Add union support

Author: DmitryTsepelev

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+- [PR#30](https://github.com/DmitryTsepelev/graphql-ruby-fragment_cache/pull/30) Add union support ([@DmitryTsepelev][])
+
 ## 1.0.3 (2020-08-31)
 
 - [PR#29](https://github.com/DmitryTsepelev/graphql-ruby-fragment_cache/pull/29) Cache result JSON instead of connection objects ([@DmitryTsepelev][])

lib/graphql/fragment_cache/cache_key_builder.rb

@@ -32,9 +32,18 @@ def alias?(val)
       end
 
       refine ::GraphQL::Execution::Lookahead do
-        def selection_with_alias(name, **kwargs)
-          return selection(name, **kwargs) if selects?(name, **kwargs)
-          alias_selection(name, **kwargs)
+        def selection_with_alias(name, selected_type:, **kwargs)
+          # In case of union we have to pass a type of object explicitly
+          # More info https://github.com/rmosolgo/graphql-ruby/pull/3007
+          kwargs[:selected_type] = selected_type if @selected_type.kind.union?
+
+          selection(name, **kwargs).then do |next_selection|
+            if next_selection.is_a?(GraphQL::Execution::Lookahead::NullLookahead)
+              alias_selection(name, **kwargs)
+            else
+              next_selection
+            end
+          end
         end
 
         def alias_selection(name, selected_type: @selected_type, arguments: nil)
@@ -48,7 +57,9 @@ def alias_selection(name, selected_type: @selected_type, arguments: nil)
           # From https://github.com/rmosolgo/graphql-ruby/blob/1a9a20f3da629e63ea8e5ee8400be82218f9edc3/lib/graphql/execution/lookahead.rb#L91
           next_field_defn = get_class_based_field(selected_type, next_field_name)
 
-          alias_selections[name] =
+          alias_name = "#{name}_#{selected_type.name}"
+
+          alias_selections[alias_name] =
             if next_field_defn
               next_nodes = []
               arguments = @query.arguments_for(alias_node, next_field_defn)
@@ -103,11 +114,12 @@ def call(**options)
 
       attr_reader :query, :path, :object, :schema
 
-      def initialize(object: nil, query:, path:, **options)
+      def initialize(object: nil, query:, path:, selected_type:, **options)
         @object = object
         @query = query
         @schema = query.schema
         @path = path
+        @selected_type = selected_type
         @options = options
       end
 
@@ -134,7 +146,7 @@ def selections_cache_key
             # Handle cached fields inside collections:
             next lkhd if field_name.is_a?(Integer)
 
-            lkhd.selection_with_alias(field_name)
+            lkhd.selection_with_alias(field_name, selected_type: @selected_type)
           }
 
         current_root.selections.to_selections_key
@@ -147,7 +159,7 @@ def path_cache_key
           # Handle cached fields inside collections:
           next field_name if field_name.is_a?(Integer)
 
-          lookahead = lookahead.selection_with_alias(field_name)
+          lookahead = lookahead.selection_with_alias(field_name, selected_type: @selected_type)
           raise "Failed to look ahead the field: #{field_name}" if lookahead.is_a?(::GraphQL::Execution::Lookahead::NullLookahead)
 
           next lookahead.field.name if lookahead.arguments.empty?

lib/graphql/fragment_cache/fragment.rb

@@ -30,7 +30,9 @@ def persist
       private
 
       def cache_key
-        @cache_key ||= CacheKeyBuilder.call(path: path, query: context.query, **options)
+        @cache_key ||= CacheKeyBuilder.call(
+          path: path, query: context.query, selected_type: selected_type, **options
+        )
       end
 
       def interpreter_context
@@ -40,6 +42,10 @@ def interpreter_context
       def final_value
         @final_value ||= interpreter_context[:runtime].final_value
       end
+
+      def selected_type
+        @selected_type ||= interpreter_context[:current_object].class
+      end
     end
   end
 end

spec/graphql/fragment_cache/cache_key_builder_spec.rb

@@ -27,10 +27,11 @@
   let(:post) { Post.find(42) }
 
   let(:object) { nil }
+  let(:selected_type) { nil }
   let(:context) { {} }
   let(:query_obj) { GraphQL::Query.new(schema, query, variables: variables, context: context) }
 
