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unterminated string literal tokenization error messages could be better #84357

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benjaminp opened this issue Apr 3, 2020 · 10 comments
Closed

unterminated string literal tokenization error messages could be better #84357

benjaminp opened this issue Apr 3, 2020 · 10 comments
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3.10 interpreter-core type-feature

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@benjaminp
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@benjaminp benjaminp commented Apr 3, 2020

BPO 40176
Nosy @benjaminp, @alex, @serhiy-storchaka, @ammaraskar, @pablogsal, @miss-islington, @isidentical
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  • #19346
  • 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 2021-01-20.21:56:51.092>
    created_at = <Date 2020-04-03.17:58:44.806>
    labels = ['interpreter-core', 'type-feature', '3.10']
    title = 'unterminated string literal tokenization error messages could be better'
    updated_at = <Date 2021-01-20.21:56:51.091>
    user = 'https://github.com/benjaminp'

    bugs.python.org fields:

    activity = <Date 2021-01-20.21:56:51.091>
    actor = 'BTaskaya'
    assignee = 'none'
    closed = True
    closed_date = <Date 2021-01-20.21:56:51.092>
    closer = 'BTaskaya'
    components = ['Interpreter Core']
    creation = <Date 2020-04-03.17:58:44.806>
    creator = 'benjamin.peterson'
    dependencies = []
    files = []
    hgrepos = []
    issue_num = 40176
    keywords = ['patch']
    message_count = 10.0
    messages = ['365713', '365730', '365743', '365749', '365765', '366036', '366303', '369541', '369542', '385374']
    nosy_count = 7.0
    nosy_names = ['benjamin.peterson', 'alex', 'serhiy.storchaka', 'ammar2', 'pablogsal', 'miss-islington', 'BTaskaya']
    pr_nums = ['19346']
    priority = 'normal'
    resolution = 'fixed'
    stage = 'resolved'
    status = 'closed'
    superseder = None
    type = 'enhancement'
    url = 'https://bugs.python.org/issue40176'
    versions = ['Python 3.10']

    @benjaminp
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    @benjaminp benjaminp commented Apr 3, 2020

    It has been pointed out to me that the errors the tokenizer produces for unterminated strings, "EOL while scanning string literal" and "EOF while scanning triple-quoted string literal", contain parsing jargon that make it difficult for new users to understand the problem, likely a missing quote.

    @benjaminp benjaminp added 3.9 interpreter-core type-feature labels Apr 3, 2020
    @serhiy-storchaka
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    @serhiy-storchaka serhiy-storchaka commented Apr 3, 2020

    It could be even better. Inside the tokenizer we know where the string literal starts and what quotes it uses. The line and the offset of the *start* of the literal can be set in a SyntaxError.

    @alex
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    @alex alex commented Apr 4, 2020

    Here's my suggestion:

    End of line reached without finding the end of string literal. Are you missing a closing quote?

    @ammaraskar
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    @ammaraskar ammaraskar commented Apr 4, 2020

    Just re-posting this here from the open PR. Rust's handling of this seems nice and beginner friendly:

    error: unterminated double quote string
    --> src/main.rs:2:19
    |
    2 | let message = "Hello world
    | __________________^
    3 | | println!(message);
    4 | | }
    | |
    ^

    Like Serhiy suggested, it points to the /start/ of the string, rather than the EOL and the message seems nice too.

    @isidentical
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    @isidentical isidentical commented Apr 4, 2020

    >>> message = "sadsa
      File "<stdin>", line 1
        message = "sadsa
                  ^
    SyntaxError: unterminated double quote

    @serhiy-storchaka
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    @serhiy-storchaka serhiy-storchaka commented Apr 9, 2020

    I afraid there may be confusion between triple, double and single quoted string literals. So I suggest to change error messages to just "unterminated triple-quoted string literal" and "unterminated string literal" (or "unterminated single-quoted string literal"). Terms "triple-quoted" and "single-quoted" are used several times in the documentation. Term "double-quoted" is used only once, and I suppose in different meaning.

    @isidentical
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    @isidentical isidentical commented Apr 13, 2020

    Fair point. I changed error messages to what you suggested

    >>> (300) * 6 + ca(e, 2 +    "dsadsa)
      File "<stdin>", line 1
        (300) * 6 + ca(e, 2 +    "dsadsa)
                                 ^
    SyntaxError: unterminated string literal
    
    >>> (300) * 6 + ca(e, 2 +    'dsadsa)
      File "<stdin>", line 1
        (300) * 6 + ca(e, 2 +    'dsadsa)
                                 ^
    SyntaxError: unterminated string literal
    
    
    >>> (300) * 6 + ca(e, 2 +    """dsadsa
    ... 
      File "<stdin>", line 1
        (300) * 6 + ca(e, 2 +    """dsadsa
                                 ^
    SyntaxError: unterminated triple-quoted string literal

    @pablogsal
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    @pablogsal pablogsal commented May 21, 2020

    New changeset 72e0aa2 by Batuhan Taskaya in branch 'master':
    bpo-40176: Improve error messages for trailing comma on from import (GH-20294)
    72e0aa2

    @pablogsal
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    @pablogsal pablogsal commented May 21, 2020

    New changeset 275d7e1 by Pablo Galindo in branch '3.9':
    [3.9] bpo-40176: Improve error messages for trailing comma on from import (GH-20294) (GH-20302)
    275d7e1

    @miss-islington
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    @miss-islington miss-islington commented Jan 20, 2021

    New changeset a698d52 by Batuhan Taskaya in branch 'master':
    bpo-40176: Improve error messages for unclosed string literals (GH-19346)
    a698d52

    @isidentical isidentical added 3.10 and removed 3.9 labels Jan 20, 2021
    @isidentical isidentical added 3.10 and removed 3.9 labels Jan 20, 2021
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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