Add FFI and JNI support to Swift and Kotlin by tarrinneal · Pull Request #11352 · flutter/packages

tarrinneal · 2026-03-25T18:52:22Z

This PR introduces optional Native Interop to Pigeon, enabling direct communication between Dart and native code without the overhead of traditional MethodChannel serialization. It leverages FFI (Foreign Function Interface) for Swift (iOS/macOS) and JNI (Java Native Interface) for Kotlin (Android).

This represents a significant architectural shift, moving from message-based passing to direct memory sharing and function calls. It also updates the concurrency model for asynchronous methods, moving from completion handlers/callbacks to modern language features: async/await in Swift and Coroutines in Kotlin.

Generators Covered

Swift Generator: Updated to support FFI bindings and async/await for asynchronous methods.
Kotlin Generator: Updated to support JNI bindings and Kotlin Coroutines for asynchronous methods.
Dart Generator: Updated to handle the generated interop bindings on the Dart side.

What's In Scope

Infrastructure: Added core support for useFfi and useJni options.
Automation: Implemented multi-step generation flows that automatically invoke jnigen and ffigen to produce final bindings.
Config Generation: Added jnigen_config_generator.dart and ffigen_config_generator.dart to generate the necessary configuration files for the external tools.
Documentation: Added a detailed native_interop_guide.md explaining prerequisites, setup, and usage.
Tests: Added ni_tests.dart and associated generated files and integration tests to verify the feature.

What's Out of Scope

Other Languages: This PR specifically targets Swift and Kotlin for the Native Interop feature. Support for Objective-C, C++, and GObject is not included in this interop implementation, and may not be in the future.
Performance Optimization for Complex Classes: As noted in the guide, there is a known performance regression when transferring complex classes with many fields compared to MethodChannel Pigeon. This PR delivers the functional infrastructure, but optimizing this specific case is left for follow-up work.
Non-instant released data. Currently all data that is sent over host or flutter api surfaces is converted to the correct shape and type for the language it is moving toward and the data created in the other language is then discarded. This presents some inefficiencies and potential workflows that are not yet available.

work toward flutter/flutter#182230
design doc flutter/flutter#181430

…o Kamyshin

stuartmorgan-g

More WIP review comments; still haven't finished the full pass.

stuartmorgan-g · 2026-05-20T18:30:43Z

Why do we have two Pigeon files in this example? I would expect just one, using FFI/JNI (and not including Windows or Linux builds).

stuartmorgan-g · 2026-06-10T18:53:28Z

+
+| Feature | MethodChannels | Native Interop |
+| :--- | :--- | :--- |
+| **Communication Mechanism** | Asynchronous message passing over platform channels | Direct memory-bound function calls (Dart FFI / JNI) |


I don't this row is adding any information that's not in the summary introducing this section, so could be removed.

stuartmorgan-g · 2026-06-10T18:54:14Z

+| Feature | MethodChannels | Native Interop |
+| :--- | :--- | :--- |
+| **Communication Mechanism** | Asynchronous message passing over platform channels | Direct memory-bound function calls (Dart FFI / JNI) |
+| **Platform Support** | All supported platforms (Android, iOS, macOS, Windows, Linux) | Android, iOS, and macOS only (Windows and Linux not supported) |


No need for the parenthetical in the last cell. Anyone interested in Windows or Linux can see it's not in the list.

stuartmorgan-g · 2026-06-10T18:57:56Z

+| :--- | :--- | :--- |
+| **Communication Mechanism** | Asynchronous message passing over platform channels | Direct memory-bound function calls (Dart FFI / JNI) |
+| **Platform Support** | All supported platforms (Android, iOS, macOS, Windows, Linux) | Android, iOS, and macOS only (Windows and Linux not supported) |
+| **Serialization Overhead** | High (data is serialized/deserialized to/from binary) | Low/Zero (uses direct memory sharing or native references) |


