Fix rewinding the Json stream when nested objects are encountered

apollo-api/src/commonMain/kotlin/com/apollographql/apollo3/api/json/MapJsonWriter.kt

@@ -54,7 +54,27 @@ class MapJsonWriter : JsonWriter {
   }
 
   override fun beginObject(): JsonWriter = apply {
-    val map = mutableMapOf<String, Any?>()
+    val map = if (stack.isEmpty()) {
+      mutableMapOf<String, Any?>()
+    } else {
+      val state = stack[stack.size - 1]
+      when (state) {
+        is State.List -> mutableMapOf<String, Any?>()
+        is State.Map -> {
+          val existingValue = state.map.get(state.name)
+          if (existingValue == null) {
+            mutableMapOf<String, Any?>()
+          } else {
+            // The stream rewinded. This happens with fragments as interface
+            check(existingValue is MutableMap<*, *>) {
+              "Trying to overwrite a non-object value with an object at $path: $existingValue"
+            }
+            @Suppress("UNCHECKED_CAST")
+            existingValue as MutableMap<String, Any?>
+          }
+        }
+      }
+    }
 
     valueInternal(map)
 
@@ -80,18 +100,7 @@ class MapJsonWriter : JsonWriter {
     when (val state = stack.lastOrNull()) {
       is State.Map -> {
         check(state.name != null)
-
-        // We support writing the same fields several time for fragments as classes
-        val existingValue = state.map[state.name!!]
-        if (existingValue != null && existingValue is Map<*, *>) {
-          check(value is Map<*, *>)
-          // merge any incoming object
-          state.map[state.name!!] = existingValue + value
-        } else {
-          // just overwrite what was previously there
-          // by construction it should be either null or the same value
-          state.map[state.name!!] = value
-        }
+        state.map[state.name!!] = value
         state.name = null
       }
       is State.List -> {

apollo-normalized-cache-api/src/commonMain/kotlin/com/apollographql/apollo3/cache/normalized/api/internal/Normalizer.kt

@@ -53,7 +53,8 @@ internal class Normalizer(
           val compiledFields = allFields.filter { it.responseName == entry.key }
           if (compiledFields.isEmpty()) {
             // If we come here, `obj` contains more data than the CompiledSelections can understand
-            // It's not 100% clear how this could happen, log what field triggered this
+            // This happened previously (see https://github.com/apollographql/apollo-android/pull/3636)
+            // This should not happen anymore but in case it does, we're logging some info here
             throw RuntimeException("Cannot find a CompiledField for entry: {${entry.key}: ${entry.value}}, __typename = $typename, key = $key")
           }
           val includedFields = compiledFields.filter {

tests/normalization-tests/build.gradle.kts

@@ -0,0 +1,17 @@
+plugins {
+  id("org.jetbrains.kotlin.jvm")
+  id("com.apollographql.apollo3")
+}
+
+dependencies {
+  implementation("com.apollographql.apollo3:apollo-runtime")
+  implementation("com.apollographql.apollo3:apollo-mockserver")
+  implementation("com.apollographql.apollo3:apollo-normalized-cache")
+  implementation("com.apollographql.apollo3:apollo-testing-support")
+  testImplementation(groovy.util.Eval.x(project, "x.dep.kotlinJunit"))
+  testImplementation(groovy.util.Eval.x(project, "x.dep.junit"))
+}
+
+apollo {
+  packageName.set("com.example")
+}

tests/normalization-tests/src/main/graphql/operations.graphql

@@ -0,0 +1,43 @@
+query Issue3672 {
+  viewer {
+    libraries(limit: 1) {
+      book { id }
+      ...nestedBook
+      ...anotherBookFragment
+    }
+  }
+}
+
+fragment nestedBook on Library {
+  name
+  book {
+    name
+  }
+}
+
+fragment anotherBookFragment on Library {
+  book {
+    year
+  }
+}
+
+fragment bookAuthor on Book {
+  author
+}
+
+
+query Issue2818 {
+  home {
+    ...sectionFragment
+    sectionA {
+      name
+    }
+  }
+}
+
+fragment sectionFragment on Home {
+  sectionA {
+    id
+    imageUrl
+  }
+}

tests/normalization-tests/src/main/graphql/schema.graphqls

@@ -0,0 +1,31 @@
+type Query {
+  viewer: Viewer!
+  home: Home!
+}
+
+type Viewer {
+  libraries(limit: Int): [Library!]!
+}
+
+type Book {
+  id: String!
+  name: String!
+  year: Int!
+  author: String!
+}
+
+type Library {
+  id: String!
+  name: String!
+  book: Book!
+}
+
+type Home {
+  sectionA: SectionA
+}
+
+type SectionA {
+  id: String!
+  name: String!
+  imageUrl: String
+}

