Tools for format and error checking in your programming language

Question

Lints and Hints: What tools are available for checking and correcting the conventions, style and common errors in my language (lint tools), and are there tools that can automatically fix them (hint tools)?

This is a follow-up to a comment posted on Is there a place for automated code reviews?

Would a list of static analysis tools help jumpstart this? – h.j.k.34 mins ago

Let's list a few tools that people can use to address easy and common issues in their code before they ask their questions, and that can help reviewers gather "easy" points to mention in their CR answers...:

• Bash (and other shells)
• C, C++ also C specific
• C#
• Delphi
• HTML, XHTML, CSS
• Go
• Java
• JavaScript
• jQuery
• JSON
• Lisp
• Lua
• MongoDB
• Objective-C
• Perl
• PHP
• Python
• Regex
• Ruby
• Scala
• SQL
• Swift
• VB.NET
• VB6 and VBA
• XML

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To keep this organized, please post one tool/language per answer; if it's a paid/commercial tool, please mention it. Also please include a link to the website.

Answer 1

Python

Python uses Python Enhancement Proposals (PEPs) to improve Python, ranging from style guides to feature requests. There are linters for a few of these:

• PEP 8 -- Style Guide for Python Code.

  There are both online (pep8online.com) and offline (pycodestyle^h) versions for this.

• PEP 257 (pydocstyle^h) -- Docstring Conventions.

• PEP 484 (mypy^h, or the faster pyright) -- Type Hints.

There is also "PEP 7 -- Style Guide for C Code [in the C implementation of Python]". But this does not seem to have a linter.

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When starting a new project you might choose to do this:

• "$ ruff check" -- fast and "not too picky" linter, you should probably do what it suggests, or let --fix do that for you.
• "$ isort ." -- "I sort imports so you don't have to", per PEP8, so just do it.
• "$ black ." -- will reformat source code, in an opinionated way.

The first two are no-brainers, they won't hurt anything. Adopting black can be a bit more of a hurdle, but once you bite the bullet there's all manner of trivial pull-request code review remarks that simply never arise any more. Blacked code will typically lint clean.

Start with "$ black -S ." followed by "git diff". The -S says don't turn single- into double- quote strings, basically noise when you're viewing the initial diffs. Go through some commits, plus one or two PRs, and watch the S/N ratio improve.

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There are also some other analysis tools:

• pylint^h

• Pyflakes^h

• PyChecker^h

  Warning: This imports the code to analyse it.

• Flake8^h

  Combines Pyflakes and pycodestyle into one tool.

• Prospector^h

  Combines all of: pylint, Pyflakes, pycodestyle, pydocstyle and more tools.

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There are also ways to incorporating some of the above tools into different editors. For a small list of incorporations:

• Sublime Text has SublimeLinter 3,
• vim has pylint.vim and pep8,
• Atom has linter-pep8,
• PyCharm has PEP 8 by default,
• Spyder has PEP 8 support by default, and
• Visual Studio Code has the Python extension that can work with a long list of linters, e.g. Pylint and Flake8.

These are good to make sure your answers are PEP 8 compliant, and so there are no contradictions when saying to follow PEP 8. However using the tools from the above sections will give a report that you can comment from.

Answer 2

C / C++

• Clang's Static Analyzer, a free static analyzer based on Clang.

• Coverity, a commercial static analyzer, free for open source developers.

• Cppcheck, an open-source static analyzer.

• CppDepend, a commercial static analyzer based on Clang.

• GCC, free compiler that closely follows C and C++ standards.

• Valgrind, run-time analyser that is particularly good for the kind of memory errors common in these languages.

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Simply compiling code with warning options such as -Wall -Wextra -pedantic catches quite a number of potential or actual problems.

Answer 3

C#

• StyleCop (free)

  It can be run from inside of Visual Studio or integrated into an MSBuild project.

• ReSharper (commercial)

  A paid Visual Studio extension (possibility for open-source "community" license though) with a free 30-day trial.

• FxCop (free)

  Can be run standalone, but later versions are bundled into Visual Studio as the "Code Analysis" feature.

Answer 4

VB6 / VBA6 / VBA7 (x86/x64)

• Rubberduck is a free (beer & speech), open-source add in for the VBE IDE maintained by several members of the vba and c# community here on Code Review. For more info see the rubberduck tag.

Features include static code analysis, code metrics, refactoring tools, Smart Indenter, a unit testing framework, and more.

Direct Link to Code Inspection Documentation

Answer 5

JavaScript

For JavaScript, there are a few options:

• JSLint (the original, created by Douglas Crockford)
• JSHint (a community-driven fork of JSLint)
• ESLint (an ES6-compatible fork of JSHint. Necessary if you want to lint ES6 code).

