[jni] Add deep conversion utils by Siya-05 · Pull Request #3635 · dart-lang/native

Siya-05 · 2026-09-14T07:32:30Z

Description

Adds deep conversion utilities to package:jni, following the conversion API pattern in package:objective_c.

This adds conversions between Dart values and JNI objects for primitive values, strings, lists, sets, and maps, with recursive conversion of nested collections and nullable values. It also adds conversion support for JArray and the primitive array variants.

Java-to-Dart collection conversions return collections of Object?, allowing callers to cast them to the expected types when needed. Unsupported types can be handled through the convertOther callback in either conversion direction.

Related Issues

Fixes #3143

PR Checklist

I’ve reviewed the contributor guide and applied the relevant portions to this PR.
I've run dart tool/ci.dart --all locally and resolved all issues identified. This ensures the PR is formatted, has no lint errors, and ran all code generators. This applies to the packages part of the toplevel pubspec.yaml workspace.
All existing and new tests are passing. I added new tests to check the change I am making.
The PR is actually solving the issue. PRs that don't solve the issue will be closed. Please be respectful of the maintainers' time. If it's not clear what the issue is, feel free to ask questions on the GitHub issue before submitting a PR.
I have updated CHANGELOG.md for the relevant packages. (Not needed for small changes such as doc typos).
I have updated the pubspec package version if necessary.

Siya-05 · 2026-09-15T02:21:35Z

Fixed the directives_ordering analyzer failure. I'm not sure about the runtime_test.dart failure.

liamappelbe · 2026-09-15T02:23:26Z

Fixed the directives_ordering analyzer failure. I'm not sure about the runtime_test.dart failure.

It's a known flake. I really need to deflake all these tests, but I haven't been able to repro them locally.

Siya-05 · 2026-09-15T02:50:48Z

Added the required jni 1.0.3 changelog entry.

Siya-05 · 2026-09-15T04:40:22Z

Do you see any logical/API changes needed here? Also, should we support DateTime conversion like package:objective_c?

liamappelbe

Also, should we support DateTime conversion like package:objective_c?

Not in this PR.

liamappelbe · 2026-09-16T01:25:31Z

+
+extension DartListToJList on List<Object?> {
+  /// Deep converts this Dart [List] to a [JList].
+  JList<JObject?> toJListDeep({


Can you delete toJListDeep and instead do this deep conversion inside toJList? It doesn't really make sense to have a distinction between deep conversion and shallow conversion, because whether or not the conversion is deep is determined by the type of the element:

If the element is a JObject, then toJObject is a no-op, so toJListDeep is a shallow conversion.

If the element is not a JObject then it's impossible to do a shallow conversion.

So ToJavaList could check the type of the element and either shallow convert or not. But even that is just an optimisation (avoiding an unnecessary .map() call if the element is a JObject). I think even if you ignored that distinction, and always do .map(toNullableJObject) in toJList, it would be behaviorally identical.

Same for the other collections.

liamappelbe · 2026-09-16T01:31:05Z

 ## 1.0.3

 - Fix JNI build errors on Linux arm64.
+- Add deep conversion utilities for converting between Dart values and Java


1.0.3 is already published, so start a new version. This is adding new APIs, so it'll need to be a minor version bump to 1.1.0-wip. Update here and the pubspec.

Siya-05 · 2026-09-16T04:46:02Z

Updated the collection conversion APIs to integrate deep conversion into toJList, toJSet, and toJMap, and bumped the package version to 1.1.0-wip.

Siya-05 · 2026-09-18T02:36:52Z

@liamappelbe, can you run the CI tests when you get the chance?

Siya-05 · 2026-09-18T06:27:53Z

I hit the version_test.dart failure after bumping jni to 1.1.0-wip. dart_generator.dart still had jniMinorVersion = '0'.

Updating it to 1 fixes the version test, but since that value is emitted as JniVersionCheck(1, 1), running regenerate_all_bindings.dart updates the version check in some generated bindings too.

Should I include those regenerated bindings here, or is there a better way to handle the JNI version bump?

liamappelbe · 2026-09-21T00:12:04Z

I hit the version_test.dart failure after bumping jni to 1.1.0-wip. dart_generator.dart still had jniMinorVersion = '0'.

Updating it to 1 fixes the version test, but since that value is emitted as JniVersionCheck(1, 1), running regenerate_all_bindings.dart updates the version check in some generated bindings too.

Should I include those regenerated bindings here, or is there a better way to handle the JNI version bump?

To avoid the churn, maybe just don't run regenerate_all_bindings.dart? The CI test will catch any real diffs. The point of weakeneing the test was that you could just not updating the bindings if the only change was a version bump.

