fix regression in dependency matching of luarocks.loader

Regression introduced in
https://github.com/luarocks/luarocks/commit/65c417e0ecda55f44c691df032163a8c08f0b52a

Thanks to @lhemkendreis for the detailed description and suggested
fix, which was applied here!

Added a regression test which exercises dependency matching.

Closes #1175.

2 files changed, 72 insertions, 2 deletions

diff --git a/spec/loader_spec.lua b/spec/loader_spec.lua
index 0f946b72..35179080 100644
--- a/spec/loader_spec.lua
+++ b/spec/loader_spec.lua
@@ -1,5 +1,7 @@
 local test_env = require("spec.util.test_env")
 local run = test_env.run
+local testing_paths = test_env.testing_paths
+local write_file = test_env.write_file
 
 describe("luarocks.loader", function()
    describe("#unit", function()
@@ -7,4 +9,66 @@ describe("luarocks.loader", function()
          assert(run.lua_bool([[-e "require 'luarocks.loader'; print(package.loaded['luarocks.loaded'])"]]))
       end)
    end)
+
+   describe("#integration", function()
+      it("respects version constraints", function()
+         test_env.run_in_tmp(function(tmpdir)
+            write_file("rock_b_01.lua", "print('ROCK B 0.1'); return {}", finally)
+            write_file("rock_b-0.1-1.rockspec", [[
+               package = "rock_b"
+               version = "0.1-1"
+               source = {
+                  url = "file://]] .. tmpdir:gsub("\\", "/") .. [[/rock_b_01.lua"
+               }
+               build = {
+                  type = "builtin", 
+                  modules = {
+                     rock_b = "rock_b_01.lua"
+                  }
+               }
+            ]], finally)
+   
+            write_file("rock_b_10.lua", "print('ROCK B 1.0'); return {}", finally)
+            write_file("rock_b-1.0-1.rockspec", [[
+               package = "rock_b"
+               version = "1.0-1"
+               source = {
+                  url = "file://]] .. tmpdir:gsub("\\", "/") .. [[/rock_b_10.lua"
+               }
+               build = {
+                  type = "builtin", 
+                  modules = {
+                     rock_b = "rock_b_10.lua"
+                  }
+               }
+            ]], finally)
+   
+            write_file("rock_a.lua", "require('rock_b'); return {}", finally)
+            write_file("rock_a-2.0-1.rockspec", [[
+               package = "rock_a"
+               version = "2.0-1"
+               source = {
+                  url = "file://]] .. tmpdir:gsub("\\", "/") .. [[/rock_a.lua"
+               }
+               dependencies = {
+                  "rock_b < 1.0",
+               }
+               build = {
+                  type = "builtin", 
+                  modules = {
+                     rock_a = "rock_a.lua"
+                  }
+               }
+            ]], finally)
+
+            print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_b-0.1-1.rockspec"))
+            print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_b-1.0-1.rockspec --keep"))
+            print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_a-2.0-1.rockspec"))
+   
+            local output = run.lua([[-e "require 'luarocks.loader'; require('rock_a')"]])
+   
+            assert.matches("ROCK B 0.1", output, 1, true)
+         end)
+      end)
+   end)
 end)
diff --git a/src/luarocks/loader.lua b/src/luarocks/loader.lua
index 0cc76027..969f4844 100644
--- a/src/luarocks/loader.lua
+++ b/src/luarocks/loader.lua
@@ -149,12 +149,18 @@ local function select_module(module, filter_file_name)
    for _, tree in ipairs(tree_manifests) do
       local entries = tree.manifest.modules[module]
       if entries then
-         add_providers(providers, entries, tree, module, filter_file_name)
+         local n, v, f = add_providers(providers, entries, tree, module, filter_file_name)
+         if n then
+            return n, v, f
+         end
       else
          initmodule = initmodule or module .. ".init"
          entries = tree.manifest.modules[initmodule]
          if entries then
-            add_providers(providers, entries, tree, initmodule, filter_file_name)
+            local n, v, f = add_providers(providers, entries, tree, initmodule, filter_file_name)
+            if n then
+               return n, v, f
+            end
          end
       end
    end