-  subject { described_class.call(object: object, query: query_obj, path: path) }
+  subject { described_class.call(object: object, query: query_obj, path: path, selected_type: selected_type) }
 
   # Make cache keys raw for easier debugging
   let(:schema_cache_key) { "schema_key" }
@@ -57,6 +58,8 @@
       GQL
     end
 
+    let(:selected_type) { Types::Post }
+
     specify { is_expected.to eq "schema_key/cachedPost(id:#{id})[id.title.author[id.name]]" }
   end
 
@@ -77,7 +80,7 @@
     end
 
     let(:path) { ["cachedPostByInput"] }
-
+    let(:selected_type) { Types::Post }
     let(:variables) { {inputWithId: {id: id, intArg: 42}} }
 
     specify { is_expected.to eq "schema_key/cachedPostByInput(input_with_id:{id:#{id},int_arg:42})[id.title.author[id.name]]" }
@@ -108,6 +111,7 @@
 
   context "when cached cached field is nested" do
     let(:path) { ["post", "cachedAuthor"] }
+    let(:selected_type) { Types::User }
 
     let(:query) do
       <<~GQL
@@ -147,6 +151,8 @@
       GQL
     end
 
+    let(:selected_type) { Types::Post }
+
     specify { is_expected.to eq "schema_key/cachedPost(id:#{id})[id.title.author[id.name]]" }
 
     context "when nested fragment is used" do
@@ -177,6 +183,7 @@
 
   context "when object is passed and responds to #cache_key" do
     let(:object) { post }
+    let(:selected_type) { Types::Post }
 
     specify { is_expected.to eq "schema_key/cachedPost(id:#{id})[id.title]/#{post.cache_key}" }
   end
@@ -186,12 +193,14 @@
       post.singleton_class.define_method(:graphql_cache_key) { "super-cache" }
     end
 
+    let(:selected_type) { Types::Post }
     let(:object) { post }
 
     specify { is_expected.to eq "schema_key/cachedPost(id:#{id})[id.title]/super-cache" }
   end
 
   context "when object is passed deosn't respond to #cache_key neither #graphql_cache_key" do
+    let(:selected_type) { Types::Post }
     let(:object) { post.author }
 
     it "fallbacks to #to_s" do
@@ -200,6 +209,7 @@
   end
 
   context "when array is passed as object" do
+    let(:selected_type) { Types::Post }
     let(:object) { [post, :custom, 99] }
 
     specify { is_expected.to eq "schema_key/cachedPost(id:#{id})[id.title]/#{post.cache_key}/custom/99" }
@@ -216,7 +226,7 @@
         }
       GQL
     end
-
+    let(:selected_type) { GraphQL::Types::String }
     let(:path) { ["posts", 0, "cachedTitle"] }
 
     specify { is_expected.to eq "schema_key/posts/0/cachedTitle[]" }
@@ -240,6 +250,7 @@
       GQL
     end
 
+    let(:selected_type) { Types::User }
     let(:path) { ["post", "author"] }
 
     specify { is_expected.to eq "schema_key/post(id:1)/cachedAuthor[name]" }
@@ -261,8 +272,57 @@
       GQL
     end
 
