keep existing data in unique HABTM closes LH 275

ported to 2.0 branch from cakephp/cakephp#93

lib/Cake/Console/Templates/default/classes/model.ctp

@@ -154,7 +154,7 @@ if (!empty($associations['hasAndBelongsToMany'])):
 		$out .= "\t\t\t'joinTable' => '{$relation['joinTable']}',\n";
 		$out .= "\t\t\t'foreignKey' => '{$relation['foreignKey']}',\n";
 		$out .= "\t\t\t'associationForeignKey' => '{$relation['associationForeignKey']}',\n";
-		$out .= "\t\t\t'unique' => true,\n";
+		$out .= "\t\t\t'unique' => 'keepExisting',\n";
 		$out .= "\t\t\t'conditions' => '',\n";
 		$out .= "\t\t\t'fields' => '',\n";
 		$out .= "\t\t\t'order' => '',\n";

lib/Cake/Model/Datasource/DboSource.php

@@ -2782,15 +2782,15 @@ class DboSource extends DataSource {
 		$statement = $this->_connection->prepare($sql);
 		$this->begin();
 
-		foreach ($values[0] as $key => $val) {
+		foreach ($values[key($values)] as $key => $val) {
 			$type = $this->introspectType($val);
 			$columnMap[$key] = $pdoMap[$type];
 		}
 
-		for ($x = 0; $x < $count; $x++) {
+		foreach ($values as $row => $value) {
 			$i = 1;
-			foreach ($values[$x] as $key => $val) {
-				$statement->bindValue($i, $val, $columnMap[$key]);
+			foreach ($value as $col => $val) {
+				$statement->bindValue($i, $val, $columnMap[$col]);
 				$i += 1;
 			}
 			$statement->execute();

lib/Cake/Model/Model.php

@@ -1715,7 +1715,7 @@ class Model extends Object {
 					)
 				);
 
-				$newData = $newValues = array();
+				$newData = $newValues = $newJoins = array();
 				$primaryAdded = false;
 
 				$fields =  array(
@@ -1731,11 +1731,12 @@ class Model extends Object {
 
 				foreach ((array)$data as $row) {
 					if ((is_string($row) && (strlen($row) == 36 || strlen($row) == 16)) || is_numeric($row)) {
+						$newJoins[] = $row;
 						$values = array($id, $row);
 						if ($isUUID && $primaryAdded) {
 							$values[] = String::uuid();
 						}
-						$newValues[] = $values;
+						$newValues[$row] = $values;
 						unset($values);
 					} elseif (isset($row[$this->hasAndBelongsToMany[$assoc]['associationForeignKey']])) {
 						$newData[] = $row;
@@ -1744,6 +1745,7 @@ class Model extends Object {
 					}
 				}
 
+				$keepExisting = $this->hasAndBelongsToMany[$assoc]['unique'] === 'keepExisting';
 				if ($this->hasAndBelongsToMany[$assoc]['unique']) {
 					$conditions = array(
 						$join . '.' . $this->hasAndBelongsToMany[$assoc]['foreignKey'] => $id
@@ -1751,16 +1753,20 @@ class Model extends Object {
 					if (!empty($this->hasAndBelongsToMany[$assoc]['conditions'])) {
 						$conditions = array_merge($conditions, (array)$this->hasAndBelongsToMany[$assoc]['conditions']);
 					}
+					$associationForeignKey = $this->{$join}->alias .'.'. $this->hasAndBelongsToMany[$assoc]['associationForeignKey'];
 					$links = $this->{$join}->find('all', array(
 						'conditions' => $conditions,
 						'recursive' => empty($this->hasAndBelongsToMany[$assoc]['conditions']) ? -1 : 0,
-						'fields' => $this->hasAndBelongsToMany[$assoc]['associationForeignKey']
+						'fields' => $associationForeignKey,
 					));
 
-					$associationForeignKey = "{$join}." . $this->hasAndBelongsToMany[$assoc]['associationForeignKey'];
 					$oldLinks = Set::extract($links, "{n}.{$associationForeignKey}");
 					if (!empty($oldLinks)) {
- 						$conditions[$associationForeignKey] = $oldLinks;
+						if ($keepExisting && !empty($newJoins)) {
+							$conditions[$associationForeignKey] = array_diff($oldLinks, $newJoins);
+						} else {
+							$conditions[$associationForeignKey] = $oldLinks;
+						}
 						$dbMulti->delete($this->{$join}, $conditions);
 					}
 				}
@@ -1774,7 +1780,21 @@ class Model extends Object {
 				}
 
 				if (!empty($newValues)) {
-					$dbMulti->insertMulti($this->{$join}, $fields, $newValues);
+					if ($keepExisting && !empty($links)) {
+						foreach ($links as $link) {
+							$oldJoin = $link[$join][$this->hasAndBelongsToMany[$assoc]['associationForeignKey']];
+							if (! in_array($oldJoin, $newJoins) ) {
+								$conditions[$associationForeignKey] = $oldJoin;
+								$db->delete($this->{$join}, $conditions);
+							} else {
+								unset($newValues[$oldJoin]);
+							}
+						}
+						$newValues = array_values($newValues);
+					}
+					if (!empty($newValues)) {
+						$dbMulti->insertMulti($this->{$join}, $fields, $newValues);
+					}
 				}
 			}
 		}