {}
+         for _, lib in ipairs(libraries) do
+            local upper = lib:upper():gsub("%+", "P"):gsub("[^%w]", "_")
+            any = true
+            extdeps[upper] = { library = lib }
+            table.insert(incdirs, "$(" .. upper .. "_INCDIR)")
+            table.insert(libdirs, "$(" .. upper .. "_LIBDIR)")
+         end
+         if not data.incdirs then
+            data.incdirs = incdirs
+         end
+         if not data.libdirs then
+            data.libdirs = libdirs
+         end
+      end
+   end
+   return any and extdeps or nil
+end
+
+--- Set up path-related variables for external dependencies.
+-- For each key in the external_dependencies table in the
+-- rockspec file, four variables are created: <key>_DIR, <key>_BINDIR,
+-- <key>_INCDIR and <key>_LIBDIR. These are not overwritten
+-- if already set (e.g. by the LuaRocks config file or through the
+-- command-line). Values in the external_dependencies table
+-- are tables that may contain a "header" or a "library" field,
+-- with filenames to be tested for existence.
+-- @param rockspec table: The rockspec table.
+-- @param mode string: if "build" is given, checks all files;
+-- if "install" is given, do not scan for headers.
+-- @return boolean or (nil, string): True if no errors occurred, or
+-- nil and an error message if any test failed.
+function deps.check_external_deps(rockspec, mode)
+   assert(rockspec:type() == "rockspec")
+
+   if not rockspec.external_dependencies then
+      rockspec.external_dependencies = deps.autodetect_external_dependencies(rockspec.build)
+   end
+   if not rockspec.external_dependencies then
+      return true
+   end
+
+   for name, ext_files in util.sortedpairs(rockspec.external_dependencies) do
+      local ok, err_dirname, err_testfile, err_files = check_external_dependency(name, ext_files, rockspec.variables, mode)
+      if not ok then
+         local lines = {"Could not find "..err_testfile.." file for "..name}
+
+         local err_paths = {}
+         for _, err_file in ipairs(err_files[err_testfile]) do
+            if not err_paths[err_file] then
+               err_paths[err_file] = true
+               table.insert(lines, "  No file "..err_file)
+            end
+         end
+
+         table.insert(lines, "You may have to install "..name.." in your system and/or pass "..name.."_DIR or "..name.."_"..err_dirname.." to the luarocks command.")
+         table.insert(lines, "Example: luarocks install "..rockspec.name.." "..name.."_DIR=/usr/local")
+
+         return nil, table.concat(lines, "\n"), "dependency"
+      end
+   end
+   return true
+end
+
+--- Recursively add satisfied dependencies of a package to a table,
+-- to build a transitive closure of all dependent packages.
+-- Additionally ensures that `dependencies` table of the manifest is up-to-date.
+-- @param results table: The results table being built, maps package names to versions.
+-- @param mdeps table: The manifest dependencies table.
+-- @param name string: Package name.
+-- @param version string: Package version.
+function deps.scan_deps(results, mdeps, name, version, deps_mode)
+   assert(type(results) == "table")
+   assert(type(mdeps) == "table")
+   assert(type(name) == "string" and not name:match("/"))
+   assert(type(version) == "string")
+
+   local fetch = require("luarocks.fetch")
+
+   if results[name] then
+      return
+   end
+   if not mdeps[name] then mdeps[name] = {} end
+   local mdn = mdeps[name]
+   local dependencies = mdn[version]
+   local rocks_provided
+   if not dependencies then
+      local rockspec, err = fetch.load_local_rockspec(path.rockspec_file(name, version), false)
+      if not rockspec then
+         return
+      end
+      dependencies = rockspec.dependencies
+      rocks_provided = rockspec.rocks_provided
+      mdn[version] = dependencies
+   else
+      rocks_provided = util.get_rocks_provided()
+   end
+
+   local get_versions = prepare_get_versions(deps_mode, rocks_provided, "dependencies")
+
+   local matched = match_all_deps(dependencies, get_versions)
+   results[name] = version
+   for _, match in pairs(matched) do
+      deps.scan_deps(results, mdeps, match.name, match.version, deps_mode)
+   end
+end
+
+local function lua_h_exists(d, luaver)
+   local major, minor = luaver:match("(%d+)%.(%d+)")
+   local luanum = ("%s%02d"):format(major, tonumber(minor))
+
