Handle empty prepared queries

lib/shopify_custom_data_graphql/prepared_query.rb

@@ -3,6 +3,7 @@
 module ShopifyCustomDataGraphQL
   class PreparedQuery
     DEFAULT_TRACER = Tracer.new
+    EMPTY_HASH= {}
 
     class Result
       attr_reader :query, :tracer, :result
@@ -22,14 +23,12 @@ def to_h
 
     def initialize(params)
       @query = params["query"]
-      @transforms = params["transforms"]
-
-      unless @query && @transforms
-        raise ArgumentError, "PreparedQuery requires params `query` and `transforms`"
-      end
+      @transforms = params["transforms"] || EMPTY_HASH
     end
 
     def as_json
+      return EMPTY_HASH if base_query?
+
       {
         "query" => @query,
         "transforms" => @transforms,
@@ -41,7 +40,9 @@ def to_json
     end
 
     def perform(tracer = DEFAULT_TRACER, source_query: nil)
-      query = source_query && @transforms.none? ? source_query : @query
+      query = source_query && base_query? ? source_query : @query
+      raise ArgumentError, "A source_query is required with empty transformations" if query.nil?
+
       raw_result = tracer.span("proxy") { yield(query) }
 
       result = if @transforms.any?
@@ -54,5 +55,11 @@ def perform(tracer = DEFAULT_TRACER, source_query: nil)
 
       Result.new(query: query, tracer: tracer, result: result)
     end
+
+    private
+
+    def base_query?
+      @transforms.none?
+    end
   end
 end

test/shopify_custom_data_graphql/prepared_query_test.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+describe "PreparedQuery" do
+  def setup
+    @query = "{ product { id extensions { toggle } } }"
+    @transformed_query = %|{ product { id ___extensions_boolean: metafield(key: "toggle") { jsonValue } } }|
+    @transforms = { "f" => { "extensions" => { "fx" => { "t" => "custom_scope" } } } }
+  end
+
+  def test_builds_from_and_serializes_to_json
+    prepared_query = ShopifyCustomDataGraphQL::PreparedQuery.new({
+      "query" => @query,
+      "transforms" => @transforms,
+    })
+
+    expected = {
+      "query" => @query,
+      "transforms" => @transforms,
+    }
+
+    assert_equal expected, prepared_query.as_json
+  end
+
+  def test_omits_query_when_transforms_are_empty
+    prepared_query = ShopifyCustomDataGraphQL::PreparedQuery.new({
+      "query" => @query,
+      "transforms" => {},
+    })
+
+    expected = {}
+
+    assert_equal expected, prepared_query.as_json
+  end
+
+  def test_performs_transformed_query_when_available
+    prepared_query = ShopifyCustomDataGraphQL::PreparedQuery.new({
+      "query" => @transformed_query,
+      "transforms" => @transforms,
+    })
+
+    prepared_query.perform(source_query: @query) do |query|
+      assert_equal @transformed_query, query
+      { "product" => { "id" => "1", "___extensions_boolean" => { "jsonValue" => true } } }
+    end
+  end
+
+  def test_performs_source_query_when_not_transformed
+    prepared_query = ShopifyCustomDataGraphQL::PreparedQuery.new({})
+
+    prepared_query.perform(source_query: @query) do |query|
+      assert_equal @query, query
+      { "product" => { "id" => "1" } }
+    end
+  end
+
+  def test_raises_for_empty_prepared_query_with_source_query
+    assert_raises(ArgumentError) do
+      ShopifyCustomDataGraphQL::PreparedQuery.new({}).perform(source_query: nil)
+    end
+  end
+end

test/shopify_custom_data_graphql/request_transformer_test.rb

@@ -3,6 +3,20 @@
 require "test_helper"
 
 describe "RequestTransformer" do
+  def test_requests_with_no_custom_data_have_no_transforms
+    expected_query = %|query {
+      product(id: "1") {
+        title
+      }
+    }|
+
+    expected_transforms = {}
+    result = transform_request(expected_query)
+
+    assert_equal expected_query.squish, result.query.squish
+    assert_equal expected_transforms, result.transforms
+  end
+
   def test_transforms_extensions_scalar_fields
     result = transform_request(%|query {
       product(id: "1") {