This seems misleading; what Pigeon returns isn't shared memory or native references, it's a copy. I think this row should be something like "Overhead | High (serialization and multiple copies) | Low (minimal copying)"

stuartmorgan-g · 2026-06-10T18:58:20Z

+| **Platform Support** | All supported platforms (Android, iOS, macOS, Windows, Linux) | Android, iOS, and macOS only (Windows and Linux not supported) |
+| **Serialization Overhead** | High (data is serialized/deserialized to/from binary) | Low/Zero (uses direct memory sharing or native references) |
+| **Latency** | Higher (requires message loop scheduling) | Extremely low (direct execution) |
+| **Synchronous Host Calls** | Not supported (always asynchronous) | Fully supported (true synchronous execution) |


Neither of the parentheticals is needed here.

stuartmorgan-g · 2026-06-22T18:50:43Z

+
+  String get fullFfiName {
+    if (type.baseName == 'List' || type.baseName == 'Map') {
+      return ffiName;


Is this supposed to be the same? If so, it seems like some refactoring along the way make this method useless.

stuartmorgan-g · 2026-06-22T18:51:03Z

+  }
+
+  String get primitiveToDartMethodName {
+    switch (type.baseName) {


As above, consider a switch expression.

stuartmorgan-g · 2026-06-22T18:59:39Z

+    if (type.isClass || type.isEnum) {
+      return '$name${_getNullableSymbol(type.isNullable)}.toJni()';
+    } else if (!type.isNullable &&
+        (type.baseName == 'int' || type.baseName == 'double' || type.baseName == 'bool')) {


The int/double/bool baseName triple occurs a number of times in this file; is there a concept you can abstract to a helper method here?

stuartmorgan-g · 2026-06-22T19:00:27Z

+  String getJniCollectionTypeAnnotations({bool isParameter = false, bool isAsynchronous = false}) {
+    if (type.baseName == 'List') {
+      return '<${getJniCollectionTypes(isParameter: isParameter, isAsynchronous: isAsynchronous)}>';
+    } else if (type.baseName == 'Map') {


The if and else if have the same outcome here, so could be consolidated.

stuartmorgan-g · 2026-06-22T20:41:36Z

+  String get jniCollectionTypes => getJniCollectionTypes();
+}
+
+String _getNullableSymbol(bool nullable) => nullable ? '?' : '';


_getNullabilitySymbol so it's clearer that it can be non-nullable?

stuartmorgan-g

Another review drop!

I believe I've made it through all the non-test code now, so the end is in sight. (After all, how much test code can there be?)

stuartmorgan-g · 2026-06-23T15:10:48Z

+  }
+}
+
+ffi_bridge.MessagesPigeonTypedData toPigeonTypedData(TypedData value) {


A lot of these helpers aren't file-private; is that intentional? Do we need to make these visible to Pigeon clients?

stuartmorgan-g · 2026-06-23T15:13:06Z

+    }
+  }
+
+  String getToDartCall(


A lot of these non-trivial helpers could use a Dart doc comment explaining very briefly what they do/are for, and what any non-obvious parameter means.

stuartmorgan-g · 2026-06-23T15:17:49Z

+      return '$name${_getNullableSymbol(type.isNullable)}.toFfi()';
+    }
+    if (type.isEnum && !type.isNullable) {
+      return 'ffi_bridge.${type.baseName}.values[$name]';


The magic string ffi_bridge appears a lot, and should be a file-level constant instead.

stuartmorgan-g · 2026-06-23T15:20:50Z

+      return 'NSObject${_getNullableSymbol((forceNullable || type.isNullable) && !forceNonNullable)}';
+    }
+
+    return '${ffiName.replaceAll('ffi_bridge.', prefix)}${_getNullableSymbol((forceNullable || type.isNullable) && !forceNonNullable)}';


If sometimes we want the prefix and sometimes we don't, why not have withPrefix as a parameter to ffiName, instead of unconditionally adding it there and then conditionally removing it?

stuartmorgan-g · 2026-06-23T15:21:27Z

+    if (type.baseName == 'List') {
+      return '<$ffiCollectionTypes>';
+    } else if (type.baseName == 'Map') {
+      return '<$ffiCollectionTypes>';


As above, List and Map are the same and can be collapsed.

stuartmorgan-g · 2026-06-23T20:30:36Z

+      environment: env,
+    );
+    if (jnigenResult.exitCode != 0) {
+      print('''


