@nestjs/graphql/dist/utils/get-number-of-arguments.util.js

Nest - modern, fast, powerful node.js web framework (@graphql)

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.getNumberOfArguments = getNumberOfArguments;
/**
 * Counts the number of arguments for a given function. This algorithm isn't tested for all cases
 * (check in the spec file), so use it carefully, since it relies on getting the function as a string.
 * Note this also counts parameters with default initializers (as opposed to checking `function.length`)
 * @param fn The function to get the number of arguments
 * @returns the number of arguments in the function's signature
 */
function getNumberOfArguments(fn) {
    // Removing newlines is necessary to use easier regex and handle multi-line functions
    const functionAsStringWithoutNewLines = fn.toString().replace(/\n/g, '');
    /* The RegExp below uses a non-greedy match (the question mark), meaning that it tries to find
     * the smallest possible match. This ensures that we don't accidentally
     * consider the function's body as part of the regex match, since we aim
     * to get only the parameters section.
     */
    const anythingEnclosedInParenthesesRegex = /\(.*?\)/;
    const regexMatchedArray = functionAsStringWithoutNewLines.match(new RegExp(anythingEnclosedInParenthesesRegex));
    if (functionHasOneOrMoreArguments(regexMatchedArray)) {
        const functionParametersAsString = regexMatchedArray[0];
        // Removing arrays and objects is also necessary because we count the number of commas in the string,
        // and both could have commas and confuse the split process below.
        const parametersWithReplacedArraysAndObjects = functionParametersAsString
            .replace(/\[.+\]/g, '"array"')
            .replace(/(\{.+\})/g, '"object"');
        const argumentsArray = parametersWithReplacedArraysAndObjects.split(',');
        return argumentsArray.length;
    }
    // Arrow functions with a single parameter can omit the parentheses
    // (e.g. `x => x + 2` or `async x => x + 2`). Match a bare identifier
    // immediately followed by `=>`, allowing an optional `async` prefix.
    const parenlessArrowRegex = /^\s*(?:async\s+)?[a-zA-Z_$][\w$]*\s*=>/;
    if (parenlessArrowRegex.test(functionAsStringWithoutNewLines)) {
        return 1;
    }
    return 0;
}
function functionHasOneOrMoreArguments(functionRegexMatchArray) {
    return functionRegexMatchArray && functionRegexMatchArray[0] !== '()';
}