Add Mutation Support in GraphQL Services

[ThisaruGuruge]

Purpose

With this PR, the Ballerina GraphQL services can support mutation operations. Mutations are supported through remote functions.

Fixes: #1492

Examples

Consider the following service:

import ballerina/graphql;

service /graphql on new graphql:Listener(9000) {
    private Person p;

    function init() {
        Address a =  { number: 308, street: "Negra Arroyo Lane", city: "Albuquerque" };
        self.p = new(1, "Walter White", 51, a);
    }

    resource function get person() returns Person {
        return self.p;
    }

    remote function updateName(string name) returns Person {
        self.p.setName(name);
        return self.p;
    }

    remote function updateAge(int age) returns Person {
        self.p.setAge(age);
        return self.p;
    }

    remote function updateCity(string city) return Person {
        self.p.updateCity(city);
        return self.p;
    }
}

public distinct service class Person {
    private final int id;
    private string name;
    private int age;
    private Address address;

    public function init(int id, string name, int age, Address address) {
        self.id = id;
        self.name = name;
        self.age = age;
        self.address = address;
    }

   resource function get id() returns int {
        return self.id;
    }

   resource function get name() returns string {
        return self.name;
    }

   function setName(string name) {
        self.name = name;
    }

    isolated resource function get subject() returns string {
        return self.subject;
    }

   resource function get address() returns Address {
        return self.address;
    }

    remote function updateCity(string city) {
        self.address.city = city;
    }

   function setAge(int age) {
        self.age = age;
    }
}

public type Address record {|
    int number;
    string street;
    string city;
|};

This generates the following schema:

type Query {
    person: Person!
}

type Mutation {
    updateName(name: String!): Person!
    updateAge(age: Int!): Person!
    updateCity(city: String!): Person!
}

type Person {
    id: Int!
    name: String!
    age: Int!
    address: Address!
}

type Address {
    number: Int!
   street: String!
    city: String!
}

This can be queried using the following document:

mutation {
    updateName(name: "Mr. Lambert") {
        name
        address {
            city
        }
    }

    updateCity(city: "New Hampshire") {
        name
        address {
            city
        }
    }
}

The result will be:

{
  "data": {
    "updateName": {
      "name": "Mr. Lambert",
      "address": {
        "city": "Albuquerque"
      }
    },
    "updateCity": {
      "name": "Mr. Lambert",
      "address": {
        "city": "New Hampshire"
      }
    }
  }
}

Note the fields are updated sequentially. The first mutation field changes the name, and the second field changes the city. These two operations are executed sequentially to avoid race conditions.

Checklist

• Linked to an issue
• Updated the changelog
• Added tests

[codecov]

Codecov Report

Merging #360 (4a1f6fa) into master (6e5b481) will increase coverage by 0.17%.
The diff coverage is 95.78%.

@@             Coverage Diff              @@
##             master     #360      +/-   ##
============================================
+ Coverage     93.76%   93.94%   +0.17%     
- Complexity      230      246      +16     
============================================
  Files            48       48              
  Lines          2326     2394      +68     
  Branches       1066     1082      +16     
============================================
+ Hits           2181     2249      +68     
+ Misses          131      130       -1     
- Partials         14       15       +1     

Impacted Files	Coverage Δ
ballerina/validator_visitor.bal	93.57% <92.85%> (+0.75%)	⬆️
...ina/stdlib/graphql/runtime/schema/FieldFinder.java	98.69% <94.73%> (+0.14%)	⬆️
...allerina/stdlib/graphql/runtime/engine/Engine.java	95.18% <95.23%> (-1.38%)	⬇️
ballerina/engine_utils.bal	100.00% <100.00%> (ø)
ballerina/executor_visitor.bal	90.00% <100.00%> (+0.81%)	⬆️
ballerina/listener_utils.bal	95.55% <100.00%> (+1.43%)	⬆️
...ina/stdlib/graphql/runtime/engine/EngineUtils.java	95.71% <100.00%> (+0.25%)	⬆️
...dlib/graphql/runtime/engine/ResponseGenerator.java	97.11% <100.00%> (ø)
.../graphql/runtime/schema/SchemaRecordGenerator.java	100.00% <100.00%> (ø)
...rina/stdlib/graphql/runtime/schema/TypeFinder.java	95.55% <100.00%> (+0.61%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6e5b481...4a1f6fa. Read the comment docs.