PHPLIB-330: Add first version of our coding standard

.gitignore

@@ -7,3 +7,7 @@ vendor/
 phpunit.phar
 phpunit.xml
 .phpunit.result.cache
+
+# phpcs
+.phpcs-cache
+phpcs.xml

.phpcs/autoload.php

+<?php
+
+// Since doctrine/coding-standard requires PHP 7, we can't add it as a dependency
+// yet. This autoload file adds more information to the phpcs error message,
+// telling the user how they can fix the error presented to them by phpcs.
+if (! file_exists(__DIR__ . '/../vendor/doctrine/coding-standard')) {
+    echo <<<ERRORMESSAGE
+==============================================================================
+ERROR: Doctrine coding standard is not installed. To rectify this, please run:
+composer require --dev doctrine/coding-standard=^6.0
+==============================================================================
+
+
+ERRORMESSAGE;
+}

composer.json

@@ -18,6 +18,7 @@
     "require-dev": {
         "phpunit/phpunit": "^5.7.27 || ^6.4 || ^8.3",
         "sebastian/comparator": "^1.0 || ^2.0 || ^3.0",
+        "squizlabs/php_codesniffer": "^3.4",
         "symfony/phpunit-bridge": "^4.4@dev"
     },
     "autoload": {

phpcs.xml.dist

+<?xml version="1.0"?>
+<ruleset>
+    <arg name="basepath" value="."/>
+    <arg name="extensions" value="php"/>
+    <arg name="parallel" value="80"/>
+    <arg name="cache" value=".phpcs-cache"/>
+    <arg name="colors" />
+
+    <!-- Ignore warnings, show progress of the run, and show sniff names -->
+    <arg value="nps"/>
+
+    <autoload>.phpcs/autoload.php</autoload>
+
+    <file>.phpcs</file>
+    <file>src</file>
+    <file>tests</file>
+
+    <rule ref="Doctrine">
+        <!-- Exclude sniffs that require newer PHP versions -->
+        <!-- Available with PHP 7.0 -->
+        <exclude name="SlevomatCodingStandard.TypeHints.DeclareStrictTypes" />
+        <!-- In addition to requiring PHP 7.0, this sniff will cause a significant amount of BC breaks. Proceed with caution! -->
+        <exclude name="SlevomatCodingStandard.TypeHints.TypeHintDeclaration" />
+        <exclude name="SlevomatCodingStandard.Exceptions.ReferenceThrowableOnly" />
+        <exclude name="SlevomatCodingStandard.ControlStructures.RequireNullCoalesceOperator" />
+
+        <!-- Available with PHP 7.1 -->
+        <exclude name="SlevomatCodingStandard.Classes.ClassConstantVisibility" />
+        <exclude name="SlevomatCodingStandard.PHP.ShortList.LongListUsed" />
+        <exclude name="SlevomatCodingStandard.TypeHints.NullableTypeForNullDefaultValue" />
+
+        <!-- No statement alignment so far -->
+        <exclude name="Generic.Formatting.MultipleStatementAlignment" />
+
+        <!-- Class naming sniffs are excluded to preserve BC -->
+        <exclude name="SlevomatCodingStandard.Classes.SuperfluousAbstractClassNaming" />
+        <exclude name="SlevomatCodingStandard.Classes.SuperfluousExceptionNaming" />
+        <exclude name="SlevomatCodingStandard.Classes.SuperfluousInterfaceNaming" />
+        <exclude name="SlevomatCodingStandard.Classes.SuperfluousTraitNaming" />
+
+        <!-- Forbid useless annotations - Git and LICENCE file provide more accurate information -->
+        <!-- Disable forbidden annotation sniff as excluding @api from the list doesn't work -->
+        <exclude name="SlevomatCodingStandard.Commenting.ForbiddenAnnotations.AnnotationForbidden" />
+
+        <!-- Keep long typehints (for now) -->
+        <exclude name="SlevomatCodingStandard.PHP.TypeCast.InvalidCastUsed" />
+        <exclude name="SlevomatCodingStandard.TypeHints.LongTypeHints" />
+
+        <!-- Don't require a full stop after @throws tags -->
+        <exclude name="Squiz.Commenting.FunctionComment.ThrowsNoFullStop" />
+
+        <!-- Disable some sniffs as they can cause functional changes. These will be enabled later -->
+        <exclude name="Generic.PHP.ForbiddenFunctions.FoundWithAlternative" />
+        <exclude name="SlevomatCodingStandard.Classes.UnusedPrivateElements" />
+        <exclude name="SlevomatCodingStandard.ControlStructures.DisallowYodaComparison" />
+        <exclude name="SlevomatCodingStandard.ControlStructures.EarlyExit" />
+        <exclude name="SlevomatCodingStandard.ControlStructures.UselessIfConditionWithReturn" />
+        <exclude name="SlevomatCodingStandard.Functions.StaticClosure" />
+        <exclude name="SlevomatCodingStandard.Functions.UnusedInheritedVariablePassedToClosure" />
+        <exclude name="SlevomatCodingStandard.Operators.DisallowEqualOperators" />
+
+        <!-- These sniffs cause a large diff, so enable them in separate steps -->
+        <exclude name="SlevomatCodingStandard.Commenting.DocCommentSpacing.IncorrectAnnotationsGroup" />
+        <exclude name="SlevomatCodingStandard.Commenting.RequireOneLinePropertyDocComment" />
+        <exclude name="Squiz.Strings.DoubleQuoteUsage" />
+
+        <!-- Sniff currently breaks, see https://github.com/slevomat/coding-standard/issues/727 -->
+        <exclude name="SlevomatCodingStandard.Namespaces.NamespaceSpacing" />
+    </rule>
+
+    <!-- Change use statement sorting to be compatible with PSR-12 -->
+    <rule ref="SlevomatCodingStandard.Namespaces.AlphabeticallySortedUses">
+        <properties>
+            <property name="psr12Compatible" value="true"/>
+        </properties>
+    </rule>
+
+    <!-- Forbid fully qualified names even for colliding names -->
+    <rule ref="SlevomatCodingStandard.Namespaces.ReferenceUsedNamesOnly">
+        <properties>
+            <property name="allowFallbackGlobalConstants" value="false"/>
+            <property name="allowFallbackGlobalFunctions" value="false"/>
+            <property name="allowFullyQualifiedGlobalClasses" value="false"/>
+            <property name="allowFullyQualifiedGlobalConstants" value="false"/>
+            <property name="allowFullyQualifiedGlobalFunctions" value="false"/>
+            <property phpcs-only="true" name="allowFullyQualifiedNameForCollidingClasses" value="false"/>
+            <property phpcs-only="true" name="allowFullyQualifiedNameForCollidingConstants" value="false"/>
+            <property phpcs-only="true" name="allowFullyQualifiedNameForCollidingFunctions" value="false"/>
+            <property name="searchAnnotations" value="true"/>
+        </properties>
+    </rule>
+
+    <rule ref="PSR1.Methods.CamelCapsMethodName.NotCamelCaps">
+        <exclude-pattern>/src/GridFS/StreamWrapper</exclude-pattern>
+        <exclude-pattern>/tests/DocumentationExamplesTest.php</exclude-pattern>
+    </rule>
+
+    <rule ref="PSR1.Classes.ClassDeclaration.MultipleClasses">
+        <exclude-pattern>/tests/Compat/PolyfillAssertTrait.php</exclude-pattern>
+    </rule>
+</ruleset>