Use APPSIGNAL_ACTIVE environment value

Before this change, the value of the `APPSIGNAL_ACTIVE` environment
variable would never be read, as the `active` config option was
read directly from the `BaseClient` constructor. After this change,
the option is read from the `Config` object, after it has been
initialised in the constructor.

Fixes #546.

packages/nodejs/.changesets/use-appsignal_active-environment-variable.md

@@ -0,0 +1,6 @@
+---
+bump: "patch"
+type: "fix"
+---
+
+Use the APPSIGNAL_ACTIVE environment variable to determine whether AppSignal is active.

packages/nodejs/src/__tests__/config.test.ts

@@ -13,6 +13,7 @@ describe("Configuration", () => {
   let initialEnv: { [key: string]: any }
 
   const expectedDefaultConfig = {
+    active: false,
     caFilePath: path.join(__dirname, "../../cert/cacert.pem"),
     debug: false,
     dnsServers: [],

packages/nodejs/src/client.ts

@@ -43,12 +43,12 @@ export class BaseClient implements Client {
    * Creates a new instance of the `Appsignal` object
    */
   constructor(options: Partial<AppsignalOptions> = {}) {
-    const {
-      active = false, // Agent is not started by default
-      ignoreInstrumentation
-    } = options
+    const { ignoreInstrumentation } = options
 
     this.config = new Configuration(options)
+
+    const active = this.config.data.active!
+
     this.extension = new Extension({ active })
 
     this.storeInGlobal()

packages/nodejs/src/config.ts

@@ -113,6 +113,7 @@ export class Configuration {
    */
   private _defaultValues(): { [key: string]: any } {
     return {
+      active: false,
       caFilePath: path.join(__dirname, "../cert/cacert.pem"),
       debug: false,
       dnsServers: [],