Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

8 files changed, 732 insertions, 0 deletions

diff --git a/devtools/server/actors/compatibility/compatibility.js b/devtools/server/actors/compatibility/compatibility.js
new file mode 100644
index 0000000000..21ff68b310
--- /dev/null
+++ b/devtools/server/actors/compatibility/compatibility.js
@@ -0,0 +1,162 @@
+/* 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 { Actor } = require("resource://devtools/shared/protocol.js");
+const {
+  compatibilitySpec,
+} = require("resource://devtools/shared/specs/compatibility.js");
+
+loader.lazyGetter(this, "mdnCompatibility", () => {
+  const MDNCompatibility = require("resource://devtools/server/actors/compatibility/lib/MDNCompatibility.js");
+  const cssPropertiesCompatData = require("resource://devtools/shared/compatibility/dataset/css-properties.json");
+  return new MDNCompatibility(cssPropertiesCompatData);
+});
+
+class CompatibilityActor extends Actor {
+  /**
+   * Create a CompatibilityActor.
+   * CompatibilityActor is responsible for providing the compatibility information
+   * for the web page using the data from the Inspector and the `MDNCompatibility`
+   * and conveys them to the compatibility panel in the DevTool Inspector. Currently,
+   * the `CompatibilityActor` only detects compatibility issues in the CSS declarations
+   * but plans are in motion to extend it to evaluate compatibility information for
+   * HTML and JavaScript.
+   * The design below has the InspectorActor own the CompatibilityActor, but it's
+   * possible we will want to move it into it's own panel in the future.
+   *
+   * @param inspector
+   *    The InspectorActor that owns this CompatibilityActor.
+   *
+   * @constructor
+   */
+  constructor(inspector) {
+    super(inspector.conn, compatibilitySpec);
+    this.inspector = inspector;
+  }
+
+  destroy() {
+    super.destroy();
+    this.inspector = null;
+  }
+
+  form() {
+    return {
+      actor: this.actorID,
+    };
+  }
+
+  getTraits() {
+    return {
+      traits: {},
+    };
+  }
+
+  /**
+   * Responsible for computing the compatibility issues for a list of CSS declaration blocks
+   *
+   * @param {Array<Array<Object>>} domRulesDeclarations: An array of arrays of CSS declaration object
+   * @param {string} domRulesDeclarations[][].name: Declaration name
+   * @param {string} domRulesDeclarations[][].value: Declaration value
+   * @param {Array<Object>} targetBrowsers: Array of target browsers () to be used to check CSS compatibility against
+   * @param {string} targetBrowsers[].id: Browser id as specified in `devtools/shared/compatibility/datasets/browser.json`
+   * @param {string} targetBrowsers[].name
+   * @param {string} targetBrowsers[].version
+   * @param {string} targetBrowsers[].status: Browser status - esr, current, beta, nightly
+   * @returns {Array<Array<Object>>} An Array of arrays of JSON objects with compatibility
+   *                                 information in following form:
+   *    {
+   *      // Type of compatibility issue
+   *      type: <string>,
+   *      // The CSS declaration that has compatibility issues
+   *      property: <string>,
+   *      // Alias to the given CSS property
+   *      alias: <Array>,
+   *      // Link to MDN documentation for the particular CSS rule
+   *      url: <string>,
+   *      deprecated: <boolean>,
+   *      experimental: <boolean>,
+   *      // An array of all the browsers that don't support the given CSS rule
+   *      unsupportedBrowsers: <Array>,
+   *    }
+   */
+  getCSSDeclarationBlockIssues(domRulesDeclarations, targetBrowsers) {
+    return domRulesDeclarations.map(declarationBlock =>
+      mdnCompatibility.getCSSDeclarationBlockIssues(
+        declarationBlock,
+        targetBrowsers
+      )
+    );
+  }
+
+  /**
+   * Responsible for computing the compatibility issues in the
+   * CSS declaration of the given node.
