TextWrap's wrap method throws unhelpful error on bytes object

[PythonCoderAS]

BPO	41924
Nosy	@MojoVampire, @PythonCoderAS
PRs	bpo-41924: Add type check to prevent weird error #22534
Files	traceback.txt: Traceback

^{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 = <Date 2020-10-04.01:15:37.957>
created_at = <Date 2020-10-04.00:54:49.662>
labels = ['3.8', 'type-bug', 'library']
title = "TextWrap's wrap method throws unhelpful error on bytes object"
updated_at = <Date 2020-10-04.01:15:37.957>
user = 'https://github.com/PythonCoderAS'

bugs.python.org fields:

activity = <Date 2020-10-04.01:15:37.957>
actor = 'ThePokestarFan'
assignee = 'none'
closed = True
closed_date = <Date 2020-10-04.01:15:37.957>
closer = 'ThePokestarFan'
components = ['Library (Lib)']
creation = <Date 2020-10-04.00:54:49.662>
creator = 'ThePokestarFan'
dependencies = []
files = ['49489']
hgrepos = []
issue_num = 41924
keywords = ['patch']
message_count = 3.0
messages = ['377910', '377912', '377913']
nosy_count = 2.0
nosy_names = ['josh.r', 'ThePokestarFan']
pr_nums = ['22534']
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41924'
versions = ['Python 3.8']

[PythonCoderAS]

The wrap() method of the TextWrapper class (and the module-level wrap method) throws an unhelpful TypeError upon getting a bytes object.

[MojoVampire]

It's not textwrap that's doing it, which is why the error is so unhelpful; the input is assumed to be a str, and the translate method is called on it with a dict argument, which is valid for str.translate, but not for bytes.translate.

You'll get other "unhelpful" error messages for other arguments (e.g. most other built-in types die because they lack an expandtabs method). Is it necessary to provide specific error messages when an API is given a type it never claimed to support? I could see issues with a "check for str" check if someone is implementing their own str-like type that matches the API but gets rejected for not being str.

[PythonCoderAS]

You're most likely right, so I'll close it. The lesson is most likely to not use weird arguments, but modules such as datetime warn against it, so I was surprised.