Update base Wire class to support a new wired() method that is called when the ProcessWire instance is assigned to the object. This usually happens immediately after __construct(), but depends on how the object was instantiated. This solves the problem of needing to access API variables in a constructor and potentially having the wrong API variable instance in a multi-instance environment.

wire/config.php

@@ -1481,8 +1481,9 @@ $config->lazyPageChunkSize = 250;
  * Uncomment and paste into /site/config.php if you want to use this
  * 
  * $config->InputfieldWrapper = array(
- *	'useDependencies' => true,
+ *   'useDependencies' => true,
- * 	'requiredLabel' => 'Missing required value', 
+ *   'requiredLabel' => 'Missing required value', 
+ *   'columnWidthSpacing' => 0, 
  *	);
  * 
  */
@@ -1680,6 +1681,8 @@ $config->versionName = '';
  * column width spacing for inputfields: used by some admin themes to communicate to InputfieldWrapper
  * 
  * Value is null, 0, or 1 or higher. This should be kept at null in this file. 
+ * 
+ * This can also be specified with $config->InputfieldWrapper('columnWidthSpacing', 0); (3.0.158+)
  *
  */
 $config->inputfieldColumnWidthSpacing = null;

wire/core/ProcessWire.php

@@ -733,12 +733,14 @@ class ProcessWire extends Wire {
 		if($profiler) $profiler->maintenance();
 
 		if($config->templateCompile) {
-			$compiler = new FileCompiler($this->wire('config')->paths->templates);
+			$compiler = new FileCompiler($config->paths->templates);
+			$this->wire($compiler);
 			$compiler->maintenance();
 		}
 		
 		if($config->moduleCompile) {
-			$compiler = new FileCompiler($this->wire('config')->paths->siteModules);
+			$compiler = new FileCompiler($config->paths->siteModules);
+			$this->wire($compiler);
 			$compiler->maintenance();
 		}
 	}
@@ -795,7 +797,16 @@ class ProcessWire extends Wire {
 		$this->fileSave = '';
 		return true; 
 	}
-	
+
+	/**
+	 * Call method
+	 * 
+	 * @param string $method
+	 * @param array $arguments
+	 * @return mixed
+	 * @throws WireException
+	 * 
+	 */
 	public function __call($method, $arguments) {
 		if(method_exists($this, "___$method")) return parent::__call($method, $arguments); 
 		$value = $this->__get($method);
@@ -816,6 +827,35 @@ class ProcessWire extends Wire {
 		if(empty($name)) return $this->fuel;
 		return $this->fuel->$name;
 	}
+
+	/**
+	 * Called if any Wire-derived object makes API calls before being wired
+	 * 
+	 * This is for debugging purposes only and is not called unless `ProcessWire::objectNotWired` is hooked. 
+	 * It is called only once per non-wired object. Uncomment code within to use. 
+	 * 
+	 * #pw-internal
+	 * 
+	 * @param Wire $obj Object that accessed API var without being assigned ProcessWire instance
+	 * @param string|Wire The $name argument that was passed to $obj->wire($name, $value)
+	 * @param mixed $value The $value argument passed to $object->wire($name, $value)
+	 * @since 3.0.158
+	 * 
+	 */
+	public function _objectNotWired(Wire $obj, $name, $value) { 
+		// Uncomment code below to enable (use in admin)
+		/*
+		if(is_string($name) && $this->wire($name)) {
+			$msg = $obj->className() . " accessed API var \$$name before being wired";
+			$this->warning("$msg\n" . Debug::backtrace(array(
+				'limit' => 2, 
+				'getString' => true,
+				'getCnt' => false,
+				'getFile' => 'basename',
+			)));
+		}
+		*/
+	}
 	
 	/*** MULTI-INSTANCE *************************************************************************************/
 	

wire/core/Wire.php

@@ -124,7 +124,11 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 	 *
 	 */
 	private $_instanceNum = 0;
-
+	
+	/**
+	 * Construct
+	 * 
+	 */
 	public function __construct() {}
 
 	/**
@@ -1586,7 +1590,7 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 	/**
 	 * ProcessWire instance
 	 *
-	 * @var ProcessWire|null
+	 * @var ProcessWire|bool|null
 	 *
 	 */
 	protected $_wire = null;
@@ -1594,16 +1598,18 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 	/**
 	 * Set the current ProcessWire instance for this object (PW 3.0)
 	 * 
-	 * Specify no arguments to get, or specify a ProcessWire instance to set.
-	 * 
 	 * #pw-internal
 	 *
 	 * @param ProcessWire $wire
 	 *
 	 */
 	public function setWire(ProcessWire $wire) {
+		$wired = $this->_wire;
+		if($wired === $wire) return;
 		$this->_wire = $wire;
+		if($wired) return;
 		$this->getInstanceNum();
+		$this->wired();
 	}
 
 	/**
@@ -1617,7 +1623,7 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 	 *
 	 */
 	public function getWire() {
-		return $this->_wire;
+		return $this->_wire ? $this->_wire : null;
 	}
 
 	/**
@@ -1695,18 +1701,18 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 	 */
 	public function wire($name = '', $value = null, $lock = false) {
 
-		if($this->_wire === null) {
+		if($this->_wire) {
+			// this instance is wired
+			$wire = $this->_wire;
+		} else {
 			// this object has not yet been wired! use last known current instance as fallback
 			// note this condition is unsafe in multi-instance mode
 			$wire = ProcessWire::getCurrentInstance();
 			if(!$wire) return null;
-			
+			if($name && $this->_wire === null) {
-			// For live hunting objects that are using the fallback, uncomment the following:
+				$this->_wire = false; // false prevents this from being called another time for this object
-			// echo "<hr /><p>Non-wired object: '$name' in " . get_class($this) . ($value ? " (value=$value)" : "") . "</p>";
+				$wire->_objectNotWired($this, $name, $value);
-			// echo "<pre>" . print_r(debug_backtrace(), true) . "</pre>";
+			}
-		} else {
-			// this instance is wired
-			$wire = $this->_wire;
 		}
 
 		if(is_object($name)) {
@@ -1743,6 +1749,38 @@ abstract class Wire implements WireTranslatable, WireFuelable, WireTrackable {
 		return $value;
 	}
 
+	/**
+	 * Initialization called when object injected with ProcessWire instance (aka “wired”)
+	 *
+	 * - Can be used for any constructor-type initialization that depends on API vars.
+	 * - Called automatically when object is “wired”, do not call it on your own.
+	 * - Expects to be called only once per object instance.
+	 * - Typically called after `__construct()` but before any other method calls.
+	 * - Please note: If object is never “wired” then this method will not be called!
+	 *
+	 * ~~~~~
+	 * class Test extends Wire {
+	 *   function wired() { 
+	 *     echo "Wired to ProcessWire instance: "; 
+	 *     echo $this->wire()->getProcessWireInstanceID();
+	 *   }
+	 * }
+	 *
+	 * // objects in ProcessWire are “wired” like this:
+	 * $o = new Test();
+	 * $this->wire($o); // outputs "ProcessWire instance: n"
+	 *
+	 * // or on one line, like this…
+	 * $this->wire(new Test()); // outputs "ProcessWire instance: n"
+	 * ~~~~~
+	 *
+	 * #pw-internal
+	 *
+	 * @since 3.0.158
+	 *
+	 */
+	public function wired() { }
+
 	/**
 	 * Get an object property by direct reference or NULL if it doesn't exist
 	 *