update config to support default definition function

CHANGELOG.md

@@ -8,7 +8,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 Please see [CONTRIBUTING.md](./CONTRIBUTING.md) on how to contribute to Cucumber.
 
 ## [Unreleased]
+### Added
 - Add error message for pending steps ([#2392](https://github.com/cucumber/cucumber-js/pull/2393))
+- Updated profiles to allow defining a default function profile to be used as profile builder ([#2384](https://github.com/cucumber/cucumber-js/pull/2384))
 
 ## [10.4.0] - 2024-04-07
 ### Added

docs/profiles.md

@@ -14,7 +14,12 @@ The short tag is `-p`
 cucumber-js -p my_profile
 ```
 
-## Simple Example
+## Default profiles
+If defined, a `default` profile is used in case no profiles are specified at runtime. A default profile is either a profile or a function that returns either a profiles object or a `Promise` of profiles object. If defined this way, no other profile shall be defined.
+
+## Examples
+
+### Simple Example
 
 Let's take the common case of having some things a bit different locally than on a continuous integration server. Here's the configuration we've been running locally:
 
@@ -67,6 +72,62 @@ Now, if we just run `cucumber-js` with no arguments, it will pick up our profile
 cucumber-js -p ci
 ```
 
+### Example using a default function
+
+```javascript
+module.exports = {
+  default: function buildProfiles() {
+    const common = {
+      requireModule: ['ts-node/register'],
+      require: ['support/**/*.ts'],
+      worldParameters: {
+        appUrl: process.env.MY_APP_URL || 'http://localhost:3000/'
+      }
+    }
+
+    return {
+      default: {
+        ...common,
+        format: ['progress-bar', 'html:cucumber-report.html'],
+      },
+      ci: {
+        ...common,
+        format: ['html:cucumber-report.html'],
+        publish: true
+      }
+    }
+  }
+}
+```
+
+or its `esm` version:
+
+```javascript
+export default function buildProfiles() {
+  const common = {
+    requireModule: ['ts-node/register'],
+    require: ['support/**/*.ts'],
+    worldParameters: {
+      appUrl: process.env.MY_APP_URL || 'http://localhost:3000/'
+    }
+  }
+
+  return {
+    default: {
+      ...common,
+      format: ['progress-bar', 'html:cucumber-report.html'],
+    },
+    ci: {
+      ...common,
+      format: ['html:cucumber-report.html'],
+      publish: true
+    }
+  }
+}
+```
+
+This way the `buildProfiles` function will be invoked to discover profiles.
+
 ## Using Profiles for Arguments
 
 Cucumber doesn't allow custom command line arguments. For example:

features/profiles.feature

@@ -95,6 +95,25 @@ Feature: default command line arguments
       | -c       |
       | --config |
 
+  Scenario Outline: specifying a esm configuration file with default function profile
+    Given a file named ".cucumber-rc.mjs" with:
+      """
+      export default function buildProfiles() {
+        return {
+          default: '--dry-run'
+        }
+      }
+      """
+    When I run cucumber-js with `-c .cucumber-rc.mjs`
+    Then it outputs the text:
+      """
+      -
+
+      1 scenario (1 skipped)
+      1 step (1 skipped)
+      <duration-stat>
+      """
+
   Scenario: specifying a configuration file that doesn't exist
     When I run cucumber-js with `--config doesntexist.js`
     Then it fails

src/configuration/from_file.ts

@@ -15,15 +15,28 @@ export async function fromFile(
   file: string,
   profiles: string[] = []
 ): Promise<Partial<IConfiguration>> {
-  const definitions = await loadFile(logger, cwd, file)
-  if (!definitions.default) {
+  let definitions = await loadFile(logger, cwd, file)
+
+  const defaultDefinition: unknown = definitions.default
+
+  if (defaultDefinition) {
+    if (typeof defaultDefinition === 'function') {
+      logger.debug('Default function found; loading profiles')
+      definitions = await handleDefaultFunctionDefinition(
+        definitions,
+        defaultDefinition
+      )
+    }
+  } else {
     logger.debug('No default profile defined in configuration file')
     definitions.default = {}
   }
+
   if (profiles.length < 1) {
     logger.debug('No profiles specified; using default profile')
     profiles = ['default']
   }
+
   const definedKeys = Object.keys(definitions)
   profiles.forEach((profileKey) => {
     if (!definedKeys.includes(profileKey)) {
@@ -42,6 +55,24 @@ export async function fromFile(
   )
 }
 
+async function handleDefaultFunctionDefinition(
+  definitions: Record<string, any>,
+  defaultDefinition: Function
+): Promise<Record<string, any>> {
+  if (Object.keys(definitions).length > 1) {
+    throw new Error(
+      'Invalid profiles specified: if a default function definition is provided, no other static profiles should be specified'
+    )
+  }
+
+  const definitionsFromDefault = await defaultDefinition()
+
+  return {
+    default: {},
+    ...definitionsFromDefault,
+  }
+}
+
 async function loadFile(
   logger: ILogger,
   cwd: string,

src/configuration/from_file_spec.ts

@@ -98,6 +98,46 @@ describe('fromFile', () => {
       expect(result).to.deep.eq({ paths: ['other/path/*.feature'] })
     })
 
+    it('should work with .mjs with default function', async () => {
+      const { logger, cwd } = await setup(
+        'cucumber.mjs',
+        `export default async function() { 
+          return {
+            default: { paths: ['default/path/*.feature'] },
+            p1: { paths: ['p1/path/*.feature'] }
+          };
+        };`
+      )
+
+      const defaultResult = await fromFile(logger, cwd, 'cucumber.mjs', [
+        'default',
+      ])
+      expect(defaultResult).to.deep.eq({ paths: ['default/path/*.feature'] })
+    })
+
+    it('should throw with .mjs with default function and additional static profiles', async () => {
+      const { logger, cwd } = await setup(
+        'cucumber.mjs',
+        `export default async function() { 
+          return {
+            default: { paths: ['default/path/*.feature'] },
+            p1: { paths: ['p1/path/*.feature'] }
+          };
+        };
+        export const p1 = { paths: ['other/p1/path/*.feature'] };
+        export const p2 = { paths: ['p2/path/*.feature'] };`
+      )
+
+      try {
+        await fromFile(logger, cwd, 'cucumber.mjs', ['default'])
+        expect.fail('should have thrown')
+      } catch (error) {
+        expect(error.message).to.eq(
+          'Invalid profiles specified: if a default function definition is provided, no other static profiles should be specified'
+        )
+      }
+    })
+
     it('should work with .cjs', async () => {
       const { logger, cwd } = await setup(
         'cucumber.cjs',