@typescript-eslint/eslint-plugin
Version:
TypeScript plugin for ESLint
232 lines • 10.2 kB
JavaScript
;
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Object.defineProperty(exports, "__esModule", { value: true });
const utils_1 = require("@typescript-eslint/utils");
const tsutils = __importStar(require("ts-api-utils"));
const ts = __importStar(require("typescript"));
const util_1 = require("../util");
exports.default = (0, util_1.createRule)({
name: 'no-unnecessary-boolean-literal-compare',
meta: {
docs: {
description: 'Disallow unnecessary equality comparisons against boolean literals',
recommended: 'strict',
requiresTypeChecking: true,
},
fixable: 'code',
messages: {
direct: 'This expression unnecessarily compares a boolean value to a boolean instead of using it directly.',
negated: 'This expression unnecessarily compares a boolean value to a boolean instead of negating it.',
comparingNullableToTrueDirect: 'This expression unnecessarily compares a nullable boolean value to true instead of using it directly.',
comparingNullableToTrueNegated: 'This expression unnecessarily compares a nullable boolean value to true instead of negating it.',
comparingNullableToFalse: 'This expression unnecessarily compares a nullable boolean value to false instead of using the ?? operator to provide a default.',
},
schema: [
{
type: 'object',
properties: {
allowComparingNullableBooleansToTrue: {
description: 'Whether to allow comparisons between nullable boolean variables and `true`.',
type: 'boolean',
},
allowComparingNullableBooleansToFalse: {
description: 'Whether to allow comparisons between nullable boolean variables and `false`.',
type: 'boolean',
},
},
additionalProperties: false,
},
],
type: 'suggestion',
},
defaultOptions: [
{
allowComparingNullableBooleansToTrue: true,
allowComparingNullableBooleansToFalse: true,
},
],
create(context, [options]) {
const services = (0, util_1.getParserServices)(context);
function getBooleanComparison(node) {
const comparison = deconstructComparison(node);
if (!comparison) {
return undefined;
}
const expressionType = services.getTypeAtLocation(comparison.expression);
if (isBooleanType(expressionType)) {
return {
...comparison,
expressionIsNullableBoolean: false,
};
}
if (isNullableBoolean(expressionType)) {
return {
...comparison,
expressionIsNullableBoolean: true,
};
}
return undefined;
}
function isBooleanType(expressionType) {
return tsutils.isTypeFlagSet(expressionType, ts.TypeFlags.Boolean | ts.TypeFlags.BooleanLiteral);
}
/**
* checks if the expressionType is a union that
* 1) contains at least one nullish type (null or undefined)
* 2) contains at least once boolean type (true or false or boolean)
* 3) does not contain any types besides nullish and boolean types
*/
function isNullableBoolean(expressionType) {
if (!expressionType.isUnion()) {
return false;
}
const { types } = expressionType;
const nonNullishTypes = types.filter(type => !tsutils.isTypeFlagSet(type, ts.TypeFlags.Undefined | ts.TypeFlags.Null));
const hasNonNullishType = nonNullishTypes.length > 0;
if (!hasNonNullishType) {
return false;
}
const hasNullableType = nonNullishTypes.length < types.length;
if (!hasNullableType) {
return false;
}
const allNonNullishTypesAreBoolean = nonNullishTypes.every(isBooleanType);
if (!allNonNullishTypesAreBoolean) {
return false;
}
return true;
}
function deconstructComparison(node) {
const comparisonType = getEqualsKind(node.operator);
if (!comparisonType) {
return undefined;
}
for (const [against, expression] of [
[node.right, node.left],
[node.left, node.right],
]) {
if (against.type !== utils_1.AST_NODE_TYPES.Literal ||
typeof against.value !== 'boolean') {
continue;
}
const { value: literalBooleanInComparison } = against;
const negated = !comparisonType.isPositive;
return {
literalBooleanInComparison,
expression,
negated,
};
}
return undefined;
}
function nodeIsUnaryNegation(node) {
return (node.type === utils_1.AST_NODE_TYPES.UnaryExpression &&
node.prefix &&
node.operator === '!');
}
return {
BinaryExpression(node) {
const comparison = getBooleanComparison(node);
if (comparison === undefined) {
return;
}
if (comparison.expressionIsNullableBoolean) {
if (comparison.literalBooleanInComparison &&
options.allowComparingNullableBooleansToTrue) {
return;
}
if (!comparison.literalBooleanInComparison &&
options.allowComparingNullableBooleansToFalse) {
return;
}
}
context.report({
*fix(fixer) {
// 1. isUnaryNegation - parent negation
// 2. literalBooleanInComparison - is compared to literal boolean
// 3. negated - is expression negated
const isUnaryNegation = nodeIsUnaryNegation(node.parent);
const shouldNegate = comparison.negated !== comparison.literalBooleanInComparison;
const mutatedNode = isUnaryNegation ? node.parent : node;
yield fixer.replaceText(mutatedNode, context.sourceCode.getText(comparison.expression));
// if `isUnaryNegation === literalBooleanInComparison === !negated` is true - negate the expression
if (shouldNegate === isUnaryNegation) {
yield fixer.insertTextBefore(mutatedNode, '!');
// if the expression `exp` is not a strong precedence node, wrap it in parentheses
if (!(0, util_1.isStrongPrecedenceNode)(comparison.expression)) {
yield fixer.insertTextBefore(mutatedNode, '(');
yield fixer.insertTextAfter(mutatedNode, ')');
}
}
// if the expression `exp` is nullable, and we're not comparing to `true`, insert `?? true`
if (comparison.expressionIsNullableBoolean &&
!comparison.literalBooleanInComparison) {
// provide the default `true`
yield fixer.insertTextBefore(mutatedNode, '(');
yield fixer.insertTextAfter(mutatedNode, ' ?? true)');
}
},
messageId: comparison.expressionIsNullableBoolean
? comparison.literalBooleanInComparison
? comparison.negated
? 'comparingNullableToTrueNegated'
: 'comparingNullableToTrueDirect'
: 'comparingNullableToFalse'
: comparison.negated
? 'negated'
: 'direct',
node,
});
},
};
},
});
function getEqualsKind(operator) {
switch (operator) {
case '==':
return {
isPositive: true,
isStrict: false,
};
case '===':
return {
isPositive: true,
isStrict: true,
};
case '!=':
return {
isPositive: false,
isStrict: false,
};
case '!==':
return {
isPositive: false,
isStrict: true,
};
default:
return undefined;
}
}
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