Migrating to Apollo Kotlin 4.0

Apollo Kotlin 3.0 was a major rewrite of Apollo in Kotlin multiplatform.

Apollo Kotlin 4.0 focuses on tooling, stability and fixing some API regrets that came with 3.x.

Because most of the common APIs stayed the same, we kept the package name unchanged. Apollo Kotlin 4.0 removes some deprecated symbols. We strongly recommend removing deprecated usages before migrating to 4.0.

If you are using a lib that depends on Apollo Kotlin transitively, you need it to update to 4.x before you can update your own app to 4.0.

Automatic migration using the Android Studio plugin

Apollo Kotlin 4 ships with a companion Android Studio plugin that automates most of the migration.

It automates most of the API replacements but cannot deal with behaviour changes like error handling.

We recommend using the plugin to automate the repetitive tasks but still go through this document for the details.

Error handling

Fetch errors do not throw

In Apollo Kotlin 3.x, non-GraphQL errors like network errors, cache misses, and parsing errors were surfaced by throwing exceptions in ApolloCall.execute() and in Flows (ApolloCall.toFlow(), ApolloCall.watch()). This was problematic because it was a difference in how to handle GraphQL errors vs other errors. Moreover, throwing terminates a Flow and consumers would have to handle re-collection.

In Apollo Kotlin 4.0, a new field ApolloResponse.exception has been added and these errors are now surfaced by returning (for execute()) or emitting (for Flows) an ApolloResponse with a non-null exception instead of throwing it.

This allows consumers to handle different kinds of errors at the same place, and it prevents Flows from being terminated.

Queries and mutations:

1
// Replace
2
try {
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  val response = client.query(MyQuery()).execute()
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  if (response.hasErrors()) {
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    // Handle GraphQL errors
6
  } else {
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    // No errors
8
    val data = response.data
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    // ...
10
  }
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} catch (e: ApolloException) {
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  // Handle network error
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}
14

15
// With
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val response = client.query(MyQuery()).execute()
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if (response.data != null) {
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  // Handle (potentially partial) data
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} else {
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  // Something wrong happened
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  if (response.exception != null) {
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    // Handle non-GraphQL errors
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  } else {
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    // Handle GraphQL errors in response.errors
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  }
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}

Subscriptions:

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// Replace
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client.subscription(MySubscription()).toFlow().collect { response ->
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  if (response.hasErrors()) {
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    // Handle GraphQL errors
5
  }
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}.catch { e ->
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  // Handle network error
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}
9

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// With
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client.subscription(MySubscription()).toFlow().collect { response ->
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  val data = response.data
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  if (data != null) {
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    // Handle (potentially partial) data
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  } else {
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    // Something wrong happened
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    if (response.exception != null) {
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      // Handle non-GraphQL errors
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    } else {
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      // Handle GraphQL errors in response.errors
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    }
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  }
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}

Note that this is true for all Flows, including watchers. If you don't want to receive error responses, filter them out:

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// Replace
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apolloClient.query(query).watch()
3

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// With
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apolloClient.query(query).watch().filter { it.exception == null }

ApolloCompositeException is not thrown anymore

When using the cache, Apollo Kotlin 3.x threw ApolloCompositeException if no response could be found. For an example, a CacheFirst fetch policy would throw ApolloCompositeException(cacheMissException, apolloNetworkException if both cache and network failed.

In those cases, Apollo Kotlin 4.0 throws the first exception and adds the second as a suppressed exception:

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// Replace
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if (exception is ApolloCompositeException) {
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  val cacheMissException = exception.first
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  val networkException = exception.second
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}
6

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// With
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val cacheMissException = exception
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val networkException = exception.suppressedExceptions.firstOrNull()

emitCacheMisses(Boolean) is removed

In Apollo Kotlin 3.x, when using the normalized cache, you could set emitCacheMisses to true to emit cache misses instead of throwing.

In Apollo Kotlin 4.0, this is now the default behavior and emitCacheMisses has been removed.

With the CacheFirst, NetworkFirst and CacheAndNetwork policies, cache misses and network errors are now emitted in ApolloResponse.exception.

Migration helpers

To ease the migration from 3.x, drop-in helpers functions are provided that restore the V3 behaviour:

• ApolloCall.executeV3()
• ApolloCall.toFlowV3()

Those helper functions:

• throw on fetch errors
• make CacheFirst, NetworkFirst and CacheAndNetwork policies ignore fetch errors.
• throw ApolloComposite exception if needed.

Because of the number of different options in 3.x and the complexity of error handling, these functions do not pretend to match 1:1 the V3 behaviour, especially in the advanced cases involving watchers. If you are in one of those cases, we strongly recommend using the 4.0 functions that are easier to reason about.

