feat: support for dynamic and async rules

Author: marionebl

documentation/rules.md

@@ -1,14 +1,36 @@
 # Rules
+Rules are made up by a name and a configuration array. The configuration array contains:
+* **Level** `[0..2]`: `0` disables the rule. For `1` it will be considered a warning for `2` an error.
+* **Applicable** `always|never`: `never` inverts the rule.
+* **Value**: value to use for this rule.
+
+Rule configurations are either of type `array` residing on a key with the rule's name as key on the rules `object` or of type function returning type `array` or `Promise<array>`. This means all of the following notations are supported.
+
+**Plain array**
 ```js
   "rules": {
     "header-max-length": [0, "always", 72],
-    // name: [level, applicable, value]
   }
 ```
-Rules are made up by a name and a configuration array. The configuration array contains:
-* **Level** `[0..2]`: `0` disables the rule. For `1` it will be considered a warning for `2` an error.
-* **Applicable** `always|never`: `never` inverts the rule.
-* **Value**: value to use for this rule.
+**Function returning array**
+```js
+  "rules": {
+    "header-max-length": () => [0, "always", 72],
+  }
+```
+**Async function returning array**
+```js
+  "rules": {
+    "header-max-length": async () => [0, "always", 72],
+  }
+```
+**Function returning a promise resolving to array**
+```js
+  "rules": {
+    "header-max-length": () => Promise.resolve([0, "always", 72]),
+  }
+```
+
 
 ### Available rules
 #### type-enum

source/cli.js

@@ -98,7 +98,7 @@ async function main(options) {
 				seed.extends = flags.extends.split(',');
 			}
 
-			const report = lint(commit, {
+			const report = await lint(commit, {
 				preset: await getPreset(flags.preset),
 				configuration: await getConfiguration(
 					'conventional-changelog-lint',
@@ -117,10 +117,7 @@ async function main(options) {
 
 			if (!flags.quiet) {
 				console.log(`${fmt.grey('⧗')}   input: ${fmt.bold(commit.split('\n')[0])}`);
-				console.log(
-					formatted
-						.join('\n')
-				);
+				console.log(formatted.join('\n'));
 			}
 
 			if (report.errors.length > 0) {

source/index.js

@@ -6,7 +6,14 @@ export getMessages from './library/get-messages';
 export getPreset from './library/get-preset';
 export format from './library/format';
 
-export default (message, options = {}) => {
+async function executeRule(entry) {
+	const [name, config] = entry;
+	return typeof config === 'function' ?
+		[name, await config()] :
+		[name, await config];
+}
+
+export default async (message, options = {}) => {
 	const {
 		preset: {
 			parserOpts: parserOptions
@@ -22,8 +29,14 @@ export default (message, options = {}) => {
 		parse(message, parserOptions)
 	);
 
+	// execute wildcard rules
+	const executedWildcards = await Promise.all(
+		Object.entries(wildcards || {})
+			.map(async entry => await executeRule(entry))
+	);
+
 	// wildcard matches skip the linting
-	const bails = Object.entries(wildcards || {})
+	const bails = executedWildcards
 		.filter(entry => {
 			const [, pattern] = entry;
 			return Array.isArray(pattern);
@@ -33,7 +46,7 @@ export default (message, options = {}) => {
 			const expression = new RegExp(...pattern);
 			return parsed.header.match(expression);
 		})
-		.map(entry => entry[0]);
+		.map(entry => entry[0])
 
 	if (bails.length > 0) {
 		return {
@@ -45,8 +58,14 @@ export default (message, options = {}) => {
 		};
 	}
 
-	// validate against all rules
-	const results = Object.entries(rules || {})
+	// execute linting rules
+	const executedRules = await Promise.all(
+		Object.entries(rules || {})
+			.map(async entry => await executeRule(entry))
+		);
+
+		// validate against all rules
+	const results = executedRules
 		.filter(entry => {
 			const [, [level]] = entry;
 			return level > 0;
@@ -70,7 +89,7 @@ export default (message, options = {}) => {
 				message
 			};
 		})
-		.filter(Boolean);
+		.filter(Boolean)
 
 	const errors = results.filter(result =>
 		result.level > 1 && !result.valid);