feat: pull the release version from package.json

This makes our calculation of system version a lot more solid. This is
going to be required for OpenTelemetry metrics, because any metric sent
without a version will end up in the Dead Letter metrics. Because of
this I want to give users of Reliability Kit more of a guarantee that
their metrics will arrive.

Author: rowanmanning

packages/app-info/lib/index.js

@@ -6,42 +6,28 @@ const path = require('node:path');
 //   - Heroku: https://devcenter.heroku.com/articles/dyno-metadata
 //   - Lambda: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
 
-/**
- * Get the application system code from a package.json file.
- *
- * @param {string} directoryPath
- *     The directory to look for a package.json file in.
- * @returns {(string | null)}
- *     Returns a system code if one is found in `process.env`.
- */
-function getSystemCodeFromPackage(directoryPath) {
-	try {
-		const manifest = require(path.join(directoryPath, 'package.json'));
-		return typeof manifest?.name === 'string'
-			? normalizePackageName(manifest.name)
-			: null;
-	} catch (error) {}
-	return null;
-}
-
-/**
- * Normalize the name property of a package.json file.
- *
- * @param {string} name
- *     The name to normalize.
- * @returns {string}
- *     Returns a normalized copy of the package name.
- */
-function normalizePackageName(name) {
-	// Remove a prefix of "ft-", this is a hangover and we have plenty of
-	// apps which use this prefix but their system code does not include
-	// it. E.g. MyFT API has a system code of "next-myft-api", but a
-	// package.json `name` field of "ft-next-myft-api"
-	//    - https://biz-ops.in.ft.com/System/next-myft-api
-	//    - https://github.com/Financial-Times/next-myft-api/blob/main/package.json
-	//
-	return name.replace(/^ft-/, '');
-}
+/** @type {null | any} */
+let manifest = null;
+try {
+	manifest = require(path.join(process.cwd(), 'package.json'));
+} catch (error) {}
+
+/** @type {string | null} */
+const manifestName =
+	typeof manifest?.name === 'string'
+		? // Remove a prefix of "ft-", this is a hangover and we have plenty of
+			// apps which use this prefix but their system code does not include
+			// it. E.g. MyFT API has a system code of "next-myft-api", but a
+			// package.json `name` field of "ft-next-myft-api"
+			//    - https://biz-ops.in.ft.com/System/next-myft-api
+			//    - https://github.com/Financial-Times/next-myft-api/blob/main/package.json
+			//
+			manifest.name.replace(/^ft-/, '')
+		: null;
+
+/** @type {string | null} */
+const manifestVersion =
+	typeof manifest?.version === 'string' ? manifest.version : null;
 
 /**
  * Extract the process type from a Heroku dyno name.
@@ -55,9 +41,6 @@ function normalizeHerokuProcessType(dyno) {
 	return dyno.split('.')[0];
 }
 
-const systemCode =
-	process.env.SYSTEM_CODE || getSystemCodeFromPackage(process.cwd()) || null;
-
 const processType =
 	process.env.AWS_LAMBDA_FUNCTION_NAME ||
 	(process.env.DYNO && normalizeHerokuProcessType(process.env.DYNO)) ||
@@ -124,15 +107,15 @@ exports.releaseDate = process.env.HEROKU_RELEASE_CREATED_AT || null;
 exports.releaseVersion =
 	process.env.HEROKU_RELEASE_VERSION ||
 	process.env.AWS_LAMBDA_FUNCTION_VERSION ||
-	null;
+	manifestVersion;
 
 /**
  * The application system code.
  *
  * @readonly
  * @type {string | null}
  */
-exports.systemCode = systemCode;
+exports.systemCode = process.env.SYSTEM_CODE || manifestName;
 
 /**
  * The dyno process type.

packages/app-info/test/unit/lib/index.spec.js

@@ -155,15 +155,60 @@ describe('@dotcom-reliability-kit/app-info', () => {
 			});
 		});
 
-		describe('when neither environment variable is defined', () => {
+		describe('when neither environment variable is defined but a package.json exists', () => {
 			beforeEach(() => {
 				jest.resetModules();
+				jest.mock(
+					'/mock-cwd/package.json',
+					() => ({ version: 'mock-package-version' }),
+					{ virtual: true }
+				);
+				delete process.env.HEROKU_RELEASE_VERSION;
 				delete process.env.AWS_LAMBDA_FUNCTION_VERSION;
+				appInfo = require('../../../lib');
+			});
+
+			it('is set to the package.json version in the current working directory', () => {
+				expect(appInfo.releaseVersion).toBe('mock-package-version');
+			});
+
+			describe('when the package.json has a non-string `version` property', () => {
+				beforeEach(() => {
+					jest.resetModules();
+					jest.mock('/mock-cwd/package.json', () => ({ version: 123 }), {
+						virtual: true
+					});
+					appInfo = require('../../../lib');
+				});
+
+				it('is set to `null`', () => {
+					expect(appInfo.releaseVersion).toBe(null);
+				});
+			});
+
+			describe('when the package.json is not an object', () => {
+				beforeEach(() => {
+					jest.resetModules();
+					jest.mock('/mock-cwd/package.json', () => null, { virtual: true });
+					appInfo = require('../../../lib');
+				});
+
+				it('is set to `null`', () => {
+					expect(appInfo.releaseVersion).toBe(null);
+				});
+			});
+		});
+
+		describe('when neither environment variable is defined and a package.json does not exist', () => {
+			beforeEach(() => {
+				jest.unmock('/mock-cwd/package.json');
+				jest.resetModules();
 				delete process.env.HEROKU_RELEASE_VERSION;
+				delete process.env.AWS_LAMBDA_FUNCTION_VERSION;
 				appInfo = require('../../../lib');
 			});
 
-			it('is set to null', () => {
+			it('is set to `null`', () => {
 				expect(appInfo.releaseVersion).toBe(null);
 			});
 		});