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no-non-null-assertion.ts
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no-non-null-assertion.ts
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import { TSESLint, AST_NODE_TYPES } from '@typescript-eslint/utils';
import * as util from '../util';
type MessageIds = 'noNonNull' | 'suggestOptionalChain';
export default util.createRule<[], MessageIds>({
name: 'no-non-null-assertion',
meta: {
type: 'problem',
docs: {
description:
'Disallow non-null assertions using the `!` postfix operator',
recommended: 'warn',
},
hasSuggestions: true,
messages: {
noNonNull: 'Forbidden non-null assertion.',
suggestOptionalChain:
'Consider using the optional chain operator `?.` instead. This operator includes runtime checks, so it is safer than the compile-only non-null assertion operator.',
},
schema: [],
},
defaultOptions: [],
create(context) {
const sourceCode = context.getSourceCode();
return {
TSNonNullExpression(node): void {
const suggest: TSESLint.ReportSuggestionArray<MessageIds> = [];
function convertTokenToOptional(
replacement: '?' | '?.',
): TSESLint.ReportFixFunction {
return (fixer: TSESLint.RuleFixer): TSESLint.RuleFix | null => {
const operator = sourceCode.getTokenAfter(
node.expression,
util.isNonNullAssertionPunctuator,
);
if (operator) {
return fixer.replaceText(operator, replacement);
}
return null;
};
}
function removeToken(): TSESLint.ReportFixFunction {
return (fixer: TSESLint.RuleFixer): TSESLint.RuleFix | null => {
const operator = sourceCode.getTokenAfter(
node.expression,
util.isNonNullAssertionPunctuator,
);
if (operator) {
return fixer.remove(operator);
}
return null;
};
}
if (
node.parent?.type === AST_NODE_TYPES.MemberExpression &&
node.parent.object === node
) {
if (!node.parent.optional) {
if (node.parent.computed) {
// it is x![y]?.z
suggest.push({
messageId: 'suggestOptionalChain',
fix: convertTokenToOptional('?.'),
});
} else {
// it is x!.y?.z
suggest.push({
messageId: 'suggestOptionalChain',
fix: convertTokenToOptional('?'),
});
}
} else {
if (node.parent.computed) {
// it is x!?.[y].z
suggest.push({
messageId: 'suggestOptionalChain',
fix: removeToken(),
});
} else {
// it is x!?.y.z
suggest.push({
messageId: 'suggestOptionalChain',
fix: removeToken(),
});
}
}
} else if (
node.parent?.type === AST_NODE_TYPES.CallExpression &&
node.parent.callee === node
) {
if (!node.parent.optional) {
// it is x.y?.z!()
suggest.push({
messageId: 'suggestOptionalChain',
fix: convertTokenToOptional('?.'),
});
} else {
// it is x.y.z!?.()
suggest.push({
messageId: 'suggestOptionalChain',
fix: removeToken(),
});
}
}
context.report({
node,
messageId: 'noNonNull',
suggest,
});
},
};
},
});