Invalidate family providers on cascade

[busslina]

Scenario: I have three providers: masterProvider, slaveOneProvider and slaveTwoProvider.

masterProvider has no state (null state). Its only purpose is to invalidate slave providers.
Both slave providers execute ref.watch(master) on build().

Before going to my main goal I encountered other problems that I must resolve first.
This are my testing files:

1. providers.dart

import 'package:riverpod_annotation/riverpod_annotation.dart';

part 'providers.g.dart';

enum Country {
  france,
  uk,
}

enum President {
  chirac,
  churchill,
}

enum Region {
  picardie,
  merseyside,
}

int _slaveOneIndex = 0;

/// 01 - Master.
@Riverpod(keepAlive: true)
class Master extends _$Master {
  int _buildCount = 0;

  @override
  Object build(Country country) {
    print('Master.build() -- $country -- Count: ${_buildCount++}');

    ref.onDispose(() {
      print('Master -- ON DISPOSE -- $country');
    });

    return Object();
  }
}

/// 02 - Slave one.
@Riverpod(keepAlive: true)
class SlaveOne extends _$SlaveOne {
  int _buildCount = 0;

  @override
  int build(Country country, President president) {
    print(
        'SlaveOne.build() -- $country, $president -- Count: ${_buildCount++}');

    ref.onDispose(() {
      print('SlaveOne -- ON DISPOSE -- $country, $president');
    });

    ref.watch(masterProvider(country));

    return _slaveOneIndex++;
  }
}

/// 03 - Slave two.
@Riverpod(keepAlive: true)
class SlaveTwo extends _$SlaveTwo {
  int _buildCount = 0;

  @override
  DateTime build(Country country, Region region) {
    print('SlaveTwo.build() -- $country, $region -- Count: ${_buildCount++}');

    ref.onDispose(() {
      print('SlaveTwo -- ON DISPOSE -- $country, $region');
    });

    ref.watch(masterProvider(country));

    return DateTime.now();
  }
}

2. riverpod_test.dart

import 'package:riverpod/riverpod.dart';
import 'package:riverpod_test/riverpod_test.dart';

final cRef = ProviderContainer();

void main(List<String> arguments) async {
  await test();
}

Future<void> test() async {
  // (01) Printing slave values I
  {
    _printTest(1, 'Printing state values I');

    _printSlaveOne();
    _printSlaveTwo();

    await _awaitSec(5);
  }

  // (02) Invalidating Master (FRANCE)
  {
    _printTest(2, 'Invalidating Master(France)');

    _invalidateMaster(Country.france);

    await _awaitSec(5);
  }

  // (03) Invalidating Master (UK)
  {
    _printTest(3, 'Invalidating Master(UK)');

    _invalidateMaster(Country.uk);

    await _awaitSec(5);
  }

  // (04) Printing slave values II
  {
    _printTest(4, 'Printing state values II');
    _printSlaveOne();
    _printSlaveTwo();
  }
}

Future<void> _awaitSec(int seconds) =>
    Future.delayed(Duration(seconds: seconds));

void _printSlaveOne() => print(
    'SlaveOne value: ${cRef.read(slaveOneProvider(Country.france, President.chirac))}');

void _printSlaveTwo() => print(
    'SlaveTwo value: ${cRef.read(slaveTwoProvider(Country.uk, Region.merseyside))}');

void _invalidateMaster(Country country) =>
    cRef.invalidate(masterProvider(country));

void _printTest(int number, [String? txt]) {
  print('\nTEST -- $number${txt == null ? '' : ' -- $txt'}\n');
}

This is the execution output:

TEST -- 1 -- Printing state values I

SlaveOne.build() -- Country.france, President.chirac -- Count: 0
Master.build() -- Country.france -- Count: 0
SlaveOne value: 0
SlaveTwo.build() -- Country.uk, Region.merseyside -- Count: 0
Master.build() -- Country.uk -- Count: 0
SlaveTwo value: 2023-10-26 12:03:39.593862

TEST -- 2 -- Invalidating Master(France)

Master -- ON DISPOSE -- Country.france
Master.build() -- Country.france -- Count: 1

TEST -- 3 -- Invalidating Master(UK)

Master -- ON DISPOSE -- Country.uk
Master.build() -- Country.uk -- Count: 1

TEST -- 4 -- Printing state values II

SlaveOne value: 0
SlaveTwo value: 2023-10-26 12:03:39.593862

Problems:

1. On test 2 and test 3, invalidating masterProvider is not followed by both slaveProviders invalidation/re-evaluation
2. Due to 1), in test 4 we get the old slaveProviders values

Thank you in advance

[rrousselGit]

1. Retuning null won't do. null == null, so no update will be done.
   Use Object()

2. Do not share ProviderContainers between tests.
   That will cause tests to share state, which is anti-pattern

[busslina]

1. Retuning null won't do. null == null, so no update will be done.
   Use Object()

Updated

[busslina]

2. Do not share ProviderContainers between tests.
   That will cause tests to share state, which is anti-pattern

I'm only have one container used in one test. I don't see the problem. Maybe you mean to create inside the main. Updating it

[rrousselGit]

You said you have 4 tests

[busslina]

You said you have 4 tests

I must call it test step. Just only one test.

I'm only have one container used in one test. I don't see the problem. Maybe you mean to create inside the main. Updating it

This resolved this problem, don't know why because I have still only one ProviderContainer, but seems that having it as top level variable was messing it:

void main(List<String> arguments) async {
  final cRef = ProviderContainer();
  await test(cRef);
}

Output:

TEST -- 1 -- Printing state values I

SlaveOne.build() -- Country.france, President.chirac -- Count: 0
Master.build() -- Country.france -- Count: 0
SlaveOne value: 0
SlaveTwo.build() -- Country.uk, Region.merseyside -- Count: 0
Master.build() -- Country.uk -- Count: 0
SlaveTwo value: 2023-10-26 12:17:22.774286

TEST -- 2 -- Invalidating Master(France)

Master -- ON DISPOSE -- Country.france
Master.build() -- Country.france -- Count: 1
SlaveOne -- ON DISPOSE -- Country.france, President.chirac

TEST -- 3 -- Invalidating Master(UK)

Master -- ON DISPOSE -- Country.uk
Master.build() -- Country.uk -- Count: 1
SlaveTwo -- ON DISPOSE -- Country.uk, Region.merseyside

TEST -- 4 -- Printing state values II

SlaveOne.build() -- Country.france, President.chirac -- Count: 1
SlaveOne value: 1
SlaveTwo.build() -- Country.uk, Region.merseyside -- Count: 1
SlaveTwo value: 2023-10-26 12:17:37.824858

[busslina]

Thank you @rrousselGit. Testing in Dart (no Flutter) make me realise that your proposed design on Discord works okay. I must missing some active listeners on my Flutter code.

Anyways it would be a help for me any mechanism to debug a provider active listeners (not just the number). Maybe a debugTag or similar. Does it exists a way for this?

[rrousselGit]

There is a devtool in progress which would list all listeners