+    let(:selected_type) { Types::User }
     let(:path) { ["post", "author"] }
 
     specify { is_expected.to eq "schema_key/post(id:1)/cachedAuthor[name]" }
   end
+
+  context "when query has union type" do
+    let(:query) do
+      <<~GQL
+        query getFeed {
+          feed {
+            ...on PostType {
+              id
+              cachedAvatarUrl
+            }
+            ...on UserType {
+              id
+              cachedAvatarUrl
+            }
+          }
+        }
+      GQL
+    end
+
+    let(:selected_type) { Types::Post }
+    let(:path) { ["feed", 0, "cachedAvatarUrl"] }
+
+    specify { is_expected.to eq "schema_key/feed/0/cachedAvatarUrl[]" }
+
+    context "when cached field has alias" do
+      let(:query) do
+        <<~GQL
+          query getFeed {
+            feed {
+              ...on PostType {
+                id
+                avatarUrl: cachedAvatarUrl
+              }
+              ...on UserType {
+                id
+                avatarUrl: cachedAvatarUrl
+              }
+            }
+          }
+        GQL
+      end
+
+      let(:selected_type) { Types::Post }
+      let(:path) { ["feed", 0, "avatarUrl"] }
+
+      specify { is_expected.to eq "schema_key/feed/0/cachedAvatarUrl[]" }
+    end
+  end
 end

spec/graphql/fragment_cache/object_helpers_spec.rb

@@ -577,4 +577,47 @@ def post(id:, expires_in: nil)
       expect(::Post).not_to have_received(:all)
     end
   end
+
+  describe "union caching" do
+    let!(:post) { Post.create(id: 1, title: "Post #1") }
+    let!(:user) { User.create(id: 2, name: "User #2") }
+
+    let(:schema) do
+      build_schema do
+        query(
+          Class.new(Types::Query) {
+            field :feed, [Types::Activity], null: false
+
+            define_method(:feed, -> { ::Post.all + ::User.all })
+          }
+        )
+      end
+    end
+
+    let(:query) do
+      <<~GQL
+        query getFeed {
+          feed {
+            ...on PostType {
+              id
+              cachedAvatarUrl
+            }
+            ...on UserType {
+              id
+              cachedAvatarUrl
+            }
+          }
+        }
+      GQL
+    end
+
+    it "returns cached data" do
+      expect(execute_query.dig("data")).to eq(
+        "feed" => [
+          {"cachedAvatarUrl" => "http://example.com/img/posts/#{post.id}", "id" => post.id.to_s},
+          {"cachedAvatarUrl" => "http://example.com/img/users/#{user.id}", "id" => user.id.to_s}
+        ]
+      )
+    end
+  end
 end

spec/graphql/fragment_cache/rails/cache_key_builder_spec.rb

@@ -26,6 +26,7 @@
 
   let(:object) { Post.find(42) }
   let(:query_obj) { GraphQL::Query.new(schema, query, variables: variables) }
+  let(:selected_type) { Types::Post }
 
   # Make cache keys raw for easier debugging
   let(:schema_cache_key) { "schema_key" }
@@ -34,7 +35,11 @@
     allow(Digest::SHA1).to receive(:hexdigest) { |val| val }
   end
 
-  subject { described_class.call(object: object, query: query_obj, path: path) }
+  subject do
+    described_class.call(
+      object: object, query: query_obj, selected_type: selected_type, path: path
+    )
+  end
 
   it "uses Cache.expand_cache_key" do
     allow(ActiveSupport::Cache).to receive(:expand_cache_key).with(object) { "as:cache:key" }

spec/support/models/post.rb

@@ -4,7 +4,7 @@ class Post
   class << self
     def find(id)
       store.fetch(id.to_i) do
-        author = User.new(id: id, name: "User ##{id}")
+        author = User.fetch(id)
         new(id: id, title: "Post ##{id}", author: author)
       end
     end

spec/support/models/user.rb

@@ -4,6 +4,26 @@ class User
   attr_reader :id
   attr_accessor :name
 
+  class << self
+    def fetch(id)
+      store.fetch(id.to_i) do
+        new(id: id, name: "User ##{id}")
+      end
+    end
+
+    def all
+      @store.values
+    end
+
+    def create(id:, **attributes)
+      store[id] = new(id: id, **attributes)
+    end
+
+    def store
+      @store ||= {}
+    end
+  end
+
   def initialize(id:, name:)
     @id = id
     @name = name