src/vs/platform/userDataSync/common/extensionsSync.ts/ExtensionsSynchroniser/resolveContent
class ExtensionsSynchroniser:	override async resolveContent(uri: URI): Promise<string | null> {
		if (this.extUri.isEqual(uri, ExtensionsSynchroniser.EXTENSIONS_DATA_URI)) {
			const installedExtensions = await this.extensionManagementService.getInstalled();
			const ignoredExtensions = this.ignoredExtensionsManagementService.getIgnoredExtensions(installedExtensions);
			const localExtensions = this.getLocalExtensions(installedExtensions).filter(e => !ignoredExtensions.some(id => areSameExtensions({ id }, e.identifier)));
			return this.stringify(localExtensions, true);
		}

		if (this.extUri.isEqual(this.remoteResource, uri)
			|| this.extUri.isEqual(this.baseResource, uri)
			|| this.extUri.isEqual(this.localResource, uri)
			|| this.extUri.isEqual(this.acceptedResource, uri)
		) {
			const content = await this.resolvePreviewContent(uri);
			return content ? this.stringify(JSON.parse(content), true) : content;
		}

		let content = await super.resolveContent(uri);
		if (content) {
			return content;
		}

		content = await super.resolveContent(this.extUri.dirname(uri));
		if (content) {
			const syncData = this.parseSyncData(content);
			if (syncData) {
				switch (this.extUri.basename(uri)) {
					case 'extensions.json':
						return this.stringify(this.parseExtensions(syncData), true);
				}
			}
		}

		return null;
	}