Fix easy cases of date related functions

Closes humbug#301

README.md

@@ -56,6 +56,7 @@ potentially very difficult to debug due to dissimilar or unsupported package ver
 - [Recommendations](#recommendations)
 - [Limitations](#limitations)
     - [Dynamic symbols](#dynamic-symbols)
+    - [Date symbols](#date-symbols)
     - [Heredoc values](#heredoc-values)
     - [Callables](#callables)
     - [String values](#string-values)
@@ -648,6 +649,19 @@ possible such as:
     - `const X = 'Symfony\\Component' . '\\Yaml\\Ya_1';`
 
 
+### Date symbols
+
+You code may be using a convention for the date string formats which could be mistaken for classes, e.g.:
+
+```php
+const ISO8601_BASIC = 'Ymd\THis\Z';
+``` 
+
+In this scenario, PHP-Scoper has no way to tell that string `'Ymd\THis\Z'` does not refer to a symbol but is
+a date format. In this case, you will have to rely on patchers. Note however that PHP-Scoper will be able to
+handle some cases such as, see the [date-spec](specs/misc/date.php).
+
+
 ### Heredoc values
 
 If you consider the following code:

specs/misc/date.php

@@ -0,0 +1,114 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the humbug/php-scoper package.
+ *
+ * Copyright (c) 2017 Théo FIDRY <[email protected]>,
+ *                    Pádraic Brady <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+return [
+    'meta' => [
+        'title' => 'Date related functions/calls',
+        // Default values. If not specified will be the one used
+        'prefix' => 'Humbug',
+        'whitelist' => [],
+        'whitelist-global-constants' => true,
+        'whitelist-global-classes' => false,
+        'whitelist-global-functions' => true,
+        'registered-classes' => [],
+        'registered-functions' => [],
+    ],
+
+    'date values' => <<<'PHP'
+<?php
+
+const ISO8601_BASIC = 'Ymd\THis\Z';
+
+new Foo('d\H\Z');
+new DateTime('d\H\Z');
+new DateTimeImmutable('d\H\Z');
+date_create('d\H\Z');
+date('d\H\Z');
+gmdate('d\H\Z');
+
+DateTime::createFromFormat('d\H\Z', '15\Feb\2009');
+DateTimeImmutable::createFromFormat('d\H\Z', '15\Feb\2009');
+date_create_from_format('d\H\Z', '15\Feb\2009');
+
+(new DateTime('now'))->format('d\H\Z');
+date_format(new DateTime('now'), 'd\H\Z');
+
+----
+<?php
+
+namespace Humbug;
+
+const ISO8601_BASIC = 'Humbug\\Ymd\\THis\\Z';
+new \Humbug\Foo('Humbug\\d\\H\\Z');
+new \DateTime('d\\H\\Z');
+new \DateTimeImmutable('d\\H\\Z');
+\date_create('d\\H\\Z');
+\date('d\\H\\Z');
+\gmdate('d\\H\\Z');
+\DateTime::createFromFormat('d\\H\\Z', '15\\Feb\\2009');
+\DateTimeImmutable::createFromFormat('d\\H\\Z', '15\\Feb\\2009');
+\date_create_from_format('d\\H\\Z', '15\\Feb\\2009');
+(new \DateTime('now'))->format('Humbug\\d\\H\\Z');
+\date_format(new \DateTime('now'), 'Humbug\\d\\H\\Z');
+
+PHP
+    ,
+
+    'date values in a namespace' => <<<'PHP'
+<?php
+
+namespace Acme;
+
+use DateTime;
+use DateTimeImmutable;
+
+const ISO8601_BASIC = 'Ymd\THis\Z';
+
+new Foo('d\H\Z');
+new DateTime('d\H\Z');
+new DateTimeImmutable('d\H\Z');
+date_create('d\H\Z');
+date('d\H\Z');
+gmdate('d\H\Z');
+
+DateTime::createFromFormat('d\H\Z', '15\Feb\2009');
+DateTimeImmutable::createFromFormat('d\H\Z', '15\Feb\2009');
+date_create_from_format('d\H\Z', '15\Feb\2009');
+
+(new DateTime('now'))->format('d\H\Z');
+date_format(new DateTime('now'), 'd\H\Z');
+
+----
+<?php
+
+namespace Humbug\Acme;
+
+use DateTime;
+use DateTimeImmutable;
+const ISO8601_BASIC = 'Humbug\\Ymd\\THis\\Z';
+new \Humbug\Acme\Foo('Humbug\\d\\H\\Z');
+new \DateTime('d\\H\\Z');
+new \DateTimeImmutable('d\\H\\Z');
+\date_create('d\\H\\Z');
+\date('d\\H\\Z');
+\gmdate('d\\H\\Z');
+\DateTime::createFromFormat('d\\H\\Z', '15\\Feb\\2009');
+\DateTimeImmutable::createFromFormat('d\\H\\Z', '15\\Feb\\2009');
+\date_create_from_format('d\\H\\Z', '15\\Feb\\2009');
+(new \DateTime('now'))->format('Humbug\\d\\H\\Z');
+\date_format(new \DateTime('now'), 'Humbug\\d\\H\\Z');
+
+PHP
+    ,
+];

