Inject custom data on old helper

Hello everyone,

I am using Dropzone.js to upload files in my Laravel application and everything is working just fine, However, I have this little issue which is handling the validations exception response. what I want to do when I get this kind of response is to inject the old() helper with some custom variable I need to use in my JavaScript code to show thumbnails of previously uploaded files with Dropzone.

What I am currently doing now is whenever I select files I upload them temporarily in the 'storage/tmp/uploads' directory. and append hidden documents[] input contains uploaded file names coming from the server on each upload. so when I submit the form I move them to the desired directory.

However when I submit the form and get 422 response. I get the file names in old('documents'), I dont just want the file names. I want then name, size, type, and full storage path and I think I can do that inside my form request failedValidation function. but I don't know how!!

<script>
            const uploadedDocumentMap = {};
         
            Dropzone.options.myTargetInput = {
                url: '{{ route('data.storeMedia') }}',
                maxFilesize: 2,
                addRemoveLinks: true,

                headers: {
                    'X-CSRF-TOKEN': "{{ csrf_token() }}"
                },

                uploadMultiple: false,

                init: function() {
                    const self = this;

                    @if (old('documents'))
                    
                        const mockFile = {
                           name: "C838MtoXoAEbnXh.jpg",
                           size: 90000,
                           type: 'image/jpeg'
                        };
                    
                        self.emit('addedfile', mockFile);
                        self.emit('thumbnail', mockFile, "http://127.0.0.1:8000/C838MtoXoAEbnXh.jpg");
                        self.emit('complete', mockFile);
                    
                        mockFile.previewElement.classList.add('dz-success');
                        mockFile.previewElement.classList.add('dz-complete');
                    @endif
                }
            };
        </script>

what I need is to get the variable mockFile which I currently hardcoded in the init function to get it from the server when I get a validation error response.