Make CSS validation an optional feature

Cargo.toml

@@ -37,8 +37,8 @@ base64 = "0.10"
 rmp-serde = "0.13.7"    # rmp-serde 0.14.0 breaks deserialization by changing how enums are deserialized
 hashbrown = { version = "0.6", features = ["serde"] }
 lifeguard = { version = "0.6", optional = true }
-cssparser = "0.25"
-selectors = "0.21"
+cssparser = { version = "0.25", optional = true }
+selectors = { version = "0.21", optional = true }
 psl = "0.4.1"
 
 [dev-dependencies]
@@ -81,3 +81,4 @@ full-domain-matching = [] # feature has no explicit dependencies
 metrics = []
 full-regex-handling = []
 object-pooling = ["lifeguard"]
+css-validation = ["cssparser", "selectors"]

src/filters/cosmetic.rs

@@ -20,6 +20,7 @@ pub enum CosmeticFilterError {
     GenericScriptInject,
     GenericStyle,
     DoubleNegation,
+    EmptyRule,
 }
 
 bitflags! {
@@ -207,6 +208,10 @@ impl CosmeticFilter {
             };
 
             let mut selector = &line[suffix_start_index..];
+
+            if selector.trim().len() == 0 {
+                return Err(CosmeticFilterError::EmptyRule);
+            }
             let mut style = None;
             if line.len() - suffix_start_index > 4 && line[suffix_start_index..].starts_with("+js(") {
                 if sharp_index == 0 {
@@ -371,6 +376,18 @@ pub fn get_hostname_hashes_from_labels(hostname: &str, domain: &str) -> Vec<Hash
     get_hashes_from_labels(hostname, hostname.len(), hostname.len() - domain.len())
 }
 
+#[cfg(not(feature="css-validation"))]
+mod css_validation {
+    pub fn is_valid_css_selector(_selector: &str) -> bool {
+        true
+    }
+
+    pub fn is_valid_css_style(_style: &str) -> bool {
+        true
+    }
+}
+
+#[cfg(feature="css-validation")]
 mod css_validation {
     //! Methods for validating CSS selectors and style rules extracted from cosmetic filter rules.
     use cssparser::ParserInput;