diff --git a/.changeset/rich-dogs-design.md b/.changeset/rich-dogs-design.md
new file mode 100644
index 000000000..0ef7fbf2c
--- /dev/null
+++ b/.changeset/rich-dogs-design.md
@@ -0,0 +1,5 @@
+---
+'eslint-plugin-svelte': minor
+---
+
+feat: added the `require-event-prefix` rule
diff --git a/README.md b/README.md
index db731dd26..ddda4b3e9 100644
--- a/README.md
+++ b/README.md
@@ -337,6 +337,7 @@ These rules relate to style guidelines, and are therefore quite subjective:
| [svelte/no-spaces-around-equal-signs-in-attribute](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-spaces-around-equal-signs-in-attribute/) | disallow spaces around equal signs in attribute | :wrench: |
| [svelte/prefer-class-directive](https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-class-directive/) | require class directives instead of ternary expressions | :wrench: |
| [svelte/prefer-style-directive](https://sveltejs.github.io/eslint-plugin-svelte/rules/prefer-style-directive/) | require style directives instead of style attribute | :wrench: |
+| [svelte/require-event-prefix](https://sveltejs.github.io/eslint-plugin-svelte/rules/require-event-prefix/) | require component event names to start with "on" | |
| [svelte/shorthand-attribute](https://sveltejs.github.io/eslint-plugin-svelte/rules/shorthand-attribute/) | enforce use of shorthand syntax in attribute | :wrench: |
| [svelte/shorthand-directive](https://sveltejs.github.io/eslint-plugin-svelte/rules/shorthand-directive/) | enforce use of shorthand syntax in directives | :wrench: |
| [svelte/sort-attributes](https://sveltejs.github.io/eslint-plugin-svelte/rules/sort-attributes/) | enforce order of attributes | :wrench: |
diff --git a/docs/rules.md b/docs/rules.md
index 58d896b10..61d96dcbf 100644
--- a/docs/rules.md
+++ b/docs/rules.md
@@ -94,6 +94,7 @@ These rules relate to style guidelines, and are therefore quite subjective:
| [svelte/no-spaces-around-equal-signs-in-attribute](./rules/no-spaces-around-equal-signs-in-attribute.md) | disallow spaces around equal signs in attribute | :wrench: |
| [svelte/prefer-class-directive](./rules/prefer-class-directive.md) | require class directives instead of ternary expressions | :wrench: |
| [svelte/prefer-style-directive](./rules/prefer-style-directive.md) | require style directives instead of style attribute | :wrench: |
+| [svelte/require-event-prefix](./rules/require-event-prefix.md) | require component event names to start with "on" | |
| [svelte/shorthand-attribute](./rules/shorthand-attribute.md) | enforce use of shorthand syntax in attribute | :wrench: |
| [svelte/shorthand-directive](./rules/shorthand-directive.md) | enforce use of shorthand syntax in directives | :wrench: |
| [svelte/sort-attributes](./rules/sort-attributes.md) | enforce order of attributes | :wrench: |
diff --git a/docs/rules/require-event-prefix.md b/docs/rules/require-event-prefix.md
new file mode 100644
index 000000000..556509c6e
--- /dev/null
+++ b/docs/rules/require-event-prefix.md
@@ -0,0 +1,71 @@
+---
+pageClass: 'rule-details'
+sidebarDepth: 0
+title: 'svelte/require-event-prefix'
+description: 'require component event names to start with "on"'
+---
+
+# svelte/require-event-prefix
+
+> require component event names to start with "on"
+
+- :exclamation: **_This rule has not been released yet._**
+
+## :book: Rule Details
+
+Starting with Svelte 5, component events are just component props that are functions and so can be called like any function. Events for HTML elements all have their name begin with "on" (e.g. `onclick`). This rule enforces that all component events (i.e. function props) also begin with "on".
+
+
+
+```svelte
+
+```
+
+```svelte
+
+```
+
+## :wrench: Options
+
+```json
+{
+ "svelte/require-event-prefix": [
+ "error",
+ {
+ "checkAsyncFunctions": false
+ }
+ ]
+}
+```
+
+- `checkAsyncFunctions` ... Whether to also report asychronous function properties. Default `false`.
