Bug #15873: FrozenError when using OpenURI.open

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-linux]
• Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN

[AlexGascon (Alex Gascon)]

I just updated from Ruby 2.5.1 to 2.6.3 and I encountered a strange problem on a part that was working fine previously. It's on a Rails application, and on one of the tests I'm stubbing (using webmock) an HTTP request that we perform to an external URL. However, when trying to access the information by using OpenURI I get a FrozenError.

The following block represents a minimal reproducible example of the problem that I'm experiencing

stub_request(:get, "https://files.lol/certificate_doc.pdf").to_return(status: 200, body: "Random information", headers: {})

file_content = open("https://files.lol/certificate_doc.pdf")

FrozenError: can't modify frozen String
from /home/alex/.rbenv/versions/2.6.3/lib/ruby/2.6.0/open-uri.rb:357:in `clear'

[nobu (Nobuyoshi Nakada)]

Does it occur even if the body is "Random information".dup?

[AlexGascon (Alex Gascon)]

nobu (Nobuyoshi Nakada) wrote:

Does it occur even if the body is "Random information".dup?

Just tried and no, when using .dup it worked as expected!

[nobu (Nobuyoshi Nakada)]

• Related to Feature #14320: [PATCH] open-uri: clear string after buffering added

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Probably you are using frozen-string-literal pragma.
Since 2.6, OpenURI clears the buffer from Net::HTTPResponse#read_body to reduce memory usage.
See [Feature #14320].