Title: Always add title to LinkCache when necessary (in 3 methods)

Unless Title::GAID_FOR_UPDATE is specified, Title::getArticleID() will not
use the link cache if the Title already has the ID of the page. Account for
this by directly calling LinkCache::addLinkObj() in three other methods of
Title: getContentModel(), isRedirect(), and getLength().

Follows-up r33008 (aed9d4b91218) and dd5c1b7fb7ff, and reapplies part of
388b14a15de6.

Bug: T86974
Change-Id: I7eff0bffd4f632ceb8d2124af317d684dbcaf2cb

2 files changed, 6 insertions, 5 deletions

diff --git a/RELEASE-NOTES-1.25 b/RELEASE-NOTES-1.25
index f0c00f34b257..aa421cbe17ab 100644
--- a/RELEASE-NOTES-1.25
+++ b/RELEASE-NOTES-1.25
@@ -131,6 +131,8 @@ production.
 * (T85192) Captcha position modified in Usercreate template. As a result:
 ** extrafields parameter added to Usercreate.php to insert additional data
 ** 'extend' method added to QuickTemplate to append additional values to any field of data array
+* (T86974) Several Title methods now load from the database when necessary
+  (instead of returning incorrect results) even when the page ID is known.
 
 === Action API changes in 1.25 ===
 * (T67403) XML tag highlighting is now only performed for formats
diff --git a/includes/Title.php b/includes/Title.php
index 2d0cfda6275a..463f75e728d7 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -942,9 +942,9 @@ class Title {
 	 * @return string Content model id
 	 */
 	public function getContentModel( $flags = 0 ) {
-		# Calling getArticleID() loads the field from cache as needed
 		if ( !$this->mContentModel && $this->getArticleID( $flags ) ) {
 			$linkCache = LinkCache::singleton();
+			$linkCache->addLinkObj( $this ); # in case we already had an article ID
 			$this->mContentModel = $linkCache->getGoodLinkFieldObj( $this, 'model' );
 		}
 
@@ -3185,13 +3185,13 @@ class Title {
 		if ( !is_null( $this->mRedirect ) ) {
 			return $this->mRedirect;
 		}
-		# Calling getArticleID() loads the field from cache as needed
 		if ( !$this->getArticleID( $flags ) ) {
 			$this->mRedirect = false;
 			return $this->mRedirect;
 		}
 
 		$linkCache = LinkCache::singleton();
+		$linkCache->addLinkObj( $this ); # in case we already had an article ID
 		$cached = $linkCache->getGoodLinkFieldObj( $this, 'redirect' );
 		if ( $cached === null ) {
 			# Trust LinkCache's state over our own
@@ -3220,12 +3220,12 @@ class Title {
 		if ( $this->mLength != -1 ) {
 			return $this->mLength;
 		}
-		# Calling getArticleID() loads the field from cache as needed
 		if ( !$this->getArticleID( $flags ) ) {
 			$this->mLength = 0;
 			return $this->mLength;
 		}
 		$linkCache = LinkCache::singleton();
+		$linkCache->addLinkObj( $this ); # in case we already had an article ID
 		$cached = $linkCache->getGoodLinkFieldObj( $this, 'length' );
 		if ( $cached === null ) {
 			# Trust LinkCache's state over our own, as for isRedirect()
@@ -3248,13 +3248,12 @@ class Title {
 		if ( !( $flags & Title::GAID_FOR_UPDATE ) && $this->mLatestID !== false ) {
 			return intval( $this->mLatestID );
 		}
-		# Calling getArticleID() loads the field from cache as needed
 		if ( !$this->getArticleID( $flags ) ) {
 			$this->mLatestID = 0;
 			return $this->mLatestID;
 		}
 		$linkCache = LinkCache::singleton();
-		$linkCache->addLinkObj( $this );
+		$linkCache->addLinkObj( $this ); # in case we already had an article ID
 		$cached = $linkCache->getGoodLinkFieldObj( $this, 'revision' );
 		if ( $cached === null ) {
 			# Trust LinkCache's state over our own, as for isRedirect()