Why doesn't build_runner generate files when serializing JSON in dart/flutter

Question

I'm just trying to generate my files with the same command i stored like 3 months ago (i'm not very good with backend and devops) and now it doesn't generate the files anymore. It tells me to use the delete command which i don't remember but even using that one my files still won't be generated. This is what my log looks like, and below you can find the code for a simple class.

One of my guesses would be this has something to do with me changing my github account, since there's the permission issue mentioned.

Im using vs code in windows 10.

log file:

E:\1 Work\flutter_pilot> flutter pub run build_runner build
[INFO] Generating build script...
[INFO] Generating build script completed, took 336ms

[WARNING] Deleted previous snapshot due to missing asset graph.
[INFO] Creating build script snapshot......
[INFO] Creating build script snapshot... completed, took 12.5s

[INFO] Initializing inputs
[INFO] Building new asset graph...
[INFO] Building new asset graph completed, took 787ms

[INFO] Checking for unexpected pre-existing outputs....
[INFO] Found 13 declared outputs which already exist on disk. This is likely because the`.dart_tool/build` folder was deleted, or you are submitting generated files to your source repository.
[SEVERE] Conflicting outputs were detected and the build is unable to prompt for permission to remove them. These outputs must be removed manually or the build can be run with `--delete-conflicting-outputs`. The outputs are: lib/models/advisory-service-item.g.dart
lib/models/advisory-service.g.dart
lib/models/auth.g.dart
lib/models/contract.g.dart
lib/models/contributor.g.dart
lib/models/exact-cost-values.g.dart
lib/models/exact-cost.g.dart
lib/models/expert.g.dart
lib/models/paginator-info.g.dart
lib/models/person.g.dart
lib/models/project.g.dart
lib/models/system-country.g.dart
lib/models/user.g.dart
pub failed (78)

class file:

import 'package:json_annotation/json_annotation.dart';
part 'organisation.g.dart';

@JsonSerializable()
class Organisation {
  final String name;
  Organisation({this.name});

  factory Organisation.fromJson(Map<String, dynamic> json) => _$OrganisationFromJson(json);

  Map<String, dynamic> toJson() => _$OrganisationToJson(this);
}

Dharmesh Mansata · Answer 1 · 2021-10-26T12:22:55.837

I had a similar issue, but I am using Android Studio IDE and I have done the following step:

File => Invalidate caches / Restart

Run following command:

flutter clean

flutter pub get

flutter packages pub run build_runner build --delete-conflicting-outputs

About --delete-conflicting-outputs

Assume conflicting outputs in the users package are from previous builds, and skip the user prompt that would usually be provided.

Reference

score 19 · Answer 2 · answered Jan 09 '20 at 17:52

19

If you read the error message carefully, you'll see that it's asking you to try adding --delete-conflicting-outputs at the end of your command. So you should try flutter packages pub run build_runner build --delete-conflicting-outputs.

answered Jan 09 '20 at 17:52

Rick

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As i already stated (mayhaps in a more broken english, since it's not my native language) i already tried that, but the files just get deleted and nothing is generated. – morgred Jan 09 '20 at 18:45
I see. Tho it seems the command stopped at user.g.dart? Have you checked on that file? I actually experience this error sometimes, and realize I just have a typo somewhere or a missing part 'something.g.dart' code – Rick Jan 09 '20 at 18:49
User is the last file in the list. Checked it it's just a name and an id get and set nothing wrong there. – morgred Jan 09 '20 at 19:15
I'm sorry for not being able to help you identify the problem. But based on my past experiences having that same error, it's usually a typo, some wrong code, or missing part 'file.g.dart' code. However, if you're willing to share your code with me, I can spend a bit of time to help you find where the problem is. – Rick Jan 09 '20 at 19:17
I Think this is a bug of build_runner delete all files related build_runner and restart the code editor , it will work – Bawantha Jan 09 '20 at 20:53
@Bawantha you mean remove the package and its generated files and have flutter update the packages again? – morgred Jan 10 '20 at 08:45
@morgred no need to remove package just delete files generated from build_runner ans start the process again – Bawantha Jan 10 '20 at 18:03

score 15 · Answer 3 · answered Apr 14 '21 at 15:19

15

You just run bellow code..

