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

@@ -8,19 +8,26 @@ export interface BatchWarnings {
 	add: (warning: RollupWarning) => void;
 	readonly count: number;
 	flush: () => void;
+	readonly warningOccurred: boolean;
 }
 
 export default function batchWarnings() {
-	let deferredWarnings = new Map<keyof typeof deferredHandlers, RollupWarning[]>();
 	let count = 0;
+	let deferredWarnings = new Map<keyof typeof deferredHandlers, RollupWarning[]>();
+	let warningOccurred = false;
 
 	return {
 		get count() {
 			return count;
 		},
 
+		get warningOccurred() {
+			return warningOccurred;
+		},
+
 		add: (warning: RollupWarning) => {
 			count += 1;
+			warningOccurred = true;
 
 			if (warning.code! in deferredHandlers) {
 				getOrCreate(deferredWarnings, warning.code!, () => []).push(warning);

cli/run/index.ts

@@ -67,6 +67,13 @@ export default async function runRollup(command: any) {
 				for (const inputOptions of options) {
 					await build(inputOptions, warnings, command.silent);
 				}
+				if (command.failAfterWarnings && warnings.warningOccurred) {
+					warnings.flush();
+					handleError({
+						code: 'FAIL_AFTER_WARNINGS',
+						message: 'Warnings occurred and --failAfterWarnings flag present'
+					});
+				}
 			} catch (err) {
 				warnings.flush();
 				handleError(err);

docs/01-command-line-reference.md

@@ -306,6 +306,7 @@ Many options have command line equivalents. In those cases, any arguments passed
 --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
@@ -387,6 +388,10 @@ _Note: While in watch mode, the `ROLLUP_WATCH` environment variable will be set
 
 Don't print warnings to the console. If your configuration file contains an `onwarn` handler, this handler will still be called. To manually prevent that, you can access the command line options in your configuration file as described at the end of [Configuration Files](guide/en/#configuration-files).
 
+#### `--failAfterWarnings`
+
+Exit the build with an error if any warnings occurred, once the build is complete.
+
 #### `--environment <values>`
 
 Pass additional settings to the config file via `process.ENV`.

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 +1,11 @@
+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');
+		return true;
+	}
+};

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

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

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

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