Deterministically merge FileGroup resolutions (#250)

This is an incomplete solution to the fact that our existing resolution
merge was non-deterministic with regard to non-qualified names. We now
always take the newer value for a conflicting key, which gets us closer
to the expected behavior.

We unfortunately still aren't implementing the correct scoping rules.
For example, this still allows a non-qualified name to "leak" from one
included file into another. This should be revisited and addressed with
a more complete solution.

lib/thrift/parser/file_group.ex

@@ -102,7 +102,12 @@ defmodule Thrift.Parser.FileGroup do
     end)
     |> Map.new
 
-    resolutions = Map.merge(file_group.resolutions, to_update)
+    # Merge the non-qualified names into the resolution map. We always replace
+    # existing entries with the same key. This produces a predictable result
+    # but is wrong in the sense that it doesn't implement the expected scoping
+    # rules. For example, this still allows a non-qualified name to "leak"
+    # from one included file into another. TODO: revisit resolution scoping
+    resolutions = Map.merge(file_group.resolutions, to_update, fn _k, _v1, v2 -> v2 end)
 
     default_namespace = if file_group.opts[:namespace] do
       %Namespace{:name => :elixir, :path => file_group.opts[:namespace]}

test/thrift/parser/resolver_test.exs

@@ -192,4 +192,33 @@ defmodule ResolverTest do
       assert %TEnum{} = FileGroup.resolve(file_group, :"enums.JobStatus")
     end
   end
+
+  test "it should be able resolve qualified and non-qualified names" do
+    with_thrift_files([
+      "included.thrift": """
+      enum SortType {
+        DESC = 100,
+        ASC = 110
+      }
+      """,
+      "local.thrift": """
+      include "included.thrift"
+      enum SortType {
+        DESC,
+        ASC
+      }
+
+      const SortType SORT1 = SortType.ASC;
+      const included.SortType SORT2 = included.SortType.ASC;
+      """, as: :file_group, parse: "local.thrift"]) do
+
+      sort1 = FileGroup.resolve(file_group, :"local.SORT1")
+      assert %TEnum{name: :"local.SortType"} = FileGroup.resolve(file_group, sort1.type)
+      assert 2 == FileGroup.resolve(file_group, sort1.value)
+
+      sort2 = FileGroup.resolve(file_group, :"local.SORT2")
+      assert %TEnum{name: :"included.SortType"} = FileGroup.resolve(file_group, sort2.type)
+      assert 110 == FileGroup.resolve(file_group, sort2.value)
+    end
+  end
 end