flutter pub run build_runner build --delete-conflicting-outputs

answered Apr 14 '21 at 15:19

Enamul Haque

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This should be the accepted answer. Simple – Alimov Shohrukh Jun 03 '21 at 07:18
Yes @AlimovShohrukh – Shashank Daima Dec 18 '22 at 19:01

score 9 · Answer 4 · answered Nov 04 '20 at 10:11

9

In my case adding part 'file_name.g.dart'; to the top of the file helped.

file_name.dart:

import 'package:json_annotation/json_annotation.dart';

part 'file_name.g.dart';

@JsonSerializable()
class YourClass {

    factory YourClass.fromJson(Map<String, dynamic> json) => _$YourClassFromJson(json);

    Map<String, dynamic> toJson() => _$YourClassToJson(this);

    // ... your class code
}

answered Nov 04 '20 at 10:11

Sergio

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I needed this for the `flutter pub run build_runner build --delete-conflicting-outputs` to pick up the file and great the `.g.dart` file. – jaredbaszler Nov 13 '20 at 22:14
Wow, I had a typo in file_name, thanks for this answer – David Holkup Mar 17 '21 at 11:04
Adding the `part` line (even though VSCode will throw error just because it isn't generated yet) works for me... – Aldy J Jun 28 '21 at 04:15

score 8 · Answer 5 · edited Oct 20 '21 at 10:35

8

I had the same issue. Solved by using the below command

flutter packages pub run build_runner build --delete-conflicting-outputs

edited Oct 20 '21 at 10:35

sourav pandit

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answered Aug 14 '21 at 16:12

Navas Koya

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works like a charm. – Shoaib Kakal Aug 07 '23 at 07:13

Ahmed Almahdie · Answer 6 · 2021-07-13T12:48:11.070

I think the main reason this happens to most of us, is the possibility that when you ran this command before, you added the generated g.dart file into your source control. this in turn prevents the build_runner from regenerating the previously generated g.dart files, which it does, even if you only need the new g.dart file. now, I understand that this might be hard to follow, but consider this:

Let's say you have a search_entry.dart file.
You ran the command, and generated the search_entry.g.dart file successfully.
You then proceed to add the generated search_entry.g.dart file to your source control repository.
You make another file, let's say maybe cached_data_entry.dart.
When you run the command a second time to generate the cached_data_entry.dart, it will try and delete the search_entry.g.dart file to regenerate it along with the cached_data_entry.dart file.
Since the search_entry.g.dart is protected under the source control, the build runner won't be able to delete it, so, it throws this error.
Now, what you need to do to fix the current situation, is delete the previously all the previously generated g.dart files, (search_entry.g.dart in our example), then add it to the ignored files in .gitignore file in your source control. then run the command again, and hopefully, you it will succeed this time.
What you should do in the future, is ignore these files from your source control right after you generated them.

Now, finally, I hope I've made it as clear as it should be.

Since when does source control not allow editing or deleting files? — vrnvorona, Nov 30 '21 at 12:46
@vrnvorona I think the wording was not precise. In OP's example, since *search_entry.g.dart* is tracked into source control, a branch change or a merge will modify it, making build_runner detect an external change and consider the file as a conflicting output. This is described in the [documentation](https://pub.dev/packages/build_runner#source-control). — enzo, Apr 19 '22 at 16:11
Anyway, this answer does a good job explaining what a conflicting output is and why does it happen. — enzo, Apr 19 '22 at 16:14

score 5 · Accepted Answer · answered Aug 25 '22 at 13:46

5

changing the part and class to the same name of the file fixed the issue with me

answered Aug 25 '22 at 13:46

7eg

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score 3 · Answer 8 · answered Jun 21 '20 at 10:08

I had the same issue. At first I generated a myFirstGeneratedFile.g.dart file then I needed another object type to store then when I tried to generate the file using this command =>

flutter packages pub run build_runner clean

I got the error message.

