Object Calisthenics rules for PHP_CodeSniffer

Object Calisthenics are set of rules in object-oriented code, that focuses of maintainability, readability, testability and comprehensibility. We're pragmatic first - they are easy to use all together or one by one.

Why Should You Use This in Your Project?

Read post by William Durand or check presentation by Guilherme Blanco.

Install

composer require object-calisthenics/phpcs-calisthenics-rules --dev

Usage

If you know what you want, jump right to the specific rule:

• 1. Only X Level of Indentation per Method
• 2. Do Not Use "else" Keyword
• 5. Use Only One Object Operator (->) per Line
• 6. Do not Abbreviate
• 7. Keep Your Classes Small
• 9. Do not Use Getters and Setters

How to quickly check 1 rule?

In PHP_CodeSniffer

vendor/bin/phpcs src tests -sp \
--standard=vendor/object-calisthenics/phpcs-calisthenics-rules/src/ObjectCalisthenics/ruleset.xml \
--sniffs=ObjectCalisthenics.Classes.ForbiddenPublicProperty

In EasyCodingStandard

# ecs.yaml
services:
    ObjectCalisthenics\Sniffs\Classes\ForbiddenPublicPropertySniff: ~

then

vendor/bin/ecs check src

---

Implemented Rule Sniffs

1. Only X Level of Indentation per Method

❌

foreach ($sniffGroups as $sniffGroup) {
    foreach ($sniffGroup as $sniffKey => $sniffClass) {
        if (! $sniffClass instanceof Sniff) {
            throw new InvalidClassTypeException;
        }
    }
}

👍

foreach ($sniffGroups as $sniffGroup) {
    $this->ensureIsAllInstanceOf($sniffGroup, Sniff::class);
}

// ...
private function ensureIsAllInstanceOf(array $objects, string $type)
{
    // ...
}

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.Metrics.MaxNestingLevel

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\Metrics\MaxNestingLevelSniff: ~

🔧 Configurable

In PHP_CodeSniffer:

<?xml version="1.0"?>
<ruleset name="my-project">
    <rule ref="ObjectCalisthenics.Metrics.MaxNestingLevel">
        <properties>
            <property name="maxNestingLevel" value="2"/>
        </properties>
    </rule>
</ruleset>

In ECS:

services:
    ObjectCalisthenics\Sniffs\Metrics\MaxNestingLevelSniff:
        maxNestingLevel: 2

---

2. Do Not Use "else" Keyword

❌

if ($status === self::DONE) {
    $this->finish();
} else {
    $this->advance();
}

👍

if ($status === self::DONE) {
    $this->finish();
    return;
}

$this->advance();

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.ControlStructures.NoElse

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\ControlStructures\NoElseSniff: ~

---

5. Use Only One Object Operator (->) per Line

❌

$this->container->getBuilder()->addDefinition(SniffRunner::class);

👍

$containerBuilder = $this->getContainerBuilder();
$containerBuilder->addDefinition(SniffRunner::class);

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.CodeAnalysis.OneObjectOperatorPerLine

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\CodeAnalysis\OneObjectOperatorPerLineSniff: ~

🔧 Configurable

In PHP_CodeSniffer:

<?xml version="1.0"?>
<ruleset name="my-project">
    <rule ref="ObjectCalisthenics.CodeAnalysis.OneObjectOperatorPerLine">
        <properties>
            <property name="variablesHoldingAFluentInterface" type="array" value="$queryBuilder,$containerBuilder"/>
            <property name="methodsStartingAFluentInterface" type="array" value="createQueryBuilder"/>
            <property name="methodsEndingAFluentInterface" type="array" value="execute,getQuery"/>
        </properties>
    </rule>
</ruleset>

In ECS:

services:
    ObjectCalisthenics\Sniffs\CodeAnalysis\OneObjectOperatorPerLineSniff:
        variablesHoldingAFluentInterface: ["$queryBuilder", "$containerBuilder"]
        methodsStartingAFluentInterface: ["createQueryBuilder"]
        methodsEndingAFluentInterface: ["execute", "getQuery"]

---

6. Do not Abbreviate

This is related to class, trait, interface, constant, function and variable names.

