3.6.0 Hashie::Mash#merge doesn't work for instances with default_proc that raise error

[andrew-hai]

2.5.1 :001 > require 'hashie'
 => true 
2.5.1 :002 > mash = Hashie::Mash.new(foo: 1) { |hash, key| raise StandardError, "Key #{key} does not exist in hash #{hash.inspect}" }
 => #<Hashie::Mash foo=1> 
2.5.1 :003 > mash.merge(bar: 2)
Traceback (most recent call last):
        8: from /home/an/.rvm/rubies/ruby-2.5.1/bin/irb:11:in `<main>'
        7: from (irb):3
        6: from /home/an/.rvm/gems/ruby-2.5.1@test/gems/hashie-3.6.0/lib/hashie/mash.rb:203:in `deep_merge'
        5: from /home/an/.rvm/gems/ruby-2.5.1@test/gems/hashie-3.6.0/lib/hashie/mash.rb:210:in `deep_update'
        4: from /home/an/.rvm/gems/ruby-2.5.1@test/gems/hashie-3.6.0/lib/hashie/mash.rb:210:in `each_pair'
        3: from /home/an/.rvm/gems/ruby-2.5.1@test/gems/hashie-3.6.0/lib/hashie/mash.rb:212:in `block in deep_update'
        2: from /home/an/.rvm/gems/ruby-2.5.1@test/gems/hashie-3.6.0/lib/hashie/mash.rb:212:in `[]'
        1: from (irb):2:in `block in irb_binding'
StandardError (Key bar does not exist in hash #<Hashie::Mash foo=1>)
2.5.1 :004 > 

[michaelherold]

Thanks for filing this issue. What do you believe the behavior should be here? Could you please submit a test?

[laertispappas]

I agree with @michaelherold what is your expectation here? Isn't the above the correct behaviour? An exception should be raised since you defined it no?

[dblock]

I think it's not the expected behavior because assignment and merge should behave the same way.

2.5.1 :002 > mash = Hashie::Mash.new(foo: 1) { |hash, key| raise StandardError, "Key #{key} does not exist in hash #{hash.inspect}" }
 => #<Hashie::Mash foo=1> 
2.5.1 :003 > mash[:bar] = 2
 => 2 

Merge doesn't imply needing to check on whether the value exists.

[laertispappas]

Hi @dblock.

On the default block we override the default value for the getter. Thus any non defined member will raise an exception. Calling mash[:bar] = 2 we send a different message to the object and we override the default value by creating the corresponding member.

So I think that merge is behaving as expected not because of merge method's definition but rather by the intention of the code written.

[dblock]

Color me confused, why does merge call any getters?

[andrew-hai]

Hi,

As for me, I expect the same behavior as for Hash#merge with the same default_proc. Also it works for previous versions. I think it because of changing alias_method definitions to alias.

[laertispappas]

@dblock You are right. It has nothing to do with merge...

[dblock]

@andrew-hai Care to try to write a spec and, hopefully, a fix?

[laertispappas]

This introduced the problematic change: https://github.com/intridea/hashie/pull/435/files. The problem is that calling regular_reader (Hash#[]) or custom_readerwill execute the default block that is passed.

I've made a super small change in a related PR where we check the key before calling any getter on the Mash.

[andrew-hai]

@laertispappas and all others, thank you, Hashie::Mash#merge method works fine now.

[dblock]

Closed via #465

[baburdick]

Do I presume correctly that this will appear in v3.6.1? Any ETA on v3.6.1? (Not pushing; really just wondering if there are any major blockages preventing its tagging/release.)

[dblock]

No ETA, sorry. My charity says I could make a release with some convincing.