Siya-05 · 2026-09-21T01:50:37Z

Fixed it by updating jniMinorVersion to 1 and leaving the generated bindings unchanged. The version test passes locally now. Could you rerun the CI tests?

Siya-05 · 2026-09-21T02:48:36Z

Looks like CI is now failing because the freshly generated bindings expect package:jni ^1.1.0, but the test environment is still importing 1.0.x. Should I update anything else for the 1.1.0-wip bump?

liamappelbe · 2026-09-21T02:59:05Z

We can use this PR as a test case to fix the remaining version test relaxation issues. Ideally a version bump like this (one that doesn't affect the generated code) should just require bumping a few constants in monorepo, not regenerating dozens of bindings files.

For example, this failure looks legit. It's another case that could be relaxed to not check the JNI version.

This failure also looks legit. There's probably some hard coded version constants that need to be bumped.

You should be able to repro both failures locally.

Siya-05 · 2026-09-21T03:18:00Z

Sounds good, I'll reproduce both failures locally and work on fixing them in this PR.

Siya-05 · 2026-09-21T15:42:47Z

Quick update on the failures:

Version consistency: bumped JniVersionCheck.actualMinorVersion to 1.
Generated binding comparisons: ignore version-only JniVersionCheck diffs in comparePaths.
Example regeneration: applied the same relaxation to its direct git diff.
jni_flutter CI: applied the same relaxation to its workflow diff.

The previously failing tests now pass locally without regenerating the bindings.

Architectural question: the JNI major/minor version is hardcoded in a few places and manually kept in sync with jni/pubspec.yaml. Would it make sense to derive these from a single source of truth, or is keeping them explicit intentional?

codecov · 2026-09-22T00:23:07Z

Codecov Report

❌ Patch coverage is 95.87629% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@f2b4942). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pkgs/jni/lib/src/converter.dart	95.87%	4 Missing ⚠️

Additional details and impacted files

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liamappelbe · 2026-09-22T01:00:26Z

+  );
+}
+
+extension DartIterableToJList on Iterable<Object?> {


Do we still need the converter in jlist.dart? Seems redundant.

Same for the ones in jmap.dart and jset.dart.

The existing converters preserve the element types (Iterable.toJList() returns JList, and similarly for sets/maps), while the new converters accept Dart values and return JList<JObject?>/JSet<JObject?>/JMap<JObject?, JObject?>. I kept both to preserve the existing typed API.

