25 files declare their use of DatasourceInterface in Search API 8

AddURL.php in src/Plugin/search_api/processor/AddURL.php

AddURLTest.php in tests/src/Unit/Processor/AddURLTest.php

AggregatedFields.php in src/Plugin/search_api/processor/AggregatedFields.php

AggregatedFieldsTest.php in tests/src/Unit/Processor/AggregatedFieldsTest.php

ContentAccess.php in src/Plugin/search_api/processor/ContentAccess.php

EntityDatasourceInterface.php in src/Plugin/search_api/datasource/EntityDatasourceInterface.php

EntityStatusTest.php in tests/src/Unit/Processor/EntityStatusTest.php

FieldsHelper.php in src/Utility/FieldsHelper.php

FieldsHelperInterface.php in src/Utility/FieldsHelperInterface.php

HighlightTest.php in tests/src/Unit/Processor/HighlightTest.php

Index.php in src/Entity/Index.php

IndexAddFieldsForm.php in src/Form/IndexAddFieldsForm.php

IndexInterface.php in src/IndexInterface.php

Item.php in src/Item/Item.php

LanguageWithFallback.php in src/Plugin/search_api/processor/LanguageWithFallback.php

ProcessorInterface.php in src/Processor/ProcessorInterface.php

ProcessorPluginBase.php in src/Processor/ProcessorPluginBase.php

RenderedItem.php in src/Plugin/search_api/processor/RenderedItem.php

ReverseEntityReferences.php in src/Plugin/search_api/processor/ReverseEntityReferences.php

ReverseEntityReferencesTest.php in tests/src/Kernel/Processor/ReverseEntityReferencesTest.php

RoleAccess.php in src/Plugin/search_api/processor/RoleAccess.php

RoleFilterTest.php in tests/src/Unit/Processor/RoleFilterTest.php

search_api.views.inc in ./search_api.views.inc

Views hook implementations for the Search API module.

SoulMate.php in tests/search_api_test_extraction/src/Plugin/search_api/processor/SoulMate.php

UnsavedIndexConfiguration.php in src/UnsavedIndexConfiguration.php