Config backend models are not populated with fieldset data

[mam08ixo]

In config backend models, it was possible to access all configured values from the current group. This is especially important for performing sanity checks/validation of config value combinations. A recent commit (faint suspicion: 4af80a2) broke that. All config values that are processed after the current field can no longer be accessed via \Magento\Framework\App\Config\Value::getFieldsetDataValue.

Preconditions

1. Magento 2.2.6-dev

Steps to reproduce

1. Log in to admin panel
2. Navigate to Stores → Configuration → Catalog → Catalog → Search Engine Optimization (in fact, every config field with backend model is affected but this one illustrates the problem quite well).
3. Enter some values in this group's config fields
4. Save Config
5. In \Magento\Config\Model\Config::_processGroup monitor the data passed into $backendModel->addData($data)

Expected result

1. All config values of the current group are passed to the backend model:

Actual result

1. Only the config values up to the current field are passed to the backend model:

[magento-engcom-team]

Hi @mam08ixo. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

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where {$VERSION} is version tags (starting from 2.2.0+) or develop branches (2.2-develop +).
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@mam08ixo do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[engcom-backlog-nickolas]

Hello @mam08ixo, thank you for your report.
We've acknowledged the issue and added to our backlog.

[magento-engcom-team]

Hi @mam08ixo
We are closing this ticket now, as this issue is already fixed with the following commits in 2.2-develop: 86b5bc0 7415171
Fix is expected to be delivered with patch 2.2.6