+   * @param NodeActor node
+   * @param targetBrowsers Array
+   *   An Array of JSON object of target browser to check compatibility against in following form:
+   *   {
+   *     // Browser id as specified in `devtools/server/actors/compatibility/lib/datasets/browser.json`
+   *     id: <string>,
+   *     name: <string>,
+   *     version: <string>,
+   *     // Browser status - esr, current, beta, nightly
+   *     status: <string>,
+   *   }
+   * @returns An Array of JSON objects with compatibility information in following form:
+   *    {
+   *      // Type of compatibility issue
+   *      type: <string>,
+   *      // The CSS declaration that has compatibility issues
+   *      property: <string>,
+   *      // Alias to the given CSS property
+   *      alias: <Array>,
+   *      // Link to MDN documentation for the particular CSS rule
+   *      url: <string>,
+   *      deprecated: <boolean>,
+   *      experimental: <boolean>,
+   *      // An array of all the browsers that don't support the given CSS rule
+   *      unsupportedBrowsers: <Array>,
+   *    }
+   */
+  async getNodeCssIssues(node, targetBrowsers) {
+    const pageStyle = await this.inspector.getPageStyle();
+    const styles = await pageStyle.getApplied(node, {
+      skipPseudo: false,
+    });
+
+    const declarationBlocks = styles.entries
+      .map(({ rule }) => {
+        // Replace form() with a function to get minimal subset
+        // of declarations from StyleRuleActor when such a
+        // function lands in the StyleRuleActor
+        const declarations = rule.form().declarations;
+        if (!declarations) {
+          return null;
+        }
+        return declarations.filter(d => !d.commentOffsets);
+      })
+      .filter(declarations => declarations && declarations.length);
+
+    return declarationBlocks
+      .map(declarationBlock =>
+        mdnCompatibility.getCSSDeclarationBlockIssues(
+          declarationBlock,
+          targetBrowsers
+        )
+      )
+      .flat()
+      .reduce((issues, issue) => {
+        // Get rid of duplicate issue
+        return issues.find(
+          i => i.type === issue.type && i.property === issue.property
+        )
+          ? issues
+          : [...issues, issue];
+      }, []);
+  }
+}
+
+exports.CompatibilityActor = CompatibilityActor;
diff --git a/devtools/server/actors/compatibility/lib/MDNCompatibility.js b/devtools/server/actors/compatibility/lib/MDNCompatibility.js
new file mode 100644
index 0000000000..9975123103
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/MDNCompatibility.js
@@ -0,0 +1,327 @@
+/* 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 _SUPPORT_STATE_BROWSER_NOT_FOUND = "BROWSER_NOT_FOUND";
+const _SUPPORT_STATE_SUPPORTED = "SUPPORTED";
+const _SUPPORT_STATE_UNSUPPORTED = "UNSUPPORTED";
+const _SUPPORT_STATE_UNSUPPORTED_PREFIX_NEEDED = "UNSUPPORTED_PREFIX_NEEDED";
+
+loader.lazyRequireGetter(
+  this,
+  "COMPATIBILITY_ISSUE_TYPE",
+  "resource://devtools/shared/constants.js",
+  true
+);
+
+loader.lazyRequireGetter(
+  this,
+  ["getCompatNode", "getCompatTable"],
+  "resource://devtools/shared/compatibility/helpers.js",
+  true
+);
+
+const PREFIX_REGEX = /^-\w+-/;
+
+/**
+ * A class with methods used to query the MDN compatibility data for CSS properties and
+ * HTML nodes and attributes for specific browsers and versions.
+ */
+class MDNCompatibility {
+  /**
+   * Constructor.
+   *
+   * @param {JSON} cssPropertiesCompatData
+   *        JSON of the compat data for CSS properties.
+   *        https://github.com/mdn/browser-compat-data/tree/master/css/properties
+   */
+  constructor(cssPropertiesCompatData) {
+    this._cssPropertiesCompatData = cssPropertiesCompatData;
+  }
+
+  /**
+   * Return the CSS related compatibility issues from given CSS declaration blocks.
+   *
+   * @param {Array} declarations
+   *                CSS declarations to check.
+   *                e.g. [{ name: "background-color", value: "lime" }, ...]
+   * @param {Array} browsers
+   *                Restrict compatibility checks to these browsers and versions.
+   *                e.g. [{ id: "firefox", name: "Firefox", version: "68" }, ...]
+   * @return {Array} issues
+   */
+  getCSSDeclarationBlockIssues(declarations, browsers) {
+    const summaries = [];
+    for (const { name: property } of declarations) {
+      // Ignore CSS custom properties as any name is valid.