I fixed it by deleting the file that i created before => myFirstGeneratedFile.g.dart then run the command again.

Cheers!

score 2 · Answer 9 · answered Jan 10 '20 at 09:31

2

Running "flutter pub upgrade" solved the problem for me.

answered Jan 10 '20 at 09:31

morgred

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score 2 · Answer 10 · answered May 17 '22 at 10:58

2

try something like this via terminal:

Delete previous generated files via command: find ./ -name '*.g.dart' -delete
then: flutter packages pub run build_runner watch —delete-conflicting-outputs

answered May 17 '22 at 10:58

dipnv

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score 2 · Answer 11 · answered Aug 19 '22 at 21:15

2

The issue is with package dependency, executing this flutter pub upgrade --major-versions will do the thing.

answered Aug 19 '22 at 21:15

Jashan PJ

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Fixed the issue for me, thanks – Nazarii Kahaniak Oct 31 '22 at 18:19

score 1 · Answer 12 · answered Feb 20 '20 at 04:08

1

Delete .dart_tool folder and run flutter pub get. After this, run the build runner command

answered Feb 20 '20 at 04:08

Iredia Ebikade

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score 1 · Answer 13 · answered Apr 21 '20 at 07:04

1

In my case , I have declared a dart file named Organisation.dart instead of small letter organisation.dart , refracting this and running the build runner again worked for me.

answered Apr 21 '20 at 07:04

B.shruti

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score 1 · Answer 14 · answered Jul 11 '21 at 03:59

1

in my case, I had forgotten to import the mobx_codegen package

answered Jul 11 '21 at 03:59

Felipe Sales

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score 1 · Answer 15 · answered Feb 07 '22 at 04:27

1

In my case the build_runner process was successful but the .g files weren't produced. I had to restart the IDE (vscode) before I start seeing the .g files.

answered Feb 07 '22 at 04:27

cksrc

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IvanPavliuk · Answer 16 · 2022-02-04T12:46:33.753

0

Add built_value_generator to the pubspec.yaml to dev_dependencies section https://pub.dev/packages/built_value_generator

You can read the official documentation - https://dart.dev/tools/build_runner

edited Feb 04 '22 at 12:46

answered Feb 04 '22 at 11:59

IvanPavliuk

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score 0 · Answer 17 · answered May 02 '23 at 12:57

Add this file in the root directory with pubspec.yaml

build.yaml file

Add the following lines

targets:
  $default:
    builders:
      freezed:
        options:
          any_map: true
          explicit_to_json: true

Then run

flutter clean
flutter pub get
flutter packages pub run build_runner build --delete-conflicting-outputs

score 0 · Answer 18 · edited Aug 09 '23 at 17:41

../../../.pub-cache/hosted/pub.dev/build_runner-2.2.0/lib/src/build_script_generate/bootstrap.dart:76:40: Error: Method not found: 'NullThrownError'.
      final error = e[0] as Object? ?? NullThrownError();

In my case, just updating all packages to the latest version solved the problem for me.

dependencies:
  freezed: ^2.4.2
  freezed_annotation: ^2.4.1
  json_serializable: ^6.7.1

dev_dependencies:
  flutter_test:
    sdk: flutter
  build_runner: ^2.4.6

score -1 · Answer 19 · answered Nov 27 '22 at 01:36

-1

Make sure this targets bit goes into build.yaml and NOT pubspec.yaml.

answered Nov 27 '22 at 01:36

Nestor Ledon

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Why doesn't build_runner generate files when serializing JSON in dart/flutter

19 Answers19

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