+
+## :books: Further Reading
+
+- [Svelte docs on events in version 5](https://svelte.dev/docs/svelte/v5-migration-guide#Event-changes)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/packages/eslint-plugin-svelte/src/rules/require-event-prefix.ts)
+- [Test source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/packages/eslint-plugin-svelte/tests/src/rules/require-event-prefix.ts)
diff --git a/packages/eslint-plugin-svelte/src/rule-types.ts b/packages/eslint-plugin-svelte/src/rule-types.ts
index 19e30a345..412df0fae 100644
--- a/packages/eslint-plugin-svelte/src/rule-types.ts
+++ b/packages/eslint-plugin-svelte/src/rule-types.ts
@@ -316,6 +316,11 @@ export interface RuleOptions {
* @see https://sveltejs.github.io/eslint-plugin-svelte/rules/require-event-dispatcher-types/
*/
'svelte/require-event-dispatcher-types'?: Linter.RuleEntry<[]>
+ /**
+ * require component event names to start with "on"
+ * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/require-event-prefix/
+ */
+ 'svelte/require-event-prefix'?: Linter.RuleEntry
/**
* require style attributes that can be optimized
* @see https://sveltejs.github.io/eslint-plugin-svelte/rules/require-optimized-style-attribute/
@@ -553,6 +558,10 @@ type SveltePreferConst = []|[{
ignoreReadBeforeAssign?: boolean
excludedRunes?: string[]
}]
+// ----- svelte/require-event-prefix -----
+type SvelteRequireEventPrefix = []|[{
+ checkAsyncFunctions?: boolean
+}]
// ----- svelte/shorthand-attribute -----
type SvelteShorthandAttribute = []|[{
prefer?: ("always" | "never")
diff --git a/packages/eslint-plugin-svelte/src/rules/require-event-prefix.ts b/packages/eslint-plugin-svelte/src/rules/require-event-prefix.ts
new file mode 100644
index 000000000..ed3c3ad08
--- /dev/null
+++ b/packages/eslint-plugin-svelte/src/rules/require-event-prefix.ts
@@ -0,0 +1,123 @@
+import { createRule } from '../utils/index.js';
+import {
+ type TSTools,
+ getTypeScriptTools,
+ isMethodSymbol,
+ isPropertySignatureKind,
+ isFunctionTypeKind,
+ isMethodSignatureKind,
+ isTypeReferenceKind,
+ isIdentifierKind
+} from '../utils/ts-utils/index.js';
+import type { Symbol, Type } from 'typescript';
+import type { CallExpression } from 'estree';
+
+export default createRule('require-event-prefix', {
+ meta: {
+ docs: {
+ description: 'require component event names to start with "on"',
+ category: 'Stylistic Issues',
+ conflictWithPrettier: false,
+ recommended: false
+ },
+ schema: [
+ {
+ type: 'object',
+ properties: {
+ checkAsyncFunctions: {
+ type: 'boolean'
+ }
+ },
+ additionalProperties: false
+ }
+ ],
+ messages: {
+ nonPrefixedFunction: 'Component event name must start with "on".'
+ },
+ type: 'suggestion',
+ conditions: [
+ {
+ svelteVersions: ['5'],
+ svelteFileTypes: ['.svelte']
+ }
+ ]
+ },
+ create(context) {
+ const tsTools = getTypeScriptTools(context);
+ if (!tsTools) {
+ return {};
+ }
+
+ const checkAsyncFunctions = context.options[0]?.checkAsyncFunctions ?? false;
+
+ return {
+ CallExpression(node) {
+ const propsType = getPropsType(node, tsTools);
+ if (propsType === undefined) {
+ return;
+ }
+ for (const property of propsType.getProperties()) {
+ if (
+ isFunctionLike(property, tsTools) &&
+ !property.getName().startsWith('on') &&
+ (checkAsyncFunctions || !isFunctionAsync(property, tsTools))
+ ) {
+ const declarationTsNode = property.getDeclarations()?.[0];
+ const declarationEstreeNode =
+ declarationTsNode !== undefined
+ ? tsTools.service.tsNodeToESTreeNodeMap.get(declarationTsNode)
+ : undefined;
+ context.report({
+ node: declarationEstreeNode ?? node,
+ messageId: 'nonPrefixedFunction'
+ });
+ }
+ }
+ }
+ };
+ }
+});
+
+function getPropsType(node: CallExpression, tsTools: TSTools): Type | undefined {
+ if (
+ node.callee.type !== 'Identifier' ||
+ node.callee.name !== '$props' ||
+ node.parent.type !== 'VariableDeclarator'
