38 files declare their use of ContextDefinition

ConditionTestNoExistingType.php in core/modules/system/tests/modules/condition_test/src/Plugin/Condition/ConditionTestNoExistingType.php
ContextAwarePluginTraitTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Context/ContextAwarePluginTraitTest.php
ContextDefinitionIsSatisfiedTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/ContextDefinitionIsSatisfiedTest.php
ContextDefinitionTest.php in core/tests/Drupal/KernelTests/Core/Plugin/ContextDefinitionTest.php
ContextDefinitionTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/ContextDefinitionTest.php
ContextDefinitionTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Annotation/ContextDefinitionTest.php
ContextHandlerTest.php in core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
ContextTypedDataTest.php in core/tests/Drupal/KernelTests/Core/Plugin/ContextTypedDataTest.php
CurrentLanguageContext.php in core/lib/Drupal/Core/Language/ContextProvider/CurrentLanguageContext.php
DefaultsSectionStorage.php in core/modules/layout_builder/src/Plugin/SectionStorage/DefaultsSectionStorage.php
DefaultsSectionStorageTest.php in core/modules/layout_builder/tests/src/Unit/DefaultsSectionStorageTest.php
DefaultsSectionStorageTest.php in core/modules/layout_builder/tests/src/Kernel/DefaultsSectionStorageTest.php
EntityContextDefinitionIsSatisfiedTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/EntityContextDefinitionIsSatisfiedTest.php
FakeViewModeContext.php in core/modules/layout_builder/tests/modules/layout_builder_fieldblock_test/src/ContextProvider/FakeViewModeContext.php
FieldBlockDeriver.php in core/modules/layout_builder/src/Plugin/Derivative/FieldBlockDeriver.php
FieldBlockTest.php in core/modules/layout_builder/tests/src/Kernel/FieldBlockTest.php
IHaveRuntimeContexts.php in core/modules/layout_builder/tests/modules/layout_builder_test/src/Plugin/Block/IHaveRuntimeContexts.php
IHaveRuntimeContexts.php in core/modules/layout_builder/tests/modules/layout_builder_test/src/ContextProvider/IHaveRuntimeContexts.php
InheritedContextDefinition.php in core/tests/Drupal/Tests/Core/Plugin/Fixtures/InheritedContextDefinition.php
Language.php in core/modules/language/src/Plugin/Condition/Language.php
LayoutBuilderEntityViewDisplay.php in core/modules/layout_builder/src/Entity/LayoutBuilderEntityViewDisplay.php
LayoutEntityHelperTrait.php in core/modules/layout_builder/src/LayoutEntityHelperTrait.php
LazyContextRepositoryTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/LazyContextRepositoryTest.php
MockBlockManager.php in core/modules/system/tests/modules/plugin_test/src/Plugin/MockBlockManager.php
NavigationLinkBlockTest.php in core/modules/navigation/tests/src/Functional/NavigationLinkBlockTest.php
NavigationRenderer.php in core/modules/navigation/src/NavigationRenderer.php
NavigationSectionStorage.php in core/modules/navigation/src/Plugin/SectionStorage/NavigationSectionStorage.php
NumericArgument.php in core/modules/views/src/Plugin/views/argument/NumericArgument.php
NumericArgumentValidator.php in core/modules/views/src/Plugin/views/argument_validator/NumericArgumentValidator.php
OverridesSectionStorage.php in core/modules/layout_builder/src/Plugin/SectionStorage/OverridesSectionStorage.php
OverridesSectionStorageTest.php in core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php
SectionStorageBase.php in core/modules/layout_builder/src/Plugin/SectionStorage/SectionStorageBase.php
SectionStorageManagerTest.php in core/modules/layout_builder/tests/src/Unit/SectionStorageManagerTest.php
SimpleConfigSectionListTest.php in core/modules/layout_builder/tests/src/Kernel/SimpleConfigSectionListTest.php
SimpleConfigSectionStorage.php in core/modules/layout_builder/tests/modules/layout_builder_test/src/Plugin/SectionStorage/SimpleConfigSectionStorage.php
StringArgument.php in core/modules/views/src/Plugin/views/argument/StringArgument.php
TestContextAwareNoValidContextOptionsBlock.php in core/modules/block/tests/modules/block_test/src/Plugin/Block/TestContextAwareNoValidContextOptionsBlock.php
TestPageDisplayVariantSubscriber.php in core/modules/system/tests/modules/display_variant_test/src/EventSubscriber/TestPageDisplayVariantSubscriber.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.