Deprecation: resource_name declaration without provides (CHEF-31)

In Chef Infra Client 12.5.1 through 15, resources could be addressed from recipe code using only the name of the resource, provided that no other provides declaration was used in the same file.

The intent was to fulfill the demands that “users should just be able to name a resource and it should work” with the demands that, for more complicated use cases, users should be able to use provides lines to arbitrarily wire up resources to the Chef recipe language.

This failed because it attempted to overly simplify user intent while generating two separate constructs with confusing interactions. Most users were entirely unaware that the resource_name statement implicitly issued a provides statement which wired up a specially designated canonical DSL entry, which was then removed behind the scenes if any subsequent provides declaration followed. When this worked it was easy to use, but when it failed the edge conditions were confusing and required too much background knowledge to debug.

An attempt was made to preserve more complete backwards compatibility between Chef Infra Client 16.0 and earlier versions by retaining some automatic wiring of the provides statement with the resource_name. This failed due to complicated interactions between cookbooks that used multiple resources with the same name wired up using provides lines to different resource implementations on different operating systems. This was a silent error and dependent upon the parse order of the resources in the cookbook for it to become apparent, and hindered detection and remediation.

The solution eventually adopted in Chef Infra Client 16.2 was to require all resources to declare a provides lines, and to make the resource_name setting only affect the display output. As a result, any cookbook which declares a resource with only a resource_name needs to add a provides line for Chef Infra Client 16. While this is more disruptive to users it is simple, it can be autocorrected using static analysis, and it results in a much simpler end state where the resource_name is just a display name and the provides statement is solely responsible for how the resource is addressed in recipe mode.

There is also the old standard that existed before resources could declare what they provided. In that standard, the resource was addressed by prepending the cookbook_name to the filename that the resource was declared in. That has remained unchanged and isn’t affected by this change.

Remediation

A resource with only a resource_name property:

resource_name :my_custom_resource

property :my_property, String

action :run do
  [ ...implementation of the action... ]
end

Should have a provides statement added:

resource_name :my_custom_resource
provides :my_custom_resource

property :my_property, String

action :run do
  [ ...implementation of the action... ]
end

It also works to have the provides line come before the resource_name, the order doesn’t matter.

For cookbooks which don’t have to support Chef Infra Client 15 or before, the resource_name can also be entirely omitted:

provides :my_custom_resource

property :my_property, String

action :run do
  [ ...implementation of the action... ]
end