Fix inline fragments without a space before "on"

lib/graphql/client.rb

@@ -153,8 +153,12 @@ def parse(str, filename = nil, lineno = nil)
 
       # Replace Ruby constant reference with GraphQL fragment names,
       # while populating `definition_dependencies` with
-      # GraphQL Fragment ASTs which this operation depends on
-      str = str.gsub(/\.\.\.([a-zA-Z0-9_]+(::[a-zA-Z0-9_]+)*)/) do
+      # GraphQL Fragment ASTs which this operation depends on.
+      #
+      # GraphQL forbids naming a fragment "on", so "...on" followed by a word
+      # boundary is unambiguously an inline fragment, never a spread
+      # referencing constant "On".
+      str = str.gsub(/\.\.\.(?!on\b)([a-zA-Z0-9_]+(::[a-zA-Z0-9_]+)*)/) do
         match = Regexp.last_match
         const_name = match[1]
 

test/test_client.rb

@@ -159,6 +159,40 @@ def test_client_parse_anonymous_query
     assert_equal(query_string, Temp::UserQuery.document.to_query_string)
   end
 
+  def test_client_parse_inline_fragment_without_space_before_on
+    Temp.const_set :NodeQuery, @client.parse(<<-'GRAPHQL')
+      query {
+        node(id: "1") {
+          id
+          ...on User {
+            name
+          }
+          ... on Organization {
+            name
+          }
+        }
+      }
+    GRAPHQL
+
+    query_string = <<-'GRAPHQL'.gsub(/^      /, "").chomp
+      query TestClient__Temp__NodeQuery {
+        node(id: "1") {
+          __typename
+          id
+          ... on User {
+            name
+          }
+          ... on Organization {
+            name
+          }
+        }
+      }
+    GRAPHQL
+
+    assert_equal(query_string, @client.document.to_query_string)
+    assert_equal(query_string, Temp::NodeQuery.document.to_query_string)
+  end
+
   def test_client_parse_query_document
     Temp.const_set :UserDocument, @client.parse(<<-'GRAPHQL')
       query GetUser {