feat(config): allow exporting async config (#13075)

* feat(config): allow exporting async config (#13035)

module.exports can now be a function and it can be/return a Promise,
allowing the results of asynchronous operations to be used in the
configuration.

The discussion leading up to this PR in #13035 assumed that
module.exports had to be a plain object.

But this commit:

  commit 9aa97af5
  Author: Nejc Habjan <hab.nejc@gmail.com>
  Date:   Thu Dec 9 13:45:48 2021 +0100

      feat(config)!: parse JSON5/YAML self-hosted admin config (#12644)

      Adds support for alternative admin config file formats.

      BREAKING CHANGE: Renovate will now fail if RENOVATE_CONFIG_FILE is specified without a file extension

Had as an undocumented side effect, that it also handled transparenty
if module.exports was assigned a Promise. With that commit, the
promise will be await-ed so the resolved value is returned from
getConfig(). That was not the case before that commit.

So in this commit, configs that export functions are handled, and
test cases for both promises and functions have been added.

* Update lib/workers/global/config/parse/__fixtures__/fileAsyncFunction.js

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>

* Update lib/workers/global/config/parse/__fixtures__/fileFunctionPromise.js

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>

* feat(config): Fixed linter problems (#13035)

* feat(config)!: Add doc for JSON5/YAML self-hosted admin config (#12644)

The code was introduced in 9aa97af5 and here is the documentation to
go with it

* feat(config): Document config.js exports (#13035)

* feat(config): Rename file*.js to config*.js because they really are config (#13035)

* Update docs/usage/getting-started/running.md

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>

* Update docs/usage/getting-started/running.md

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>
Co-authored-by: Michael Kriese <michael.kriese@visualon.de>

docs/usage/getting-started/running.md

@@ -92,7 +92,7 @@ WhiteSource Renovate On-Premises and WhiteSource Remediate both run as long-live
 
 ### Global config
 
-Renovate's server-side/admin config is referred to as its "global" config, and can be specified using either a config file (`config.js` or `config.json`), environment variables, or CLI parameters.
+Renovate's server-side/admin config is referred to as its "global" config, and can be specified using either a config file (`config.js`, `config.json`, `config.json5`, `config.yaml` or `config.yml`), environment variables, or CLI parameters.
 
 Some config is global-only, meaning that either it is only applicable to the bot administrator or it can only be controlled by the administrator and not repository users.
 Those are documented in [Self-hosted Configuration](../self-hosted-configuration.md).
@@ -108,6 +108,21 @@ If you combine both of the above then any single config option in the environmen
 
 Note: it's also possible to change the default prefix from `RENOVATE_` using `ENV_PREFIX`. e.g. `ENV_PREFIX=RNV_ RNV_TOKEN=abc123 renovate`.
 
+#### Using `config.js`
+
+If you use a `config.js`, it will be expected to export a configuration via `module.exports`.
+The value can be either a plain JavaScript object like in this example where `config.js` exports a plain object:
+
+```javascript
+module.exports = {
+  token: 'abcdefg',
+};
+```
+
+`config.js` may also export a `Promise` of such an object, or a function that will return either a plain Javascript object or a `Promise` of such an object.
+This allows one to include the results of asynchronous operations in the exported value.
+An example of a `config.js` that exports an async function (which is a function that returns a `Promise`) can be seen in a comment for [#10011: Allow autodiscover filtering for repo topic](https://github.com/renovatebot/renovate/issues/10011#issuecomment-992568583) and more examples can be seen in [`file.spec.ts`](https://github.com/renovatebot/renovate/blob/main/lib/workers/global/config/parse/file.spec.ts).
+
 ### Authentication
 
 Regardless of platform, you need to select a user account for `renovate` to assume the identity of, and generate a Personal Access Token.

lib/workers/global/config/parse/__fixtures__/config-async-function.js

+// This is functionally equivalent to config-function-promise.js but syntactically different
+
+// @ts-ignore
+module.exports = async function () {
+  return {
+        token: 'abcdefg',
+  }
+};

lib/workers/global/config/parse/__fixtures__/config-function-promise.js

+// This is functionally equivalent to config-async-function.js but syntactically different
+
+// @ts-ignore
+module.exports = function () {
+  return new Promise(resolve => {
+    resolve({
+          token: 'abcdefg',
+    })
+  });
+};

lib/workers/global/config/parse/__fixtures__/config-function.js

+// @ts-ignore
+module.exports = function () {
+  return {
+        token: 'abcdefg',
+  }
+};

lib/workers/global/config/parse/__fixtures__/config-promise.js

+// @ts-ignore
+module.exports = new Promise( resolve => {
+  resolve(
+    {
+      token: 'abcdefg',
+    }
+  );
+});

lib/workers/global/config/parse/file.spec.ts

@@ -2,7 +2,7 @@ import fs from 'fs';
 import { DirectoryResult, dir } from 'tmp-promise';
 import upath from 'upath';
 import { logger } from '../../../../logger';
-import customConfig from './__fixtures__/file';
+import customConfig from './__fixtures__/config';
 import * as file from './file';
 
 describe('workers/global/config/parse/file', () => {
@@ -18,7 +18,18 @@ describe('workers/global/config/parse/file', () => {
 
   describe('.getConfig()', () => {
     it.each([
-      ['custom config file with extension', 'file.js'],
+      ['custom js config file', 'config.js'],
+      ['custom js config file exporting a Promise', 'config-promise.js'],
+      ['custom js config file exporting a function', 'config-function.js'],
+      // The next two are different syntactic ways of expressing the same thing
+      [
+        'custom js config file exporting a function returning a Promise',
+        'config-function-promise.js',
+      ],
+      [
+        'custom js config file exporting an async function',
+        'config-async-function.js',
+      ],
       ['JSON5 config file', 'config.json5'],
       ['YAML config file', 'config.yaml'],
     ])('parses %s', async (fileType, filePath) => {
@@ -29,7 +40,7 @@ describe('workers/global/config/parse/file', () => {
     });
 
     it('migrates', async () => {
-      const configFile = upath.resolve(__dirname, './__fixtures__/file2.js');
+      const configFile = upath.resolve(__dirname, './__fixtures__/config2.js');
       const res = await file.getConfig({ RENOVATE_CONFIG_FILE: configFile });
       expect(res).toMatchSnapshot();
       expect(res.rangeStrategy).toBe('bump');

lib/workers/global/config/parse/file.ts

+import is from 'is';
 import { load } from 'js-yaml';
 import JSON5 from 'json5';
 import upath from 'upath';
@@ -18,7 +19,12 @@ export async function getParsedContent(file: string): Promise<RenovateConfig> {
       return JSON5.parse(await readFile(file, 'utf8'));
     case '.js': {
       const tmpConfig = await import(file);
-      return tmpConfig.default ? tmpConfig.default : tmpConfig;
+      let config = tmpConfig.default ? tmpConfig.default : tmpConfig;
+      // Allow the config to be a function
+      if (is.fn(config)) {
+        config = config();
+      }
+      return config;
     }
     default:
       throw new Error('Unsupported file type');