From fcb8a1fcf52a63eb79db406072bd3ee85d73a5d4 Mon Sep 17 00:00:00 2001
From: Ankit Ahuja <ahuja.ankit@gmail.com>
Date: Wed, 29 Jul 2020 12:33:35 -0700
Subject: [PATCH] do not inject important for declarations whose ancestor is an
 atrule. #559

---
 src/background/styles.ts              | 16 ++---
 src/css/__tests__/declaration.test.ts | 88 ++++++++++++++++++++++++++-
 src/css/declaration.ts                | 22 +++++++
 src/css/index.ts                      |  2 +-
 src/css/inject-style.ts               |  6 +-
 5 files changed, 116 insertions(+), 18 deletions(-)

diff --git a/src/background/styles.ts b/src/background/styles.ts
index d0696f54..af827173 100644
--- a/src/background/styles.ts
+++ b/src/background/styles.ts
@@ -1,4 +1,6 @@
 import * as postcss from 'postcss';
+import { appendImportantToDeclarations } from '@stylebot/css';
+
 import BackgroundPageUtils from './utils';
 
 import {
@@ -63,7 +65,7 @@ class BackgroundPageStyles {
         const { styles, defaultStyle } = this.getStylesForPage(tab.url);
         this.updateIcon(tab, styles, defaultStyle);
 
-        const css = this.addImportantToCss(this.styles[url].css);
+        const css = appendImportantToDeclarations(this.styles[url].css);
         const message: EnableStyleForTab = {
           name: 'EnableStyleForTab',
           url,
@@ -161,7 +163,7 @@ class BackgroundPageStyles {
 
       if (matches && this.styles[url]) {
         const css = important
-          ? this.addImportantToCss(this.styles[url].css)
+          ? appendImportantToDeclarations(this.styles[url].css)
           : this.styles[url].css;
 
         const { enabled, readability } = this.styles[url];
@@ -182,16 +184,6 @@ class BackgroundPageStyles {
     return { styles, defaultStyle };
   }
 
-  addImportantToCss(css: string): string {
-    const root = postcss.parse(css);
-
-    root.walkDecls(decl => {
-      decl.important = true;
-    });
-
-    return root.toString();
-  }
-
   getImportCss(url: string): Promise<string> {
     return new Promise(resolve => {
       const xhr = new XMLHttpRequest();
diff --git a/src/css/__tests__/declaration.test.ts b/src/css/__tests__/declaration.test.ts
index eb241ec8..454e0ff6 100644
--- a/src/css/__tests__/declaration.test.ts
+++ b/src/css/__tests__/declaration.test.ts
@@ -2,7 +2,7 @@
 const dedent = require('dedent');
 
 import 'jest-fetch-mock';
-import { addDeclaration } from '../declaration';
+import { addDeclaration, appendImportantToDeclarations } from '../declaration';
 
 describe('declaration', () => {
   describe('addDeclaration', () => {
@@ -141,4 +141,90 @@ describe('declaration', () => {
       expect(output).toBe('');
     });
   });
+
+  describe('appendImportantToDeclarations', () => {
+    it('correctly appends !important to declarations', () => {
+      const css = dedent`
+        * {
+          font-family: Helvetica;
+        }
+
+        a {
+          color: red;
+        }
+        `;
+
+      const output = appendImportantToDeclarations(css);
+      expect(output).toEqual(dedent`
+        * {
+          font-family: Helvetica !important;
+        }
+
+        a {
+          color: red !important;
+        }  
+      `);
+    });
+
+    it('does not append !important to declarations whose ancestor is an atrule', () => {
+      const css = dedent`
+        @font-face {
+          font-family: 'MS PGothic';
+          src: local('Meiryo');
+        }
+
+        @page {
+          margin: 1cm;
+        }
+
+        @keyframes slidein {
+          from {
+            transform: translateX(0%);
+          }
+        
+          to {
+            transform: translateX(100%);
+          }
+        }
+
+        * {
+          font-family: Helvetica;
+        }
+
+        a {
+          color: red;
+        }
+        `;
+
+      const output = appendImportantToDeclarations(css);
+      expect(output).toEqual(dedent`
+        @font-face {
+          font-family: 'MS PGothic';
+          src: local('Meiryo');
+        }
+
+        @page {
+          margin: 1cm;
+        }
+
+        @keyframes slidein {
+          from {
+            transform: translateX(0%);
+          }
+        
+          to {
+            transform: translateX(100%);
+          }
+        }
+
+        * {
+          font-family: Helvetica !important;
+        }
+
+        a {
+          color: red !important;
+        }  
+      `);
+    });
+  });
 });
diff --git a/src/css/declaration.ts b/src/css/declaration.ts
index f74d1f17..0d1fa348 100644
--- a/src/css/declaration.ts
+++ b/src/css/declaration.ts
@@ -58,3 +58,25 @@ export const addDeclaration = (
 
   return css;
 };
+
+export const appendImportantToDeclarations = (css: string): string => {
+  const root = postcss.parse(css);
+
+  const isAncestorAnAtRule = (node: postcss.Node): boolean => {
+    if (node.type === 'atrule') {
+      return true;
+    } else if (node.type === 'decl' || node.type === 'rule') {
+      return isAncestorAnAtRule(node.parent);
+    } else {
+      return false;
+    }
+  };
+
+  root.walkDecls(decl => {
+    if (!isAncestorAnAtRule(decl)) {
+      decl.important = true;
+    }
+  });
+
+  return root.toString();
+};
diff --git a/src/css/index.ts b/src/css/index.ts
index 5328e650..3d17c27c 100644
--- a/src/css/index.ts
+++ b/src/css/index.ts
@@ -19,4 +19,4 @@ export {
 
 export { addGoogleWebFont, cleanGoogleWebFonts } from './webfont';
 
-export { addDeclaration } from './declaration';
+export { addDeclaration, appendImportantToDeclarations } from './declaration';
diff --git a/src/css/inject-style.ts b/src/css/inject-style.ts
index 5ebf47e1..4131fdcd 100644
--- a/src/css/inject-style.ts
+++ b/src/css/inject-style.ts
@@ -1,4 +1,5 @@
 import * as postcss from 'postcss';
+import { appendImportantToDeclarations } from './declaration';
 import { getCssWithExpandedImports } from './import';
 
 const getStylesheetId = (id: string) => {
@@ -32,10 +33,7 @@ export const injectRootIntoDocument = (
   root: postcss.Root,
   id: string
 ): void => {
-  const rootWithImportant = root.clone();
-  rootWithImportant.walkDecls(decl => (decl.important = true));
-
-  const css = rootWithImportant.toString();
+  const css = appendImportantToDeclarations(root.toString());
   injectCSSIntoDocument(css, id);
 };