eslint-plugin-svelte/lib/rules/valid-each-key.js

ESLint plugin for Svelte using AST

import { createRule } from '../utils/index.js';
import { getScope } from '../utils/ast-utils.js';
export default createRule('valid-each-key', {
    meta: {
        docs: {
            description: 'enforce keys to use variables defined in the `{#each}` block',
            category: 'Best Practices',
            recommended: true
        },
        schema: [],
        messages: {
            keyUseEachVars: 'Expected key to use the variables which are defined by the `{#each}` block.'
        },
        type: 'suggestion'
    },
    create(context) {
        return {
            SvelteEachBlock(node) {
                if (node.key == null) {
                    return;
                }
                const scope = getScope(context, node.key);
                for (const variable of scope.variables) {
                    if (!variable.defs.some((def) => (node.context &&
                        node.context.range[0] <= def.name.range[0] &&
                        def.name.range[1] <= node.context.range[1]) ||
                        (node.index &&
                            node.index.range[0] <= def.name.range[0] &&
                            def.name.range[1] <= node.index.range[1]) ||
                        (node.expression &&
                            node.expression.range[0] <= def.name.range[0] &&
                            def.name.range[1] <= node.expression.range[1]))) {
                        // It's not an iteration variable.
                        continue;
                    }
                    for (const reference of variable.references) {
                        if (node.key.range[0] <= reference.identifier.range[0] &&
                            reference.identifier.range[1] <= node.key.range[1]) {
                            // A variable is used in the key.
                            return;
                        }
                    }
                }
                context.report({
                    node: node.key,
                    messageId: 'keyUseEachVars'
                });
            }
        };
    }
});