Merge @supports declarations with the same property (minus prefix) and value

Author: devongovett

src/lib.rs

@@ -13123,6 +13123,68 @@ mod tests {
         ..Default::default()
       },
     );
+    prefix_test(
+      r#"
+      @supports ((-webkit-backdrop-filter: blur(10px)) or (backdrop-filter: blur(10px))) {
+        div {
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#,
+      indoc! { r#"
+      @supports ((-webkit-backdrop-filter: blur(10px)) or (backdrop-filter: blur(10px))) {
+        div {
+          -webkit-backdrop-filter: blur(10px);
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#},
+      Browsers {
+        safari: Some(14 << 16),
+        ..Default::default()
+      },
+    );
+    prefix_test(
+      r#"
+      @supports ((-webkit-backdrop-filter: blur(20px)) or (backdrop-filter: blur(10px))) {
+        div {
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#,
+      indoc! { r#"
+      @supports ((-webkit-backdrop-filter: blur(20px))) or ((-webkit-backdrop-filter: blur(10px)) or (backdrop-filter: blur(10px))) {
+        div {
+          -webkit-backdrop-filter: blur(10px);
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#},
+      Browsers {
+        safari: Some(14 << 16),
+        ..Default::default()
+      },
+    );
+    prefix_test(
+      r#"
+      @supports ((-webkit-backdrop-filter: blur(10px)) or (backdrop-filter: blur(10px))) {
+        div {
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#,
+      indoc! { r#"
+      @supports (backdrop-filter: blur(10px)) {
+        div {
+          backdrop-filter: blur(10px);
+        }
+      }
+    "#},
+      Browsers {
+        chrome: Some(80 << 16),
+        ..Default::default()
+      },
+    );
     minify_test(
       r#"
       @supports (width: calc(10px * 2)) {

src/properties/mod.rs

@@ -322,7 +322,7 @@ macro_rules! define_properties {
         }
       }
 
-      fn with_prefix(&self, prefix: VendorPrefix) -> PropertyId<'i> {
+      pub(crate) fn with_prefix(&self, prefix: VendorPrefix) -> PropertyId<'i> {
         use PropertyId::*;
         match self {
           $(
@@ -344,6 +344,26 @@ macro_rules! define_properties {
         }
       }
 
+      pub(crate) fn add_prefix(&mut self, prefix: VendorPrefix) {
+        use PropertyId::*;
+        match self {
+          $(
+            $(#[$meta])*
+            $property$((vp_name!($vp, p)))? => {
+              macro_rules! get_prefixed {
+                ($v: ty) => {{
+                  *p |= prefix;
+                }};
+                () => {{}};
+              }
+
+              get_prefixed!($($vp)?)
+            },
+          )+
+          _ => {}
+        }
+      }
+
       pub(crate) fn set_prefixes_for_targets(&mut self, targets: Targets) {
         match self {
           $(

src/rules/supports.rs

@@ -1,5 +1,7 @@
 //! The `@supports` rule.
 
+use std::collections::HashMap;
+
 use super::Location;
 use super::{CssRuleList, MinifyContext};
 use crate::error::{MinifyError, ParserError, PrinterError};
@@ -159,6 +161,7 @@ impl<'i> Parse<'i> for SupportsCondition<'i> {
     let in_parens = Self::parse_in_parens(input)?;
     let mut expected_type = None;
     let mut conditions = Vec::new();
+    let mut seen_declarations = HashMap::new();
 
     loop {
       let condition = input.try_parse(|input| {
@@ -185,14 +188,40 @@ impl<'i> Parse<'i> for SupportsCondition<'i> {
 
       if let Ok(condition) = condition {
         if conditions.is_empty() {
-          conditions.push(in_parens.clone())
+          conditions.push(in_parens.clone());
+          if let SupportsCondition::Declaration { property_id, value } = &in_parens {
+            seen_declarations.insert((property_id.with_prefix(VendorPrefix::None), value.clone()), 0);
+          }
+        }
+
+        if let SupportsCondition::Declaration { property_id, value } = condition {
+          // Merge multiple declarations with the same property id (minus prefix) and value together.
+          let property_id = property_id.with_prefix(VendorPrefix::None);
+          let key = (property_id.clone(), value.clone());
+          if let Some(index) = seen_declarations.get(&key) {
+            if let SupportsCondition::Declaration {
+              property_id: cur_property,
+              ..
+            } = &mut conditions[*index]
+            {
+              cur_property.add_prefix(property_id.prefix());
+            }
+          } else {
+            seen_declarations.insert(key, conditions.len());
+            conditions.push(SupportsCondition::Declaration { property_id, value });
+          }
+        } else {
+          conditions.push(condition);
         }
-        conditions.push(condition)
       } else {
         break;
       }
     }
 
+    if conditions.len() == 1 {
+      return Ok(conditions.pop().unwrap());
+    }
+
     match expected_type {
       Some(1) => Ok(SupportsCondition::And(conditions)),
       Some(2) => Ok(SupportsCondition::Or(conditions)),