config: Properly type the change events from config module

Change-type: patch
Signed-off-by: Cameron Diver <cameron@balena.io>

package.json

@@ -91,6 +91,7 @@
     "rimraf": "^2.6.2",
     "rwlock": "^5.0.0",
     "shell-quote": "^1.6.1",
+    "strict-event-emitter-types": "^2.0.0",
     "ts-loader": "^5.3.0",
     "typed-error": "^2.0.0",
     "typescript": "^3.2.2",

src/config/index.ts

@@ -3,6 +3,7 @@ import { EventEmitter } from 'events';
 import { Transaction } from 'knex';
 import * as _ from 'lodash';
 import { generateUniqueKey } from 'resin-register-device';
+import StrictEventEmitter from 'strict-event-emitter-types';
 
 import { Either } from 'fp-ts/lib/Either';
 import * as t from 'io-ts';
@@ -25,8 +26,19 @@ interface ConfigOpts {
 }
 
 type ConfigMap<T extends SchemaTypeKey> = { [key in T]: SchemaReturn<key> };
+type ConfigChangeMap<T extends SchemaTypeKey> = {
+	[key in T]: SchemaReturn<key> | undefined
+};
 
-export class Config extends EventEmitter {
+interface ConfigEvents {
+	change: ConfigChangeMap<SchemaTypeKey>;
+}
+
+type ConfigEventEmitter = StrictEventEmitter<EventEmitter, ConfigEvents>;
+
+export class Config extends (EventEmitter as {
+	new (): ConfigEventEmitter;
+}) {
 	private db: DB;
 	private configJsonBackend: ConfigJsonConfigBackend;
 
@@ -173,7 +185,7 @@ export class Config extends EventEmitter {
 					.return();
 			}
 		}).then(() => {
-			this.emit('change', keyValues);
+			this.emit('change', keyValues as ConfigMap<SchemaTypeKey>);
 		});
 	}
 

src/local-mode.ts

@@ -3,7 +3,6 @@ import * as Docker from 'dockerode';
 import * as _ from 'lodash';
 
 import Config from './config';
-import { SchemaReturn, SchemaTypeKey } from './config/schema-type';
 import Database from './db';
 import { Logger } from './logger';
 
@@ -25,23 +24,20 @@ export class LocalModeManager {
 
 	public async init() {
 		// Setup a listener to catch state changes relating to local mode
-		this.config.on(
-			'change',
-			(changed: { [key in SchemaTypeKey]: SchemaReturn<key> }) => {
-				if (changed.localMode != null) {
-					const localMode = changed.localMode || false;
+		this.config.on('change', changed => {
+			if (changed.localMode != null) {
+				const localMode = changed.localMode || false;
 
-					// First switch the logger to it's correct state
-					this.logger.switchBackend(localMode);
+				// First switch the logger to it's correct state
+				this.logger.switchBackend(localMode);
 
-					// If we're leaving local mode, make sure to remove all of the
-					// leftover artifacts
-					if (!localMode) {
-						this.removeLocalModeArtifacts();
-					}
+				// If we're leaving local mode, make sure to remove all of the
+				// leftover artifacts
+				if (!localMode) {
+					this.removeLocalModeArtifacts();
 				}
-			},
-		);
+			}
+		});
 
 		// On startup, check if we're in unmanaged mode,
 		// as local mode needs to be set

src/supervisor-api.ts

@@ -4,7 +4,6 @@ import * as _ from 'lodash';
 import * as morgan from 'morgan';
 
 import Config from './config';
-import { SchemaReturn, SchemaTypeKey } from './config/schema-type';
 import { EventTracker } from './event-tracker';
 import blink = require('./lib/blink');
 import * as iptables from './lib/iptables';
@@ -147,18 +146,15 @@ export class SupervisorAPI {
 
 		// Monitor the switching of local mode, and change which interfaces will
 		// be listened to based on that
-		this.config.on(
-			'change',
-			(changedConfig: { [key in SchemaTypeKey]: SchemaReturn<key> }) => {
-				if (changedConfig.localMode != null) {
-					this.applyListeningRules(
-						changedConfig.localMode || false,
-						port,
-						allowedInterfaces,
-					);
-				}
-			},
-		);
+		this.config.on('change', changedConfig => {
+			if (changedConfig.localMode != null) {
+				this.applyListeningRules(
+					changedConfig.localMode || false,
+					port,
+					allowedInterfaces,
+				);
+			}
+		});
 
 		this.server = this.api.listen(port);
 		this.server.timeout = apiTimeout;