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var config = require('../config');
var flag = require('./flag');
var getProperties = require('./getProperties');
var isProxyEnabled = require('./isProxyEnabled');
/*!
* Chai - proxify utility
* Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
* MIT Licensed
*/
/**
* ### .proxify(object)
*
* Return a proxy of given object that throws an error when a non-existent
* property is read. By default, the root cause is assumed to be a misspelled
* property, and thus an attempt is made to offer a reasonable suggestion from
* the list of existing properties. However, if a nonChainableMethodName is
* provided, then the root cause is instead a failure to invoke a non-chainable
* method prior to reading the non-existent property.
*
* If proxies are unsupported or disabled via the user's Chai config, then
* return object without modification.
*
* @param {Object} obj
* @param {String} nonChainableMethodName
* @namespace Utils
* @name proxify
*/
var builtins = ['__flags', '__methods', '_obj', 'assert'];
module.exports = function proxify(obj, nonChainableMethodName) {
if (!isProxyEnabled()) return obj;
return new Proxy(obj, {
get: function proxyGetter(target, property) {
// This check is here because we should not throw errors on Symbol properties
// such as `Symbol.toStringTag`.
// The values for which an error should be thrown can be configured using
// the `config.proxyExcludedKeys` setting.
if (typeof property === 'string' &&
config.proxyExcludedKeys.indexOf(property) === -1 &&
!Reflect.has(target, property)) {
// Special message for invalid property access of non-chainable methods.
if (nonChainableMethodName) {
throw Error('Invalid Chai property: ' + nonChainableMethodName + '.' +
property + '. See docs for proper usage of "' +
nonChainableMethodName + '".');
}
// If the property is reasonably close to an existing Chai property,
// suggest that property to the user. Only suggest properties with a
// distance less than 4.
var suggestion = null;
var suggestionDistance = 4;
getProperties(target).forEach(function(prop) {
if (
!Object.prototype.hasOwnProperty(prop) &&
builtins.indexOf(prop) === -1
) {
var dist = stringDistanceCapped(
property,
prop,
suggestionDistance
);
if (dist < suggestionDistance) {
suggestion = prop;
suggestionDistance = dist;
}
}
});
if (suggestion !== null) {
throw Error('Invalid Chai property: ' + property +
'. Did you mean "' + suggestion + '"?');
} else {
throw Error('Invalid Chai property: ' + property);
}
}
// Use this proxy getter as the starting point for removing implementation
// frames from the stack trace of a failed assertion. For property
// assertions, this prevents the proxy getter from showing up in the stack
// trace since it's invoked before the property getter. For method and
// chainable method assertions, this flag will end up getting changed to
// the method wrapper, which is good since this frame will no longer be in
// the stack once the method is invoked. Note that Chai builtin assertion
// properties such as `__flags` are skipped since this is only meant to
// capture the starting point of an assertion. This step is also skipped
// if the `lockSsfi` flag is set, thus indicating that this assertion is
// being called from within another assertion. In that case, the `ssfi`
// flag is already set to the outer assertion's starting point.
if (builtins.indexOf(property) === -1 && !flag(target, 'lockSsfi')) {
flag(target, 'ssfi', proxyGetter);
}
return Reflect.get(target, property);
}
});
};
/**
* # stringDistanceCapped(strA, strB, cap)
* Return the Levenshtein distance between two strings, but no more than cap.
* @param {string} strA
* @param {string} strB
* @param {number} number
* @return {number} min(string distance between strA and strB, cap)
* @api private
*/
function stringDistanceCapped(strA, strB, cap) {
if (Math.abs(strA.length - strB.length) >= cap) {
return cap;
}
var memo = [];
// `memo` is a two-dimensional array containing distances.
// memo[i][j] is the distance between strA.slice(0, i) and
// strB.slice(0, j).
for (var i = 0; i <= strA.length; i++) {
memo[i] = Array(strB.length + 1).fill(0);
memo[i][0] = i;
}
for (var j = 0; j < strB.length; j++) {
memo[0][j] = j;
}
for (var i = 1; i <= strA.length; i++) {
var ch = strA.charCodeAt(i - 1);
for (var j = 1; j <= strB.length; j++) {
if (Math.abs(i - j) >= cap) {
memo[i][j] = cap;
continue;
}
memo[i][j] = Math.min(
memo[i - 1][j] + 1,
memo[i][j - 1] + 1,
memo[i - 1][j - 1] +
(ch === strB.charCodeAt(j - 1) ? 0 : 1)
);
}
}
return memo[strA.length][strB.length];
}
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