+   local lua_h = dir.path(d, "lua.h")
+   local fd = io.open(lua_h)
+   if fd then
+      local data = fd:read("*a")
+      fd:close()
+      if data:match("LUA_VERSION_NUM%s*" .. tostring(luanum)) then
+         return d
+      end
+      return nil, "Lua header lua.h found at " .. d .. " does not match Lua version " .. luaver .. ". You can use `luarocks config variables.LUA_INCDIR <path>` to set the correct location.", "dependency", 2
+   end
+
+   return nil, "Failed finding Lua header lua.h (searched at " .. d .. "). You may need to install Lua development headers. You can use `luarocks config variables.LUA_INCDIR <path>` to set the correct location.", "dependency", 1
+end
+
+local function find_lua_incdir(prefix, luaver, luajitver)
+   luajitver = luajitver and luajitver:gsub("%-.*", "")
+   local shortv = luaver:gsub("%.", "")
+   local incdirs = {
+      prefix .. "/include/lua/" .. luaver,
+      prefix .. "/include/lua" .. luaver,
+      prefix .. "/include/lua-" .. luaver,
+      prefix .. "/include/lua" .. shortv,
+      prefix .. "/include",
+      prefix,
+      luajitver and (prefix .. "/include/luajit-" .. (luajitver:match("^(%d+%.%d+)") or "")),
+   }
+   local errprio = 0
+   local mainerr
+   for _, d in ipairs(incdirs) do
+      local ok, err, _, prio = lua_h_exists(d, luaver)
+      if ok then
+         return d
+      end
+      if prio > errprio then
+         mainerr = err
+         errprio = prio
+      end
+   end
+
+   -- not found, will fallback to a default
+   return nil, mainerr
+end
+
+function deps.check_lua_incdir(vars)
+   if vars.LUA_INCDIR_OK == true
+      then return true
+   end
+
+   local ljv = util.get_luajit_version()
+
+   if vars.LUA_INCDIR then
+      local ok, err = lua_h_exists(vars.LUA_INCDIR, cfg.lua_version)
+      if ok then
+         vars.LUA_INCDIR_OK = true
+      end
+      return ok, err
+   end
+
+   if vars.LUA_DIR then
+      local d, err = find_lua_incdir(vars.LUA_DIR, cfg.lua_version, ljv)
+      if d then
+         vars.LUA_INCDIR = d
+         vars.LUA_INCDIR_OK = true
+         return true
+      end
+      return nil, err
+   end
+
+   return nil, "Failed finding Lua headers; neither LUA_DIR or LUA_INCDIR are set. You may need to install them or configure LUA_INCDIR.", "dependency"
+end
+
+function deps.check_lua_libdir(vars)
+   if vars.LUA_LIBDIR_OK == true
+      then return true
+   end
+
+   local fs = require("luarocks.fs")
+   local ljv = util.get_luajit_version()
+
+   if vars.LUA_LIBDIR and vars.LUALIB and fs.exists(dir.path(vars.LUA_LIBDIR, vars.LUALIB)) then
+      vars.LUA_LIBDIR_OK = true
+      return true
+   end
+
+   local shortv = cfg.lua_version:gsub("%.", "")
+   local libnames = {
+      "lua" .. cfg.lua_version,
+      "lua" .. shortv,
+      "lua-" .. cfg.lua_version,
+      "lua-" .. shortv,
+      "lua",
+   }
+   if ljv then
+      table.insert(libnames, 1, "luajit-" .. cfg.lua_version)
+      table.insert(libnames, 2, "luajit")
+   end
+   local cache = {}
+   local save_LUA_INCDIR = vars.LUA_INCDIR
+   local ok, _, _, errfiles = check_external_dependency("LUA", { library = libnames }, vars, "build", cache)
+   vars.LUA_INCDIR = save_LUA_INCDIR
+   local err
+   if ok then
+      local filename = dir.path(vars.LUA_LIBDIR, vars.LUA_LIBDIR_FILE)
+      local fd = io.open(filename, "r")
+      if fd then
+         if not vars.LUA_LIBDIR_FILE:match((cfg.lua_version:gsub("%.", "%%.?"))) then
+            -- if filename isn't versioned, check file contents
+            local txt = fd:read("*a")
+            ok = txt:match("Lua " .. cfg.lua_version, 1, true)
+                 or txt:match("lua" .. (cfg.lua_version:gsub("%.", "")), 1, true)
+            if not ok then
+               err = "Lua library at " .. filename .. " does not match Lua version " .. cfg.lua_version .. ". You can use `luarocks config variables.LUA_LIBDIR <path>` to set the correct location."
+            end
+         end
+
+         fd:close()
+      end
+   end
+
+   if ok then
+      vars.LUALIB = vars.LUA_LIBDIR_FILE
+      vars.LUA_LIBDIR_OK = true
+      return true
+   else
+      err = err or "Failed finding the Lua library. You can use `luarocks config variables.LUA_LIBDIR <path>` to set the correct location."
+      return nil, err, "dependency", errfiles
+   end
+end
+
+function deps.get_deps_mode(args)
+   return args.deps_mode or cfg.deps_mode
+end
+
+return deps