Description

assignee = 'https://github.com/ezio-melotti'
closed_at = <Date 2020-07-16.06:39:25.857>
created_at = <Date 2017-10-23.08:27:23.318>
labels = ['type-bug', 'library', '3.10']
title = 'HTMLParser: undocumented not implemented method'
updated_at = <Date 2020-07-16.06:39:25.857>
user = 'https://github.com/srittau'

activity = <Date 2020-07-16.06:39:25.857>
actor = 'berker.peksag'
assignee = 'ezio.melotti'
closed = True
closed_date = <Date 2020-07-16.06:39:25.857>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2017-10-23.08:27:23.318>
creator = 'srittau'
dependencies = []
files = []
hgrepos = []
issue_num = 31844
keywords = ['patch']
message_count = 10.0
messages = ['304782', '304783', '305303', '305306', '322662', '322672', '323968', '371500', '373745', '373746']
nosy_count = 5.0
nosy_names = ['srittau', 'ezio.melotti', 'berker.peksag', 'cheryl.sabella', 'William Ayd']
pr_nums = ['8562', '21504']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue31844'
versions = ['Python 3.10']

Activity

1. srittau commented on Oct 23, 2017

   

   srittaumannequin

   on Oct 23, 2017

   MannequinAuthor

   More actions

   HTMLParser derives from _markupbase.ParserBase, which has the following method:

   class HTMLParser:

   ...
   

       def error(self, message):
           raise NotImplementedError(
               "subclasses of ParserBase must override error()")

   HTMLParser does not implement this method and the documentation for HTMLParser (https://docs.python.org/3.6/library/html.parser.html) does not mention that its sub-classes need to override it.

   I am not sure whether this is a documentation omission, whether HTMLParser should provide an (empty?) implementation, or whether ParserBase should not raise a NotImplementedError (to make linters happy).
2. srittau commented on Oct 23, 2017

   

   srittaumannequin

   on Oct 23, 2017

   MannequinAuthor

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   The quoted code above should have used ParserBase:

   class ParserBase:

   ...
   

       def error(self, message):
           raise NotImplementedError(
               "subclasses of ParserBase must override error()")
3. WilliamAyd commented on Oct 31, 2017

   

   WilliamAydmannequin

   on Oct 31, 2017

   Mannequin

   More actions

   Would we be open to setting the meta class of the ParserBase to ABCMeta and setting error as an abstract method? That at the very least would make the expectation clearer for subclasses.

   I haven’t contributed to Python before but am open to this as a first attempt if the direction makes sense.
4. WilliamAyd commented on Oct 31, 2017

   

   WilliamAydmannequin

   on Oct 31, 2017

   Mannequin

   More actions

   And assuming that subclass requirement is intentional we could add an optional keyword argument to the HTMLParser that indicates what to do with errors, much like how encoding issues are handled within codecs. For backwards compatibility it can default to ignore, but fail and warn could be two alternate approaches that the error method could account for
5. serhiy-storchaka

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Oct 31, 2017
6. berkerpeksag commented on Jul 30, 2018

   

   berkerpeksag

   on Jul 30, 2018

   Member

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   HTMLParser.error() method was deprecated in Python 3.4 (88ebfb1#diff-1a7486df8279dbac7f20abd487947845R157) and removed in Python 3.5 (73a4359#diff-1a7486df8279dbac7f20abd487947845L171)

   _markupbase is a private and undocumented module and its only user is HTMLParser (sgmllib was removed from the stdlib in 2008) Since we already have removed HTMLParser.error(), I think we can just remove _markupbase.ParserBase.error() without a deprecation period.
7. berkerpeksag

   added

   3.8 (EOL)end of lifeend of life

   on Jul 30, 2018
8. srittau commented on Jul 30, 2018

   

   srittaumannequin

   on Jul 30, 2018

   MannequinAuthor

   More actions

   Good call. Maybe it's actually time to retire _markupbase and merge ParserBase into HTMLParser.
9. berkerpeksag commented on Aug 23, 2018

   

   berkerpeksag

   on Aug 23, 2018

   Member

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   After triaging bpo-34480, I realized that we can't simply remove the error() method because the _markupbase.ParserBase() class still uses it. I've just closed PR 8562.
10. ezio-melotti

    self-assigned this

    on Aug 25, 2018
11. csabella commented on Jun 14, 2020

    

    csabella

    on Jun 14, 2020

    Contributor

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    @berker.peksag's last comment was he closed the PR on 23 August 2018. However, he reopened it on 6 January 2020 as @ezio.melotti mentioned that they are both needed.

    The PR for this issue is waiting to be re-reviewed by Ezio.
12. csabella

    added

    3.10 (EOL)end of lifeend of life

    and removed

    3.8 (EOL)end of lifeend of life

    on Jun 14, 2020
13. berkerpeksag commented on Jul 16, 2020

    

    berkerpeksag

    on Jul 16, 2020

    Member

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    New changeset e34bbfd by Berker Peksag in branch 'master':
    bpo-31844: Remove _markupbase.ParserBase.error() (GH-8562)
    e34bbfd
14. berkerpeksag commented on Jul 16, 2020

    

    berkerpeksag

    on Jul 16, 2020

    Member

    More actions

    New changeset d4d127f by Berker Peksag in branch 'master':
    bpo-31844: Move whatsnew note to 3.10.rst (GH-21504)
    d4d127f
15. berkerpeksag

    closed this as completedon Jul 16, 2020
16. ezio-melotti

    transferred this issue fromon Apr 10, 2022
17. return42

    added 2 commits that reference this issue on Oct 18, 2023

    [fix] HTMLParser: undocumented not implemented method

    01cfc55

    [fix] HTMLParser: undocumented not implemented method

    8903910
18. dalf

    added a commit that references this issue on Oct 22, 2023

    [fix] HTMLParser: undocumented not implemented method

    ef56e1d
19. serhiy-storchaka

    added this to html.parser issueson Jun 20, 2025
20. github-project-automation

    moved this to Todo in html.parser issueson Jun 20, 2025

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