Add supportedFields property

[MaryanneNjeri]

This PR

App Configuration recently added support for description field. Importer library also needs an update to support importing description field. Not all configuration sources support importing description field (eg: Importing from a file with content profile as default).

Proposed solution

Adds the supportedFields property to ConfigurationSettingsSource. We support a couple of configuration settings source including:
- StringConfigurationSettingsSource
- IterableConfigurationSettingsSource
- ReadableConfigurationSettingsSource
- ConfigurationChangeSource

With the addition of the supportedFields property we are able to distinguish which configuration setting source support which fields

Usage example

let importer = new AppConfigImporter(client: AppconfigClient);

importer.import(
new StringConfigurationSource({data: "app:foo", sourceOptions: {profile: ConfigurationProfile.default}}))

[Copilot]

Pull request overview

Adds an explicit capability flag (supportsDescriptionField) to ConfigurationSettingsSource so the importer can conditionally include the App Configuration description field when computing updates.

Changes:

• Introduces supportsDescriptionField on ConfigurationSettingsSource and sets it across all built-in sources (String/ReadableStream/Iterable/Changes).
• Extends isConfigSettingEqual and change detection to optionally compare description based on the source capability.
• Updates unit tests to include description in test data and pass the new equality parameter.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
libraries/azure-app-configuration-importer/tests/util.spec.ts	Updates equality tests to include description and pass the new “description supported” flag.
libraries/azure-app-configuration-importer/tests/appConfigurationImporter.spec.ts	Updates ConfigurationChangesSource construction to pass the new description-support flag.
libraries/azure-app-configuration-importer/src/settingsImport/stringConfigurationSettingsSource.ts	Adds and initializes supportsDescriptionField based on profile (Default vs KvSet).
libraries/azure-app-configuration-importer/src/settingsImport/readableStreamConfigurationSettingsSource.ts	Adds and initializes supportsDescriptionField based on profile (Default vs KvSet).
libraries/azure-app-configuration-importer/src/settingsImport/iterableConfigurationSettingsSource.ts	Adds supportsDescriptionField (currently always true) for iterable sources.
libraries/azure-app-configuration-importer/src/settingsImport/configurationSettingsSource.ts	Extends the public ConfigurationSettingsSource interface with supportsDescriptionField.
libraries/azure-app-configuration-importer/src/settingsImport/configurationChangesSource.ts	Adds supportsDescriptionField to the changes source and updates constructor signature.
libraries/azure-app-configuration-importer/src/internal/utils.ts	Extends isConfigSettingEqual to optionally compare description.
libraries/azure-app-configuration-importer/src/appConfigurationImporter.ts	Passes source capability into equality checks when determining updates.

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