resourceloader: Use SVG url when ResourceLoaderImageModule can't embed

When the SVG is too big to be embeded it is now included via URL.
Previously it would produce an empty/broken 'url()' value.

Bug: T160532
Change-Id: I158781f9430cfa35737397ac7537a471634c4480

includes/resourceloader/ResourceLoaderImageModule.php

@@ -315,11 +315,7 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 		$selectors = $this->getSelectors();
 
 		foreach ( $this->getImages( $context ) as $name => $image ) {
-			$declarations = $this->getCssDeclarations(
+			$declarations = $this->getStyleDeclarations( $context, $image, $script );
-				$image->getDataUri( $context, null, 'original' ),
-				$image->getUrl( $context, $script, null, 'rasterized' )
-			);
-			$declarations = implode( "\n\t", $declarations );
 			$selector = strtr(
 				$selectors['selectorWithoutVariant'],
 				[
@@ -331,11 +327,7 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 			$rules[] = "$selector {\n\t$declarations\n}";
 
 			foreach ( $image->getVariants() as $variant ) {
-				$declarations = $this->getCssDeclarations(
+				$declarations = $this->getStyleDeclarations( $context, $image, $script, $variant );
-					$image->getDataUri( $context, $variant, 'original' ),
-					$image->getUrl( $context, $script, $variant, 'rasterized' )
-				);
-				$declarations = implode( "\n\t", $declarations );
 				$selector = strtr(
 					$selectors['selectorWithVariant'],
 					[
@@ -352,6 +344,28 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 		return [ 'all' => $style ];
 	}
 
+	/**
+	 * @param ResourceLoaderContext $context
+	 * @param ResourceLoaderImage $image Image to get the style for
+	 * @param string $script URL to load.php
+	 * @param string|null $variant Variant to get the style for
+	 * @return string
+	 */
+	private function getStyleDeclarations(
+		ResourceLoaderContext $context,
+		ResourceLoaderImage $image,
+		$script,
+		$variant = null
+	) {
+		$imageDataUri = $image->getDataUri( $context, $variant, 'original' );
+		$primaryUrl = $imageDataUri ?: $image->getUrl( $context, $script, $variant, 'original' );
+		$declarations = $this->getCssDeclarations(
+			$primaryUrl,
+			$image->getUrl( $context, $script, $variant, 'rasterized' )
+		);
+		return implode( "\n\t", $declarations );
+	}
+
 	/**
 	 * SVG support using a transparent gradient to guarantee cross-browser
 	 * compatibility (browsers able to understand gradient syntax support also SVG).

tests/phpunit/includes/resourceloader/ResourceLoaderImageModuleTest.php

@@ -197,6 +197,62 @@ class ResourceLoaderImageModuleTest extends ResourceLoaderTestCase {
 		] ) );
 		$this->assertInstanceOf( ResourceLoaderImage::class, $context->getImageObj() );
 	}
+
+	public static function providerGetStyleDeclarations() {
+		return [
+			[
+				false,
+<<<TEXT
+background-image: url(rasterized.png);
+	background-image: linear-gradient(transparent, transparent), url(original.svg);
+	background-image: -o-linear-gradient(transparent, transparent), url(rasterized.png);
+TEXT
+			],
+			[
+				'data:image/svg+xml',
+<<<TEXT
+background-image: url(rasterized.png);
+	background-image: linear-gradient(transparent, transparent), url(data:image/svg+xml);
+	background-image: -o-linear-gradient(transparent, transparent), url(rasterized.png);
+TEXT
+			],
+
+		];
+	}
+
+	/**
+	 * @dataProvider providerGetStyleDeclarations
+	 * @covers ResourceLoaderContext::getStyleDeclarations
+	 */
+	public function testGetStyleDeclarations( $dataUriReturnValue, $expected ) {
+		$module = TestingAccessWrapper::newFromObject( new ResourceLoaderImageModule() );
+		$context = $this->getResourceLoaderContext();
+		$image = $this->getImageMock( $context, $dataUriReturnValue );
+
+		$styles = $module->getStyleDeclarations(
+			$context,
+			$image,
+			'load.php'
+		);
+
+		$this->assertEquals( $expected, $styles );
+	}
+
+	private function getImageMock( ResourceLoaderContext $context, $dataUriReturnValue ) {
+		$image = $this->getMockBuilder( 'ResourceLoaderImage' )
+			->disableOriginalConstructor()
+			->getMock();
+		$image->method( 'getDataUri' )
+			->will( $this->returnValue( $dataUriReturnValue ) );
+		$image->expects( $this->any() )
+			->method( 'getUrl' )
+			->will( $this->returnValueMap( [
+				[ $context, 'load.php', null, 'original', 'original.svg' ],
+				[ $context, 'load.php', null, 'rasterized', 'rasterized.png' ],
+			] ) );
+
+		return $image;
+	}
 }
 
 class ResourceLoaderImageModuleTestable extends ResourceLoaderImageModule {