Linked GraphQL docs output

This changes the GraphQL markdown documentation to have links to
types.

app/graphql/types/global_id_type.rb

@@ -19,7 +19,14 @@ end
 module Types
   class GlobalIDType < BaseScalar
     graphql_name 'GlobalID'
-    description 'A global identifier'
+    description <<~DESC
+      A global identifier.
+
+      A global identifier represents an object uniquely across the application.
+      An example of such an identifier is "gid://gitlab/User/1".
+
+      Global identifiers are encoded as strings.
+    DESC
 
     # @param value [GID]
     # @return [String]
@@ -46,38 +53,40 @@ module Types
 
       @id_types[model_class] ||= Class.new(self) do
         graphql_name "#{model_class.name.gsub(/::/, '')}ID"
-        description "Identifier of #{model_class.name}."
+        description <<~MD
+          A `#{graphql_name}` is a global ID. It is encoded as a string.
 
-        self.define_singleton_method(:to_s) do
+          An example `#{graphql_name}` is: `"#{::Gitlab::GlobalId.build(model_name: model_class.name, id: 1)}"`.
+        MD
+
+        define_singleton_method(:to_s) do
           graphql_name
         end
 
-        self.define_singleton_method(:inspect) do
+        define_singleton_method(:inspect) do
           graphql_name
         end
 
-        self.define_singleton_method(:coerce_result) do |gid, ctx|
+        define_singleton_method(:coerce_result) do |gid, ctx|
           global_id = ::Gitlab::GlobalId.as_global_id(gid, model_name: model_class.name)
 
-          if suitable?(global_id)
-            global_id.to_s
-          else
-            raise GraphQL::CoercionError, "Expected a #{model_class.name} ID, got #{global_id}"
-          end
+          next global_id.to_s if suitable?(global_id)
+
+          raise GraphQL::CoercionError, "Expected a #{model_class.name} ID, got #{global_id}"
         end
 
-        self.define_singleton_method(:suitable?) do |gid|
+        define_singleton_method(:suitable?) do |gid|
           next false if gid.nil?
 
           gid.model_name.safe_constantize.present? &&
             gid.model_class.ancestors.include?(model_class)
         end
 
-        self.define_singleton_method(:coerce_input) do |string, ctx|
+        define_singleton_method(:coerce_input) do |string, ctx|
           gid = super(string, ctx)
-          raise GraphQL::CoercionError, "#{string.inspect} does not represent an instance of #{model_class.name}" unless suitable?(gid)
+          next gid if suitable?(gid)
 
-          gid
+          raise GraphQL::CoercionError, "#{string.inspect} does not represent an instance of #{model_class.name}"
         end
       end
     end

app/graphql/types/time_type.rb

@@ -3,7 +3,13 @@
 module Types
   class TimeType < BaseScalar
     graphql_name 'Time'
-    description 'Time represented in ISO 8601'
+    description <<~DESC
+      Time represented in ISO 8601.
+
+      For example: "2021-03-09T14:58:50+00:00".
+
+      See `https://www.iso.org/iso-8601-date-and-time-format.html`.
+    DESC
 
     def self.coerce_input(value, ctx)
       Time.parse(value)

changelogs/unreleased/ajk-linked-graphql-docs.yml

+---
+title: Link fields to types in GraphQL reference documentation
+merge_request: 55901
+author:
+type: changed

lib/gitlab/graphql/docs/helper.rb

@@ -27,16 +27,18 @@ module Gitlab
           MD
         end
 
-        def render_name_and_description(object)
-          content = "### `#{object[:name]}`\n"
+        def render_name_and_description(object, level = 3)
+          content = []
+
+          content << "#{'#' * level} `#{object[:name]}`"
 
           if object[:description].present?
-            content += "\n#{object[:description]}"
-            content += '.' unless object[:description].ends_with?('.')
-            content += "\n"
+            desc = object[:description].strip
+            desc += '.' unless desc.ends_with?('.')
+            content << desc
           end
 
-          content
+          content.join("\n\n")
         end
 
         def sorted_by_name(objects)
@@ -46,18 +48,15 @@ module Gitlab
         end
 
         def render_field(field)
-          '| %s | %s | %s |' % [
-            render_name(field),
-            render_field_type(field[:type][:info]),
-            render_description(field)
-            ]
+          row(render_name(field), render_field_type(field[:type]), render_description(field))
         end
 
         def render_enum_value(value)
-          '| %s | %s |' % [
-            render_name(value),
-            render_description(value)
-            ]
+          row(render_name(value), render_description(value))
+        end
+
+        def row(*values)
+          "| #{values.join(' | ')} |"
         end
 
         def render_name(object)
@@ -74,27 +73,19 @@ module Gitlab
           "**Deprecated:** #{object[:deprecation_reason]}"
         end
 
