rfc: add descriptions to open dd objects

GITHUB_PR_NUMBER: 10117
GITHUB_PR_URL: #10117

PR-URL: hasura/graphql-engine-mono#10648
Co-authored-by: Karthikeyan Chinnakonda <15602904+codingkarthik@users.noreply.github.com>
GitOrigin-RevId: 2fa07eb479bb2e4dbb112dbba703a08ded87b009

rfcs/v3-descriptions.md

@@ -0,0 +1,279 @@
+
+# Introduction
+
+This RFC proposes adding support to adding descriptions to open DD objects which will ultimately show up in the description of different types of entities in the GraphQL schema.
+
+Description can be added to the following user facing types:
+
+1. Scalars
+2. Objects
+3. Models
+4. Commands
+5. Relationships
+
+Descriptions can be useful to the users of the GraphQL schema to understand a type/root field/argument better.
+
+
+## Adding a description field to the metadata object
+
+
+### `ScalarType` metadata object
+
+The scalar type can only have one type of description associated with it, i.e.
+the description of the GraphQL type.
+
+```json
+{
+  "kind": "ScalarType",
+  "version": "v1",
+  "definition": {
+    "name": "NonNegativeInt",
+    "description": "Type to represent integers that are greater than or equal to 0",
+    "graphql": {
+      "typeName": "NonNegativeInt"
+    }
+  }
+}
+```
+
+The description will show up in the GraphQL schema, as following:
+
+
+```graphql
+"""
+Type to represent integers that are greater than or equal to 0
+"""
+scalar NonNegativeInt
+```
+
+### `ObjectType` metadata object
+
+The `ObjectType` can have two kinds of descriptions:
+
+1. Description of the object type.
+2. Description of the individual fields.
+
+```json
+{
+  "kind": "ObjectType",
+  "version": "v1",
+  "definition": {
+    "name": "author",
+    "description": "Author object containing unique identifier and name.",
+    "fields": [
+      {
+        "name": "author_id",
+        "type": "CustomInt!",
+        "description": "ID to uniquely identify an author."
+      },
+      {
+        "name": "first_name",
+        "type": "String!"
+      },
+      {
+        "name": "last_name",
+        "type": "String!"
+      }
+    ],
+    "globalIdFields": [
+      "author_id"
+    ],
+    "graphql": {
+      "typeName": "Author"
+    }
+  }
+}
+```
+
+The description will show up in the GraphQL schema, as following:
+
+```graphql
+"""
+Author object containing unique identifier and name.
+"""
+type Author {
+  """
+  ID to uniquely identify an author.
+  """
+  author_id: CustomInt!,
+  first_name: String!,
+  last_name: String!
+}
+```
+
+### `Model` metadata object
+
+A model can have three diffrent types of descriptions, the number of descriptions correspond
+to the number of GraphQL APIs that are chosen to expose. At the moment of writing this
+document, two types of GraphQL APIs are supported, `select_many` and `select_one`.
+
+Models can also accept arguments and the argument fields can also accept descriptions.
+
+
+```json
+{
+  "kind": "Model",
+  "version": "v1",
+  "definition": {
+    "name": "Authors",
+    "objectType": "author",
+    "globalIdSource": true,
+    "arguments": [
+      {
+        "name": "include_inactive",
+        "type": "boolean",
+        "description": "If set to true, returns authors even if they are inactive."
+      }
+    ],
+    "graphql": {
+      "selectUniques": [
+        {
+          "queryRootField": "AuthorByID",
+          "description": "Returns at most an author identified by the given author_id, returns null if author is not found with the provided ID.",
+          "uniqueIdentifier": [
+            "author_id"
+          ]
+        }
+      ],
+      "selectMany": {
+        "queryRootField": "AuthorMany",
+        "description": "Selects multiple authors and supports filtering and pagination."
+      },
+      "filterExpressionType": "Author_Where_Exp",
+      "orderByExpressionType": "Author_Order_By",
+      "argumentsInputType": "Author_Arguments"
+    },
+    "filterableFields": [
+      "author_id"
+    ],
+    "orderableFields": [
+      "author_id"
+    ]
+  }
+}
+```
+
+The descriptions will show up in the GraphQL schema, as following:
+
+```graphql
+
+
+type Query {
+  """
+  Selects multiple authors and supports filtering and pagination.
+  """
+  AuthorMany(
+    args: Author_Arguments,
+    where: Author_Where_Exp,
+    limit: Int,
+    offset: Int,
+    order_by: Author_Order_By): [Author!]
+  """
+  Returns at most an author identified by the given author_id, returns null if author is not found with the provided ID.
+  """
+  AuthorByID(
+    author_id: Int!,
+    """If set to true, returns authors even if they are inactive."""
+    include_inactive: boolean
+    ): Author
+}
+```
+
+### `Command` metadata object
+
+Commands can have two kinds of descriptions. One is the description of the
+root field that will be exposed by the command and second is the description
+of the input arguments to the command.
+
+```json
+{
+  "kind": "Command",
+  "version": "v1",
+  "definition": {
+    "name": "get_article_by_id",
+    "description": "Command to get an article by using the ID.",
+    "arguments": [
+      {
+        "name": "article_id",
+        "type": "Int!",
+        "description": "ID of the article."
+      }
+    ],
+    "outputType": "commandArticle",
+    "graphql": {
+      "rootFieldName": "getArticleById",
+      "rootFieldKind": "Query"
+    }
+  }
+}
+```
+
+The descriptions will show up in the GraphQL schema, as following:
+
+```graphql
+type Query {
+  """
+  Command to get an article by using the ID.
+  """
+  getArticleById(
+    "ID of the article."
+    article_id: Int!
+  )
+}
+```
+
+### `Relationship` metadata object
+
+Relationships can have one kind of description. This description will become the
+GraphQL description of the relationship field.
+
+
+```json
+{
+  "kind": "Relationship",
+  "version": "v1",
+  "definition": {
+    "source": "author",
+    "name": "Articles",
+    "description": "Fetches the corresponding articles of the author.",
+    "target": {
+        "model": {
+          "name": "Articles",
+          "relationshipType": "Array"
+        }
+      },
+    "mapping": [
+      {
+        "source": {
+          "fieldPath": [
+            {
+              "fieldName": "article_id"
+            }
+          ]
+        },
+        "target": {
+          "modelField": [
+            {
+              "fieldName": "article_id"
+            }
+          ]
+        }
+      }
+    ]
+  }
+}
+
+```
+
+The descriptions will show up in the GraphQL schema, as following:
+
+```graphql
+  type author {
+    author_id: Int!,
+    article_id: Int!,
+    """
+    Fetches the corresponding articles of the author.
+    """
+    Articles: [Articles!]
+  }
+```