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/**
* @fileoverview Disallow unnecessary calls to sourceCode.getFirstToken and sourceCode.getLastToken
* @author Teddy Katz
*/
'use strict';
const utils = require('../utils');
// ------------------------------------------------------------------------------
// Rule Definition
// ------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: 'disallow unnecessary calls to sourceCode.getFirstToken and sourceCode.getLastToken',
category: 'Rules',
recommended: true,
},
type: 'suggestion',
fixable: 'code',
schema: [],
},
create (context) {
const sourceCode = context.getSourceCode();
// ----------------------------------------------------------------------
// Helpers
// ----------------------------------------------------------------------
/**
* Determines whether a second argument to getFirstToken or getLastToken changes the output of the function.
* This occurs when the second argument exists and is not an object literal, or has keys other than `includeComments`.
* @param {ASTNode} arg The second argument to `sourceCode.getFirstToken` or `sourceCode.getLastToken`
* @returns {boolean} `true` if the argument affects the output of getFirstToken or getLastToken
*/
function affectsGetTokenOutput (arg) {
if (!arg) {
return false;
}
if (arg.type !== 'ObjectExpression') {
return true;
}
return arg.properties.length >= 2 || (
arg.properties.length === 1 && (
utils.getKeyName(arg.properties[0]) !== 'includeComments' ||
arg.properties[0].value.type !== 'Literal'
));
}
/**
* Determines whether a node is a MemberExpression that accesses the `range` property
* @param {ASTNode} node The node
* @returns {boolean} `true` if the node is a MemberExpression that accesses the `range` property
*/
function isRangeAccess (node) {
return node.type === 'MemberExpression' && node.property.type === 'Identifier' && node.property.name === 'range';
}
/**
* Determines whether a MemberExpression accesses the `start` property (either `.range[0]` or `.start`).
* Note that this will also work correctly if the `.range` MemberExpression is passed.
* @param {ASTNode} memberExpression The MemberExpression node to check
* @returns {boolean} `true` if this node accesses either `.range[0]` or `.start`
*/
function isStartAccess (memberExpression) {
if (isRangeAccess(memberExpression) && memberExpression.parent.type === 'MemberExpression') {
return isStartAccess(memberExpression.parent);
}
return (
(memberExpression.property.type === 'Identifier' && memberExpression.property.name === 'start') ||
(
memberExpression.computed && memberExpression.property.type === 'Literal' && memberExpression.property.value === 0 &&
isRangeAccess(memberExpression.object)
)
);
}
/**
* Determines whether a MemberExpression accesses the `start` property (either `.range[1]` or `.end`).
* Note that this will also work correctly if the `.range` MemberExpression is passed.
* @param {ASTNode} memberExpression The MemberExpression node to check
* @returns {boolean} `true` if this node accesses either `.range[1]` or `.end`
*/
function isEndAccess (memberExpression) {
if (isRangeAccess(memberExpression) && memberExpression.parent.type === 'MemberExpression') {
return isEndAccess(memberExpression.parent);
}
return (
(memberExpression.property.type === 'Identifier' && memberExpression.property.name === 'end') ||
(
memberExpression.computed && memberExpression.property.type === 'Literal' && memberExpression.property.value === 1 &&
isRangeAccess(memberExpression.object)
)
);
}
// ----------------------------------------------------------------------
// Public
// ----------------------------------------------------------------------
return {
'Program:exit' (ast) {
Array.from(utils.getSourceCodeIdentifiers(context, ast))
.filter(identifier => identifier.parent.type === 'MemberExpression' &&
identifier.parent.object === identifier &&
identifier.parent.property.type === 'Identifier' &&
identifier.parent.parent.type === 'CallExpression' &&
identifier.parent === identifier.parent.parent.callee &&
identifier.parent.parent.arguments.length <= 2 &&
!affectsGetTokenOutput(identifier.parent.parent.arguments[1]) &&
identifier.parent.parent.parent.type === 'MemberExpression' &&
identifier.parent.parent === identifier.parent.parent.parent.object && (
(isStartAccess(identifier.parent.parent.parent) && identifier.parent.property.name === 'getFirstToken') ||
(isEndAccess(identifier.parent.parent.parent) && identifier.parent.property.name === 'getLastToken'))
)
.forEach(identifier => {
const fullRangeAccess = isRangeAccess(identifier.parent.parent.parent)
? identifier.parent.parent.parent.parent
: identifier.parent.parent.parent;
const replacementText = sourceCode.text.slice(fullRangeAccess.range[0], identifier.parent.parent.range[0]) +
sourceCode.getText(identifier.parent.parent.arguments[0]) +
sourceCode.text.slice(identifier.parent.parent.range[1], fullRangeAccess.range[1]);
context.report({
node: identifier.parent.parent,
message: "Use '{{replacementText}}' instead.",
data: { replacementText },
fix (fixer) {
return fixer.replaceText(identifier.parent.parent, sourceCode.getText(identifier.parent.parent.arguments[0]));
},
});
});
},
};
},
};
|