-        # Some fields types are arrays of other types and are displayed
-        # on docs wrapped in square brackets, for example: [String!].
-        # This makes GitLab docs renderer thinks they are links so here
-        # we change them to be rendered as: String! => Array.
         def render_field_type(type)
-          array_type = type[/\[(.+)\]/, 1]
+          "[`#{type[:info]}`](##{type[:name].downcase})"
+        end
 
-          if array_type
-            "#{array_type} => Array"
-          else
-            type
-          end
+        def render_return_type(query)
+          "Returns #{render_field_type(query[:type])}.\n"
         end
 
         # We are ignoring connections and built in types for now,
         # they should be added when queries are generated.
         def objects
           object_types = graphql_object_types.select do |object_type|
-            !object_type[:name]["Connection"] &&
-              !object_type[:name]["Edge"] &&
-              !object_type[:name]["__"]
+            !object_type[:name]["__"]
           end
 
           object_types.each do |type|
@@ -109,7 +100,7 @@ module Gitlab
         # We ignore the built-in enum types.
         def enums
           graphql_enum_types.select do |enum_type|
-            !enum_type[:name].in?(%w(__DirectiveLocation __TypeKind))
+            !enum_type[:name].in?(%w[__DirectiveLocation __TypeKind])
           end
         end
       end

lib/gitlab/graphql/docs/templates/default.md.haml

@@ -28,6 +28,8 @@
 
 - sorted_by_name(queries).each do |query|
   = render_name_and_description(query)
+  \
+  = render_return_type(query)
   - unless query[:arguments].empty?
     ~ "#### Arguments\n"
     ~ "| Name | Type | Description |"
@@ -52,6 +54,7 @@
 - objects.each do |type|
   - unless type[:fields].empty?
     = render_name_and_description(type)
+    \
     ~ "| Field | Type | Description |"
     ~ "| ----- | ---- | ----------- |"
     - sorted_by_name(type[:fields]).each do |field|
@@ -72,8 +75,74 @@
 - enums.each do |enum|
   - unless enum[:values].empty?
     = render_name_and_description(enum)
+    \
     ~ "| Value | Description |"
     ~ "| ----- | ----------- |"
     - sorted_by_name(enum[:values]).each do |value|
       = render_enum_value(value)
     \
+
+:plain
+  ## Scalar types
+
+  Scalar values are atomic values, and do not have fields of their own.
+  Basic scalars include strings, boolean values, and numbers. This schema also
+  defines various custom scalar values, such as types for times and dates.
+
+  This schema includes custom scalar types for identifiers, with a specific type for
+  each kind of object.
+
+  For more information, read about [Scalar Types](https://graphql.org/learn/schema/#scalar-types) on `graphql.org`.
+\
+
+- graphql_scalar_types.each do |type|
+  = render_name_and_description(type)
+  \
+
+:plain
+  ## Abstract types
+
+  Abstract types (unions and interfaces) are ways the schema can represent
+  values that may be one of several concrete types.
+
+  - A [`Union`](https://graphql.org/learn/schema/#union-types) is a set of possible types.
+    The types might not have any fields in common.
+  - An [`Interface`](https://graphql.org/learn/schema/#interfaces) is a defined set of fields.
+    Types may `implement` an interface, which
+    guarantees that they have all the fields in the set. A type may implement more than
+    one interface.
+
+  See the [GraphQL documentation](https://graphql.org/learn/) for more information on using
+  abstract types.
+\
+
+:plain
+  ### Unions
+\
+
+- graphql_union_types.each do |type|
+  = render_name_and_description(type, 4)
+  \
+  One of:
+  \
+  - type[:possible_types].each do |type_name|
+    ~ "- [`#{type_name}`](##{type_name.downcase})"
+  \
+
+:plain
+  ### Interfaces
+\
+
+- graphql_interface_types.each do |type|
+  = render_name_and_description(type, 4)
+  \
+  Implementations:
+  \
+  - type[:implemented_by].each do |type_name|
+    ~ "- [`#{type_name}`](##{type_name.downcase})"
+  \
+  ~ "| Field | Type | Description |"
+  ~ "| ----- | ---- | ----------- |"
+  - sorted_by_name(type[:fields] + type[:connections]).each do |field|
+    = render_field(field)
+  \

spec/lib/gitlab/graphql/docs/renderer_spec.rb

@@ -15,10 +15,13 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
         end
       end
 
