Extend existing example

Author: Rhys Madigan

.gitignore

@@ -4,3 +4,7 @@
 /.pids
 /.pants.workdir.file_lock*
 
+node_modules
+
+# Build output when build invoked with `npm run build`
+dist_npm

.prettierrc.yaml

@@ -0,0 +1,3 @@
+# Example prettier config - try changing this and running `pants fmt ::`
+# See https://prettier.io/docs/en/configuration.html for more options
+singleQuote: true

BUILD

@@ -1 +1,15 @@
-package_json(name="hello_pkg")
+package_json(
+    name="hello_pkg",
+    scripts=[
+        node_test_script(
+            coverage_args=["--coverage", "--coverage-directory=.coverage/"],
+            coverage_output_files=[".coverage/lcov-report/index.html"],
+            coverage_output_directories=[".coverage/lcov-report"],
+        ),
+        node_build_script(
+            entry_point="build",
+            extra_env_vars=["FOO=BAR"],
+            output_files=["dist_npm/index.js"],
+        ),
+    ],
+)

README.md

@@ -17,6 +17,32 @@ Try these out in this repo.
 
 ```
 pants dependencies src/index.js
+pants dependencies --transitive src/index.js
+```
+
+## Lint and format
+
+```
+pants lint ::
+pants fmt ::
+```
+
+## Test
+
+```
+pants test ::
+pants test --use-coverage ::
+```
+
+The example is configured to use Jest as the test runner via `package.json` "scripts.test" key.
+Mocha is also supported by the Javascript backend.
+
+## Package
+
+The example uses esbuild to package the source into a single file in the `dist` directory.
+
+```
+pants package ::
 ```
 
 ## Generate lockfiles

package-lock.json

@@ -1,5 +1,13 @@
 {
-    "main": "src/index.js",
-    "name": "demo",
-    "version": "0.0.1"
-}
+  "main": "src/index.js",
+  "name": "demo",
+  "version": "0.0.1",
+  "scripts": {
+    "test": "jest",
+    "build": "esbuild --bundle --platform=node --target=node12 --outdir=./dist_npm src/index.js"
+  },
+  "devDependencies": {
+    "esbuild": "^0.20.1",
+    "jest": "^29.7.0"
+  }
+}

package.json

@@ -1,5 +1,5 @@
 [GLOBAL]
-pants_version = "2.18.0"
+pants_version = "2.19.0"
 
 backend_packages.add = [
   "pants.backend.experimental.javascript",

pants.toml

@@ -1 +1,8 @@
 javascript_sources()
+
+javascript_tests(
+    name="tests",
+    # Set this so the two test files run in the same process
+    # (necessary for coverage)
+    batch_compatibility_tag="hello1",
+)

src/BUILD

@@ -1,3 +1,9 @@
-const hello = () => console.log("Hello World!");
+// Example of a transitive dep for index.js
+const dep2fn = require('./dep2.js');
+
+const hello = () => {
+  dep2fn();
+  console.log('Hello World!');
+};
 
 module.exports = hello;

src/dep.js

@@ -0,0 +1,3 @@
+const dep2fn = () => console.log('Hello from Dep2 function!');
+
+module.exports = dep2fn;

src/dep2.js

@@ -1 +1,6 @@
-const dep = require("./dep.js");
+const hello = require('./dep.js');
+const { isEven } = require('./numbers.js');
+
+if (isEven(4)) {
+  hello();
+}

src/index.js

@@ -0,0 +1,19 @@
+const { isEven } = require('./numbers.js');
+
+describe('isEven', () => {
+  test('returns true if number is even', () => {
+    expect(isEven(2)).toBe(true);
+  });
+
+  test('returns false if number is odd', () => {
+    expect(isEven(3)).toBe(false);
+  });
+
+  test('throws an error if number is negative', () => {
+    expect(() => isEven(-1)).toThrow();
+  });
+
+  test('throws an error if number is not a number', () => {
+    expect(() => isEven('1')).toThrow();
+  });
+});

src/isEven.test.js

@@ -0,0 +1,13 @@
+// Adding a separarate test file for demo purposes
+
+const { isOdd } = require('./numbers.js');
+
+describe('isOdd', () => {
+  test('returns true if number is odd', () => {
+    expect(isOdd(3)).toBe(true);
+  });
+
+  test('returns false if number is even', () => {
+    expect(isOdd(2)).toBe(false);
+  });
+});

src/isOdd.test.js

@@ -0,0 +1,11 @@
+function isEven(number) {
+  if (number < 0) throw new Error('Number must be positive');
+  if (typeof number !== 'number') throw new Error('Number must be a number');
+  return number % 2 === 0;
+}
+
+function isOdd(number) {
+  return !isEven(number);
+}
+
+module.exports = { isEven, isOdd };