Ensure all environment variables are transformed

Ensure that the keys of `ENV_TO_KEY_MAPPING` (the known environment
variables that need to be transformed) all have one, and only one,
declared transformation mechanism (as `BOOL_KEYS`, `STRING_KEYS`, ...)

Use type hints to ensure the members of these lists are valid keys of
`ENV_TO_KEY_MAPPING` -- this is not quite the same assertion as the
tests, but provides immediate feedback when making a typo.

Author: unflxw

src/__tests__/config.test.ts

@@ -3,6 +3,14 @@ import fs from "fs"
 
 import { VERSION } from "../version"
 import { Configuration } from "../config"
+import {
+  ENV_TO_KEY_MAPPING,
+  BOOL_KEYS,
+  FLOAT_KEYS,
+  LIST_KEYS,
+  LIST_OR_BOOL_KEYS,
+  STRING_KEYS
+} from "../config/configmap"
 
 describe("Configuration", () => {
   const name = "TEST APP"
@@ -73,6 +81,22 @@ describe("Configuration", () => {
     resetEnv()
   })
 
+  it("knows how to transform all environment variables into options", () => {
+    const allKeys = Object.keys(ENV_TO_KEY_MAPPING).sort()
+
+    const allKeyTransformations = [
+      BOOL_KEYS,
+      STRING_KEYS,
+      LIST_KEYS,
+      LIST_OR_BOOL_KEYS,
+      FLOAT_KEYS
+    ]
+      .flat()
+      .sort()
+
+    expect(allKeys).toEqual(allKeyTransformations)
+  })
+
   describe("with only default options", () => {
     it("loads all default options", () => {
       config = new Configuration({})

src/config/configmap.ts

@@ -1,6 +1,6 @@
 import type { AppsignalOptions } from "./options"
 
-export const ENV_TO_KEY_MAPPING: Record<string, keyof AppsignalOptions> = {
+export const ENV_TO_KEY_MAPPING = {
   APPSIGNAL_ACTIVE: "active",
   APPSIGNAL_APP_ENV: "environment",
   APPSIGNAL_APP_NAME: "name",
@@ -39,7 +39,7 @@ export const ENV_TO_KEY_MAPPING: Record<string, keyof AppsignalOptions> = {
   APPSIGNAL_STATSD_PORT: "statsdPort",
   APPSIGNAL_WORKING_DIRECTORY_PATH: "workingDirectoryPath",
   APP_REVISION: "revision"
-}
+} satisfies Record<string, keyof AppsignalOptions>
 
 export const PRIVATE_ENV_MAPPING: Record<string, keyof AppsignalOptions> = {
   _APPSIGNAL_ACTIVE: "active",
@@ -118,7 +118,7 @@ export const JS_TO_RUBY_MAPPING: Record<keyof AppsignalOptions, string> = {
   workingDirectoryPath: "working_directory_path"
 }
 
-export const BOOL_KEYS: string[] = [
+export const BOOL_KEYS: (keyof typeof ENV_TO_KEY_MAPPING)[] = [
   "APPSIGNAL_ACTIVE",
   "APPSIGNAL_ENABLE_HOST_METRICS",
   "APPSIGNAL_ENABLE_OPENTELEMETRY_HTTP",
@@ -132,7 +132,7 @@ export const BOOL_KEYS: string[] = [
   "APPSIGNAL_SEND_SESSION_DATA"
 ]
 
-export const STRING_KEYS: string[] = [
+export const STRING_KEYS: (keyof typeof ENV_TO_KEY_MAPPING)[] = [
   "APPSIGNAL_APP_ENV",
   "APPSIGNAL_APP_NAME",
   "APPSIGNAL_BIND_ADDRESS",
@@ -153,7 +153,7 @@ export const STRING_KEYS: string[] = [
   "APP_REVISION"
 ]
 
-export const LIST_KEYS: string[] = [
+export const LIST_KEYS: (keyof typeof ENV_TO_KEY_MAPPING)[] = [
   "APPSIGNAL_DNS_SERVERS",
   "APPSIGNAL_FILTER_PARAMETERS",
   "APPSIGNAL_FILTER_SESSION_DATA",
@@ -163,8 +163,10 @@ export const LIST_KEYS: string[] = [
   "APPSIGNAL_REQUEST_HEADERS"
 ]
 
-export const LIST_OR_BOOL_KEYS: string[] = [
+export const LIST_OR_BOOL_KEYS: (keyof typeof ENV_TO_KEY_MAPPING)[] = [
   "APPSIGNAL_DISABLE_DEFAULT_INSTRUMENTATIONS"
 ]
 
-export const FLOAT_KEYS: string[] = ["APPSIGNAL_CPU_COUNT"]
+export const FLOAT_KEYS: (keyof typeof ENV_TO_KEY_MAPPING)[] = [
+  "APPSIGNAL_CPU_COUNT"
+]