+ ) {
+ return undefined;
+ }
+
+ const tsNode = tsTools.service.esTreeNodeToTSNodeMap.get(node.parent.id);
+ if (tsNode === undefined) {
+ return undefined;
+ }
+
+ return tsTools.service.program.getTypeChecker().getTypeAtLocation(tsNode);
+}
+
+function isFunctionLike(functionSymbol: Symbol, tsTools: TSTools): boolean {
+ return (
+ isMethodSymbol(functionSymbol, tsTools.ts) ||
+ (functionSymbol.valueDeclaration !== undefined &&
+ isPropertySignatureKind(functionSymbol.valueDeclaration, tsTools.ts) &&
+ functionSymbol.valueDeclaration.type !== undefined &&
+ isFunctionTypeKind(functionSymbol.valueDeclaration.type, tsTools.ts))
+ );
+}
+
+function isFunctionAsync(functionSymbol: Symbol, tsTools: TSTools): boolean {
+ return (
+ functionSymbol.getDeclarations()?.some((declaration) => {
+ if (!isMethodSignatureKind(declaration, tsTools.ts)) {
+ return false;
+ }
+ if (declaration.type === undefined || !isTypeReferenceKind(declaration.type, tsTools.ts)) {
+ return false;
+ }
+ return (
+ isIdentifierKind(declaration.type.typeName, tsTools.ts) &&
+ declaration.type.typeName.escapedText === 'Promise'
+ );
+ }) ?? false
+ );
+}
diff --git a/packages/eslint-plugin-svelte/src/utils/rules.ts b/packages/eslint-plugin-svelte/src/utils/rules.ts
index 3151d17f1..825edea9e 100644
--- a/packages/eslint-plugin-svelte/src/utils/rules.ts
+++ b/packages/eslint-plugin-svelte/src/utils/rules.ts
@@ -62,6 +62,7 @@ import preferDestructuredStoreProps from '../rules/prefer-destructured-store-pro
import preferStyleDirective from '../rules/prefer-style-directive.js';
import requireEachKey from '../rules/require-each-key.js';
import requireEventDispatcherTypes from '../rules/require-event-dispatcher-types.js';
+import requireEventPrefix from '../rules/require-event-prefix.js';
import requireOptimizedStyleAttribute from '../rules/require-optimized-style-attribute.js';
import requireStoreCallbacksUseSetParam from '../rules/require-store-callbacks-use-set-param.js';
import requireStoreReactiveAccess from '../rules/require-store-reactive-access.js';
@@ -137,6 +138,7 @@ export const rules = [
preferStyleDirective,
requireEachKey,
requireEventDispatcherTypes,
+ requireEventPrefix,
requireOptimizedStyleAttribute,
requireStoreCallbacksUseSetParam,
requireStoreReactiveAccess,
diff --git a/packages/eslint-plugin-svelte/src/utils/ts-utils/index.ts b/packages/eslint-plugin-svelte/src/utils/ts-utils/index.ts
index cbe430c99..f8085947a 100644
--- a/packages/eslint-plugin-svelte/src/utils/ts-utils/index.ts
+++ b/packages/eslint-plugin-svelte/src/utils/ts-utils/index.ts
@@ -307,3 +307,48 @@ export function getTypeOfPropertyOfType(
// eslint-disable-next-line @typescript-eslint/no-explicit-any -- getTypeOfPropertyOfType is an internal API of TS.
return (checker as any).getTypeOfPropertyOfType(type, name);
}
+
+/**
+ * Check whether the given symbol is a method type or not.
+ */
+export function isMethodSymbol(type: TS.Symbol, ts: TypeScript): boolean {
+ return (type.getFlags() & ts.SymbolFlags.Method) !== 0;
+}
+
+/**
+ * Check whether the given node is a property signature kind or not.
+ */
+export function isPropertySignatureKind(
+ node: TS.Node,
+ ts: TypeScript
+): node is TS.PropertySignature {
+ return node.kind === ts.SyntaxKind.PropertySignature;
+}
+
+/**
+ * Check whether the given node is a function type kind or not.
+ */
+export function isFunctionTypeKind(node: TS.Node, ts: TypeScript): node is TS.FunctionTypeNode {
+ return node.kind === ts.SyntaxKind.FunctionType;
+}
+
+/**
+ * Check whether the given node is a method signature kind or not.
+ */
+export function isMethodSignatureKind(node: TS.Node, ts: TypeScript): node is TS.MethodSignature {
+ return node.kind === ts.SyntaxKind.MethodSignature;
+}
+
+/**
+ * Check whether the given node is a type reference kind or not.
