Get rid of warnings on PHP 8.1

This is mostly about adding return types to methods that implement PHP
interfaces, and not passing null to core functions that want a string.
After this patch, and an update to return types in RemexHtml,
tests/phpunit/integration/ has no more errors than in PHP 8.0.

Bug: T289879
Bug: T289926
Change-Id: Ia424f5cc897070f4188ae126b5bf6a1f552db0e1

5 files changed, 12 insertions, 9 deletions

diff --git a/includes/libs/filebackend/fileiteration/FSFileBackendList.php b/includes/libs/filebackend/fileiteration/FSFileBackendList.php
index 0783cc646ecd..047aa1dfeb35 100644
--- a/includes/libs/filebackend/fileiteration/FSFileBackendList.php
+++ b/includes/libs/filebackend/fileiteration/FSFileBackendList.php
@@ -89,7 +89,7 @@ abstract class FSFileBackendList implements Iterator {
 	 * @see Iterator::key()
 	 * @return int
 	 */
-	public function key() {
+	public function key(): int {
 		return $this->pos;
 	}
 
@@ -97,6 +97,7 @@ abstract class FSFileBackendList implements Iterator {
 	 * @see Iterator::current()
 	 * @return string|false
 	 */
+	#[\ReturnTypeWillChange]
 	public function current() {
 		return $this->getRelPath( $this->iter->current()->getPathname() );
 	}
@@ -105,7 +106,7 @@ abstract class FSFileBackendList implements Iterator {
 	 * @see Iterator::next()
 	 * @throws FileBackendError
 	 */
-	public function next() {
+	public function next(): void {
 		try {
 			$this->iter->next();
 			$this->filterViaNext();
@@ -121,7 +122,7 @@ abstract class FSFileBackendList implements Iterator {
 	 * @see Iterator::rewind()
 	 * @throws FileBackendError
 	 */
-	public function rewind() {
+	public function rewind(): void {
 		$this->pos = 0;
 		try {
 			$this->iter->rewind();
@@ -137,7 +138,7 @@ abstract class FSFileBackendList implements Iterator {
 	 * @see Iterator::valid()
 	 * @return bool
 	 */
-	public function valid() {
+	public function valid(): bool {
 		return $this->iter && $this->iter->valid();
 	}
 
diff --git a/includes/libs/filebackend/fileiteration/FileBackendStoreShardListIterator.php b/includes/libs/filebackend/fileiteration/FileBackendStoreShardListIterator.php
index 5f6b76242645..9dc7cab4c6f9 100644
--- a/includes/libs/filebackend/fileiteration/FileBackendStoreShardListIterator.php
+++ b/includes/libs/filebackend/fileiteration/FileBackendStoreShardListIterator.php
@@ -79,7 +79,7 @@ abstract class FileBackendStoreShardListIterator extends FilterIterator {
 		}
 	}
 
-	public function rewind() {
+	public function rewind(): void {
 		parent::rewind();
 		$this->multiShardPaths = [];
 	}
diff --git a/includes/libs/filebackend/fileiteration/SwiftFileBackendDirList.php b/includes/libs/filebackend/fileiteration/SwiftFileBackendDirList.php
index b0b784d389c2..ca6f3d88bb0c 100644
--- a/includes/libs/filebackend/fileiteration/SwiftFileBackendDirList.php
+++ b/includes/libs/filebackend/fileiteration/SwiftFileBackendDirList.php
@@ -30,6 +30,7 @@ class SwiftFileBackendDirList extends SwiftFileBackendList {
 	 * @see Iterator::current()
 	 * @return string|bool String (relative path) or false
 	 */
+	#[\ReturnTypeWillChange]
 	public function current() {
 		return substr( current( $this->bufferIter ), $this->suffixStart, -1 );
 	}
diff --git a/includes/libs/filebackend/fileiteration/SwiftFileBackendFileList.php b/includes/libs/filebackend/fileiteration/SwiftFileBackendFileList.php
index 045b8f878cd0..106193d710e0 100644
--- a/includes/libs/filebackend/fileiteration/SwiftFileBackendFileList.php
+++ b/includes/libs/filebackend/fileiteration/SwiftFileBackendFileList.php
@@ -30,6 +30,7 @@ class SwiftFileBackendFileList extends SwiftFileBackendList {
 	 * @see Iterator::current()
 	 * @return string|bool String (relative path) or false
 	 */
+	#[\ReturnTypeWillChange]
 	public function current() {
 		list( $path, $stat ) = current( $this->bufferIter );
 		$relPath = substr( $path, $this->suffixStart );
diff --git a/includes/libs/filebackend/fileiteration/SwiftFileBackendList.php b/includes/libs/filebackend/fileiteration/SwiftFileBackendList.php
index 45f3f4cd6f6c..a603900d65b6 100644
--- a/includes/libs/filebackend/fileiteration/SwiftFileBackendList.php
+++ b/includes/libs/filebackend/fileiteration/SwiftFileBackendList.php
@@ -81,14 +81,14 @@ abstract class SwiftFileBackendList implements Iterator {
 	 * @see Iterator::key()
 	 * @return int
 	 */
-	public function key() {
+	public function key(): int {
 		return $this->pos;
 	}
 
 	/**
 	 * @inheritDoc
 	 */
-	public function next() {
+	public function next(): void {
 		// Advance to the next file in the page
 		next( $this->bufferIter );
 		++$this->pos;
@@ -104,7 +104,7 @@ abstract class SwiftFileBackendList implements Iterator {
 	/**
 	 * @inheritDoc
 	 */
-	public function rewind() {
+	public function rewind(): void {
 		$this->pos = 0;
 		$this->bufferAfter = null;
 		$this->bufferIter = $this->pageFromList(
@@ -117,7 +117,7 @@ abstract class SwiftFileBackendList implements Iterator {
 	 * @see Iterator::valid()
 	 * @return bool
 	 */
-	public function valid() {
+	public function valid(): bool {
 		if ( $this->bufferIter === null ) {
 			return false; // some failure?
 		} else {