In all cases, if you're using a transpiler like Babel or Traceur, you should run the linter before the transpile step. Don't lint compiled code.

Note that all major browsers and other interpreters support the "use strict"; directive in code, and will ensure that many common mistakes in code are identified before running the code. See: What does “use strict” do in JavaScript, and what is the reasoning behind it?

Answer 6

VB.NET

• ReSharper (commercial)

  A paid Visual Studio extension (possibility for open-source "community" license though) with a free 30-day trial.

Answer 7

HTML5, XHTML, CSS

Tool:Markup validation checker

Also, there are beautifiers to help improve formatting, CodeBeautify.org has a good one.

Answer 8

Delphi

Tool: FixInsight (commercial)

Website:https://www.tmssoftware.com/site/fixinsight.asp

Answer 9

Java

Java lint tools are usually dependent of the IDE you develop in. All the major IDE's (Eclipse, IntelliJ, Netbeans, etc. - alphabetical order) have mechanisms in place for not only checking for lint-like problems, but also for fixing them too.

Features to expect from your IDE - identification of, and correction of:

1. automatic code formatting (indentation, brace positions, line-wrapping, etc.)
2. redundant code, or impossible code
3. incomplete documentation
4. variable and function name "shadowing"
5. and much, much more.

Standalone tools:

1. PMD
2. FindBugs

Answer 10

Regex:

JS-Flavored

• Debuggex.com - online regex visual debugger

• Regexr.com - online regex tester

• Regex101.com - online tester and debugger

Offline-Tools:

• RegexBuddy - commercial regex-development helper tool, supporting a multitude of regex-flavors and programming languages

Answer 11

Perl

Plugins:

• Perl::Lint

• linter-perl

• Perl::Critic

Or natively using B::Lint module.

Answer 12

PHP

Online:

• PHP Linter Online

• PHPCodeChecker.com

Plugins:

• NuSphere

You can also use the native php_check_syntax from an IDE or command line.

Answer 13

C

• splint

Although not currently actively developed, this free, open-source software provides error checking that can be enhanced with in-code commenting.

Answer 14

Bash, Shell

Online:

• ShellCheck.net

Plugins:

• bashlint

• ShellCheck

Answer 15

SQL

General:

• Program: Mimer SQL Validator

• Online: FreeFormatter.com

SQL Server / Transact-SQL

Online: SQL-Format.org

Natively: SET SHOWPLAN_XML

MySQL

Online: MySQL Syntax Check

Natively: EXPLAIN

PostgreSQL & PL/pgSQL

Plugin: pg-validator

Natively: EXPLAIN

SQLite

Plugin: sqllogictest

Natively: EXPLAIN

Oracle:

Natively: EXPLAIN

Answer 16

Objective-C

Plugins:

• OCLint.org

• Uncrustify

• linter(for Atom.io)

_{These should also work for C/C++}

Answer 17

XML

Online validators:

• XML Validation.com

• W3Schools.com

Plugins:

• Maven

• Grails

• Notepad++

• FireFox

Answer 18

jQuery

Plugins:

• jQueryValidation.org

• FormValidator.net

You can also use JavaScriptLint.com.

Answer 19

Lisp

Plugins:

• LINT: Lint for Common Lisp

• clavier

Answer 20

MongoDB

Plugins:

• Mongoose(for Node.js)

• revalidator(for Node.js)

• lx-valid(for Node.js)

• Mongoid(for Ruby)

Or natively use validate

Answer 21

Lua

Plugins:

• lua-checker

Answer 22

Ruby

Gems:

• rubocop is probably the most popular

But there are many more each with emphasis on different things (style, code complexity, etc.).

Online:

• Don't know if this counts as it's more like CI, but there's always CodeClimate (also works for JavaScript, PHP, and Python)

Answer 23

Swift

• swiftlint
  • Metova's fork

Answer 24

Go

• golint Style and convention problems with documentation, naming, dead-code analysis, and more.
• go fmt adjusts your go code to conform to standard Go style (indentation, spacing, import orders, etc.)
• go vet does deeper static analysis on your code and determines if there are more serious problems in the code, including poorly structured printf statements, etc.

In addition, there are profiling tools, race-condition-analysis tools, and so on that work at program runtime.

Answer 25

Scala

Style checker plug-in: ScalaStyle.org

Answer 26

JSON

Online validator: JSONLint.com

They also have a free Pro Version

For those at the linux command line, use jq for all sorts of cool features.