+ */
+export function isTypeReferenceKind(node: TS.Node, ts: TypeScript): node is TS.TypeReferenceNode {
+ return node.kind === ts.SyntaxKind.TypeReference;
+}
+
+/**
+ * Check whether the given node is an identifier kind or not.
+ */
+export function isIdentifierKind(node: TS.Node, ts: TypeScript): node is TS.Identifier {
+ return node.kind === ts.SyntaxKind.Identifier;
+}
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/_requirements.json b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/_requirements.json
new file mode 100644
index 000000000..498661308
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/_requirements.json
@@ -0,0 +1,3 @@
+{
+ "svelte": ">=5.0.0"
+}
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_config.json b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_config.json
new file mode 100644
index 000000000..a0f52ed6e
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_config.json
@@ -0,0 +1,3 @@
+{
+ "options": [{ "checkAsyncFunctions": true }]
+}
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_requirements.json b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_requirements.json
new file mode 100644
index 000000000..498661308
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/_requirements.json
@@ -0,0 +1,3 @@
+{
+ "svelte": ">=5.0.0"
+}
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-errors.yaml b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-errors.yaml
new file mode 100644
index 000000000..4c26d4e62
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-errors.yaml
@@ -0,0 +1,4 @@
+- message: Component event name must start with "on".
+ line: 3
+ column: 5
+ suggestions: null
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-input.svelte
new file mode 100644
index 000000000..0b0502984
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async-arrow01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-errors.yaml b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-errors.yaml
new file mode 100644
index 000000000..4c26d4e62
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-errors.yaml
@@ -0,0 +1,4 @@
+- message: Component event name must start with "on".
+ line: 3
+ column: 5
+ suggestions: null
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-input.svelte
new file mode 100644
index 000000000..4f6f3ee49
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/checkAsyncFunctions/async01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-errors.yaml b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-errors.yaml
new file mode 100644
index 000000000..4c26d4e62
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-errors.yaml
@@ -0,0 +1,4 @@
+- message: Component event name must start with "on".
+ line: 3
+ column: 5
+ suggestions: null
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-input.svelte
new file mode 100644
index 000000000..7874e51da
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-arrow01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-errors.yaml b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-errors.yaml
new file mode 100644
index 000000000..affa6e169
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-errors.yaml
@@ -0,0 +1,4 @@
+- message: Component event name must start with "on".
+ line: 2
+ column: 21
+ suggestions: null
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-input.svelte
new file mode 100644
index 000000000..3fc3c616b
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix-inline-type01-input.svelte
@@ -0,0 +1,5 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-errors.yaml b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-errors.yaml
new file mode 100644
index 000000000..4c26d4e62
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-errors.yaml
@@ -0,0 +1,4 @@
+- message: Component event name must start with "on".
+ line: 3
+ column: 5
+ suggestions: null
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-input.svelte
new file mode 100644
index 000000000..036a1d65b
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/invalid/no-prefix01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/_requirements.json b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/_requirements.json
new file mode 100644
index 000000000..498661308
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/_requirements.json
@@ -0,0 +1,3 @@
+{
+ "svelte": ">=5.0.0"
+}
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/any01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/any01-input.svelte
new file mode 100644
index 000000000..deeb82509
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/any01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/async01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/async01-input.svelte
new file mode 100644
index 000000000..4f6f3ee49
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/async01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/non-function01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/non-function01-input.svelte
new file mode 100644
index 000000000..d23e387a1
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/non-function01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/with-prefix01-input.svelte b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/with-prefix01-input.svelte
new file mode 100644
index 000000000..e3396af33
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/fixtures/rules/require-event-prefix/valid/with-prefix01-input.svelte
@@ -0,0 +1,9 @@
+
diff --git a/packages/eslint-plugin-svelte/tests/src/rules/require-event-prefix.ts b/packages/eslint-plugin-svelte/tests/src/rules/require-event-prefix.ts
new file mode 100644
index 000000000..7818735b5
--- /dev/null
+++ b/packages/eslint-plugin-svelte/tests/src/rules/require-event-prefix.ts
@@ -0,0 +1,12 @@
+import { RuleTester } from '../../utils/eslint-compat.js';
+import rule from '../../../src/rules/require-event-prefix.js';
+import { loadTestCases } from '../../utils/utils.js';
+
+const tester = new RuleTester({
+ languageOptions: {
+ ecmaVersion: 2020,
+ sourceType: 'module'
+ }
+});
+
+tester.run('require-event-prefix', rule as any, loadTestCases('require-event-prefix'));