tests/normalization-tests/src/test/kotlin/com/example/NormalizationTest.kt

@@ -0,0 +1,82 @@
+package com.example
+
+import com.apollographql.apollo3.api.CompiledField
+import com.apollographql.apollo3.api.CustomScalarAdapters
+import com.apollographql.apollo3.api.Executable
+import com.apollographql.apollo3.api.json.jsonReader
+import com.apollographql.apollo3.api.parseJsonResponse
+import com.apollographql.apollo3.cache.normalized.ApolloStore
+import com.apollographql.apollo3.cache.normalized.FetchPolicy
+import com.apollographql.apollo3.cache.normalized.api.CacheKey
+import com.apollographql.apollo3.cache.normalized.api.CacheKeyGenerator
+import com.apollographql.apollo3.cache.normalized.api.CacheKeyGeneratorContext
+import com.apollographql.apollo3.cache.normalized.api.CacheResolver
+import com.apollographql.apollo3.cache.normalized.api.FieldPolicyCacheResolver
+import com.apollographql.apollo3.cache.normalized.api.MemoryCacheFactory
+import com.apollographql.apollo3.cache.normalized.api.TypePolicyCacheKeyGenerator
+import com.example.fragment.SectionFragment
+import kotlinx.coroutines.runBlocking
+import okio.Buffer
+import org.junit.Test
+
+internal object IdBasedCacheKeyResolver : CacheResolver, CacheKeyGenerator {
+
+  override fun cacheKeyForObject(obj: Map<String, Any?>, context: CacheKeyGeneratorContext) =
+      obj["id"]?.toString()?.let(::CacheKey) ?: TypePolicyCacheKeyGenerator.cacheKeyForObject(obj, context)
+
+  override fun resolveField(field: CompiledField, variables: Executable.Variables, parent: Map<String, Any?>, parentId: String) =
+      FieldPolicyCacheResolver.resolveField(field, variables, parent, parentId)
+}
+
+class NormalizationTest() {
+
+  @Test
+  fun issue3672() = runBlocking {
+    val store = ApolloStore(
+        normalizedCacheFactory = MemoryCacheFactory(),
+        cacheKeyGenerator = IdBasedCacheKeyResolver,
+        cacheResolver = IdBasedCacheKeyResolver
+    )
+
+    val query = Issue3672Query()
+
+    val data1 = query.parseJsonResponse(Buffer().writeUtf8(nestedResponse).jsonReader(), CustomScalarAdapters.Empty).dataAssertNoErrors
+    store.writeOperation(query, data1)
+
+    val data2 = store.readOperation(query)
+    check(data1 == data2)
+  }
+
+
+  @Test
+  fun issue2818() = runBlocking {
+    val apolloStore = ApolloStore(
+        normalizedCacheFactory = MemoryCacheFactory(),
+        cacheKeyGenerator = IdBasedCacheKeyResolver,
+        cacheResolver = IdBasedCacheKeyResolver
+    )
+
+    apolloStore.writeOperation(
+        Issue2818Query(),
+        Issue2818Query.Data(
+            Issue2818Query.Home(
+                __typename = "Home",
+                sectionA = Issue2818Query.SectionA(
+                    name = "section-name",
+                ),
+                sectionFragment = SectionFragment(
+                    sectionA = SectionFragment.SectionA(
+                        id = "section-id",
+                        imageUrl = "https://...",
+                    ),
+                ),
+            ),
+        ),
+    )
+
+    val data = apolloStore.readOperation(Issue2818Query())
+    check(data.home.sectionA?.name == "section-name")
+    check(data.home.sectionFragment.sectionA?.id == "section-id")
+    check(data.home.sectionFragment.sectionA?.imageUrl == "https://...")
+  }
+}

tests/normalization-tests/src/test/kotlin/com/example/response.kt

@@ -0,0 +1,28 @@
+package com.example
+
+import org.intellij.lang.annotations.Language
+
+
+@Language("JSON")
+val nestedResponse = """
+  {
+    "data": {
+      "viewer": {
+        "__typename": "Viewer",
+        "libraries": [
+          {
+            "__typename": "Library",
+            "name": "library-1",
+            "book":{
+                "__typename": "Book",
+                "id": "book=1",
+                "name": "name-1",
+                "year": 1991,
+                "author": "John Doe"
+              }
+            }
+        ]
+      }
+    }
+  }
+""".trimIndent()