LowFile-scopeJavaScript / TypeScript Plug & play

Do not reassign imported variables

Ensure that imported variables are not reassigned. This can cause runtime errors, especially in TypeScript. Modify object properties instead of reassigning variables.

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Why this matters

Reassigning imported variables causes runtime errors and is prohibited in TypeScript. Modify properties on the imported object instead of reassigning the variable itself.

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

import { exportedObject } from 'module.js';
exportedObject = 'hello world!';   // Noncompliant: TypeError: Assignment to constant variable.

Prefer

import { exportedObject } from 'module.js';
exportedObject.newAttribute = 'hello world!'; // exportedObject now contains newAttribute and can be seen from all other modules importing it

More snippets

Bad

import { exportedObject } from 'module.js';
exportedObject = 'hello world!';   // Noncompliant: TypeError: Assignment to constant variable.

Good

import { exportedObject } from 'module.js';
exportedObject.newAttribute = 'hello world!'; // exportedObject now contains newAttribute and can be seen from all other modules importing it

Related rules

From the same buckets as this rule.

Critical
Avoid equality operators in loop termination conditions
Check if loops use equality operators (== or !=) in termination conditions. These can lead to infinite loops if the condition is never met exactly. Instead, use relational operators like < or > for safer loop termination.
error-handlingreadability-refactor
Critical
Avoid Returning Null in Non-Async Task Methods
Returning null from a Task or Task<T> method causes a NullReferenceException if awaited. Use Task.CompletedTask or Task.FromResult<T>(null) instead.
error-handlingreadability-refactor+1
Critical
Avoid Using Boolean Expressions in `except` Statements
Detect `except` clauses that use `or` or `and` to catch multiple exceptions. This does not work as intended. Recommend using a tuple of exceptions instead.
error-handlingstack-python

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

import { exportedObject } from 'module.js';
exportedObject = 'hello world!';   // Noncompliant: TypeError: Assignment to constant variable.

Prefer

import { exportedObject } from 'module.js';
exportedObject.newAttribute = 'hello world!'; // exportedObject now contains newAttribute and can be seen from all other modules importing it

More snippets

Bad

import { exportedObject } from 'module.js';
exportedObject = 'hello world!';   // Noncompliant: TypeError: Assignment to constant variable.

Good

import { exportedObject } from 'module.js';
exportedObject.newAttribute = 'hello world!'; // exportedObject now contains newAttribute and can be seen from all other modules importing it

Related rules

From the same buckets as this rule.

Critical

Avoid equality operators in loop termination conditions

Check if loops use equality operators (== or !=) in termination conditions. These can lead to infinite loops if the condition is never met exactly. Instead, use relational operators like < or > for safer loop termination.

error-handlingreadability-refactor

Critical

Avoid Returning Null in Non-Async Task Methods

Returning null from a Task or Task<T> method causes a NullReferenceException if awaited. Use Task.CompletedTask or Task.FromResult<T>(null) instead.

error-handlingreadability-refactor+1

Critical

Avoid Using Boolean Expressions in `except` Statements

Detect `except` clauses that use `or` or `and` to catch multiple exceptions. This does not work as intended. Recommend using a tuple of exceptions instead.

error-handlingstack-python