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Fix: incorrect logic for required parens in no-extra-boolean-cast fix…
…er (#13061)

* Fix: incorrect logic for required parens in no-extra-boolean-cast fixer

* Specify assumptions for `needsParens`
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mdjermanovic committed Mar 25, 2020
1 parent 6c069f9 commit 3e4e7f8
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Showing 2 changed files with 1,125 additions and 23 deletions.
125 changes: 102 additions & 23 deletions lib/rules/no-extra-boolean-cast.js
Expand Up @@ -10,6 +10,9 @@
//------------------------------------------------------------------------------

const astUtils = require("./utils/ast-utils");
const eslintUtils = require("eslint-utils");

const precedence = astUtils.getPrecedence;

//------------------------------------------------------------------------------
// Rule Definition
Expand Down Expand Up @@ -126,6 +129,60 @@ module.exports = {
return Boolean(sourceCode.getCommentsInside(node).length);
}

/**
* Checks if the given node is wrapped in grouping parentheses. Parentheses for constructs such as if() don't count.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is parenthesized.
* @private
*/
function isParenthesized(node) {
return eslintUtils.isParenthesized(1, node, sourceCode);
}

/**
* Determines whether the given node needs to be parenthesized when replacing the previous node.
* It assumes that `previousNode` is the node to be reported by this rule, so it has a limited list
* of possible parent node types. By the same assumption, the node's role in a particular parent is already known.
* For example, if the parent is `ConditionalExpression`, `previousNode` must be its `test` child.
* @param {ASTNode} previousNode Previous node.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node needs to be parenthesized.
*/
function needsParens(previousNode, node) {
if (isParenthesized(previousNode)) {

// parentheses around the previous node will stay, so there is no need for an additional pair
return false;
}

// parent of the previous node will become parent of the replacement node
const parent = previousNode.parent;

switch (parent.type) {
case "CallExpression":
case "NewExpression":
return node.type === "SequenceExpression";
case "IfStatement":
case "DoWhileStatement":
case "WhileStatement":
case "ForStatement":
return false;
case "ConditionalExpression":
return precedence(node) <= precedence(parent);
case "UnaryExpression":
return precedence(node) < precedence(parent);
case "LogicalExpression":
if (previousNode === parent.left) {
return precedence(node) < precedence(parent);
}
return precedence(node) <= precedence(parent);

/* istanbul ignore next */
default:
throw new Error(`Unexpected parent type: ${parent.type}`);
}
}

return {
UnaryExpression(node) {
const parent = node.parent;
Expand All @@ -143,32 +200,34 @@ module.exports = {
context.report({
node: parent,
messageId: "unexpectedNegation",
fix: fixer => {
fix(fixer) {
if (hasCommentsInside(parent)) {
return null;
}

if (needsParens(parent, node.argument)) {
return fixer.replaceText(parent, `(${sourceCode.getText(node.argument)})`);
}

let prefix = "";
const tokenBefore = sourceCode.getTokenBefore(parent);
const firstReplacementToken = sourceCode.getFirstToken(node.argument);

if (tokenBefore && tokenBefore.range[1] === parent.range[0] &&
!astUtils.canTokensBeAdjacent(tokenBefore, firstReplacementToken)) {
if (
tokenBefore &&
tokenBefore.range[1] === parent.range[0] &&
!astUtils.canTokensBeAdjacent(tokenBefore, firstReplacementToken)
) {
prefix = " ";
}

if (astUtils.getPrecedence(node.argument) < astUtils.getPrecedence(parent.parent)) {
return fixer.replaceText(parent, `(${sourceCode.getText(node.argument)})`);
}

return fixer.replaceText(parent, prefix + sourceCode.getText(node.argument));
}
});
}
},
CallExpression(node) {
const parent = node.parent;

CallExpression(node) {
if (node.callee.type !== "Identifier" || node.callee.name !== "Boolean") {
return;
}
Expand All @@ -177,11 +236,15 @@ module.exports = {
context.report({
node,
messageId: "unexpectedCall",
fix: fixer => {
if (!node.arguments.length) {
fix(fixer) {
const parent = node.parent;

if (node.arguments.length === 0) {
if (parent.type === "UnaryExpression" && parent.operator === "!") {

// !Boolean() -> true
/*
* !Boolean() -> true
*/

if (hasCommentsInside(parent)) {
return null;
Expand All @@ -191,32 +254,48 @@ module.exports = {
let prefix = "";
const tokenBefore = sourceCode.getTokenBefore(parent);

if (tokenBefore && tokenBefore.range[1] === parent.range[0] &&
!astUtils.canTokensBeAdjacent(tokenBefore, replacement)) {
if (
tokenBefore &&
tokenBefore.range[1] === parent.range[0] &&
!astUtils.canTokensBeAdjacent(tokenBefore, replacement)
) {
prefix = " ";
}

return fixer.replaceText(parent, prefix + replacement);
}

// Boolean() -> false
/*
* Boolean() -> false
*/

if (hasCommentsInside(node)) {
return null;
}

return fixer.replaceText(node, "false");
}

if (node.arguments.length > 1 || node.arguments[0].type === "SpreadElement" ||
hasCommentsInside(node)) {
return null;
}
if (node.arguments.length === 1) {
const argument = node.arguments[0];

if (argument.type === "SpreadElement" || hasCommentsInside(node)) {
return null;
}

/*
* Boolean(expression) -> expression
*/

const argument = node.arguments[0];
if (needsParens(node, argument)) {
return fixer.replaceText(node, `(${sourceCode.getText(argument)})`);
}

if (astUtils.getPrecedence(argument) < astUtils.getPrecedence(node.parent)) {
return fixer.replaceText(node, `(${sourceCode.getText(argument)})`);
return fixer.replaceText(node, sourceCode.getText(argument));
}
return fixer.replaceText(node, sourceCode.getText(argument));

// two or more arguments
return null;
}
});
}
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