[ruby-core:100164] [Ruby master Feature#15815] Add option to raise NoMethodError for OpenStruct

[ruby-core:100164] [Ruby master Feature#15815] Add option to raise NoMethodError for OpenStruct

[marcandre-ruby-core]

Issue #15815 has been updated by marcandre (Marc-Andre Lafortune).


I'm proposing to add `OpenStruct::Strict`, that will not return `nil` for unknown attributes and instead raise a `NotMethodError`. See PR https://github.com/ruby/ruby/pull/3594 (last commit)

Usage with `JSON` is easy:

```ruby
JSON.parse(response, object_class: OpenStruct::Strict)
```

This seems to me to avoid issues that other solutions had:

* Any other solutions is difficult to use with `JSON.parse` API
* I considered adding `OpenStruct#strict!` (returning `self` after mutating it), seems the 2nd best option.
* `OpenStruct.new({...}, exception: true)` made it difficult to remain compatible with `OpenStruct.new(using: 'keyword arguments')`. Also seemed confusing API.
* `OpenStruct.new(...) { block to handle unknown attribute }` was longer to write, and potentially less/not Ractor compatible, and not serializable in general.

The downside to `OpenStruct::Strict` is that it makes adding any other configuration more difficult. Given the fact that `OpenStruct` is to mature now though, I feel it is not an actual issue. Anyone wanting to subclass has to pick a base class (or define it's own `respond_to_unknown_attribute!`).

Comments welcome.

----------------------------------------
Feature #15815: Add option to raise NoMethodError for OpenStruct
https://bugs.ruby-lang.org/issues/15815#change-87735

* Author: mtsmfm (Fumiaki Matsushima)
* Status: Open
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
GitHub PR: https://github.com/ruby/ruby/pull/2164

Currently, `OpenStruct#method_missing` returns `nil` even if the key isn't registered.

```ruby
require 'ostruct'
os = OpenStruct.new({a: 1})
os.a #=> 1
os.b #=> nil
```

I'd like to add `exception` option to raise `NoMethodError` in such case.

```ruby
require 'ostruct'
os = OpenStruct.new({a: 1}, exception: true)
os.a #=> 1
os.b #=> NoMethodError
```

## Use case

I sometimes use OpenStruct as a JSON API response wrapper.
It's useful to use method call instead of key access (`obj[:key]`) because we can use `Symbol#to_proc` if it's a method (for example `users.map(&:id)`)

But I want to prevent typo for a key name. Currently `users.map(&:idd)` just returns `[nil,...]`

Even if we have this `exception` option, we can't enable this option for JSON parser easily though:

```ruby
JSON.parse(response, object_class: Class.new(OpenStruct) { def initialize(hash); super(hash, exception: true); end })
```

What do you think?

----

I've searched with "openstruct nomethoderror" on bugs.ruby-lang.org though, please let me know if it's duplicated.
https://bugs.ruby-lang.org/search?utf8=%E2%9C%93&scope=&q=nomethoderror+openstruct



-- 
https://bugs.ruby-lang.org/

[ruby-core:100191] [Ruby master Feature#15815] Add option to raise NoMethodError for OpenStruct

[mtsmfm]

Issue #15815 has been updated by mtsmfm (Fumiaki Matsushima).


Cool.
It's much better API to integrate with `JSON.parse`.

----------------------------------------
Feature #15815: Add option to raise NoMethodError for OpenStruct
https://bugs.ruby-lang.org/issues/15815#change-87763

* Author: mtsmfm (Fumiaki Matsushima)
* Status: Open
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
----------------------------------------
GitHub PR: https://github.com/ruby/ruby/pull/2164

Currently, `OpenStruct#method_missing` returns `nil` even if the key isn't registered.

```ruby
require 'ostruct'
os = OpenStruct.new({a: 1})
os.a #=> 1
os.b #=> nil
```

I'd like to add `exception` option to raise `NoMethodError` in such case.

```ruby
require 'ostruct'
os = OpenStruct.new({a: 1}, exception: true)
os.a #=> 1
os.b #=> NoMethodError
```

## Use case

I sometimes use OpenStruct as a JSON API response wrapper.
It's useful to use method call instead of key access (`obj[:key]`) because we can use `Symbol#to_proc` if it's a method (for example `users.map(&:id)`)

But I want to prevent typo for a key name. Currently `users.map(&:idd)` just returns `[nil,...]`

Even if we have this `exception` option, we can't enable this option for JSON parser easily though:

```ruby
JSON.parse(response, object_class: Class.new(OpenStruct) { def initialize(hash); super(hash, exception: true); end })
```

What do you think?

----

I've searched with "openstruct nomethoderror" on bugs.ruby-lang.org though, please let me know if it's duplicated.
https://bugs.ruby-lang.org/search?utf8=%E2%9C%93&scope=&q=nomethoderror+openstruct



-- 
https://bugs.ruby-lang.org/