cli: implement --failAfterWarnings flag

cli/help.md

@@ -49,6 +49,7 @@ Basic options:
 --preserveSymlinks          Do not follow symlinks when resolving files
 --shimMissingExports        Create shim variables for missing exports
 --silent                    Don't print warnings
+--failAfterWarnings         Exit with an error code if there was a warning during the build
 --sourcemapExcludeSources   Do not include source code in source maps
 --sourcemapFile <file>      Specify bundle position for source maps
 --no-stdin                  do not read "-" from stdin

cli/run/batchWarnings.ts

@@ -5,20 +5,27 @@ import { stderr } from '../logging';
 
 export interface BatchWarnings {
 	add: (warning: RollupWarning) => void;
+	readonly total: number;
 	readonly count: number;
 	flush: () => void;
 }
 
 export default function batchWarnings() {
 	let deferredWarnings = new Map<keyof typeof deferredHandlers, RollupWarning[]>();
+	let total = 0;
 	let count = 0;
 
 	return {
+		get total() {
+			return total;
+		},
+
 		get count() {
 			return count;
 		},
 
 		add: (warning: RollupWarning) => {
+			total += 1;
 			count += 1;
 
 			if (warning.code! in deferredHandlers) {

cli/run/index.ts

@@ -67,6 +67,12 @@ export default async function runRollup(command: any) {
 				for (const inputOptions of options) {
 					await build(inputOptions, warnings, command.silent);
 				}
+				if (command.failAfterWarnings && warnings.total) {
+					throw {
+						code: 'FAIL_AFTER_WARNINGS',
+						message: 'Warnings occurred and --failAfterWarnings flag present'
+					};
+				}
 			} catch (err) {
 				warnings.flush();
 				handleError(err);

src/utils/options/mergeOptions.ts

@@ -53,6 +53,7 @@ export function mergeOptions(
 			'environment',
 			'plugin',
 			'silent',
+			'failAfterWarnings',
 			'stdin',
 			'waitForBundleInput'
 		),

test/cli/samples/fail-after-warnings/_config.js

@@ -0,0 +1,9 @@
+const { assertIncludes } = require('../../../utils.js');
+
+module.exports = {
+	description: 'errors on warnings with --failAfterWarnings',
+	command: 'rollup -i main.js --failAfterWarnings',
+	error: () => true,
+	stderr: stderr =>
+		assertIncludes(stderr, '[!] Warnings occurred and --failAfterWarnings flag present')
+};

test/cli/samples/fail-after-warnings/_expected.js

@@ -0,0 +1,5 @@
+'use strict';
+
+require('unknown');
+
+console.log(42);

test/cli/samples/fail-after-warnings/main.js

@@ -0,0 +1,3 @@
+import something from 'unknown';
+
+console.log(42);