-      GraphQL::Schema.define(query: query_type)
+      GraphQL::Schema.define(
+        query: query_type,
+        resolve_type: ->(obj, ctx) { raise 'Not a real schema' }
+      )
     end
 
-    let_it_be(:template) { Rails.root.join('lib/gitlab/graphql/docs/templates/', 'default.md.haml') }
+    let_it_be(:template) { Rails.root.join('lib/gitlab/graphql/docs/templates/default.md.haml') }
     let(:field_description) { 'List of objects.' }
 
     subject(:contents) do
@@ -29,7 +32,23 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
       ).contents
     end
 
-    context 'A type with a field with a [Array] return type' do
+    describe 'headings' do
+      let(:type) { ::GraphQL::INT_TYPE }
+
+      it 'contains the expected sections' do
+        expect(contents.lines.map(&:chomp)).to include(
+          '## `Query` type',
+          '## Object types',
+          '## Enumeration types',
+          '## Scalar types',
+          '## Abstract types',
+          '### Unions',
+          '### Interfaces'
+        )
+      end
+    end
+
+    context 'when a field has a list type' do
       let(:type) do
         Class.new(Types::BaseObject) do
           graphql_name 'ArrayTest'
@@ -39,29 +58,33 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
       end
 
       specify do
+        type_name = '[String!]!'
+        inner_type = 'string'
         expectation = <<~DOC
           ### `ArrayTest`
 
           | Field | Type | Description |
           | ----- | ---- | ----------- |
-          | `foo` | String! => Array | A description. |
+          | `foo` | [`#{type_name}`](##{inner_type}) | A description. |
         DOC
 
         is_expected.to include(expectation)
       end
 
-      context 'query generation' do
+      describe 'a top level query field' do
         let(:expectation) do
           <<~DOC
             ### `foo`
 
             List of objects.
 
+            Returns [`ArrayTest`](#arraytest).
+
             #### Arguments
 
             | Name | Type | Description |
             | ---- | ---- | ----------- |
-            | `id` | ID | ID of the object. |
+            | `id` | [`ID`](#id) | ID of the object. |
           DOC
         end
 
@@ -79,7 +102,7 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
       end
     end
 
-    context 'A type with fields defined in reverse alphabetical order' do
+    describe 'when fields are not defined in alphabetical order' do
       let(:type) do
         Class.new(Types::BaseObject) do
           graphql_name 'OrderingTest'
@@ -89,49 +112,56 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
         end
       end
 
-      specify do
+      it 'lists the fields in alphabetical order' do
         expectation = <<~DOC
           ### `OrderingTest`
 
           | Field | Type | Description |
           | ----- | ---- | ----------- |
-          | `bar` | String! | A description of bar field. |
-          | `foo` | String! | A description of foo field. |
+          | `bar` | [`String!`](#string) | A description of bar field. |
+          | `foo` | [`String!`](#string) | A description of foo field. |
         DOC
 
         is_expected.to include(expectation)
       end
     end
 
-    context 'A type with a deprecated field' do
+    context 'when a field is deprecated' do
       let(:type) do
         Class.new(Types::BaseObject) do
           graphql_name 'DeprecatedTest'
 
-          field :foo, GraphQL::STRING_TYPE, null: false, deprecated: { reason: 'This is deprecated', milestone: '1.10' }, description: 'A description.'
+          field :foo,
+                type: GraphQL::STRING_TYPE,
+                null: false,
+                deprecated: { reason: 'This is deprecated', milestone: '1.10' },
+                description: 'A description.'
         end
       end
 
-      specify do
+      it 'includes the deprecation' do
         expectation = <<~DOC
           ### `DeprecatedTest`
 
           | Field | Type | Description |
           | ----- | ---- | ----------- |
-          | `foo` **{warning-solid}** | String! | **Deprecated:** This is deprecated. Deprecated in 1.10. |
+          | `foo` **{warning-solid}** | [`String!`](#string) | **Deprecated:** This is deprecated. Deprecated in 1.10. |
         DOC
 
         is_expected.to include(expectation)
       end
     end
 
-    context 'A type with an emum field' do
+    context 'when a field has an Enumeration type' do
       let(:type) do
         enum_type = Class.new(Types::BaseEnum) do
           graphql_name 'MyEnum'
 
