1 files changed, 143 insertions, 0 deletions
diff --git a/devtools/server/actors/utils/stylesheet-utils.js b/devtools/server/actors/utils/stylesheet-utils.js
new file mode 100644
index 0000000000..19456dae9e
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+++ b/devtools/server/actors/utils/stylesheet-utils.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { fetch } = require("resource://devtools/shared/DevToolsUtils.js");
+
+/**
+ * For imported stylesheets, `ownerNode` is null.
+ *
+ * To resolve the ownerNode for an imported stylesheet, loop on `parentStylesheet`
+ * until we reach the topmost stylesheet, which should have a valid ownerNode.
+ *
+ * Constructable stylesheets do not have an owner node and this method will
+ * return null.
+ *
+ * @param {StyleSheet}
+ *        The stylesheet for which we want to retrieve the ownerNode.
+ * @return {DOMNode|null} The ownerNode or null for constructable stylesheets.
+ */
+function getStyleSheetOwnerNode(sheet) {
+  // If this is not an imported stylesheet and we have an ownerNode available
+  // bail out immediately.
+  if (sheet.ownerNode) {
+    return sheet.ownerNode;
+  }
+
+  let parentStyleSheet = sheet;
+  while (
+    parentStyleSheet.parentStyleSheet &&
+    parentStyleSheet !== parentStyleSheet.parentStyleSheet
+  ) {
+    parentStyleSheet = parentStyleSheet.parentStyleSheet;
+  }
+
+  return parentStyleSheet.ownerNode;
+}
+
+exports.getStyleSheetOwnerNode = getStyleSheetOwnerNode;
+
+/**
+ * Get the text of a stylesheet.
+ *
+ * TODO: A call site in window-global.js expects this method to return a promise
+ * so it is mandatory to keep it as an async function even if we are not using
+ * await explicitly. Bug 1810572.
+ *
+ * @param {StyleSheet}
+ *        The stylesheet for which we want to retrieve the text.
+ * @returns {Promise}
+ */
+async function getStyleSheetText(styleSheet) {
+  if (!styleSheet.href) {
+    if (styleSheet.ownerNode) {
+      // this is an inline <style> sheet
+      return styleSheet.ownerNode.textContent;
+    }
+    // Constructed stylesheet.
+    // TODO(bug 1769933, bug 1809108): Maybe preserve authored text?
+    return "";
+  }
+
+  return fetchStyleSheetText(styleSheet);
+}
+
+exports.getStyleSheetText = getStyleSheetText;
+
+/**
+ * Retrieve the content of a given stylesheet
+ *
+ * @param {StyleSheet} styleSheet
+ * @returns {String}
+ */
+async function fetchStyleSheetText(styleSheet) {
+  const href = styleSheet.href;
+
+  const options = {
+    loadFromCache: true,
+    policy: Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET,
+    charset: getCSSCharset(styleSheet),
+  };
+
+  // Bug 1282660 - We use the system principal to load the default internal
+  // stylesheets instead of the content principal since such stylesheets
+  // require system principal to load. At meanwhile, we strip the loadGroup
+  // for preventing the assertion of the userContextId mismatching.
+
+  // chrome|file|resource|moz-extension protocols rely on the system principal.
+  const excludedProtocolsRe = /^(chrome|file|resource|moz-extension):\/\//;
+  if (!excludedProtocolsRe.test(href)) {
+    // Stylesheets using other protocols should use the content principal.
+    const ownerNode = getStyleSheetOwnerNode(styleSheet);
+    if (ownerNode) {
+      // eslint-disable-next-line mozilla/use-ownerGlobal
+      options.window = ownerNode.ownerDocument.defaultView;
+      options.principal = ownerNode.ownerDocument.nodePrincipal;
+    }
+  }
+
+  let result;
+
+  try {
+    result = await fetch(href, options);
+  } catch (e) {
+    // The list of excluded protocols can be missing some protocols, try to use the
+    // system principal if the first fetch failed.
+    console.error(
+      `stylesheets: fetch failed for ${href},` +
+        ` using system principal instead.`
+    );
+    options.window = undefined;
+    options.principal = undefined;
+    result = await fetch(href, options);
+  }
+
+  return result.content;
+}
+
+/**
+ * Get charset of a given stylesheet
+ *
+ * @param {StyleSheet} styleSheet
+ * @returns {String}
+ */
+function getCSSCharset(styleSheet) {
+  if (styleSheet) {
+    // charset attribute of <link> or <style> element, if it exists
+    if (styleSheet.ownerNode?.getAttribute) {
+      const linkCharset = styleSheet.ownerNode.getAttribute("charset");
+      if (linkCharset != null) {
+        return linkCharset;
+      }
+    }
+
+    // charset of referring document.
+    if (styleSheet.ownerNode?.ownerDocument.characterSet) {
+      return styleSheet.ownerNode.ownerDocument.characterSet;
+    }
+  }
+
+  return "UTF-8";
+}