clear memoized data when updating meta data

src/class-tiny-image-size.php

@@ -22,11 +22,29 @@ class Tiny_Image_Size {
 	public $filename;
 	public $meta = array();
 
-	/* Used more than once and not trivial, so we are memoizing these */
+	/**
+	 * Whether the file exists on disk.
+	 *
+	 * @var bool|null $exists
+	 */
 	private $exists;
+
+	/**
+	 * File size in bytes.
+	 *
+	 * @var int|null $file_size
+	 */
 	private $file_size;
+
+	/**
+	 * MIME type of the file.
+	 *
+	 * @var string|null $mime_type
+	 */
 	private $mime_type;
-	private $duplicate         = false;
+
+	private $duplicate = false;
+
 	private $duplicate_of_size = '';
 
 	public function __construct( $filename = null ) {
@@ -53,9 +71,26 @@ public function add_tiny_meta( $response ) {
 		if ( isset( $this->meta['start'] ) ) {
 			$this->meta        = $response;
 			$this->meta['end'] = time();
+			$this->clear_memoized_filesystem();
 		}
 	}
 
+	/**
+	 * Clears the memoized exists/file_size/mime_type values.
+	 *
+	 * Must be called whenever the file on disk changed after those were
+	 * memoized, e.g. after compression overwrites it, so the next read
+	 * reflects the new file instead of the stale cached one.
+	 *
+	 * @return void
+	 */
+	private function clear_memoized_filesystem() {
+		clearstatcache( true, $this->filename );
+		$this->exists    = null;
+		$this->file_size = null;
+		$this->mime_type = null;
+	}
+
 	public function add_tiny_meta_error( $exception ) {
 		if ( isset( $this->meta['start'] ) ) {
 			$this->meta = array(

test/unit/TinyImageSizeTest.php

@@ -58,6 +58,25 @@ public function test_add_tiny_meta_should_add_end_time() {
 		$this->assertEqualWithinDelta( time(), $this->large->meta['end'], 2 );
 	}
 
+	/**
+	 * After compression overwrites the file on disk, add_tiny_meta() must clear
+	 * the memoized file_size so the next filesize() call reflects the new file
+	 * rather than returning the stale pre-compression value.
+	 */
+	public function test_add_tiny_meta_clears_memoized_data_after_compression() {
+		$this->original->add_tiny_meta_start();
+		$this->assertEquals( 137856, $this->original->filesize(), 'expected filesize to be original' );
+
+		file_put_contents( $this->original->filename, str_repeat( 'a', 90000 ) );
+
+		$this->original->add_tiny_meta( array(
+			'input'  => array( 'size' => 137856 ),
+			'output' => array( 'size' => 90000 ),
+		) );
+
+		$this->assertEquals( 90000, $this->original->filesize(), 'should return refreshed filesize' );
+	}
+
 	public function test_add_response_should_response() {
 		$this->large->add_tiny_meta_start();
 		$this->large->add_tiny_meta( array(