codtracker-js/node_modules/eslint/lib/rules/no-param-reassign.js

/**
 * @fileoverview Disallow reassigning function parameters.
 * @author Nat Burns
 */
'use strict';

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

const stopNodePattern =
  /(?:Statement|Declaration|Function(?:Expression)?|Program)$/u;

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
  meta: {
    type: 'suggestion',

    docs: {
      description: 'Disallow reassigning function parameters',
      recommended: false,
      url: 'https://eslint.org/docs/latest/rules/no-param-reassign',
    },

    schema: [
      {
        oneOf: [
          {
            type: 'object',
            properties: {
              props: {
                enum: [false],
              },
            },
            additionalProperties: false,
          },
          {
            type: 'object',
            properties: {
              props: {
                enum: [true],
              },
              ignorePropertyModificationsFor: {
                type: 'array',
                items: {
                  type: 'string',
                },
                uniqueItems: true,
              },
              ignorePropertyModificationsForRegex: {
                type: 'array',
                items: {
                  type: 'string',
                },
                uniqueItems: true,
              },
            },
            additionalProperties: false,
          },
        ],
      },
    ],

    messages: {
      assignmentToFunctionParam: "Assignment to function parameter '{{name}}'.",
      assignmentToFunctionParamProp:
        "Assignment to property of function parameter '{{name}}'.",
    },
  },

  create(context) {
    const props = context.options[0] && context.options[0].props;
    const ignoredPropertyAssignmentsFor =
      (context.options[0] &&
        context.options[0].ignorePropertyModificationsFor) ||
      [];
    const ignoredPropertyAssignmentsForRegex =
      (context.options[0] &&
        context.options[0].ignorePropertyModificationsForRegex) ||
      [];
    const sourceCode = context.sourceCode;

    /**
     * Checks whether or not the reference modifies properties of its variable.
     * @param {Reference} reference A reference to check.
     * @returns {boolean} Whether or not the reference modifies properties of its variable.
     */
    function isModifyingProp(reference) {
      let node = reference.identifier;
      let parent = node.parent;

      while (
        parent &&
        (!stopNodePattern.test(parent.type) ||
          parent.type === 'ForInStatement' ||
          parent.type === 'ForOfStatement')
      ) {
        switch (parent.type) {
          // e.g. foo.a = 0;
          case 'AssignmentExpression':
            return parent.left === node;

          // e.g. ++foo.a;
          case 'UpdateExpression':
            return true;

          // e.g. delete foo.a;
          case 'UnaryExpression':
            if (parent.operator === 'delete') {
              return true;
            }
            break;

          // e.g. for (foo.a in b) {}
          case 'ForInStatement':
          case 'ForOfStatement':
            if (parent.left === node) {
              return true;
            }

            // this is a stop node for parent.right and parent.body
            return false;

          // EXCLUDES: e.g. cache.get(foo.a).b = 0;
          case 'CallExpression':
            if (parent.callee !== node) {
              return false;
            }
            break;

          // EXCLUDES: e.g. cache[foo.a] = 0;
          case 'MemberExpression':
            if (parent.property === node) {
              return false;
            }
            break;

          // EXCLUDES: e.g. ({ [foo]: a }) = bar;
          case 'Property':
            if (parent.key === node) {
              return false;
            }

            break;

          // EXCLUDES: e.g. (foo ? a : b).c = bar;
          case 'ConditionalExpression':
            if (parent.test === node) {
              return false;
            }

            break;

          // no default
        }

        node = parent;
        parent = node.parent;
      }

      return false;
    }

    /**
     * Tests that an identifier name matches any of the ignored property assignments.
     * First we test strings in ignoredPropertyAssignmentsFor.
     * Then we instantiate and test RegExp objects from ignoredPropertyAssignmentsForRegex strings.
     * @param {string} identifierName A string that describes the name of an identifier to
     * ignore property assignments for.
     * @returns {boolean} Whether the string matches an ignored property assignment regular expression or not.
     */
    function isIgnoredPropertyAssignment(identifierName) {
      return (
        ignoredPropertyAssignmentsFor.includes(identifierName) ||
        ignoredPropertyAssignmentsForRegex.some((ignored) =>
          new RegExp(ignored, 'u').test(identifierName)
        )
      );
    }

    /**
     * Reports a reference if is non initializer and writable.
     * @param {Reference} reference A reference to check.
     * @param {int} index The index of the reference in the references.
     * @param {Reference[]} references The array that the reference belongs to.
     * @returns {void}
     */
    function checkReference(reference, index, references) {
      const identifier = reference.identifier;

      if (
        identifier &&
        !reference.init &&
        /*
         * Destructuring assignments can have multiple default value,
         * so possibly there are multiple writeable references for the same identifier.
         */
        (index === 0 || references[index - 1].identifier !== identifier)
      ) {
        if (reference.isWrite()) {
          context.report({
            node: identifier,
            messageId: 'assignmentToFunctionParam',
            data: { name: identifier.name },
          });
        } else if (
          props &&
          isModifyingProp(reference) &&
          !isIgnoredPropertyAssignment(identifier.name)
        ) {
          context.report({
            node: identifier,
            messageId: 'assignmentToFunctionParamProp',
            data: { name: identifier.name },
          });
        }
      }
    }

    /**
     * Finds and reports references that are non initializer and writable.
     * @param {Variable} variable A variable to check.
     * @returns {void}
     */
    function checkVariable(variable) {
      if (variable.defs[0].type === 'Parameter') {
        variable.references.forEach(checkReference);
      }
    }

    /**
     * Checks parameters of a given function node.
     * @param {ASTNode} node A function node to check.
     * @returns {void}
     */
    function checkForFunction(node) {
      sourceCode.getDeclaredVariables(node).forEach(checkVariable);
    }

    return {
      // `:exit` is needed for the `node.parent` property of identifier nodes.
      'FunctionDeclaration:exit': checkForFunction,
      'FunctionExpression:exit': checkForFunction,
      'ArrowFunctionExpression:exit': checkForFunction,
    };
  },
};