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Allow read-only methods to work against a frozen StringIO#122

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headius wants to merge 4 commits intoruby:masterfrom
headius:frozen_readonly_methods
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Allow read-only methods to work against a frozen StringIO#122
headius wants to merge 4 commits intoruby:masterfrom
headius:frozen_readonly_methods

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@headius headius commented Feb 20, 2025

Add tests and fix behavior to allow several read-only StringIO methods to function when the StringIO is frozen.

  • string (returns underlying String but does not mutate anything)
  • lineno
  • pos
  • closed?/closed_read?/closed_write?
  • eof/eof?
  • sync
  • pid (a dummy method but it writes nothing)
  • fileno (dummy)
  • pread (by definition does not modify state)
  • isatty/tty?
  • size/length
  • external_encoding
  • internal_encoding
  • initialize_copy (allow original to be frozen)

See #120 for details.

@headius
Don't require the string be modifiable to seek
2bbb856 
seek only modifies the StringIO pos, and should work when the
underlying String is frozen.

Fixes ruby#119
@headius
Add test for seek with frozen String
b946d46 
See ruby#119
@headius
Add tests for read-only methods on frozen StringIO
7bb821a 
See ruby#120
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headius commented Feb 20, 2025

This is based on #121 and those commits will drop off when that PR is merged.

I would like input from @nobu @kou @hsbt @byroot since you all have related changes here. 🙇

@headius
Allow read-only methods to work with frozen StringIO
38303a4 
This fixes the JRuby extension to allow read-only methods to work
against a frozen StringIO, as described in ruby#119.
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headius commented Feb 20, 2025

I can make the same change in the C extension (mostly switching a few StringIO() macro calls to check_strio() function calls, but @nobu @kou please advise me.

@headius headius mentioned this pull request Feb 20, 2025
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byroot commented Feb 21, 2025

I would like input

It would make sense to me that StringIO.new(str.freeze) would try to behave like a read only file. But I'm not StringIO maintainer.

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kou commented Aug 9, 2025

See also: https://bugs.ruby-lang.org/issues/21151

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headius commented Aug 11, 2025

StringIO.new(str.freeze) would try to behave like a read only file

This isn't really the use case here. What I'm seeking is a way to freeze a StringIO so it can no longer be read from or written to, but still be able to access its current state like lineno and pos.

There's no reason I can think of that accessing current StringIO state should require that the StringIO be mutable, since we're just reading that state.

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3 participants

@headius @byroot @kou