Fix issue processwire/processwire-issues#60 where multi-language fields weren't working correctly with multi-instance

wire/core/Modules.php

@@ -504,6 +504,22 @@ class Modules extends WireArray {
 			$className = $this->getModuleNamespace($moduleName) . $moduleName;
 		}
 
+		if(ProcessWire::getNumInstances() > 1) {
+			// in a multi-instance environment, ensures that anything happening during
+			// the module __construct is using the right instance. necessary because the
+			// construct method runs before the wire instance is set to the module
+			$wire1 = ProcessWire::getCurrentInstance();
+			$wire2 = $this->wire();
+			if($wire1 !== $wire2) {
+				ProcessWire::setCurrentInstance($wire2);
+			} else {
+				$wire1 = null;
+			}
+		} else {
+			$wire1 = null;
+			$wire2 = null;
+		}
+		
 		try {
 			$module = $this->wire(new $className());
 		} catch(\Exception $e) {
@@ -511,6 +527,7 @@ class Modules extends WireArray {
 			$module = null;
 		}
 		if($this->debug) $this->debugTimerStop($debugKey);
+		if($wire1) ProcessWire::setCurrentInstance($wire1);
 		return $module; 
 	}
 

wire/core/ProcessWire.php

@@ -560,6 +560,16 @@ class ProcessWire extends Wire {
 		return self::$instances;
 	}
 
+	/**
+	 * Return number of instances
+	 * 
+	 * @return int
+	 * 
+	 */
+	public static function getNumInstances() {
+		return count(self::$instances);
+	}
+
 	/**
 	 * Get a ProcessWire instance by ID
 	 * 

wire/core/WireFileTools.php

@@ -765,8 +765,20 @@ class WireFileTools extends Wire {
 	 * 
 	 */
 	public function compile($file, array $options = array()) {
+		static $compiled = array();
+		if(strpos($file, '/modules/')) {
+			// for multi-instance support, use the same compiled version
+			// otherwise, require_once() statements in a file may not work as intended
+			// applied just to site/modules for the moment, but may need to do site/templates too
+			$f = str_replace($this->wire('config')->paths->root, '', $file);
+			if(isset($compiled[$f])) return $compiled[$f];
+		} else {
+			$f = '';
+		}
 		$compiler = new FileCompiler(dirname($file), $options);
-		return $compiler->compile(basename($file));
+		$compiledFile = $compiler->compile(basename($file));
+		if($f) $compiled[$f] = $compiledFile;
+		return $compiledFile;
 	}
 
 	/**