docs: update How to create own Rector tutorial

README.md

@@ -94,12 +94,12 @@ vendor/bin/rector levels
 Let's say you pick `symfony40` level and you want to upgrade your `/src` directory:
 
 ```bash
-# show known changes to Symfony 4.0
+# show known changes in Symfony 4.0
 vendor/bin/rector process src --level symfony40 --dry-run
 ```
 
 ```bash
-# apply known changes to Symfony 4.0
+# apply
 vendor/bin/rector process src --level symfony40
 ```
 

docs/AllRectorsOverview.md

@@ -1186,7 +1186,7 @@ Changes rand, srand and getrandmax by new md_* alternatives.
 
 - class: `Rector\Php\Rector\FuncCall\TrailingCommaArgumentsRector`
 
-Adds trailing commas to function and methods calls 
+Adds trailing commas to function and methods calls
 
 ```diff
  calling(

docs/HowToCreateOwnRector.md

@@ -1,38 +1,122 @@
-## 6 Steps to Add New Rector
+# 4 Steps Create Own Rector
 
-In case you need a transformation that you didn't find in General Rectors, you can create your own:
+First, make sure your needs is not covered by [any existing Rectors](/docs/AllRectorsOverview.md).
 
-1. Just extend `Rector\Rector\AbstractRector` class. It will prepare **2 methods**:
+Let's say you want to prefix private method call names starting with "internal" with `_`. Not very practical, but it will show the Rector flow.
 
-```php
-public function isCandidate(Node $node): bool
-{
-}
+## 1. New Class
 
-public function refactor(Node $node): ?Node
-{
-}
-```
+Create class that extends [`Rector\Rector\AbstractRector`](/src/Rector/AbstractRector.php). It has many useful methods for checking node type, name, add nodes or remove one. Just run `$this->` and let PHPStorm show you all possible methods.
 
-2. Put it under `namespace Rector\Contrib\<set>;` namespace
+There 3 methods to implement:
 
 ```php
 <?php declare(strict_types=1);
 
-namespace Rector\Contrib\Symfony;
+namespace App\Rector;
 
+use PhpParser\Node;
 use Rector\Rector\AbstractRector;
+use Rector\RectorDefinition\RectorDefinition;
 
-final class MyRector extends AbstractRector
+final class MyFirstRector extends AbstractRector
 {
-    // ...
+    public function getDefinition(): RectorDefinition
+    {
+        // what does this do?
+        // minimalistic before/after sample - to explain in code
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getNodeTypes(): array
+    {
+        // what node types we look for?
+        // String_? FuncCall?
+        // pick any from https://github.com/nikic/PHP-Parser/tree/master/lib/PhpParser/Node
+        return [];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        // what will happen with the node?
+        // common work flow:
+        // - should skip? → return null;
+        // - modify it? → do it, then return $node;
+        // - remove/add nodes elsewhere? → do it, then return null;
+    }
 }
 ```
 
-3. Add a Test Case - [see PHPUnit example](https://github.com/rectorphp/rector/blob/master/tests/Rector/Contrib/PHPUnit/ExceptionAnnotationRector/Test.php)
+## 2. Add Methods
 
-4. Add to specific level, e.g. [`/src/config/level/symfony/symfony33.yml`](/src/config/level/symfony/symfony33.yml)
+```php
+<?php declare(strict_types=1);
 
-5. Submit PR
+namespace App\Rector;
 
-6. :+1:
+use PhpParser\Node;
+use PhpParser\Node\Identifier;
+use PhpParser\Node\Expr\MethodCall;
+use Rector\Rector\AbstractRector;
+use Rector\RectorDefinition\CodeSample;
+use Rector\RectorDefinition\RectorDefinition;
+
+final class MyFirstRector extends AbstractRector
+{
+    public function getDefinition(): RectorDefinition
+    {
+        return new RectorDefinition('Add "_" to private method calls that start with "internal"', [
+            new CodeSample('$this->internalMethod();', '$this->_internalMethod();')
+        ]);
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getNodeTypes(): array
+    {
+        return [MethodCall::class];
+    }
+
+    /**
+     * @param MethodCall $node - we can add "MethodCall" type here, because only this node is in "getNodeTypes()"
+     */
+    public function refactor(Node $node): ?Node
+    {
+        // we only care about "internal*" method names
+        if (! $this->nameStartsWith($node, 'internal')) {
+            return null;
+        }
+
+        $node->name = new Identifier('_' . $this->getName($node));
+
+        return $node;
+    }
+}
+```
+
+## 3. Register it `rector.yml`
+
+```diff
+ services:
++    App\Rector\MyFirstRector: ~
+```
+
+## 4. Let Rector Refactor Your Code
+
+```bash
+vendor/bin/rector process src --dry-run
+
+# apply it
+vendor/bin/rector process src
+```
+
+If you use `rector.yml` from another directory or another name, set it with `--config` option:
+
+```bash
+vendor/bin/rector process src --config ../custom-rector.yml
+```
+
+That's it!

src/Rector/NameResolverTrait.php

@@ -2,6 +2,7 @@
 
 namespace Rector\Rector;
 
+use Nette\Utils\Strings;
 use PhpParser\Node;
 use Rector\PhpParser\Node\Resolver\NameResolver;
 
@@ -29,6 +30,11 @@ trait NameResolverTrait
         return $this->getName($node) === $name;
     }
 
+    public function nameStartsWith(Node $node, string $name): bool
+    {
+        return Strings::startsWith($this->getName($node), $name);
+    }
+
     public function isNameInsensitive(Node $node, string $name): bool
     {
         return strtolower((string) $this->getName($node)) === strtolower($name);