From 4ed0f518fb9b16096506f31f6a542c2b6571e5c6 Mon Sep 17 00:00:00 2001
From: CanadaHonk <oj@oojmed.com>
Date: Sat, 25 Feb 2023 23:53:02 +0000
Subject: [PATCH] style: Fix parsing nested image-set funcs as valid

Nested image-set CSS functions should fail to parse as per spec.

WPT tests (2 newly pass):
https://github.com/web-platform-tests/wpt/blob/a2154e3f971f3630643741206ce02bbbc5f31d6f/css/css-images/image-set/image-set-parsing.html#L223-L239

Differential Revision: https://phabricator.services.mozilla.com/D170829
---
 components/style/values/specified/image.rs | 53 +++++++++++++---------
 1 file changed, 31 insertions(+), 22 deletions(-)

diff --git a/components/style/values/specified/image.rs b/components/style/values/specified/image.rs
index 3be84c5a7b2..a9eb6bf6571 100644
--- a/components/style/values/specified/image.rs
+++ b/components/style/values/specified/image.rs
@@ -177,6 +177,14 @@ pub type MozImageRect = generic::GenericMozImageRect<NumberOrPercentage, Specifi
 /// Empty enum on non-Gecko
 pub enum MozImageRect {}
 
+bitflags! {
+    struct ParseImageFlags: u8 {
+        const FORBID_NONE = 1 << 0;
+        const FORBID_IMAGE_SET = 1 << 1;
+        const FORBID_NON_URL = 1 << 2;
+    }
+}
+
 impl Parse for Image {
     fn parse<'i, 't>(
         context: &ParserContext,
@@ -186,8 +194,7 @@ impl Parse for Image {
             context,
             input,
             CorsMode::None,
-            /* allow_none = */ true,
-            /* only_url = */ false,
+            ParseImageFlags::empty()
         )
     }
 }
@@ -197,10 +204,9 @@ impl Image {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
-        allow_none: bool,
-        only_url: bool,
+        flags: ParseImageFlags
     ) -> Result<Image, ParseError<'i>> {
-        if allow_none && input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+        if !flags.contains(ParseImageFlags::FORBID_NONE) && input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
             return Ok(generic::Image::None);
         }
 
@@ -210,13 +216,15 @@ impl Image {
             return Ok(generic::Image::Url(url));
         }
 
-        if image_set_enabled() {
-            if let Ok(is) = input.try_parse(|input| ImageSet::parse(context, input, cors_mode, only_url)) {
+        if !flags.contains(ParseImageFlags::FORBID_IMAGE_SET) && image_set_enabled() {
+            if let Ok(is) =
+                input.try_parse(|input| ImageSet::parse(context, input, cors_mode, flags))
+            {
                 return Ok(generic::Image::ImageSet(Box::new(is)));
             }
         }
 
-        if only_url {
+        if flags.contains(ParseImageFlags::FORBID_NON_URL) {
             return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
         }
 
@@ -225,7 +233,7 @@ impl Image {
         }
 
         if cross_fade_enabled() {
-            if let Ok(cf) = input.try_parse(|input| CrossFade::parse(context, input, cors_mode)) {
+            if let Ok(cf) = input.try_parse(|input| CrossFade::parse(context, input, cors_mode, flags)) {
                 return Ok(generic::Image::CrossFade(Box::new(cf)));
             }
         }
@@ -279,8 +287,7 @@ impl Image {
             context,
             input,
             CorsMode::Anonymous,
-            /* allow_none = */ true,
-            /* only_url = */ false,
+            ParseImageFlags::empty()
         )
     }
 
@@ -293,8 +300,7 @@ impl Image {
             context,
             input,
             CorsMode::None,
-            /* allow_none = */ false,
-            /* only_url = */ true,
+            ParseImageFlags::FORBID_NONE | ParseImageFlags::FORBID_NON_URL
         )
     }
 }
@@ -305,10 +311,11 @@ impl CrossFade {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
+        flags: ParseImageFlags
     ) -> Result<Self, ParseError<'i>> {
         input.expect_function_matching("cross-fade")?;
         let elements = input.parse_nested_block(|input| {
-            input.parse_comma_separated(|input| CrossFadeElement::parse(context, input, cors_mode))
+            input.parse_comma_separated(|input| CrossFadeElement::parse(context, input, cors_mode, flags))
         })?;
         let elements = crate::OwnedSlice::from(elements);
         Ok(Self { elements })
@@ -335,11 +342,12 @@ impl CrossFadeElement {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
+        flags: ParseImageFlags
     ) -> Result<Self, ParseError<'i>> {
         // Try and parse a leading percent sign.
         let mut percent = Self::parse_percentage(context, input);
         // Parse the image
-        let image = CrossFadeImage::parse(context, input, cors_mode)?;
+        let image = CrossFadeImage::parse(context, input, cors_mode, flags)?;
         // Try and parse a trailing percent sign.
         if percent.is_none() {
             percent = Self::parse_percentage(context, input);
@@ -356,11 +364,12 @@ impl CrossFadeImage {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
+        flags: ParseImageFlags
     ) -> Result<Self, ParseError<'i>> {
         if let Ok(image) = input.try_parse(|input| {
             Image::parse_with_cors_mode(
-                context, input, cors_mode, /* allow_none = */ false,
-                /* only_url = */ false,
+                context, input, cors_mode,
+                flags | ParseImageFlags::FORBID_NONE
             )
         }) {
             return Ok(Self::Image(image));
@@ -374,7 +383,7 @@ impl ImageSet {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
-        only_url: bool,
+        flags: ParseImageFlags
     ) -> Result<Self, ParseError<'i>> {
         let function = input.expect_function()?;
         match_ignore_ascii_case! { &function,
@@ -386,7 +395,7 @@ impl ImageSet {
         }
         let items = input.parse_nested_block(|input| {
             input.parse_comma_separated(|input| {
-                ImageSetItem::parse(context, input, cors_mode, only_url)
+                ImageSetItem::parse(context, input, cors_mode, flags)
             })
         })?;
         Ok(Self {
@@ -406,7 +415,7 @@ impl ImageSetItem {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
         cors_mode: CorsMode,
-        only_url: bool,
+        flags: ParseImageFlags
     ) -> Result<Self, ParseError<'i>> {
         let image = match input.try_parse(|i| i.expect_url_or_string()) {
             Ok(url) => Image::Url(SpecifiedImageUrl::parse_from_string(
@@ -415,8 +424,8 @@ impl ImageSetItem {
                 cors_mode,
             )),
             Err(..) => Image::parse_with_cors_mode(
-                context, input, cors_mode, /* allow_none = */ false,
-                /* only_url = */ only_url,
+                context, input, cors_mode,
+                flags | ParseImageFlags::FORBID_NONE | ParseImageFlags::FORBID_IMAGE_SET
             )?,
         };