Other Apollo Runtime changes

HTTP headers

X-APOLLO-OPERATION-NAME and X-APOLLO-OPERATION-ID are non-standard headers and are not sent by default anymore. If you used them for logging purposes or if you are using Apollo Server CSRF prevention, you can add them back using an ApolloInterceptor:

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val apolloClient = ApolloClient.Builder()
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        .serverUrl(mockServer.url())
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        .addInterceptor(object : ApolloInterceptor {
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          override fun <D : Operation.Data> intercept(request: ApolloRequest<D>, chain: ApolloInterceptorChain): Flow<ApolloResponse<D>> {
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            return chain.proceed(request.newBuilder()
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                .addHttpHeader("X-APOLLO-OPERATION-NAME", request.operation.name())
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                .addHttpHeader("X-APOLLO-OPERATION-ID", request.operation.id())
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                .build()
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            )
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          }
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        })
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        .build()

In v3, if HTTP headers were set on an ApolloCall, they would replace the ones set on ApolloClient. In v4 they are added instead by default. To replace them, call ApolloCall.Builder.ignoreApolloClientHttpHeaders(true).

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// Replace
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val call = client.query(MyQuery())
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  .httpHeaders(listOf("key", "value"))
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  .execute()
5

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// With
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val call = client.query(MyQuery())
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  .httpHeaders(listOf("key", "value"))
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  .ignoreApolloClientHttpHeaders(true)
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  .execute()

HttpEngine now implements Closeable

HttpEngine now implements Closeable and has its dispose method renamed to close. If you have a custom HttpEngine, you need to implement close instead of dispose.

Apollo Gradle Plugin

Multi-module dependsOn

In Apollo Kotlin 3, you could depend on an upstream GraphQL module by using the apolloMetadata configuration.

In Apollo Kotlin 4, this is now done with the Service.dependsOn(). This allows better management of dependencies when multiple services are used as better symmetry with isADependencyOf below.

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// feature1/build.gradle.kts
2

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// Replace
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dependencies {
5
  // ...
6

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  // Get the generated schema types (and fragments) from the upstream schema module 
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  apolloMetadata(project(":schema"))
9

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  // You also need to declare the schema module as a regular dependency
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  implementation(project(":schema"))
12
}
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// With
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dependencies {
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  // ...
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18
  // You still need to declare the schema module as a regular dependency
19
  implementation(project(":schema"))
20
}
21

22
apollo {
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  service("service") {
24
    // ...
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    // Get the generated schema types (and fragments) from the upstream schema module 
27
    dependsOn(project(":schema"))
28
  }
29
}

Auto-detection of used types

In multi-module projects, by default, all the types of an upstream module are generated because there is no way to know in advance what types are going to be used by downstream modules. For large projects this can lead to a lot of unused code and an increased build time.

To avoid this, in v3 you could manually specify which types to generate by using alwaysGenerateTypesMatching. In v4 this can now be computed automatically by detecting which types are used by the downstream modules.

To enable this, add the "opposite" link of dependencies with isADependencyOf().

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// schema/build.gradle.kts
2

3
// Replace
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apollo {
5
  service("service") {
6
    // ...
7
    
8
    // Generate all the types in the schema module
9
    alwaysGenerateTypesMatching.set(listOf(".*"))
10

11
    // Enable generation of metadata for use by downstream modules 
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    generateApolloMetadata.set(true)
13
  }
14
}
15

16
// With
17
apollo {
18
  service("service") {
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    // ...
20

21
    // Enable generation of metadata for use by downstream modules 
22
    generateApolloMetadata.set(true)
23

24
    // Get used types from the downstream module1
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    isADependencyOf(project(":feature1"))
26

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    // Get used types from the downstream module2
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    isADependencyOf(project(":feature2"))
29
    
30
    // ...
31
  }
32
}

If you were using apolloUsedCoordinates, you can also remove it:

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dependencies {
2
  // Remove this 
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  apolloUsedCoordinates(project(":feature1"))
4
}

Custom scalars declaration

customScalarsMapping is removed and replaced with mapScalar() which makes it easier to map to built-in types and/or provide a compile type adapter for a given type:

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// Replace
2
customScalarsMapping.set(mapOf(
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    "Date" to "kotlinx.datetime.LocalDate"
4
))
5

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// With
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mapScalar("Date", "kotlinx.datetime.LocalDate")
8

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// Replace
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customScalarsMapping.put("MyLong", "kotlin.Long")
11

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// With
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mapScalarToKotlinLong("MyLong")

schemaFile is deprecated

Because there might be several schema files, schemaFile is deprecated. Instead use schemaFiles:

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// replace
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    schemaFile.set("src/main/graphql/com/example/schema.graphqls")
3

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    // with
5
    schemaFiles.from("src/main/graphql/com/example/schema.graphqls")

If you are using packageNamesFromFilePaths and schemaFile, you'll need to use a Gradle FileTree to carry the appropriate normalized path.