src/PhpParser/NodeVisitor/StringScalarPrefixer.php

@@ -23,6 +23,9 @@
 use PhpParser\Node\Expr\ArrayItem;
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\FuncCall;
+use PhpParser\Node\Expr\New_;
+use PhpParser\Node\Expr\StaticCall;
+use PhpParser\Node\Identifier;
 use PhpParser\Node\Name;
 use PhpParser\Node\Name\FullyQualified;
 use PhpParser\Node\Param;
@@ -38,6 +41,7 @@
 use function is_string;
 use function preg_match;
 use function strpos;
+use function strtolower;
 
 /**
  * Prefixes the string scalar values when appropriate.
@@ -68,6 +72,11 @@ final class StringScalarPrefixer extends NodeVisitorAbstract
         'trait_exists',
     ];
 
+    private const DATETIME_CLASSES = [
+        'datetime',
+        'datetimeimmutable',
+    ];
+
     private $prefix;
     private $whitelist;
     private $reflector;
@@ -138,26 +147,52 @@ private function prefixStringScalar(String_ $string): String_
 
     private function prefixStringArg(String_ $string, Arg $parentNode): String_
     {
-        $functionNode = ParentNodeAppender::getParent($parentNode);
+        $callerNode = ParentNodeAppender::getParent($parentNode);
 
-        if (false === ($functionNode instanceof FuncCall)) {
-            // If belongs to the global namespace then we cannot differentiate the value from a symbol and a regular string
-            return $this->belongsToTheGlobalNamespace($string)
-                ? $string
-                : $this->createPrefixedString($string)
-            ;
+        if ($callerNode instanceof New_) {
+            return $this->prefixNewStringArg($string, $callerNode);
+        }
+
+        if ($callerNode instanceof FuncCall) {
+            return $this->prefixFunctionStringArg($string, $callerNode);
+        }
+
+        if ($callerNode instanceof StaticCall) {
+            return $this->prefixStaticCallStringArg($string, $callerNode);
         }
-        /** @var FuncCall $functionNode */
 
+        // If belongs to the global namespace then we cannot differentiate the value from a symbol and a regular
+        // string
+        return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+    }
+
+    private function prefixNewStringArg(String_ $string, New_ $newNode): String_
+    {
+        $class = $newNode->class;
+
+        if (false === ($class instanceof FullyQualified)) {
+            return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+        }
+
+        if (in_array(strtolower($class->toString()), self::DATETIME_CLASSES, true)) {
+            return $string;
+        }
+
+        return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+    }
+
+    private function prefixFunctionStringArg(String_ $string, FuncCall $functionNode): String_
+    {
         // In the case of a function call, we allow to prefix strings which could be classes belonging to the global
         // namespace in some cases
         $functionName = $functionNode->name instanceof Name ? (string) $functionNode->name : null;
 
+        if (in_array($functionName, ['date_create', 'date', 'gmdate', 'date_create_from_format'], true)) {
+            return $string;
+        }
+
         if (false === in_array($functionName, self::SPECIAL_FUNCTION_NAMES, true)) {
-            return $this->belongsToTheGlobalNamespace($string)
-                ? $string
-                : $this->createPrefixedString($string)
-            ;
+            return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
         }
 
         if ('function_exists' === $functionName) {
@@ -193,6 +228,27 @@ private function prefixStringArg(String_ $string, Arg $parentNode): String_
         ;
     }
 
+    private function prefixStaticCallStringArg(String_ $string, StaticCall $callNode): String_
+    {
+        $class = $callNode->class;
+
+        if (false === ($class instanceof FullyQualified)) {
+            return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+        }
+
+        if (false === in_array(strtolower($class->toString()), self::DATETIME_CLASSES, true)) {
+            return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+        }
+
+        if ($callNode->name instanceof Identifier
+            && 'createFromFormat' === $callNode->name->toString()
+        ) {
+            return $string;
+        }
+
+        return $this->createPrefixedStringIfDoesNotBelongToGlobalNamespace($string);
+    }
+
     private function prefixArrayItemString(String_ $string, ArrayItem $parentNode): String_
     {
         // ArrayItem can lead to two results: either the string is used for `spl_autoload_register()`, e.g.
@@ -269,6 +325,15 @@ private function isConstantNode(String_ $node): bool
         return $parent === $argParent->args[0];
     }
 
+    private function createPrefixedStringIfDoesNotBelongToGlobalNamespace(String_ $string): String_
+    {
+        // If belongs to the global namespace then we cannot differentiate the value from a symbol and a regular string
+        return $this->belongsToTheGlobalNamespace($string)
+            ? $string
+            : $this->createPrefixedString($string)
+        ;
+    }
+
     private function createPrefixedString(String_ $previous): String_
     {
         $previousValueParts = array_values(