NSAttributedString+TraitCollection.swift

extension NSAttributedString {

    /// Iterates over all embedded `UIImage` instances within the string, updating the configuration 
    /// to include the provided `UITraitCollection`.
    ///
    func updatingImageAttachments(to traitCollection: UITraitCollection) -> NSAttributedString {
        var updatedImages = [(Int, UIImage)]()
        enumerateAttributes(in: NSRange(location: 0, length: length), options: .init(rawValue: 0)) { attributes, range, _ in
           if let attachment = attributes[.attachment] as? NSTextAttachment,
              let image = attachment.image ?? attachment.image(forBounds: .zero, textContainer: nil, characterIndex: 0),
              let configuration = image.configuration {
                 let newImage = image.withConfiguration(configuration.withTraitCollection(traitCollection))
                 updatedImages.append((range.location, newImage))
            }
        }
        guard !updatedImages.isEmpty else { return self }

        let copy = NSMutableAttributedString(attributedString: self)
        for (index, image) in updatedImages {
            var attributes = copy.attributes(at: index, effectiveRange: nil)
            attributes[.attachment] = NSTextAttachment(image: image)
            copy.setAttributes(attributes, range: NSRange(location: index, length: 1))
        }
        return NSAttributedString(attributedString: copy)
    }
}