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packageNameFromFilePaths()
2

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    // replace
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    schemaFile.set("src/main/graphql/com/example/schema.graphqls")
5

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    // with
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    schemaFiles.from(fileTree("src/main/graphql/").apply {
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      include("com/example/schema.graphqls")
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    })

Misc

• Publishing is no longer configured automatically.
• Because Apollo Kotlin now supports different operation manifest formats, operationOutput.json has moved from "build/generated/operationOutput/apollo/$service/operationOutput.json" to "build/generated/manifest/apollo/$service/operationOutput.json"
• useSchemaPackageNameForFragments is removed

Apollo Compiler

"compat" codegenModels is removed

The "compat" codegen models was provided for compatibility with 2.x and is now removed. "operationBased" is more consistent and generates less code:

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// Replace
2
apollo {
3
  service("service") {
4
    codegenModels.set("compat")
5
  }
6
}
7

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// With
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apollo {
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  service("service") {
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    codegenModels.set("codegenModels")
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  }
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}

In the generated models, inline fragments accessors are prefixed with on:

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// Replace
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data.hero.asDroid
3

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// With
5
data.hero.onDroid

The fragments synthetic property is not needed anymore:

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// Replace
2
data.hero.fragments.heroDetails
3

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// With
5
data.hero.heroDetails

Finally some fields that were merged from inline fragments in their parents must now be accessed through the inline fragment:

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// Replace
2
/**
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 * {
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 *   hero {
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 *     # this condition is always true
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 *     # allowing to merge the name field
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 *     ... on Character {
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 *       name
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 *     }
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 *   }
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 * }
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 */
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data.hero.name
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// With 
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/**
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 * name is not marged anymore
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 */
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data.hero.onCharacter?.name

For consistency with other types, GraphQL enums are now capitalized in Kotlin. You can restore the previous behaviour using @targetName:

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# Make sure `someEnum` isn't renamed to `SomeEnum`
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enum someEnum @targetName(name: "someEnum"){
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  A
4
  B
5
}

__Schema is in the schema subpackage

If using the generateSchema option, and to avoid a name clash with the introspection type of the same name, the __Schema type is now generated in a schema subpackage (instead of type) when using the generateSchema option:

1
// Replace
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import com.example.type.__Schema
3

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// With
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import data.builders.schema.__Schema

KotlinLabs directives are now version 0.2

The embedded kotlinlabs/0.2 directives are now version 0.2.

These are the client directives supported by Apollo Kotlin. They are imported automatically but if you relied on an explicit import for renames or another reason, you'll need to bump the version:

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# Replace
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extend schema @link(url: "https://specs.apollo.dev/kotlin_labs/v0.1/", import: ["@typePolicy"])
3

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# With
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extend schema @link(url: "https://specs.apollo.dev/kotlin_labs/v0.2/", import: ["@typePolicy"])

This is a backward compatible change.

Cache

ApolloStore

In Apollo Kotlin 3.x, most ApolloStore functions were marked as suspend even though they were not actually suspending and perform the work in the thread they are called from. In particular, they can be blocking when the underlying cache is doing IO, so calling them from the main thread can lead to ANRs.

In Apollo Kotlin 4.0 this is still the case but the functions are no longer marked as suspend to avoid any confusion.

Configuration order

The normalized cache must be configured before the auto persisted queries, configuring it after will now fail (see https://github.com/apollographql/apollo-kotlin/pull/4709).

apollo-ast

The AST classes (GQLNode and subclasses) as well as Introspection classes are not data classes anymore (see https://github.com/apollographql/apollo-kotlin/pull/4704/). The class hierarchy has been tweaked so that GQLNamed, GQLDescribed and GQLHasDirectives are more consistently inherited from.

GQLSelectionSet and GQLArguments are deprecated and removed from GQLField and GQLInlineFragment. Use .selections directly

GQLInlineFragment.typeCondition is now nullable to account for inline fragments who inherit their type condition.

SourceLocation.position is renamed SourceLocation.column and is now 1-indexed. GQLNode.sourceLocation is now nullable to account for the cases where the nodes are constructed programmatically.

It is not possible to create a Schema from a File or String directly anymore. Instead, create a GQLDocument first and convert it to a schema with toSchema().

Using RxJava artifacts is now an error

The apollo-rx2-support and apollo-rx3-support artifacts are very thin wrappers around kotlinx-coroutines-rx2 or kotlinx-coroutines-rx3 and will be removed in a future version.

In Apollo Kotlin 4, use kotlinx-coroutines-rx${version} instead. Replace the artifact in your build script:

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dependencies {
2
  // Replace
3
  implementation("com.apollographql.apollo3:apollo-rx2-support:$version")
4
  
5
  // With
6
  implementation("org.jetbrains.kotlinx:kotlinx-coroutines-rx2:$version")
7
}

In your code, use asFLowable():

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// Replace
2
apolloClient.query().rxFlowable()
3

4
// With
5
apolloClient.query().toFlow().asFlowable()
6

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// Replace
8
apolloClient.query().rxSingle()
9

10
// With
11
apolloClient.query().toFlow().asFlowable().firstOrError()

Example of a migration

If you are looking for inspiration, we updated the 3.x integration tests to use 4.0. If you have an open source project that migrated, feel free to share it and we'll include it here.