feat: add ability to ignore warnings through compiler option

.changeset/little-seals-reflect.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+feat: add ability to ignore warnings through `warningFilter` compiler option

packages/svelte/scripts/process-messages/templates/compile-warnings.js

@@ -1,4 +1,4 @@
-import { warnings, ignore_stack, ignore_map } from './state.js';
+import { warnings, ignore_stack, ignore_map, warning_filter } from './state.js';
 import { CompileDiagnostic } from './utils/compile_diagnostic.js';
 
 /** @typedef {{ start?: number, end?: number }} NodeLike */
@@ -28,13 +28,15 @@ function w(node, code, message) {
 	}
 	if (stack && stack.at(-1)?.has(code)) return;
 
-	warnings.push(
-		new InternalCompileWarning(
-			code,
-			message,
-			node && node.start !== undefined ? [node.start, node.end ?? node.start] : undefined
-		)
+	const warning = new InternalCompileWarning(
+		code,
+		message,
+		node && node.start !== undefined ? [node.start, node.end ?? node.start] : undefined
 	);
+
+	if (!warning_filter(warning)) return;
+
+	warnings.push(warning);
 }
 
 export const codes = CODES;

packages/svelte/src/compiler/index.js

@@ -20,6 +20,7 @@ export { default as preprocess } from './preprocess/index.js';
  * @returns {CompileResult}
  */
 export function compile(source, options) {
+	state.reset_warning_filter(options.warningFilter);
 	const validated = validate_component_options(options, '');
 	state.reset(source, validated);
 
@@ -58,6 +59,7 @@ export function compile(source, options) {
  * @returns {CompileResult}
  */
 export function compileModule(source, options) {
+	state.reset_warning_filter(options.warningFilter);
 	const validated = validate_module_options(options, '');
 	state.reset(source, validated);
 
@@ -103,6 +105,7 @@ export function compileModule(source, options) {
  * @returns {Root | LegacyRoot}
  */
 export function parse(source, { filename, rootDir, modern } = {}) {
+	state.reset_warning_filter(() => false);
 	state.reset(source, { filename, rootDir }); // TODO it's weird to require filename/rootDir here. reconsider the API
 
 	const ast = _parse(source);

packages/svelte/src/compiler/migrate/index.js

@@ -10,7 +10,7 @@ import { parse } from '../phases/1-parse/index.js';
 import { analyze_component } from '../phases/2-analyze/index.js';
 import { validate_component_options } from '../validate-options.js';
 import { get_rune } from '../phases/scope.js';
-import { reset } from '../state.js';
+import { reset, reset_warning_filter } from '../state.js';
 import { extract_identifiers } from '../utils/ast.js';
 import { regex_is_valid_identifier } from '../phases/patterns.js';
 import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
@@ -24,6 +24,7 @@ import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
  */
 export function migrate(source) {
 	try {
+		reset_warning_filter(() => false);
 		reset(source, { filename: 'migrate.svelte' });
 
 		let parsed = parse(source);

packages/svelte/src/compiler/state.js

@@ -1,4 +1,4 @@
-/** @import { SvelteNode } from './types' */
+/** @import { CompileOptions, SvelteNode } from './types' */
 /** @import { Warning } from '#compiler' */
 import { getLocator } from 'locate-character';
 
@@ -22,6 +22,9 @@ export let source;
 
 export let locator = getLocator('', { offsetLine: 1 });
 
+/** @type {NonNullable<CompileOptions['warningFilter']>} */
+export let warning_filter;
+
 /**
  * The current stack of ignored warnings
  * @type {Set<string>[]}
@@ -48,6 +51,14 @@ export function pop_ignore() {
 	ignore_stack.pop();
 }
 
+/**
+ *
+ * @param {(warning: Warning) => boolean} fn
+ */
+export function reset_warning_filter(fn = () => true) {
+	warning_filter = fn;
+}
+
 /**
  * @param {string} _source
  * @param {{ filename?: string, rootDir?: string }} options

packages/svelte/src/compiler/types/index.d.ts

@@ -203,12 +203,16 @@ export interface ModuleCompileOptions {
 	 * Used for debugging hints and sourcemaps. Your bundler plugin will set it automatically.
 	 */
 	filename?: string;
-
 	/**
 	 * Used for ensuring filenames don't leak filesystem information. Your bundler plugin will set it automatically.
 	 * @default process.cwd() on node-like environments, undefined elsewhere
 	 */
 	rootDir?: string;
+	/**
+	 * A function that gets a `Warning` as an argument and returns a boolean.
+	 * Use this to filter out warnings. Return `true` to keep the warning, `false` to discard it.
+	 */
+	warningFilter?: (warning: Warning) => boolean;
 }
 
