Refactor route and namespace combination logic

[numbata]

Motivation

The current implementation of route and namespace combinations uses @target_class.combined_* accessors that inadvertently trigger hash copies due to transform_values. This leads to inefficiencies and unexpected behavior where changes to supposedly original hashes do not persist.

Solution

Shortly

The proposed refactor avoids using @target_class.combined_* until the final step, instead using local variables to accumulate and combine routes and namespaces directly. This change prevents premature hash copying and streamlines the combination process, ensuring that changes are properly reflected and improving overall performance.

TLTR;

All @target_class.combined_* calls go through the add_setup method of the grape gem (caused by override_all_methods!). In the depths of the add_setup method it does:

argument.transform_values { |value| evaluate_arguments(configuration, value).first }

The transform_values makes a copy of the original hash object and returns it. This leads to unexpected behavior in cases such as:

@target_class.combined_routes[resource] ||= []

Where expected flow:

1. The @target_class.combined_routes returns an original hash.
2. The empty array sets under the resource key on the original hash.
3. The original combined_routes is filled with a new key-value.

But actual flow:

1. The @target_class.combined_routes creates a copy of the empty hash
2. The empty array is set to the empty hash under the resource key
3. The original combined_routes is still an empty hash.

[numbata]

@LeFnord just a friendly reminder, no rush.

[LeFnord]

awesome … thanks @numbata

[numbata]

Ouch. I forgot about changelog 🙈

[LeFnord]

no problem … I'll add the entry by the next release