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prefer-to-be-null.ts
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prefer-to-be-null.ts
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import {
AST_NODE_TYPES,
TSESTree,
} from '@typescript-eslint/experimental-utils';
import {
MaybeTypeCast,
ParsedEqualityMatcherCall,
ParsedExpectMatcher,
createRule,
followTypeAssertionChain,
isExpectCall,
isParsedEqualityMatcherCall,
parseExpectCall,
} from './utils';
const isNullLiteral = (node: TSESTree.Node): node is TSESTree.NullLiteral =>
node.type === AST_NODE_TYPES.Literal && node.value === null;
/**
* Checks if the given `ParsedExpectMatcher` is a call to one of the equality matchers,
* with a `null` literal as the sole argument.
*
* @param {ParsedExpectMatcher} matcher
*
* @return {matcher is ParsedEqualityMatcherCall<MaybeTypeCast<NullLiteral>>}
*/
const isNullEqualityMatcher = (
matcher: ParsedExpectMatcher,
): matcher is ParsedEqualityMatcherCall<MaybeTypeCast<TSESTree.NullLiteral>> =>
isParsedEqualityMatcherCall(matcher) &&
isNullLiteral(followTypeAssertionChain(matcher.arguments[0]));
export default createRule({
name: __filename,
meta: {
docs: {
category: 'Best Practices',
description: 'Suggest using `toBeNull()`',
recommended: false,
},
messages: {
useToBeNull: 'Use toBeNull() instead',
},
fixable: 'code',
type: 'suggestion',
schema: [],
},
defaultOptions: [],
create(context) {
return {
CallExpression(node) {
if (!isExpectCall(node)) {
return;
}
const { matcher } = parseExpectCall(node);
if (matcher && isNullEqualityMatcher(matcher)) {
context.report({
fix: fixer => [
fixer.replaceText(matcher.node.property, 'toBeNull'),
fixer.remove(matcher.arguments[0]),
],
messageId: 'useToBeNull',
node: matcher.node.property,
});
}
},
};
},
});