fix(5313-dataloaders-not-found): use SimpleInventory collection to fe…

[alex-haproff]

Resolves #5313
Impact: major
Type: bugfix

Issue

DataLoaders do not exist when Reaction is running in a topic consumer mode or any other "non-web-request-serving" mode. DataLoaders are only supposed to be used in the context of a web request.

Solution

Check if context.dataLoaders is not empty, otherwise fallback to Mongo collection.

Breaking changes

None

[focusaurus]

Thanks for the quick fix!

[willopez]

@alex-haproff I see the error reported on #5313 when publishing the example product in the Operator UI.

Steps to reproduce:

1. Start app with fresh db, on this PR's branch
2. Attempt to publish example product
3. Inspect console, to find this error:

Exception while invoking method 'catalog/publish/products' TypeError: Cannot read property 'SimpleInventoryByProductVariantId' of undefined
reaction_1  |     at Promise.asyncApply (imports/plugins/included/simple-inventory/server/no-meteor/utils/inventoryForProductConfigurations.js:31:27)
.
.
.

[willopez]

See comment.

[alex-haproff]

hi @willopez thanks for reporting!
At this point I think I will just have to check if DataLoaders are registered and fall back to Mongo collection if needed. It looks like there are few places in Reaction where context is initialised in a different way to the web one.

[willopez]

LGTM