mimetype default list make a wrong guess for illustrator file

[inkhey]

BPO	43544
Nosy	@inkhey

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-03-18.15:49:43.313>
labels = ['3.8', '3.9', '3.10']
title = 'mimetype default list make a wrong guess for illustrator file'
updated_at = <Date 2021-03-20.01:55:14.300>
user = 'https://github.com/inkhey'

bugs.python.org fields:

activity = <Date 2021-03-20.01:55:14.300>
actor = 'terry.reedy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-03-18.15:49:43.313>
creator = 'Inkhey'
dependencies = []
files = []
hgrepos = []
issue_num = 43544
keywords = []
message_count = 1.0
messages = ['389023']
nosy_count = 1.0
nosy_names = ['Inkhey']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue43544'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

Linked PRs

• gh-87710: Update mime type for .ai #141239

[inkhey]

mimetypes lib consider illustrator file ('.ai') as 'application/postscript' type. This is correct... but also wrong.

Old illustrator file (illustrator 9) are real postscript file but modern one are technically pdf. So guessing .ai as postscript lead to wrong guessing if you're using some software that make decision based on mimetype, you can of course, check both file_extension and mimetype but this remove usefulness of mimetype.