[IMPROVE] Missing addCustomField method in MessageBuilder (#363)

* Add custom fields to messageBuilder

* Add tests to the addCustomField method and catch error when key contains a period

src/definition/accessors/IMessageBuilder.ts

@@ -221,4 +221,14 @@ export interface IMessageBuilder {
      * Gets the block collection of the message
      */
     getBlocks(): Array<IBlock>;
+
+    /**
+     * Adds a custom field to the message.
+     * Note: This key can not already exist or it will throw an error.
+     * Note: The key must not contain a period in it, an error will be thrown.
+     *
+     * @param key the name of the custom field
+     * @param value the value of this custom field
+     */
+    addCustomField(key: string, value: any): IMessageBuilder;
 }

src/server/accessors/MessageBuilder.ts

@@ -200,4 +200,21 @@ export class MessageBuilder implements IMessageBuilder {
     public getBlocks() {
         return this.msg.blocks;
     }
+
+    public addCustomField(key: string, value: any): IMessageBuilder {
+        if (!this.msg.customFields) {
+            this.msg.customFields = {};
+        }
+
+        if (this.msg.customFields[key]) {
+            throw new Error(`The message already contains a custom field by the key: ${ key }`);
+        }
+
+        if (key.includes('.')) {
+            throw new Error(`The given key contains a period, which is not allowed. Key: ${ key }`);
+        }
+
+        this.msg.customFields[key] = value;
+        return this;
+    }
 }

tests/server/accessors/MessageBuilder.spec.ts

@@ -115,5 +115,11 @@ export class MessageBuilderAccessorTestFixture {
         Expect(mb.setParseUrls(false)).toBe(mb);
         Expect(msg.parseUrls).toEqual(false);
         Expect(mb.getParseUrls()).toEqual(false);
+
+        Expect(mb.addCustomField('thing', 'value')).toBe(mb);
+        Expect(msg.customFields).toBeDefined();
+        Expect(msg.customFields.thing).toBe('value');
+        Expect(() => mb.addCustomField('thing', 'second')).toThrowError(Error, 'The message already contains a custom field by the key: thing');
+        Expect(() => mb.addCustomField('thing.', 'second')).toThrowError(Error, 'The given key contains a period, which is not allowed. Key: thing.');
     }
 }