+      if (property.startsWith("--")) {
+        continue;
+      }
+
+      summaries.push(this._getCSSPropertyCompatSummary(browsers, property));
+    }
+
+    // Classify to aliases summaries and normal summaries.
+    const { aliasSummaries, normalSummaries } =
+      this._classifyCSSCompatSummaries(summaries, browsers);
+
+    // Finally, convert to CSS issues.
+    return this._toCSSIssues(normalSummaries.concat(aliasSummaries));
+  }
+
+  /**
+   * Classify the compatibility summaries that are able to get from
+   * `getCSSPropertyCompatSummary`.
+   * There are CSS properties that can specify the style with plural aliases such as
+   * `user-select`, aggregates those as the aliases summaries.
+   *
+   * @param {Array} summaries
+   *                Assume the result of _getCSSPropertyCompatSummary().
+   * @param {Array} browsers
+   *                All browsers that to check
+   *                e.g. [{ id: "firefox", name: "Firefox", version: "68" }, ...]
+   * @return Object
+   *                {
+   *                  aliasSummaries: Array of alias summary,
+   *                  normalSummaries: Array of normal summary
+   *                }
+   */
+  _classifyCSSCompatSummaries(summaries, browsers) {
+    const aliasSummariesMap = new Map();
+    const normalSummaries = summaries.filter(s => {
+      const {
+        database,
+        invalid,
+        terms,
+        unsupportedBrowsers,
+        prefixNeededBrowsers,
+      } = s;
+
+      if (invalid) {
+        return true;
+      }
+
+      const alias = this._getAlias(database, terms);
+      if (!alias) {
+        return true;
+      }
+
+      if (!aliasSummariesMap.has(alias)) {
+        aliasSummariesMap.set(
+          alias,
+          Object.assign(s, {
+            property: alias,
+            aliases: [],
+            unsupportedBrowsers: browsers,
+            prefixNeededBrowsers: browsers,
+          })
+        );
+      }
+
+      // Update alias summary.
+      const terminal = terms.pop();
+      const aliasSummary = aliasSummariesMap.get(alias);
+      if (!aliasSummary.aliases.includes(terminal)) {
+        aliasSummary.aliases.push(terminal);
+      }
+      aliasSummary.unsupportedBrowsers =
+        aliasSummary.unsupportedBrowsers.filter(b =>
+          unsupportedBrowsers.includes(b)
+        );
+      aliasSummary.prefixNeededBrowsers =
+        aliasSummary.prefixNeededBrowsers.filter(b =>
+          prefixNeededBrowsers.includes(b)
+        );
+      return false;
+    });
+
+    const aliasSummaries = [...aliasSummariesMap.values()].map(s => {
+      s.prefixNeeded = s.prefixNeededBrowsers.length !== 0;
+      return s;
+    });
+
+    return { aliasSummaries, normalSummaries };
+  }
+
+  _getAlias(compatNode, terms) {
+    const targetNode = getCompatNode(compatNode, terms);
+    return targetNode ? targetNode._aliasOf : null;
+  }
+
+  /**
+   * Return the compatibility summary of the terms.
+   *
+   * @param {Array} browsers
+   *                All browsers that to check
+   *                e.g. [{ id: "firefox", name: "Firefox", version: "68" }, ...]
+   * @param {Array} database
+   *                MDN compatibility dataset where finds from
+   * @param {Array} terms
+   *                The terms which is checked the compatibility summary from the
+   *                database. The paremeters are passed as `rest parameters`.
+   *                e.g. _getCompatSummary(browsers, database, "user-select", ...)