I highly recommend printing this second, not first, so it's the most obvious thing someone sees when the command fails.

stuartmorgan-g · 2026-06-23T20:37:26Z

+
+  String? pubspecPath;
+  if (appDirectory != null && appDirectory.isNotEmpty) {
+    pubspecPath = findPubspecPath(path.join(appDirectory, 'placeholder.dart'));


Let's just adjust findPubspecPath to take a Directory instead of appending placeholders in some cases, and then the places where we start with a Dart path we can call it with File(dartPath).parent

stuartmorgan-g · 2026-06-23T20:38:30Z

+  pubspecPath ??= findPubspecPath(path.join(Directory.current.path, 'placeholder.dart'));
+
+  if (pubspecPath == null) {
+    return errors;


We want to return no errors if we couldn't find a pubspec? If so, please add a comment here saying why.

stuartmorgan-g · 2026-06-23T20:39:02Z

+        }
+      }
+    }
+  } catch (_) {}


Why are we silently dropping all exceptions without returning any errors?

stuartmorgan-g · 2026-06-23T20:41:23Z

+            Error(
+              message:
+                  'Missing required dependency "$dep" in pubspec.yaml for $apiName native interop support.\n'
+                  'Please add "$dep" to your dependencies or dev_dependencies in your pubspec.yaml file.',


We should be distinguishing between dev and non-dev dependencies in both the validation and the error message. E.g., if someone adds objective_c as a dev dependency, it shouldn't pass validation. Similarly, if they are completely missing objective_c, as a dependency, they shouldn't have to guess where to add it.

…o Kamyshin

tarrinneal added 30 commits October 29, 2025 19:00

kotlin jni impementation

b9b0b5e

analyzer

e599d1e

test fixes w jetski

726975d

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

f636cdb

remove future code

72a305e

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

4e59659

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

e22c55a

Merge remote-tracking branch 'origin/Frillback' into Kamyshin

3f0be1d

minor cleanup

0d09615

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

e0f23a9

omit types

025376c

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

aa01700

format

6a0df05

flutter api

022ed51

fix swift optional bug

43f2e5a

add nullable tests and more sync tests

5fd46e8

flutter api async methods

a0c56ab

error handling and tests

2c252ae

basic thread tests

5072a47

fix swftFunction

b0cd2ec

add back tests for named/optional params

38bd37e

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

850cb2e

fix const gen adapter classes

9bb4bc5

performance improvements to typedData and isEquals

0c7ef63

stuff that I'm going to move to a different branch

110ab70

Improve efficiency in some methods

82065a8

analyze this

9861c00

format

11daedd

less repeating, and less listing

e197fc0

allow individual class types to not have colliding hashes

cbf4096

github-actions Bot removed CICD Run CI/CD p: go_router_builder p: go_router p: animations p: camera p: file_selector p: google_maps_flutter p: google_sign_in p: image_picker p: in_app_purchase p: local_auth labels May 4, 2026

tarrinneal added 14 commits May 4, 2026 14:22

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

3d271c9

relocate, rename and revert files

f945e36

update ffi instructoins

98dedbf

update readme's and add header

2167218

Merge branch 'Kamyshin' of https://github.com/tarrinneal/packages int…

2d2b115

…o Kamyshin

use flags

fe2a3ce

ez

36f37d1

cleaner

6bc9813

check for deps

8c778d8

unimp

625df07

add example

85e3f30

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

0bcef49

Merge branch 'main' of https://github.com/flutter/packages into Kamyshin

75217be

weird formatting issues with objc headers

aa2cb69

stuartmorgan-g reviewed Jun 22, 2026

View reviewed changes

stuartmorgan-g reviewed Jun 23, 2026

View reviewed changes

tarrinneal added 3 commits June 23, 2026 17:46

fix dependancy issues

4de0740

Merge branch 'Kamyshin' of https://github.com/tarrinneal/packages int…

0fe78ed

…o Kamyshin

don't generate jni code when not using jni

4880a8b

Uh oh!

Conversation

tarrinneal commented Mar 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

stuartmorgan-g left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

stuartmorgan-g left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

tarrinneal commented Mar 25, 2026 •

edited

Loading