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Allow to dump instance variables on non-primitive binary strings:#774

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Edouard-chin wants to merge 1 commit intoruby:masterfrom
Shopify:ec-ivars-binary-string
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Allow to dump instance variables on non-primitive binary strings:#774
Edouard-chin wants to merge 1 commit intoruby:masterfrom
Shopify:ec-ivars-binary-string

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@Edouard-chin
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@Edouard-chin Edouard-chin commented Feb 4, 2026

Allow to dump instance variables on non-primitive binary strings:

Hello 👋

I'd like to propose the feature to dump instance variables when dumpin a binary string created from a String subclass.

One of the the use case I have is in Rails for the PostgreSQL adapter where we need to make sure that we aren't escaping the result twice. We decode the result and set an instance variable on the string to tell that it was decoded so that we later don't redo-this.

The problem is that when we dump that string, we lose this information since Psych don't dump ivars for binary strings.

Psych already allows to dump ivars on strings for string subclass. In this patch, it will now be possible to create a String subclass, and when it gets dumped it will retain ivars.

A behaviour worth highlighting is that the subclass information isn't retained. When the dumped string gets loaded, a String object is created with the previously dumped ivars set. Prior to this patch, this is already the case so there is no behaviour difference.

  class MyString < String
  end

  Psych.load(Psych.dump(MyString.new("\xE2".b))).class # => String

- I'd like to propose the feature to dump instance variables when
  dumpin a binary string created from a String subclass.

  One of the the use case I have is in Rails for the PostgreSQL
  adapter where we need to make sure that we aren't escaping the
  result twice. We decode the result and set an instance variable
  on the string to tell that it was decoded so that we later
  don't redo-this.

  The problem is that when we dump that string, we lose this
  information since Psych don't dump ivars for binary strings.

  Psych already allows to dump ivars on strings for string subclass.
  In this patch, it will now be possible to create a String subclass,
  and when it gets dumped it will retain ivars.

  A behaviour worth highlighting is that the subclass information
  isn't retained. When the dumped string gets loaded, a `String`
  object is created with the previously dumped ivars set.
  Prior to this patch, this is already the case so there is no
  behaviour difference.

  ```ruby
  class MyString < String
  end

  Psych.load(Psych.dump(MyString.new("\xE2".b))) => String object
  ```
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