Singletons: Default collection_name to singleton_name

[seanpdoyle]

The problem

Active Resource's custom methods are operations outside of the
conventional collection of CRUD actions. For typical collections of
resources, custom methods operate on the collection itself. For example,
consider a custom refresh action for a Product resource triggered by
POST requests: POST /products/:product_id/refresh. The route
utilizes a :product_id dynamic segment to identify the Product in
question, and the path includes /refresh to signify the custom method
to perform.

The concept of a "singleton" resource is that there is only one singular
resource, and operations should consistently modify the same resource.
Since the resource is singular in nature, paths do not identify that
resource with an ID. For example, consider a singleton Inventory
resource that belongs to a Product. Its singleton path would be
/products/:product_id/inventory.

Prior to this commit, custom methods invoked by both instances and
classes of singleton resources ignored the "singleton" nature of
route, and use pluralize nouns instead of singular ones.

For example, consider calls to custom "report" and "reset" methods for
an instance of a singleton Inventory resource:

inventory = Inventory.find(params: { product_id: 1 }) # => GET /products/1/inventory.json

  # BEFORE
inventory.get(:report, product_id: 1)   # => GET /products/1/inventories/report.json
inventory.delete(:reset, product_id: 1) # => DELETE /products/1/inventories/reset.json

Note the /inventories/ portion of the URL prefix. The same occurs for
class methods. For example, consider calls to the same custom "report"
and "reset" routes for a singleton Inventory resource class:

 # BEFORE
Inventory.get(:report, product_id: 1)   # => GET /products/1/inventories/report.json
Inventory.delete(:reset, product_id: 1) # => DELETE /products/1/inventories/reset.json

The proposal

In order to make "singleton" resources behave more consistently with a
singular mental model, this commit proposes that Active Resource change
instance-level custom methods (through the same get, post, put,
patch, and delete style methods) to use the singular singleton name
in their paths.

When declaring a resource as a "singleton" (through including the
ActiveResource::Singleton module), ensure that subsequent calls to
class-level custom methods (through the get, post, put, patch,
and delete class and instance methods) use the singleton name by
default.

  # AFTER
Inventory.get(:report, product_id: 1)   # => GET /products/1/inventory/report.json
Inventory.delete(:reset, product_id: 1) # => DELETE /products/1/inventory/reset.json

When a collection_name is explicitly configured, use that value
instead of the singleton_name default.

Apply the same changes to instances of singleton resources:

inventory = Inventory.find(params: { product_id: 1 }) # => GET /products/1/inventory.json

  # AFTER
inventory.get(:report)    # => GET /products/1/inventory/report.json
inventory.delete(:reset)  # => DELETE /products/1/inventory/reset.json

[seanpdoyle]

This implementation is copied directly from ActiveResource::CustomMethods, then altered to omit the id portion of the path:

activeresource/lib/active_resource/custom_methods.rb

Lines 121 to 123 in 9c8a2ee

	def custom_method_element_url(method_name, options = {})
	"#{self.class.prefix(prefix_options)}#{self.class.collection_name}/#{URI.encode_www_form_component(id.to_s)}/#{method_name}#{self.class.format_extension}#{self.class.__send__(:query_string, options)}"
	end

 def custom_method_element_url(method_name, options = {})
-  "#{self.class.prefix(prefix_options)}#{self.class.collection_name}/#{URI.encode_www_form_component(id.to_s)}/#{method_name}#{self.class.format_extension}#{self.class.__send__(:query_string, options)}"
+  "#{self.class.prefix(prefix_options)}#{self.class.collection_name}/#{method_name}#{self.class.format_extension}#{self.class.__send__(:query_string, options)}"
 end