[Bug] rbs-inline fails to generate parent module definitions for nested constants

[tommy-314]

Describe the bug

When rbs-inline generates an RBS file for a nested constant (e.g., Foo::Bar::Baz), it does not automatically create the necessary parent module definitions (Foo and Foo::Bar) in a separate RBS file.

This leads to a RBS::UnknownTypeName error when running steep check, because the parent types are not found.

Version

• rails (7.0.8.7)
• rbs (3.9.4)
• rbs-inline (0.11.0)
• steep (1.10.0)

To Reproduce

1. Set up a project with rbs-inline and steep.

2. Create a Ruby file with a nested class, without a separate module definition:

   # app/models/foo/bar/baz.rb
   # rbs_inline: enabled
   
   class Foo::Bar::Baz
     # @rbs () -> String
     def hello
       "world"
     end
   end

3. Run bundle exec rbs-inline.

4. Run bundle exec steep check.

5. This command fails with the following error.

sig/generated/models/foo/bar/baz.rbs:3:0: [error] Cannot find type `::Foo::Bar`
│ Diagnostic ID: RBS::UnknownTypeName
│
└ class Foo::Bar::Baz
  ~~~~~~~~~~~~~~~~~~~

Expected behavior

rbs-inline should automatically generate the parent module definitions needed for a type checker to run without error.

For the example above, it should generate:

# sig/generated/models/foo.rbs
module Foo
end

# sig/generated/models/foo/bar.rbs
module Foo::Bar
end

Possible solutions

I believe the fix would be to modify the RBS generation logic to recursively check and generate RBS files for all parent modules of a given constant, if they don't already exist.

[tk0miya]

In Rails apps, the zeitwerk gem helps to load transparently without Foo and Foo::Bar definition.
So, your example works fine in RoR.

But it does not work with Ruby. Ruby without Rails (zeitwerk) raises a NameError for the example.

tkomiya@tarf> cat baz.rb
class Foo::Bar::Baz
  # @rbs () -> String
  def hello
    "world"
  end
end

tkomiya@tarf> ruby baz.rb
baz.rb:1:in '<main>': uninitialized constant Foo (NameError)

class Foo::Bar::Baz
      ^^^

How about using type generators supporting Ruby on Rails (ex. rbs_rails)?

[tommy-314]

@tk0miya
Thank you for your reply!

I'm using rbs_rails, but the target model is not a descendant of ActiveRecord::Base, the rbs files are not being generated.