Improve generate ID

Get the right source if extending the Todo class

src/TodoOrDie/System/Trace.php

@@ -0,0 +1,56 @@
+<?php
+declare(strict_types=1);
+
+namespace Robertology\TodoOrDie\System;
+
+class Trace {
+
+  /**
+   * Get a trace starting from the first call to the given class
+   *
+   * Considers parent & child class to be same as class
+   * Note: this is a backtrace, so "start" means "going backward"
+   */
+  static public function fromOutside(string $class) : array {
+    $trace = static::startAt($class);
+
+    foreach ($trace as $key => $entry) {
+      $check = $entry['class'] ?? '';
+      if (empty($check) || ! static::_isA($check, $class)) {
+        $key--;
+        break;
+      }
+    }
+
+    return isset($key) ? array_splice($trace, $key) : [];
+  }
+
+  /**
+   * Get a trace starting at calls involving the given class
+   *
+   * Considers parent & child class to be same as class
+   * Note: this is a backtrace, so "start" means "going backward"
+   */
+  static public function startAt(string $class) : array {
+    $trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+
+    $check = $trace[0];
+    while (! static::_isA($class, $check['class'] ?? '')) {
+      array_shift($trace);
+      $check = reset($trace);
+    }
+
+
+    // renumber the keys with array_values()
+    return array_values($trace);
+  }
+
+  /**
+   * Companre the class names for match or subclass in either direction
+   */
+  static protected function _isA(string $a, string $b) : bool {
+    return is_a($a, $b, true) ||
+      is_a($b, $a, true);
+  }
+
+}

src/TodoOrDie/Todo.php

@@ -7,6 +7,7 @@
   Check,
   Check\Defined as BooleanCheck,
   OverdueError as Exception,
+  TodoIdGenerator,
   TodoState,
 };
 
@@ -63,12 +64,7 @@ protected function _dieIf(Check $check) {
   }
 
   protected function _generateId() : string {
-    // The first entry will be the call to this method; use the second one
-    $trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 2)[1] ?? [];
-    $file = $trace['file'] ?? '';
-    $line = $trace['line'] ?? 0;
-
-    return "{$file}:{$line}";
+    return (new TodoIdGenerator($this))();
   }
 
   protected function _getState() : TodoState {

src/TodoOrDie/TodoIdGenerator.php

@@ -0,0 +1,28 @@
+<?php
+declare(strict_types=1);
+
+namespace Robertology\TodoOrDie;
+
+use Robertology\TodoOrDie\ {
+  System\Trace,
+  Todo,
+};
+
+class TodoIdGenerator {
+
+  private Todo $_todo;
+
+  public function __construct(Todo $todo) {
+    $this->_todo = $todo;
+  }
+
+  public function __invoke() : string {
+    $entry = Trace::fromOutside(get_class($this->_todo))[0] ?? [];
+
+    $file = $entry['file'] ?? '';
+    $line = $entry['line'] ?? 0;
+
+    return "{$file}:{$line}";
+  }
+
+}

test/TodoOrDie/TodoTest.php

@@ -160,6 +160,21 @@ public function testConstructingWithTriggeringCheckObject() {
     new Todo('Some message', new BooleanCheck(true));
   }
 
+  public function testGenerateId() {
+    $file = __FILE__;
+    $line = __LINE__ + 1;
+    $todo = new Todo('test', false);
+
+    $this->assertSame("{$file}:{$line}", $todo->getId());
+  }
+
+  public function testGenerateIdOfExtendedTodo() {
+    $file = __FILE__;
+    $line = __LINE__ + 1;
+    $todo = new ExtendedTodo('test', false);
+
+    $this->assertSame("{$file}:{$line}", $todo->getId());
+  }
 
 }
 
@@ -180,6 +195,10 @@ protected function _die() {
     self::$_mock->die();
   }
 
+  protected function _generateId() : string {
+    return parent::_generateId();
+  }
+
 }
 
 /**