Handling Multiple File Uploads in Django Formsets

Based on the Django documentation, simply setting the multiple attribute to True in the widget isn't sufficient for properly handling multiple file uploads. You need to create a custom field that can properly validate and process multiple files.

Creating a Custom MultipleFileField

First, you need to create a custom MultipleFileField and MultipleFileInput as shown in the Django documentation:

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from django import forms

class MultipleFileInput(forms.ClearableFileInput):
    allow_multiple_selected = True

class MultipleFileField(forms.FileField):
    def __init__(self, *args, **kwargs):
        kwargs.setdefault("widget", MultipleFileInput())
        super().__init__(*args, **kwargs)

    def clean(self, data, initial=None):
        single_file_clean = super().clean
        if isinstance(data, (list, tuple)):
            result = [single_file_clean(d, initial) for d in data]
        else:
            result = [single_file_clean(data, initial)]
        return result

Update Your Form

Then update your form to use this custom field:

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class BuildSubmissionForm(forms.Form):
    peak_annotation_file = MultipleFileField(
        required=False,
    )

Processing Files in the Formset

When processing the formset, you'll now receive a list of files for each form:

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for index, rowform in enumerate(formset.cleaned_data):
    peak_annotation_files = rowform.get("peak_annotation_file")
    if peak_annotation_files:
        for file in peak_annotation_files:
            # Process each file
            # file is a UploadedFile object
            pass

Important Notes

1. Make sure your HTML form has the correct enctype attribute:

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   <form method="post" enctype="multipart/form-data">

2. When instantiating your formset, be sure to include the request.FILES:

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   formset = YourFormSet(request.POST, request.FILES)

3. The Django documentation notes that this approach only works at the form level and cannot be used to assign multiple files to a single model instance field.

4. In your formset, each form will have its own set of files, so you don't need to use request.FILES.getlist() directly - the custom field's clean() method handles converting the uploaded files into a list.

This approach should allow you to handle multiple file uploads for each form in your formset without requiring additional JavaScript to map files to forms.