id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30179	Merging 3 or more media objects can throw unnecessary MediaOrderConflictWarnings	Matt Westcott	nobody	"Consider the following form definition, where `text-editor-extras.js` depends on `text-editor.js` but all other JS files are independent:

{{{
from django import forms


class ColorPicker(forms.Widget):
    class Media:
        js = ['color-picker.js']


class SimpleTextWidget(forms.Widget):
    class Media:
        js = ['text-editor.js']


class FancyTextWidget(forms.Widget):
    class Media:
        js = ['text-editor.js', 'text-editor-extras.js', 'color-picker.js']


class MyForm(forms.Form):
    background_color = forms.CharField(widget=ColorPicker())
    intro = forms.CharField(widget=SimpleTextWidget())
    body = forms.CharField(widget=FancyTextWidget())
}}}

Django should be able to resolve the JS files for the final form into the order text-editor.js, text-editor-extras.js, color-picker.js. However, accessing `MyForm().media` results in:

{{{
/projects/django/django/forms/widgets.py:145: MediaOrderConflictWarning: Detected duplicate Media files in an opposite order:
text-editor-extras.js
text-editor.js
  MediaOrderConflictWarning,
Media(css={}, js=['text-editor-extras.js', 'color-picker.js', 'text-editor.js'])
}}}

The `MediaOrderConflictWarning` is a result of the order that the additions happen in: `ColorPicker().media + SimpleTextWidget().media` produces `Media(css={}, js=['color-picker.js', 'text-editor.js'])`, which (wrongly) imposes the constraint that color-picker.js must appear before text-editor.js.

The final result is particularly unintuitive here, as it's worse than the ""naïve"" result produced by Django 1.11 before order-checking was added (color-picker.js, text-editor.js, text-editor-extras.js), and the pair of files reported in the warning message seems wrong too (aren't color-picker.js and text-editor.js the wrong-ordered ones?)"	Bug	closed	Forms	dev	Normal	fixed		Johannes Maron Matthias Kestenholz	Accepted	1	0	0	1	0	0