Support schema-deprecated arguments for GraphQL

The newer version of the graphql gem updated in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53697 supports
marking arguments as deprecated within the schema
(https://github.com/rmosolgo/graphql-ruby/pull/3015).

Previously, deprecated arguments were only marked as such in their
description.

This change enables them to be fully marked as deprecated in the schema,
and therefore introspection queries.

app/graphql/types/base_argument.rb

@@ -6,7 +6,6 @@ module Types
 
     def initialize(*args, **kwargs, &block)
       kwargs = gitlab_deprecation(kwargs)
-      kwargs.delete(:deprecation_reason)
 
       super(*args, **kwargs, &block)
     end

app/graphql/types/concerns/gitlab_style_deprecations.rb

@@ -10,7 +10,7 @@ module GitlabStyleDeprecations
   def gitlab_deprecation(kwargs)
     if kwargs[:deprecation_reason].present?
       raise ArgumentError, 'Use `deprecated` property instead of `deprecation_reason`. ' \
-                           'See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#deprecating-fields-and-enum-values'
+                           'See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#deprecating-fields-arguments-and-enum-values'
     end
 
     deprecation = kwargs.delete(:deprecated)

changelogs/unreleased/ld-graphql-version-bump-gem-for-argument-deprecations.yml

+---
+title: Mark `startDate` and `endDate` arguments as deprecated in the GraphQL schema for `Project.milestones` and `Group.milestones`
+       (FOSS and EE), and `Project.iterations`, `Project.milestones`, `Group.epic`, `Group.epics`, `Group.iterations`, `Group.milestones`,
+       `BoardEpic.children`, and `Epic.children` fields (EE-only). Previously these arguments were marked as deprecated only in their descriptions
+merge_request: 45229
+author:
+type: changed

doc/development/api_graphql_styleguide.md

@@ -490,15 +490,18 @@ def foo
 end
 ```
 
-## Deprecating fields and enum values
+## Deprecating fields, arguments, and enum values
 
 The GitLab GraphQL API is versionless, which means we maintain backwards
-compatibility with older versions of the API with every change. Rather
-than removing a field or [enum value](#enums), we need to _deprecate_ it instead.
+compatibility with older versions of the API with every change.
+
+Rather than removing fields, arguments, or [enum values](#enums), they
+must be _deprecated_ instead.
+
 The deprecated parts of the schema can then be removed in a future release
 in accordance with the [GitLab deprecation process](../api/graphql/index.md#deprecation-process).
 
-Fields and enum values are deprecated using the `deprecated` property.
+Fields, arguments, and enum values are deprecated using the `deprecated` property.
 The value of the property is a `Hash` of:
 
 - `reason` - Reason for the deprecation.
@@ -518,14 +521,15 @@ is appended to the `description`.
 
 ### Deprecation reason style guide
 
-Where the reason for deprecation is due to the field or enum value being
-replaced, the `reason` must be:
+Where the reason for deprecation is due to the field, argument, or enum value being
+replaced, the `reason` must indicate the replacement. For example, the
+following is a `reason` for a replaced field:
 
 ```plaintext
 Use `otherFieldName`
 ```
 
-Example:
+Examples:
 
 ```ruby
 field :designs, ::Types::DesignManagement::DesignCollectionType, null: true,
@@ -544,8 +548,8 @@ module Types
 end
 ```
 
-If the field is not being replaced by another field, a descriptive
-deprecation `reason` should be given.
+If the field, argument, or enum value being deprecated is not being replaced,
+a descriptive deprecation `reason` should be given.
 
 See also [Aliasing and deprecating mutations](#aliasing-and-deprecating-mutations).
 
@@ -594,7 +598,7 @@ end
 ```
 
 Enum values can be deprecated using the
-[`deprecated` keyword](#deprecating-fields-and-enum-values).
+[`deprecated` keyword](#deprecating-fields-arguments-and-enum-values).
 
 ### Defining GraphQL enums dynamically from Rails enums
 
@@ -1567,7 +1571,7 @@ mount_aliased_mutation 'BarMutation', Mutations::FooMutation
 ```
 
 This allows us to rename a mutation and continue to support the old name,
-when coupled with the [`deprecated`](#deprecating-fields-and-enum-values)
+when coupled with the [`deprecated`](#deprecating-fields-arguments-and-enum-values)
 argument.
 
 Example:

spec/graphql/types/base_argument_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Types::BaseArgument do
+  include_examples 'Gitlab-style deprecations' do
+    let_it_be(:field) do
+      Types::BaseField.new(name: 'field', type: String, null: true)
+    end
+
+    let(:base_args) { { name: 'test', type: String, required: false, owner: field } }
+
+    def subject(args = {})
+      described_class.new(**base_args.merge(args))
+    end
+  end
+end

spec/support/shared_examples/graphql/types/gitlab_style_deprecations_shared_examples.rb

@@ -6,7 +6,7 @@ RSpec.shared_examples 'Gitlab-style deprecations' do
       expect { subject(deprecation_reason: 'foo') }.to raise_error(
         ArgumentError,
         'Use `deprecated` property instead of `deprecation_reason`. ' \
-        'See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#deprecating-fields-and-enum-values'
+        'See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#deprecating-fields-arguments-and-enum-values'
       )
     end