From b0414278f8a55b35bfe19ca1426f55cf7f1ed51e Mon Sep 17 00:00:00 2001
From: Ryan Cramer <ryan@processwire.com>
Date: Fri, 15 Sep 2023 08:22:09 -0400
Subject: [PATCH] Update PagesEditor to throw descriptive exception when
 attempting to save a NullPage. This is to fix what were previously ambiguous
 error messages.

---
 wire/core/NullPage.php    |  8 ++++++++
 wire/core/PagesEditor.php | 12 ++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/wire/core/NullPage.php b/wire/core/NullPage.php
index 2ad7af44..7d4dd9e0 100644
--- a/wire/core/NullPage.php
+++ b/wire/core/NullPage.php
@@ -97,6 +97,14 @@ class NullPage extends Page implements WireNull {
 	 */
 	public function isHidden() { return true; }
 
+	/**
+	 * #pw-internal
+	 *
+	 * @return bool
+	 *
+	 */
+	public function isNew() { return false; }
+
 	/**
 	 * #pw-internal
 	 * 
diff --git a/wire/core/PagesEditor.php b/wire/core/PagesEditor.php
index f53c0919..937edfc2 100644
--- a/wire/core/PagesEditor.php
+++ b/wire/core/PagesEditor.php
@@ -447,9 +447,9 @@ class PagesEditor extends Wire {
 		$language = null;
 
 		// if language support active, switch to default language so that saved fields and hooks don't need to be aware of language
-		if($languages && $page->id != $user->id) {
-			$language = $user->language && $user->language->id ? $user->language : null;
-			if($language) $user->language = $languages->getDefault();
+		if($languages && $page->id != $user->id && "$user->language") {
+			$language = $user->language;
+			$user->setLanguage($languages->getDefault());
 		}
 
 		$reason = '';
@@ -457,8 +457,8 @@ class PagesEditor extends Wire {
 		if($isNew) $this->pages->setupNew($page);
 
 		if(!$this->isSaveable($page, $reason, '', $options)) {
-			if($language) $user->language = $language;
-			throw new WireException("Can’t save page {$page->id}: {$page->path}: $reason");
+			if($language) $user->setLanguage($language);
+			throw new WireException(rtrim("Can’t save page (id=$page->id): $page->path", ": ") . ": $reason");
 		}
 
 		if($page->hasStatus(Page::statusUnpublished) && $page->template->noUnpublish) {
@@ -476,7 +476,7 @@ class PagesEditor extends Wire {
 		if($options['adjustName']) $this->pages->names()->checkNameConflicts($page);
 		if(!$this->savePageQuery($page, $options)) return false;
 		$result = $this->savePageFinish($page, $isNew, $options);
-		if($language) $user->language = $language; // restore language
+		if($language) $user->setLanguage($language); // restore language
 		
 		return $result;
 	}