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Flutter 3.47: what actually breaks, and what to do before November

· 3 min read
Evgenii Novikov
Founder, DartWay

Summer produced exactly one stable Flutter release. 3.45 and 3.46 never reached stable at all, and 3.47 arrived on 12 August carrying 1358 commits on top of 3.44. The headline is not a feature. It is a repackaging: material and cupertino moved out of the SDK into separate packages.

That sounds alarming and mostly is not — today. Here is what we found migrating a real project from 3.44.0 to 3.47.2, and the one widely repeated claim about this release that does not survive contact with the code.

Nothing is on fire today​

We took a live project from 3.44.0 to 3.47.2 and ran it: flutter analyze clean, tests green, the libraries still inside the SDK and not marked deprecated. The deprecation is scheduled for the November release. That is when the clock starts.

So this is a good month to migrate and a bad month to panic. The window exists precisely so the migration is boring.

The migration is one command, with two traps​

dart fix --apply --code=migrate_design_widgets

Trap one: plain dart fix --apply will not do it. The fix is not in the default set; without --code=migrate_design_widgets the command runs, reports success, and changes nothing relevant. It is the kind of failure that reads as "already migrated".

Trap two: it writes material_ui: any into your pubspec. any means the next breaking release of that package lands in your build without a word. Replace it with a caret and a version the moment the fix finishes.

The claim that is not true: ChangeNotifier did not move​

The most repeated line about this release is that ChangeNotifier and friends were pulled out of the SDK into package:listen. In 3.47.2 that is not what happened.

The classes are still in the SDK, and they are not marked deprecated. listen is a second, independent implementation of the same names — not a new home for the old ones. The two are separate types, and the compiler treats them that way:

  • hand a listen ValueNotifier to a Flutter ValueListenableBuilder and you get a compile error, not a subtle runtime bug;
  • the same applies in reverse, and to every other pair with a shared name.

Where listen earns its place is code that has no Flutter in it: a server, a CLI, logic shared between the two. There the SDK types were never available and now there is an equivalent. Inside a Flutter app, switching to it today buys nothing and costs you type compatibility with every widget that expects the SDK version.

Primary constructors will not turn themselves on​

Dart 3.13 ships primary constructors, and they are behind a language version gate. Without sdk: ^3.13.0 in pubspec.yaml you get experiment_not_enabled even on the right SDK — the toolchain is correct and the project is not asking.

Worth saying plainly, though: the value of saving constructor boilerplate drops a long way once the boilerplate is not written by a human. If your constructors are generated, this is a readability change, not a productivity one.

The rest​

Impeller by default on desktop, iOS 15 and macOS 12 as the new floors, and the Wasm work — all real, none of it urgent, and none of it changes what you do this month.

What to actually do before November: run the migration on a branch, pin material_ui properly, and leave ChangeNotifier alone.

Checked by migrating a live project from 3.44.0 to 3.47.2 — before/ and after/ each build and pass their tests on their own SDK. The video walkthrough is on YouTube.