❌

class EM
{
    // ...
}

👍

class EntityMailer
{
    // ...
}

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.NamingConventions.ElementNameMinimalLength

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\NamingConventions\ElementNameMinimalLengthSniff: ~

🔧 Configurable

In PHP_CodeSniffer:

<?xml version="1.0"?>
<ruleset name="my-project">
    <rule ref="ObjectCalisthenics.NamingConventions.ElementNameMinimalLength">
        <properties>
            <property name="minLength" value="3"/>
            <property name="allowedShortNames" type="array" value="i,id,to,up"/>
        </properties>
    </rule>
</ruleset>

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\NamingConventions\ElementNameMinimalLengthSniff:
        minLength: 3
        allowedShortNames: ["i", "id", "to", "up"]

---

7. Keep Your Classes Small

❌

class SimpleStartupController
{
    // 300 lines of code
}

👍

class SimpleStartupController
{
    // 50 lines of code
}

❌

class SomeClass
{
    public function simpleLogic()
    {
        // 30 lines of code
    }
}

👍

class SomeClass
{
    public function simpleLogic()
    {
        // 10 lines of code
    }
}

❌

class SomeClass
{
    // 20 properties
}

👍

class SomeClass
{
    // 5 properties
}

❌

class SomeClass
{
    // 20 methods
}

👍

class SomeClass
{
    // 5 methods
}

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.Files.ClassTraitAndInterfaceLength,ObjectCalisthenics.Files.FunctionLength,ObjectCalisthenics.Metrics.MethodPerClassLimit,ObjectCalisthenics.Metrics.PropertyPerClassLimit

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\Files\ClassTraitAndInterfaceLengthSniff: ~
    ObjectCalisthenics\Sniffs\Files\FunctionLengthSniff: ~
    ObjectCalisthenics\Sniffs\Metrics\MethodPerClassLimitSniff: ~
    ObjectCalisthenics\Sniffs\Metrics\PropertyPerClassLimitSniff: ~

🔧 Configurable

In PHP_CodeSniffer:

<?xml version="1.0"?>
<ruleset name="my-project">
    <rule ref="ObjectCalisthenics.Files.ClassTraitAndInterfaceLength">
        <properties>
            <property name="maxLength" value="200"/>
        </properties>
    </rule>
    <rule ref="ObjectCalisthenics.Files.FunctionLength">
        <properties>
            <property name="maxLength" value="20"/>
        </properties>
    </rule>
    <rule ref="ObjectCalisthenics.Metrics.PropertyPerClassLimit">
        <properties>
            <property name="maxCount" value="10"/>
        </properties>
    </rule>
    <rule ref="ObjectCalisthenics.Metrics.MethodPerClassLimit">
        <properties>
            <property name="maxCount" value="10"/>
        </properties>
    </rule>
</ruleset>

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\Files\ClassTraitAndInterfaceLengthSniff:
        maxLength: 200
    ObjectCalisthenics\Sniffs\Files\FunctionLengthSniff:
        maxLength: 20
    ObjectCalisthenics\Sniffs\Metrics\PropertyPerClassLimitSniff:
        maxCount: 10
    ObjectCalisthenics\Sniffs\Metrics\MethodPerClassLimitSniff:
        maxCount: 10

---

9. Do not Use Getters and Setters

This rules is partially related to Domain Driven Design.

• Classes should not contain public properties.
• Method should represent behavior, not set values.

❌

class ImmutableBankAccount
{
    public $currency = 'USD';

    private $amount;

    public function setAmount(int $amount)
    {
        $this->amount = $amount;
    }
}

👍

class ImmutableBankAccount
{
    private $currency = 'USD';

    private $amount;

    public function withdrawAmount(int $withdrawnAmount)
    {
        $this->amount -= $withdrawnAmount;
    }
}

Use Only This Rule?

In PHP_CodeSniffer:

vendor/bin/phpcs ... --sniffs=ObjectCalisthenics.Classes.ForbiddenPublicProperty,ObjectCalisthenics.NamingConventions.NoSetter

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\Classes\ForbiddenPublicPropertySniff: ~
    ObjectCalisthenics\Sniffs\NamingConventions\NoSetterSniff: ~

🔧 Configurable

In PHP_CodeSniffer:

<?xml version="1.0"?>
<ruleset name="my-project">
    <rule ref="ObjectCalisthenics.NamingConventions.NoSetter">
        <properties>
            <property name="allowedClasses" type="array" value="*\DataObject"/>
        </properties>
    </rule>
</ruleset>

In ECS:

# ecs.yml
services:
    ObjectCalisthenics\Sniffs\NamingConventions\NoSetterSniff:
        allowedClasses: 
            - '*\DataObject'

---

Not Implemented Rules - Too Strict, Vague or Annoying

While using in practice, we found these rule to be too strict, vague or even annoying, rather than helping to write cleaner and more pragmatic code. They're also closely related with Domain Driven Design.

3. Wrap Primitive Types and Strings - Since PHP 7, you can use define(strict_types=1) and scalar type hints. For other cases, e.g. email, you can deal with that in your Domain via Value Objects.

4. Use First Class Collections - This rule makes sense, yet is too strict to be useful in practice. Even our code didn't pass it at all.

8. Do Not Use Classes With More Than Two Instance Variables - This depends on individual domain of each project. It doesn't make sense to make a rule for that.

---

3 Rules for Contributing

• 1 feature per PR

• every new feature must be covered by tests

• all tests and style checks must pass

  composer complete-check

We will be happy to merge your feature then.