 // The following two somewhat scary looking types ensure that certain types are required but can be undefined still

packages/svelte/src/compiler/validate-options.js

@@ -104,6 +104,8 @@ export const validate_component_options =
 
 			hmr: boolean(false),
 
+			warningFilter: fun(() => true),
+
 			sourcemap: validator(undefined, (input) => {
 				// Source maps can take on a variety of values, including string, JSON, map objects from magic-string and source-map,
 				// so there's no good way to check type validity here
@@ -259,6 +261,20 @@ function string(fallback, allow_empty = true) {
 	});
 }
 
+/**
+ * @param {string[]} fallback
+ * @returns {Validator}
+ */
+function string_array(fallback) {
+	return validator(fallback, (input, keypath) => {
+		if (input && !Array.isArray(input)) {
+			throw_error(`${keypath} should be a string array, if specified`);
+		}
+
+		return input;
+	});
+}
+
 /**
  * @param {boolean | undefined} fallback
  * @returns {Validator}

packages/svelte/src/compiler/warnings.js

@@ -1,6 +1,12 @@
 /* This file is generated by scripts/process-messages/index.js. Do not edit! */
 
-import { warnings, ignore_stack, ignore_map } from './state.js';
+import {
+	warnings,
+	ignore_stack,
+	ignore_map,
+	warning_filter
+} from './state.js';
+
 import { CompileDiagnostic } from './utils/compile_diagnostic.js';
 
 /** @typedef {{ start?: number, end?: number }} NodeLike */
@@ -30,7 +36,11 @@ function w(node, code, message) {
 	}
 
 	if (stack && stack.at(-1)?.has(code)) return;
-	warnings.push(new InternalCompileWarning(code, message, node && node.start !== undefined ? [node.start, node.end ?? node.start] : undefined));
+
+	const warning = new InternalCompileWarning(code, message, node && node.start !== undefined ? [node.start, node.end ?? node.start] : undefined);
+
+	if (!warning_filter(warning)) return;
+	warnings.push(warning);
 }
 
 export const codes = [

packages/svelte/tests/validator/samples/ignore-warning-compiler-option/_config.js

@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		warningFilter: (warning) =>
+			!['a11y_missing_attribute', 'a11y_misplaced_scope'].includes(warning.code)
+	}
+});

packages/svelte/tests/validator/samples/ignore-warning-compiler-option/input.svelte

@@ -0,0 +1,8 @@
+<div>
+	<img src="this-is-fine.jpg" />
+	<marquee>but this is still discouraged</marquee>
+</div>
+
+<div scope></div>
+
+<img src="potato.jpg" />

packages/svelte/tests/validator/samples/ignore-warning-compiler-option/warnings.json

@@ -0,0 +1,14 @@
+[
+	{
+		"code": "a11y_distracting_elements",
+		"end": {
+			"column": 49,
+			"line": 3
+		},
+		"message": "Avoid `<marquee>` elements",
+		"start": {
+			"column": 1,
+			"line": 3
+		}
+	}
+]

packages/svelte/types/index.d.ts

@@ -864,12 +864,16 @@ declare module 'svelte/compiler' {
 		 * Used for debugging hints and sourcemaps. Your bundler plugin will set it automatically.
 		 */
 		filename?: string;
-
 		/**
 		 * Used for ensuring filenames don't leak filesystem information. Your bundler plugin will set it automatically.
 		 * @default process.cwd() on node-like environments, undefined elsewhere
 		 */
 		rootDir?: string;
+		/**
+		 * A function that gets a `Warning` as an argument and returns a boolean.
+		 * Use this to filter out warnings. Return `true` to keep the warning, `false` to discard it.
+		 */
+		warningFilter?: (warning: Warning) => boolean;
 	}
 
 	type DeclarationKind =
@@ -2672,12 +2676,16 @@ declare module 'svelte/types/compiler/interfaces' {
 		 * Used for debugging hints and sourcemaps. Your bundler plugin will set it automatically.
 		 */
 		filename?: string;
-
 		/**
 		 * Used for ensuring filenames don't leak filesystem information. Your bundler plugin will set it automatically.
 		 * @default process.cwd() on node-like environments, undefined elsewhere
 		 */
 		rootDir?: string;
+		/**
+		 * A function that gets a `Warning` as an argument and returns a boolean.
+		 * Use this to filter out warnings. Return `true` to keep the warning, `false` to discard it.
+		 */
+		warningFilter?: (warning: Warning_1) => boolean;
 	}
 	/**
 	 * - `html`    — the default, for e.g. `<div>` or `<span>`