-          value 'BAZ', description: 'A description of BAZ.'
-          value 'BAR', description: 'A description of BAR.', deprecated: { reason: 'This is deprecated', milestone: '1.10' }
+          value 'BAZ',
+                description: 'A description of BAZ.'
+          value 'BAR',
+                description: 'A description of BAR.',
+                deprecated: { reason: 'This is deprecated', milestone: '1.10' }
         end
 
         Class.new(Types::BaseObject) do
@@ -141,7 +171,7 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
         end
       end
 
-      specify do
+      it 'includes the description of the Enumeration' do
         expectation = <<~DOC
           ### `MyEnum`
 
@@ -154,5 +184,129 @@ RSpec.describe Gitlab::Graphql::Docs::Renderer do
         is_expected.to include(expectation)
       end
     end
+
+    context 'when a field has a global ID type' do
+      let(:type) do
+        Class.new(Types::BaseObject) do
+          graphql_name 'IDTest'
+          description 'A test for rendering IDs.'
+
+          field :foo, ::Types::GlobalIDType[::User], null: true, description: 'A user foo.'
+        end
+      end
+
+      it 'includes the field and the description of the ID, so we can link to it' do
+        type_section = <<~DOC
+          ### `IDTest`
+
+          A test for rendering IDs.
+
+          | Field | Type | Description |
+          | ----- | ---- | ----------- |
+          | `foo` | [`UserID`](#userid) | A user foo. |
+        DOC
+
+        id_section = <<~DOC
+          ### `UserID`
+
+          A `UserID` is a global ID. It is encoded as a string.
+
+          An example `UserID` is: `"gid://gitlab/User/1"`.
+        DOC
+
+        is_expected.to include(type_section, id_section)
+      end
+    end
+
+    context 'when there is an interface and a union' do
+      let(:type) do
+        user = Class.new(::Types::BaseObject)
+        user.graphql_name 'User'
+        user.field :user_field, ::GraphQL::STRING_TYPE, null: true
+        group = Class.new(::Types::BaseObject)
+        group.graphql_name 'Group'
+        group.field :group_field, ::GraphQL::STRING_TYPE, null: true
+
+        union = Class.new(::Types::BaseUnion)
+        union.graphql_name 'UserOrGroup'
+        union.description 'Either a user or a group.'
+        union.possible_types user, group
+
+        interface = Module.new
+        interface.include(::Types::BaseInterface)
+        interface.graphql_name 'Flying'
+        interface.description 'Something that can fly.'
+        interface.field :flight_speed, GraphQL::INT_TYPE, null: true, description: 'Speed in mph.'
+
+        african_swallow = Class.new(::Types::BaseObject)
+        african_swallow.graphql_name 'AfricanSwallow'
+        african_swallow.description 'A swallow from Africa.'
+        african_swallow.implements interface
+        interface.orphan_types african_swallow
+
+        Class.new(::Types::BaseObject) do
+          graphql_name 'AbstactTypeTest'
+          description 'A test for abstract types.'
+
+          field :foo, union, null: true, description: 'The foo.'
+          field :flying, interface, null: true, description: 'A flying thing.'
+        end
+      end
+
+      it 'lists the fields correctly, and includes descriptions of all the types' do
+        type_section = <<~DOC
+          ### `AbstactTypeTest`
+
+          A test for abstract types.
+
+          | Field | Type | Description |
+          | ----- | ---- | ----------- |
+          | `flying` | [`Flying`](#flying) | A flying thing. |
+          | `foo` | [`UserOrGroup`](#userorgroup) | The foo. |
+        DOC
+
+        union_section = <<~DOC
+          #### `UserOrGroup`
+
+          Either a user or a group.
+
+          One of:
+
+          - [`Group`](#group)
+          - [`User`](#user)
+        DOC
+
+        interface_section = <<~DOC
+          #### `Flying`
+
+          Something that can fly.
+
+          Implementations:
+
+          - [`AfricanSwallow`](#africanswallow)
+
+          | Field | Type | Description |
+          | ----- | ---- | ----------- |
+          | `flightSpeed` | [`Int`](#int) | Speed in mph. |
+        DOC
+
+        implementation_section = <<~DOC
+          ### `AfricanSwallow`
+
+          A swallow from Africa.
+
+          | Field | Type | Description |
+          | ----- | ---- | ----------- |
+          | `flightSpeed` | [`Int`](#int) | Speed in mph. |
+        DOC
+
+        is_expected.to include(
+          type_section,
+          union_section,
+          interface_section,
+          implementation_section
+        )
+      end
+    end
   end
 end