fix: preserve default border image shorthand values

src/lib.rs

@@ -2350,6 +2350,72 @@ mod tests {
 
   #[test]
   pub fn test_border_image() {
+    minify_test(
+      r#"
+      .foo {
+        border-image: none;
+      }
+      "#,
+      ".foo{border-image:none}",
+    );
+
+    test(
+      r#"
+      .foo {
+        border-image: none;
+      }
+      "#,
+      indoc! {r#"
+      .foo {
+        border-image: none;
+      }
+      "#},
+    );
+
+    minify_test(
+      r#"
+      .foo {
+        border-image: none 100% / 1 / 0 stretch;
+      }
+      "#,
+      ".foo{border-image:none}",
+    );
+
+    minify_test(
+      r#"
+      .foo {
+        border-image-source: none;
+        border-image-slice: 100%;
+        border-image-width: 1;
+        border-image-outset: 0;
+        border-image-repeat: stretch;
+      }
+      "#,
+      ".foo{border-image:none}",
+    );
+
+    minify_test(
+      r#"
+      .foo {
+        -webkit-border-image: none;
+        border-image: none !important;
+      }
+      "#,
+      ".foo{-webkit-border-image:none;border-image:none!important}",
+    );
+
+    minify_test(
+      r#"
+      .foo {
+        border-image: url(border.png) 1;
+      }
+      .foo.active {
+        border-image: none;
+      }
+      "#,
+      ".foo{border-image:url(border.png) 1}.foo.active{border-image:none}",
+    );
+
     property_range_test(
       &[
         "border-image-outset",
@@ -29891,6 +29957,22 @@ mod tests {
       ".foo{mask:url(masks.svg#star) 0/16px repeat-y,url(masks.svg#circle) 100%/16px repeat-y}",
     );
 
+    minify_test(
+      r#"
+      .foo {
+        mask-border: none;
+      }
+      "#,
+      ".foo{mask-border:none}",
+    );
+    minify_test(
+      r#"
+      .foo {
+        -webkit-mask-box-image: none;
+      }
+      "#,
+      ".foo{-webkit-mask-box-image:none}",
+    );
     minify_test(
       ".foo { mask-border: url('border-mask.png') 25; }",
       ".foo{mask-border:url(border-mask.png) 25}",

src/properties/border_image.rs

@@ -293,12 +293,21 @@ impl<'i> BorderImage<'i> {
     repeat: &BorderImageRepeat,
     dest: &mut PrinterT,
   ) -> Result<(), PrinterError> {
-    if *source != Image::default() {
-      source.to_css(dest)?;
-    }
+    let has_source = *source != Image::default();
     let has_slice = *slice != BorderImageSlice::default();
     let has_width = *width != Rect::all(BorderImageSideWidth::default());
     let has_outset = *outset != Rect::all(NonNegative(LengthOrNumber::Number(0.0)));
+    let has_repeat = *repeat != BorderImageRepeat::default();
+
+    // A shorthand with only initial components must still have a value.
+    if !has_source && !has_slice && !has_width && !has_outset && !has_repeat {
+      dest.write_str("none")?;
+      return Ok(());
+    }
+
+    if has_source {
+      source.to_css(dest)?;
+    }
     if has_slice || has_width || has_outset {
       dest.write_str(" ")?;
       slice.to_css(dest)?;
@@ -315,7 +324,7 @@ impl<'i> BorderImage<'i> {
       }
     }
 
-    if *repeat != BorderImageRepeat::default() {
+    if has_repeat {
       dest.write_str(" ")?;
       repeat.to_css(dest)?;
     }