[perf] Return Promise types

lib/modules/perf/HttpMetric.js

@@ -16,7 +16,7 @@ export default class HttpMetric {
     this.httpMethod = httpMethod;
   }
 
-  getAttribute(attribute: string): Promise<string> {
+  getAttribute(attribute: string): Promise<string | null> {
     return getNativeModule(this._perf).getHttpMetricAttribute(
       this.url,
       this.httpMethod,
@@ -31,7 +31,8 @@ export default class HttpMetric {
     );
   }
 
-  putAttribute(attribute: string, value: string): Promise<null> {
+  // TODO return true or false
+  putAttribute(attribute: string, value: string): Promise<true | false> {
     return getNativeModule(this._perf).putHttpMetricAttribute(
       this.url,
       this.httpMethod,

lib/modules/perf/Trace.js

@@ -14,7 +14,7 @@ export default class Trace {
     this.identifier = identifier;
   }
 
-  getAttribute(attribute: string): Promise<string> {
+  getAttribute(attribute: string): Promise<string | null> {
     return getNativeModule(this._perf).getTraceAttribute(
       this.identifier,
       attribute
@@ -40,7 +40,8 @@ export default class Trace {
     );
   }
 
-  putAttribute(attribute: string, value: string): Promise<null> {
+  // TODO return true or false
+  putAttribute(attribute: string, value: string): Promise<true | false> {
     return getNativeModule(this._perf).putTraceAttribute(
       this.identifier,
       attribute,

lib/modules/perf/index.js

@@ -12,6 +12,29 @@ import type App from '../core/app';
 export const MODULE_NAME = 'RNFirebasePerformance';
 export const NAMESPACE = 'perf';
 
+const HTTP_METHODS = {
+  CONNECT: true,
+  DELETE: true,
+  GET: true,
+  HEAD: true,
+  OPTIONS: true,
+  PATCH: true,
+  POST: true,
+  PUT: true,
+  TRACE: true,
+};
+
+type HttpMethod =
+  | 'CONNECT'
+  | 'DELETE'
+  | 'GET'
+  | 'HEAD'
+  | 'OPTIONS'
+  | 'PATCH'
+  | 'POST'
+  | 'PUT'
+  | 'TRACE';
+
 export default class PerformanceMonitoring extends ModuleBase {
   constructor(app: App) {
     super(app, {
@@ -49,13 +72,27 @@ export default class PerformanceMonitoring extends ModuleBase {
     return new Trace(this, trace);
   }
 
-  newHttpMetric(url: string, httpMethod: string) {
+  /**
+   * Return a new HttpMetric instance
+   * @param url
+   * @param httpMethod
+   * @returns {HttpMetric}
+   */
+  newHttpMetric(url: string, httpMethod: HttpMethod): HttpMetric {
     if (typeof url !== 'string' || typeof httpMethod !== 'string') {
       throw new Error(
         'firebase.perf().newHttpMetric() requires url and httpMethod string values'
       );
     }
 
+    if (!HTTP_METHODS[httpMethod]) {
+      throw new Error(
+        `firebase.perf().newHttpMetric() httpMethod should be one of ${Object.keys(
+          HTTP_METHODS
+        ).join(', ')}`
+      );
+    }
+
     return new HttpMetric(this, url, httpMethod);
   }
 }