Effect CommunityEC
Effect Community•12mo ago•
24 replies
Dave Meehan

Help with understanding Effect.Service dependencies

I'm struggling to understand dependencies in 
Effect.Service
, which seem to require a different shape than when specified in a test. The test setup seems more logical, but in the Service dependencies I can't just list them as an array, but find in order for the DefaultPowerToolsLogger to apply to all of the other dependencies, I have to merge them all into a single layer.

export class DecoderService extends Effect.Service<DecoderService>()('DecoderService', {
  effect: Effect.gen(function* () {
    const config = yield* DecoderConfig
    const devices = yield* DeviceRepository
    const events = yield* PayloadPublishingService

    return {
      handler: Effect.succeed((unknown: unknown, _context: Context) => Effect.gen(function* () {
        // ...
      })),
    }
  }),
  dependencies: [
    DecoderConfig.Default.pipe(
      Layer.provideMerge(DeviceRepository.Default),
      Layer.provideMerge(PayloadPublishingService.Default),
      Layer.provideMerge(DefaultPowerToolsLoggerLayer),
    ),
  ],
  accessors: true,
}) {}


Test setup:

    const layer = DecoderService.DefaultWithoutDependencies.pipe(
      Layer.provide(DecoderConfig.Default),
      Layer.provide(DeviceRepository.Default),
      Layer.provide(PayloadPublishingService.Default),
      Layer.provide(Layer.setConfigProvider(configProvider)),
      Layer.provide(DefaultPowerToolsLoggerLayer),
    )


NB: I appreciate in the test I could use the Default 'with dependencies' layer as the only difference is the injection of the ConfigProvider but what I'm struggling with is why the Layer.provide's produce a different result to the list of dependencies. How does 
Effect.Service
 under the hood treat the dependencies? (I tried searching the code base but couldn't find the relevant module).
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