add support for @starting-style

src/parse/index.ts

@@ -19,6 +19,7 @@ import {
   CssNamespaceAST,
   CssPageAST,
   CssRuleAST,
+  CssStartingStyleAST,
   CssStylesheetAST,
   CssSupportsAST,
   CssTypes,
@@ -680,6 +681,31 @@ export const parse = (
     });
   }
 
+  /**
+   * Parse starting style.
+   */
+  function atstartingstyle(): CssStartingStyleAST | void {
+    const pos = position();
+    const m = match(/^@starting-style\s*/);
+    if (!m) {
+      return;
+    }
+
+    if (!open()) {
+      return error("@starting-style missing '{'");
+    }
+    const style = comments<CssAtRuleAST>().concat(rules());
+
+    if (!close()) {
+      return error("@starting-style missing '}'");
+    }
+
+    return pos<CssStartingStyleAST>({
+      type: CssTypes.startingStyle,
+      rules: style,
+    });
+  }
+
   /**
    * Parse import
    */
@@ -742,6 +768,7 @@ export const parse = (
       athost() ||
       atfontface() ||
       atcontainer() ||
+      atstartingstyle() ||
       atlayer()
     );
   }

src/stringify/compiler.ts

@@ -17,6 +17,7 @@ import {
   CssNamespaceAST,
   CssPageAST,
   CssRuleAST,
+  CssStartingStyleAST,
   CssStylesheetAST,
   CssSupportsAST,
   CssTypes,
@@ -92,6 +93,8 @@ class Compiler {
         return this.namespace(node);
       case CssTypes.page:
         return this.page(node);
+      case CssTypes.startingStyle:
+        return this.startingStyle(node);
       case CssTypes.supports:
         return this.supports(node);
     }
@@ -242,6 +245,26 @@ class Compiler {
     return this.emit('@namespace ' + node.namespace + ';', node.position);
   }
 
+  /**
+   * Visit container node.
+   */
+  startingStyle(node: CssStartingStyleAST) {
+    if (this.compress) {
+      return (
+        this.emit('@starting-style', node.position) +
+        this.emit('{') +
+        this.mapVisit(node.rules) +
+        this.emit('}')
+      );
+    }
+    return (
+      this.emit(this.indent() + '@starting-style', node.position) +
+      this.emit(' {\n' + this.indent(1)) +
+      this.mapVisit(node.rules, '\n\n') +
+      this.emit('\n' + this.indent(-1) + this.indent() + '}')
+    );
+  }
+
   /**
    * Visit supports node.
    */

src/type.ts

@@ -19,6 +19,7 @@ export enum CssTypes {
   media = 'media',
   namespace = 'namespace',
   page = 'page',
+  startingStyle = 'starting-style',
   supports = 'supports',
 }
 
@@ -125,6 +126,11 @@ export type CssSupportsAST = CssCommonPositionAST & {
   rules: Array<CssAtRuleAST>;
 };
 
+export type CssStartingStyleAST = CssCommonPositionAST & {
+  type: CssTypes.startingStyle;
+  rules: Array<CssAtRuleAST>;
+};
+
 export type CssAtRuleAST =
   | CssRuleAST
   | CssCommentAST
@@ -140,7 +146,8 @@ export type CssAtRuleAST =
   | CssMediaAST
   | CssNamespaceAST
   | CssPageAST
-  | CssSupportsAST;
+  | CssSupportsAST
+  | CssStartingStyleAST;
 
 export type CssAllNodesAST =
   | CssAtRuleAST

test/cases/starting-style/ast.json

@@ -0,0 +1 @@
+{"type":"stylesheet","stylesheet":{"source":"input.css","rules":[{"type":"starting-style","rules":[{"type":"rule","selectors":["h2"],"declarations":[{"type":"declaration","property":"font-size","value":"1.5em","position":{"start":{"line":3,"column":5},"end":{"line":3,"column":21},"source":"input.css"}}],"position":{"start":{"line":2,"column":3},"end":{"line":4,"column":4},"source":"input.css"}}],"position":{"start":{"line":1,"column":1},"end":{"line":5,"column":2},"source":"input.css"}},{"type":"media","media":"screen","rules":[{"type":"starting-style","rules":[{"type":"rule","selectors":["h2"],"declarations":[{"type":"declaration","property":"font-size","value":"1.5em","position":{"start":{"line":10,"column":7},"end":{"line":10,"column":23},"source":"input.css"}}],"position":{"start":{"line":9,"column":5},"end":{"line":11,"column":6},"source":"input.css"}}],"position":{"start":{"line":8,"column":3},"end":{"line":12,"column":4},"source":"input.css"}}],"position":{"start":{"line":7,"column":1},"end":{"line":13,"column":2},"source":"input.css"}},{"type":"starting-style","rules":[{"type":"media","media":"screen","rules":[{"type":"rule","selectors":["h2"],"declarations":[{"type":"declaration","property":"font-size","value":"1.5em","position":{"start":{"line":18,"column":7},"end":{"line":18,"column":23},"source":"input.css"}}],"position":{"start":{"line":17,"column":5},"end":{"line":19,"column":6},"source":"input.css"}}],"position":{"start":{"line":16,"column":3},"end":{"line":20,"column":4},"source":"input.css"}}],"position":{"start":{"line":15,"column":1},"end":{"line":21,"column":2},"source":"input.css"}}],"parsingErrors":[]}}

test/cases/starting-style/input.css

@@ -0,0 +1,21 @@
+@starting-style {
+  h2 {
+    font-size: 1.5em;
+  }
+}
+
+@media screen {
+  @starting-style {
+    h2 {
+      font-size: 1.5em;
+    }
+  }
+}
+
+@starting-style {
+  @media screen {
+    h2 {
+      font-size: 1.5em;
+    }
+  }
+}

test/cases/starting-style/output.css

@@ -0,0 +1,21 @@
+@starting-style {
+  h2 {
+    font-size: 1.5em;
+  }
+}
+
+@media screen {
+  @starting-style {
+    h2 {
+      font-size: 1.5em;
+    }
+  }
+}
+
+@starting-style {
+  @media screen {
+    h2 {
+      font-size: 1.5em;
+    }
+  }
+}