Ignore adding key fields if the cache compiler plugin is present

Author: martinbonnin

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/definitions.kt

@@ -35,7 +35,41 @@ internal val kotlinLabsDefinitions_0_3 = """
   ""${'"'}
   directive @typePolicy(
       ""${'"'}
-      a selection set containing fields used to compute the cache key of an object. Order is important.
+      A selection set containing fields used to compute the cache key of an object. 
+      Nested selection sets are currently not supported. Order is important. 
+      
+      Key fields can be defined on interfaces. In that case, the key fields apply to all sub-types. Sub-types are not allowed to define their own key fields.
+      
+      The key fields are automatically added to the operations by the compiler.
+      Aliased key fields are not recognized and the compiler adds a non-aliased version of the field if that happens.
+      If a type is queried through an interface/union, this may add fragments.
+
+      For an example, this query:
+      
+      ```graphql
+      query {
+        product {
+          price
+        }
+      }
+      ```
+      
+      is turned into this one after compilation: 
+      
+      ```graphql
+      query {
+        product {
+          ... on Book {
+            isbn
+          }
+          ... on Movie {
+            id
+          }
+          price
+        }
+      }
+      ```
+      
       ""${'"'}
       keyFields: String! = "",
       ""${'"'}

libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompiler.kt

@@ -232,15 +232,16 @@ object ApolloCompiler {
 
     /**
      * Step 2, Modify the AST to add typename, key fields and call any user-provided transform.
-     * We only do this if we detect that the cache plugin is not applied since it's also doing those same computations.
+     * If we detect that the cache compiler plugin is present, we skip adding the keyfields because it will do it.
+     * TODO: deprecate `addTypename`
      */
     val hasCacheCompilerPlugin = try {
       Class.forName("com.apollographql.cache.apollocompilerplugin.internal.ApolloCacheCompilerPlugin")
       true
     } catch (_: ClassNotFoundException) {
       false
     }
-    
+
     var document = ApolloOperationsTransform(options.addTypename ?: defaultAddTypename, !hasCacheCompilerPlugin).transform(
       schema = schema,
       document = GQLDocument(userDefinitions, sourceLocation = null),

libraries/apollo-compiler/src/test/kotlin/com/apollographql/apollo/compiler/TypenameTest.kt

@@ -1,14 +1,10 @@
 package com.apollographql.apollo.compiler
 
-import com.apollographql.apollo.ast.GQLDocument
-import com.apollographql.apollo.ast.GQLFragmentDefinition
-import com.apollographql.apollo.ast.GQLOperationDefinition
 import com.apollographql.apollo.ast.toExecutableDocument
 import com.apollographql.apollo.ast.toGQLDocument
 import com.apollographql.apollo.ast.toSchema
 import com.apollographql.apollo.ast.toUtf8
-import com.apollographql.apollo.ast.validateAsSchema
-import com.apollographql.apollo.compiler.internal.addRequiredFields
+import com.apollographql.apollo.compiler.internal.ApolloOperationsTransform
 import com.google.common.truth.Truth.assertThat
 import com.google.testing.junit.testparameterinjector.TestParameter
 import com.google.testing.junit.testparameterinjector.TestParameterInjector
@@ -28,19 +24,9 @@ class TypenameTest(
     val schemaFile = File("src/test/graphql/schema.graphqls")
     val schema = schemaFile.toGQLDocument().toSchema()
 
-    val definitions = graphQLFile.source().buffer().toExecutableDocument(schema).definitions
+    val document = graphQLFile.source().buffer().toExecutableDocument(schema)
 
-    val fragments = definitions.filterIsInstance<GQLFragmentDefinition>().associateBy { it.name }
-    val documentWithTypename = GQLDocument(
-        definitions = definitions.map {
-          when (it) {
-            is GQLOperationDefinition -> addRequiredFields(it, addTypename, schema, fragments)
-            is GQLFragmentDefinition -> addRequiredFields(it, addTypename, schema, fragments)
-            else -> it
-          }
-        },
-        sourceLocation = null
-    ).toUtf8()
+    val documentWithTypename = ApolloOperationsTransform(addTypename, false).transform(schema, document, emptyList()).toUtf8()
 
     val extra = when(addTypename) {
       "ifFragments" -> "" // for backward compat