Revisions updated by `dart tools/rev_sdk_deps.dart`. native (https://github.com/dart-lang/native/compare/f628b26..27f7678): 27f767827 Mon Sep 28 14:51:28 2026 +0200 Daco Harkes [hooks_runner] Remove `KernelAssets` and `Target` (dart-lang/native#3703) ddc7d6deb Mon Sep 28 05:40:03 2026 +0200 Jakob Kordež [ffigen] Skip typedefs to function pointers with unsupported parameter types (dart-lang/native#3694) 177d283d9 Mon Sep 28 04:30:28 2026 +0200 Jakob Kordež [ffigen] Generate bindings for C++ enums, structs and unions nested in namespaces and records (dart-lang/native#3644) 5ee8f67d8 Mon Sep 28 11:39:14 2026 +1000 Liam Appelbe [objective_c] Clarify block isolate scoping (dart-lang/native#3692) 25f090116 Fri Sep 25 12:09:12 2026 +1000 Liam Appelbe [ffigen][jnigen] Deprecate YAML config (dart-lang/native#3654) 8364413eb Fri Sep 25 10:09:50 2026 +1000 Liam Appelbe [jnigen] Document nullability (dart-lang/native#3690) e8d518574 Thu Sep 24 18:02:46 2026 +1000 Liam Appelbe [ffigen] Code snippet-ify ffigen and objective_c (dart-lang/native#3685) 663385955 Thu Sep 24 03:21:53 2026 +0300 Manar Elhabbal [ffigen] prevent setting both cpp and objectiveC in ffigenerator (dart-lang/native#3687) 1cf40952a Thu Sep 24 09:27:09 2026 +1000 Liam Appelbe [objective_c] Remove arm64e build hack (dart-lang/native#3680) c44550b6e Wed Sep 23 13:01:33 2026 +0200 Simon Binder [web_assets] Scaffold package (dart-lang/native#3610) 57b4bad69 Wed Sep 23 16:21:27 2026 +1000 Liam Appelbe [swift2objc] Code snippet-ify swift2objc (dart-lang/native#3684) 5cee1d0be Wed Sep 23 10:16:29 2026 +0530 Rachit Vikram Singh [ffigen] Add Input.appendCompilerOptions to append clang args to defaults (`#3630`) (dart-lang/native#3676) 225a648df Wed Sep 23 14:37:13 2026 +1000 Liam Appelbe [jnigen] Code snippet-ify jnigen and co (dart-lang/native#3641) 2030decf9 Wed Sep 23 13:51:24 2026 +1000 Liam Appelbe [infra] Move snippets_tool to its own package (dart-lang/native#3683) 6fa2beea2 Wed Sep 23 12:14:28 2026 +1000 Liam Appelbe [objective_c] Revert `#3664` (dart-lang/native#3681) ed7605f8a Tue Sep 22 12:03:22 2026 +0530 Sivapriya [jni] Add deep conversion utils (dart-lang/native#3635) 8574b7422 Tue Sep 22 08:31:11 2026 +0200 Lukas Klingsbo [ffigen] Allow package:cli_util 0.5.x and 0.6.x (dart-lang/native#3673) test (https://github.com/dart-lang/test/compare/9946c95..4f92d53): 4f92d530 Fri Sep 25 16:46:22 2026 -0700 Nate Bosch Unskip a test on windows (dart-lang/test#2772) 7fb84866 Fri Sep 25 14:52:39 2026 -0700 Nate Bosch Bundle skips at the end of the GitHub reporter (dart-lang/test#2768) 603e5ec5 Thu Sep 24 14:00:41 2026 -0700 Nate Bosch Clean up the runner's temporary directories (dart-lang/test#2763) 4bf04d90 Thu Sep 24 12:41:15 2026 -0700 Nate Bosch Refactor signal handling in executable.dart (dart-lang/test#2765) 2c660a84 Tue Sep 22 15:33:34 2026 -0700 Nate Bosch Regenerate mono_repo output (dart-lang/test#2767) tools (https://github.com/dart-lang/tools/compare/3614ce0..d87eaf7): d87eaf79 Thu Sep 24 08:31:33 2026 -0700 Kevin Moore fix(benchmark_harness): migrate subprocess spawning to package:cli_util (dart-lang/tools#2585) 8ccf8ccf Wed Sep 23 05:09:10 2026 +0530 Aman Maurya [string_scanner] Extract a mixin for LineScanner and deduplicate eager scanning logic (dart-lang/tools#2569) afcdd6d9 Tue Sep 22 15:38:07 2026 +0200 Morgan :) Document that watch events converge on filesystem state. (dart-lang/tools#2607) f2157cbc Tue Sep 22 04:52:58 2026 +0300 Hasan Armoush [code_builder] Add null-aware cascades, cascade index, and fluent cascade helpers (dart-lang/tools#2540) web (https://github.com/dart-lang/web/compare/e5c6c02..ec71a4c): ec71a4c Mon Sep 28 10:07:01 2026 -0700 Kevin Moore [js_interop_gen] Require `code_builder: ^4.12.0` and update golden headers (dart-lang/web#576) [email protected] Change-Id: I766bc5b2b1297e3251990821bb73387ba685e39b Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/556320 Commit-Queue: Nate Bosch <[email protected]> Reviewed-by: Brian Quinlan <[email protected]>

github-actions Bot added type-infra A repository infrastructure change or enhancement package:jnigen package:jni labels Sep 14, 2026

[jni] Add deep conversion utilities

90bb7ec

Siya-05 force-pushed the jni-deep-conversion-utils branch from cefc389 to 90bb7ec Compare September 14, 2026 07:36

github-actions Bot removed type-infra A repository infrastructure change or enhancement package:jnigen labels Sep 14, 2026

liamappelbe self-requested a review September 15, 2026 00:14

[jni] Fix converter export ordering

38c1909

[jni] Added to changelog

d4ad880

liamappelbe reviewed Sep 16, 2026

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Siya-05 added 2 commits September 16, 2026 04:36

[jni] Integrate deep conversion into collection utils

7c64843

[jni] Bump version to 1.1.0-wip

080f30e

[jnigen] Update JNI version check for 1.1

fa2d405

github-actions Bot added the package:jnigen label Sep 21, 2026

[jnigen] Relax JNI version-only binding checks

c6c08da

github-actions Bot added the type-infra A repository infrastructure change or enhancement label Sep 21, 2026

liamappelbe reviewed Sep 22, 2026

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liamappelbe approved these changes Sep 22, 2026

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liamappelbe merged commit ed7605f into dart-lang:main Sep 22, 2026
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kevmoo mentioned this pull request Sep 23, 2026

Dart Ecosystem What's New Digest (2026-09-16 to 2026-09-23) kevmoo/whats_new#4

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Hassnaa9 pushed a commit to Hassnaa9/native that referenced this pull request Sep 27, 2026

[jni] Add deep conversion utils (dart-lang#3635)

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Siya-05 commented Sep 14, 2026

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