python / python/cpython

When using bz2 and lzma in mode 'wt', the BOM is not written

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3.7 (EOL) topic-IO type-bug
Dominant language
Python
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Description

BPO 36304
Nosy @malemburg, @benjaminp, @ezio-melotti, @vadmium, @janLuke
Files
  • demonstrate_BOM_issue.py: Demonstrate the issue
  • 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 2019-03-15.13:19:03.624>
    labels = ['type-bug', '3.7', 'expert-IO']
    title = "When using bz2 and lzma in mode 'wt', the BOM is not written"
    updated_at = <Date 2019-03-18.16:16:40.549>
    user = 'https://github.com/janLuke'
    

    bugs.python.org fields:

    activity = <Date 2019-03-18.16:16:40.549>
    actor = 'vstinner'
    assignee = 'none'
    closed = False
    closed_date = None
    closer = None
    components = ['IO']
    creation = <Date 2019-03-15.13:19:03.624>
    creator = 'janluke'
    dependencies = []
    files = ['48209']
    hgrepos = []
    issue_num = 36304
    keywords = []
    message_count = 4.0
    messages = ['337987', '338001', '338045', '338241']
    nosy_count = 5.0
    nosy_names = ['lemburg', 'benjamin.peterson', 'ezio.melotti', 'martin.panter', 'janluke']
    pr_nums = []
    priority = 'normal'
    resolution = None
    stage = None
    status = 'open'
    superseder = None
    type = 'behavior'
    url = 'https://bugs.python.org/issue36304'
    versions = ['Python 3.7']
    

    Contributor guide

    Open the contributing guide

    First steps

    1. Read the whole issue, then the project's contributing guide.
    2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
    3. Fork the repository and make your change on a branch.
    4. Open a pull request that references the issue number.

    Research direction

    Start with the attached demonstrate_BOM_issue.py script to reproduce the behavior. Trace how bz2 and lzma handle text-mode writing, then add or update coverage for the expected BOM behavior; done means the BOM is written when either format is opened in mode 'wt'.

    Written by the indexing model from the issue text.

    Assessment

    Tech stack
    python
    Domain
    backend
    Issue type
    Bug
    Difficulty
    4/5
    Estimated time
    3-5 days
    Activity status
    Stale
    Clarity
    Mostly clear
    Newbie friendliness
    35/100

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