[FEATURE] Support Vendor.Package as namespace name

Using this format (or simply Package if no vendor name is
used for the package) makes ViewHelperResolver look in
that namespace + ViewHelpers, for example:

```xml
<TYPO3Fluid.Fluid:render partial="Partial" />
```

Will internally resolve to:

```php
\TYPO3Fluid\Fluid\ViewHelpers\RenderViewHelper
```

Without the need to register the namespace. Note that the
example uses the native Fluid namespace to demonstrate,
although this namespace is always present (unless explicitly
removed by a TemplatePaths override).

Author: NamelessCoder

src/Core/ViewHelper/ViewHelperResolver.php

@@ -173,6 +173,10 @@ public function setNamespaces(array $namespaces)
      */
     public function isNamespaceValid($namespaceIdentifier)
     {
+        if (strpos($namespaceIdentifier, '.')) {
+            return true;
+        }
+
         if (!array_key_exists($namespaceIdentifier, $this->namespaces)) {
             return false;
         }
@@ -245,18 +249,8 @@ public function isNamespaceIgnored($namespaceIdentifier)
     public function resolveViewHelperClassName($namespaceIdentifier, $methodIdentifier)
     {
         if (!isset($this->resolvedViewHelperClassNames[$namespaceIdentifier][$methodIdentifier])) {
-            $resolvedViewHelperClassName = $this->resolveViewHelperName($namespaceIdentifier, $methodIdentifier);
-            $actualViewHelperClassName = implode('\\', array_map('ucfirst', explode('.', $resolvedViewHelperClassName)));
-            if (false === class_exists($actualViewHelperClassName) || $actualViewHelperClassName === false) {
-                throw new ParserException(sprintf(
-                    'The ViewHelper "<%s:%s>" could not be resolved.' . chr(10) .
-                    'Based on your spelling, the system would load the class "%s", however this class does not exist.',
-                    $namespaceIdentifier,
-                    $methodIdentifier,
-                    $resolvedViewHelperClassName
-                ), 1407060572);
-            }
-            $this->resolvedViewHelperClassNames[$namespaceIdentifier][$methodIdentifier] = $actualViewHelperClassName;
+            $this->resolvedViewHelperClassNames[$namespaceIdentifier][$methodIdentifier] =
+                $this->resolveViewHelperName($namespaceIdentifier, $methodIdentifier);
         }
         return $this->resolvedViewHelperClassNames[$namespaceIdentifier][$methodIdentifier];
     }
@@ -320,13 +314,42 @@ protected function resolveViewHelperName($namespaceIdentifier, $methodIdentifier
         } else {
             $className = ucfirst($explodedViewHelperName[0]);
         }
-        $className .= 'ViewHelper';
+        $classNames = [
+            $className . 'ViewHelper',
+            $className
+        ];
 
-        $namespaces = (array) $this->namespaces[$namespaceIdentifier];
+        if ($this->namespaces[$namespaceIdentifier] ?? false) {
+            $namespaces = (array) $this->namespaces[$namespaceIdentifier];
+        } else {
+            $namespacePrefix = $this->namespaces[$namespaceIdentifier] = str_replace('.', '\\', $namespaceIdentifier);
+            $namespaces = [
+                $namespacePrefix . '\\ViewHelpers',
+                $namespacePrefix
+            ];
+        }
+
+        $checked = [];
+        foreach (array_reverse($namespaces) as $namespace) {
+            $namespace = rtrim($namespace, '\\');
+            foreach ($classNames as $className) {
+                $name = $namespace . '\\' . $className;
+                if (class_exists($name) && is_a($name, ViewHelperInterface::class, true)) {
+                    return $name;
+                }
+                $checked[] = $name;
+            }
+        }
 
-        do {
-            $name = rtrim(array_pop($namespaces), '\\') . '\\' . $className;
-        } while (!class_exists($name) && count($namespaces));
+        throw new ParserException(
+            sprintf(
+                'The ViewHelper "<%s:%s>" could not be resolved. Fluid checked for "%s" but none of those classes exist.',
+                $namespaceIdentifier,
+                $methodIdentifier,
+                implode(', ', $checked)
+            ),
+            1407060572
+        );
 
         return $name;
     }

tests/Functional/ExamplesTest.php

@@ -251,7 +251,7 @@ public function getExampleScriptTestValues()
                     'Section rendering error: Section "DoesNotExist" does not exist. Section rendering is mandatory; "optional" is false.',
                     'ViewHelper error: Undeclared arguments passed to ViewHelper TYPO3Fluid\Fluid\ViewHelpers\IfViewHelper: notregistered. Valid arguments are: then, else, condition - Offending code: <f:if notregistered="1" />',
                     'Parser error: The ViewHelper "<f:invalid>" could not be resolved.',
-                    'Based on your spelling, the system would load the class "TYPO3Fluid\Fluid\ViewHelpers\InvalidViewHelper", however this class does not exist. Offending code: <f:invalid />',
+                    'Fluid checked for "TYPO3Fluid\Fluid\ViewHelpers\InvalidViewHelper, TYPO3Fluid\Fluid\ViewHelpers\Invalid" but none of those classes exist. Offending code: <f:invalid />',
                     'Invalid expression: Invalid target conversion type "invalidtype" specified in casting expression "{foobar as invalidtype}".',
                 ]
             ]

tests/Unit/Core/ViewHelper/ViewHelperResolverTest.php

@@ -92,6 +92,16 @@ public function testResolveViewHelperClassNameSupportsMultipleNamespaces()
         $this->assertEquals('TYPO3Fluid\\Fluid\\ViewHelpers\\RenderViewHelper', $result);
     }
 
+    /**
+     * @test
+     */
+    public function testResolveViewHelperClassNameSupportsDirectDottedNamespace()
+    {
+        $resolver = $this->getAccessibleMock(ViewHelperResolver::class, ['dummy']);
+        $result = $resolver->_call('resolveViewHelperName', 'TYPO3Fluid.Fluid', 'render');
+        $this->assertEquals('TYPO3Fluid\\Fluid\\ViewHelpers\\RenderViewHelper', $result);
+    }
+
     /**
      * @test
      */
@@ -103,6 +113,16 @@ public function testResolveViewHelperClassNameTrimsBackslashSuffixFromNamespace(
         $this->assertEquals('TYPO3Fluid\\Fluid\\ViewHelpers\\RenderViewHelper', $result);
     }
 
+    /**
+     * @test
+     */
+    public function testResolveViewHelperClassNameSupportsVendorAndPackageNameAsNamespace()
+    {
+        $resolver = $this->getAccessibleMock(ViewHelperResolver::class, ['dummy']);
+        $result = $resolver->_call('resolveViewHelperName', 'TYPO3Fluid.Fluid', 'render');
+        $this->assertEquals('TYPO3Fluid\\Fluid\\ViewHelpers\\RenderViewHelper', $result);
+    }
+
     /**
      * @test
      */
@@ -255,6 +275,7 @@ public function getIsNamespaceValidTestValues()
             [['foo' => ['test']], 'foo', true],
             [['foo' => ['test']], 'foobar', false],
             [['foo*' => null], 'foo', false],
+            [[], 'Vendor.Namespace', true],
         ];
     }