Bad state: Unexpected diagnostics: sky_engine\lib\ui\channel_buffers.dart - This requires the 'non-nullable' language feature to be enabled

[SandroMaglione]

Steps to Reproduce

1. I created a new code generation project, following different resources
   • https://www.youtube.com/watch?v=mYDFOdl-aWM&list=WL&index=17&t=2149s
   • https://www.youtube.com/watch?v=H4HWB2Pmgcw
   • https://medium.com/flutter-community/part-1-code-generation-in-dart-the-basics-3127f4c842cc
2. Create a flutter app to test code generation
3. Run flutter pub run build_runner build

Expected results:
Since no annotation is present inside the flutter app (only original main.dart), the generation process should complete without any code generated and without any failure.

Actual results:
The build process is unsuccessful and fails with the following result (from flutter pub run build_runner build --verbose):

[INFO] Generating build script...
[INFO] Generating build script completed, took 466ms

[INFO] Initializing inputs
[INFO] Reading cached asset graph...
[INFO] Reading cached asset graph completed, took 71ms

[INFO] Checking for updates since last build...
[INFO] Checking for updates since last build completed, took 697ms

[WARNING] Invalidating asset graph due to build script update!
[INFO] Cleaning up outputs from previous builds....
[INFO] Cleaning up outputs from previous builds. completed, took 3ms

[INFO] Generating build script...
[INFO] Generating build script completed, took 99ms

[INFO] Creating build script snapshot......
[INFO] Creating build script snapshot... completed, took 12.9s

[INFO] Initializing inputs
[INFO] Building new asset graph...
[INFO] Building new asset graph completed, took 1.3s

[INFO] Checking for unexpected pre-existing outputs....
[INFO] Checking for unexpected pre-existing outputs. completed, took 1ms

[INFO] Running build...
[INFO] Generating SDK summary...
[SEVERE] repo_case_generator:repo_case on lib/main.dart:

Bad state: Unexpected diagnostics:
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:119:41 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:152:17 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:88:62 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:153:38 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:186:51 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:133:32 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:154:25 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:18:17 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:64:4 - This requires the 'non-nullable' 
language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:168:32 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:47:14 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:159:38 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:132:37 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:118:48 - This requires the 'non-nullable' language feature to be enabled.
C:\Users\Sandro Maglione\flutter\flutter\bin\cache\pkg\sky_engine\lib\ui\channel_buffers.dart:19:11 - This requires the 'non-nullable' language feature to be enabled.
[INFO] Running build completed, took 1.4s

[INFO] Caching finalized dependency graph...
[INFO] Caching finalized dependency graph completed, took 48ms

[SEVERE] Failed after 1.5s
pub finished with exit code 1

The flutter app contains only the default main.dart created after running flutter create.

• build_runner: ^1.10.0
• analyzer: ^0.39.16
• build: ">=0.12.6 <2.0.0"
• sdk: ">=2.6.0 <3.0.0"

[√] Flutter (Channel stable, 1.20.0, on Microsoft Windows [Version 10.0.18362.959], locale en-US)
    • Flutter version 1.20.0 at C:\Users\Sandro Maglione\flutter\flutter   
    • Framework revision 840c9205b3 (2 days ago), 2020-08-04 20:55:12 -0700
    • Engine revision c8e3b94853
    • Dart version 2.9.0

 
[√] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at C:\Users\Sandro Maglione\AppData\Local\Android\sdk
    • Platform android-29, build-tools 29.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)
    • All Android licenses accepted.

[!] Android Studio (version 3.5)
    • Android Studio at C:\Program Files\Android\Android Studio
    X Flutter plugin not installed; this adds Flutter specific functionality.
    X Dart plugin not installed; this adds Dart specific functionality.
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)

[√] VS Code (version 1.47.3) 
    • VS Code at C:\Users\Sandro Maglione\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.13.2

[!] Connected device
    ! No devices available

! Doctor found issues in 2 categories.

May be related to #56779, #41820

[CaLouro]

I'm having the same issue. It is due to the inclusion of the non-nullable Dart 2.9 feature in Flutter 1.20 stable channel.

I tried updating my pubspec.yaml with the lines

environment:
  sdk: ">=2.9.0 <3.0.0"
  flutter: ^1.20.0

to try to force Flutter to use the most recent versions of both tools, but it doesn't seem to be working even if my flutter doctor shows as having the newest versions, as shown bellow.

[√] Flutter (Channel stable, 1.20.0, on Microsoft Windows [versão 10.0.19041.388], locale pt-BR)
    • Flutter version 1.20.0 at V:\flutter
    • Framework revision 840c9205b3 (2 days ago), 2020-08-04 20:55:12 -0700
    • Engine revision c8e3b94853
    • Dart version 2.9.0


[√] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at C:\Users\caios\AppData\Local\Android\sdk
    • Platform android-29, build-tools 29.0.3
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
    • All Android licenses accepted.

[√] Android Studio (version 4.0)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 48.0.2
    • Dart plugin version 193.7361
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)

[√] VS Code (version 1.47.3)
    • VS Code at C:\Users\caios\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.13.0

[!] Connected device
    ! No devices available

! Doctor found issues in 1 category.

If there is no guide as to migrate the code or how to activate non-nullable support, I think the way is to downgrade Flutter as of now.

[CaLouro]

Hey, I'm back with a better answer. After the last comment I kept searching.

According to issues #62996 and #62240 the problem lies in the 'analyzer' package version '0.39.15' and '0.39.16'. Adding the override bellow to pubspec seems to solve the issue.

dependency_overrides:
  analyzer: '0.39.14'

[SandroMaglione]

I tried your solution.

It worked on one of my project, in which I am using code generation for third party packages.

However, the solution does not work on my own code generator project. The same error occurs.

I tried to upgrade build_runner to 1.10.1, but this version requires sdk >=2.10.0-0.0. In fact, in the pubspec.yaml of build runner is stated:

environment:
  # The min sdk can be reduced once analyzer releases a fix for
  # https://github.com/dart-lang/build/issues/2763
  sdk: ">=2.10.0-0.0 <3.0.0"

#2763 from dart-lang.

[CaLouro]

I see. Maybe downgrading Flutter, Dart and packages versions of your generator project is your best option now until they fix the analyzer.

[TahaTesser]

Hi @SandroMaglione
I see there's an open issue addressing the case you described. #62240
Please follow up on that issue, I'm closing the current one as a duplicate.
If you disagree, please write in the comments and I will reopen it.
Thank you

[frr149]

Upgrading the sdk version to a min of 2.9 also solved the issue for me.

environment:
  sdk: ">=2.9.0 <3.0.0"

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.