+   * @return {Object}
+   *                {
+   *                  database: The passed database as a parameter,
+   *                  terms: The passed terms as a parameter,
+   *                  url: The link which indicates the spec in MDN,
+   *                  deprecated: true if the spec of terms is deprecated,
+   *                  experimental: true if the spec of terms is experimental,
+   *                  unsupportedBrowsers: Array of unsupported browsers,
+   *                }
+   */
+  _getCompatSummary(browsers, database, terms) {
+    const compatTable = getCompatTable(database, terms);
+
+    if (!compatTable) {
+      return { invalid: true, unsupportedBrowsers: [] };
+    }
+
+    const unsupportedBrowsers = [];
+    const prefixNeededBrowsers = [];
+
+    for (const browser of browsers) {
+      const state = this._getSupportState(
+        compatTable,
+        browser,
+        database,
+        terms
+      );
+
+      switch (state) {
+        case _SUPPORT_STATE_UNSUPPORTED_PREFIX_NEEDED: {
+          prefixNeededBrowsers.push(browser);
+          unsupportedBrowsers.push(browser);
+          break;
+        }
+        case _SUPPORT_STATE_UNSUPPORTED: {
+          unsupportedBrowsers.push(browser);
+          break;
+        }
+      }
+    }
+
+    const { deprecated, experimental } = compatTable.status || {};
+
+    return {
+      database,
+      terms,
+      url: compatTable.mdn_url,
+      specUrl: compatTable.spec_url,
+      deprecated,
+      experimental,
+      unsupportedBrowsers,
+      prefixNeededBrowsers,
+    };
+  }
+
+  /**
+   * Return the compatibility summary of the CSS property.
+   * This function just adds `property` filed to the result of `_getCompatSummary`.
+   *
+   * @param {Array} browsers
+   *                All browsers that to check
+   *                e.g. [{ id: "firefox", name: "Firefox", version: "68" }, ...]
+   * @return {Object} compatibility summary
+   */
+  _getCSSPropertyCompatSummary(browsers, property) {
+    const summary = this._getCompatSummary(
+      browsers,
+      this._cssPropertiesCompatData,
+      [property]
+    );
+    return Object.assign(summary, { property });
+  }
+
+  _getSupportState(compatTable, browser, compatNode, terms) {
+    const supportList = compatTable.support[browser.id];
+    if (!supportList) {
+      return _SUPPORT_STATE_BROWSER_NOT_FOUND;
+    }
+
+    const version = parseFloat(browser.version);
+    const terminal = terms.at(-1);
+    const prefix = terminal.match(PREFIX_REGEX)?.[0];
+
+    let prefixNeeded = false;
+    for (const support of supportList) {
+      const { alternative_name: alternativeName, added, removed } = support;
+
+      if (
+        // added id true when feature is supported, but we don't know the version
+        (added === true ||
+          // `null` and `undefined` is when we don't know if it's supported.
+          // Since we don't want to have false negative, we consider it as supported
+          added === null ||
+          added === undefined ||
+          // It was added on a previous version number
+          added <= version) &&
+        // `added` is false when the property isn't supported
+        added !== false &&
+        // `removed` is false when the feature wasn't removevd
+        (removed === false ||
+          // `null` and `undefined` is when we don't know if it was removed.
+          // Since we don't want to have false negative, we consider it as supported
+          removed === null ||
+          removed === undefined ||
+          // It was removed, but on a later version, so it's still supported
+          version <= removed)
+      ) {
+        if (alternativeName) {
+          if (alternativeName === terminal) {
+            return _SUPPORT_STATE_SUPPORTED;
+          }
+        } else if (
+          support.prefix === prefix ||
+          // There are compat data that are defined with prefix like "-moz-binding".
+          // In this case, we don't have to check the prefix.
+          (prefix && !this._getAlias(compatNode, terms))
+        ) {
+          return _SUPPORT_STATE_SUPPORTED;
+        }
+
+        prefixNeeded = true;
+      }
+    }
+
+    return prefixNeeded
+      ? _SUPPORT_STATE_UNSUPPORTED_PREFIX_NEEDED
+      : _SUPPORT_STATE_UNSUPPORTED;
+  }
+
+  _hasIssue({ unsupportedBrowsers, deprecated, experimental, invalid }) {
+    // Don't apply as issue the invalid term which was not in the database.
+    return (
+      !invalid && (unsupportedBrowsers.length || deprecated || experimental)
+    );
+  }
+
+  _toIssue(summary, type) {
+    const issue = Object.assign({}, summary, { type });
+    delete issue.database;
+    delete issue.terms;
+    delete issue.prefixNeededBrowsers;
+    return issue;
+  }
+
+  _toCSSIssues(summaries) {
+    const issues = [];
+
+    for (const summary of summaries) {
+      if (!this._hasIssue(summary)) {
+        continue;
+      }
+
+      const type = summary.aliases
+        ? COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY_ALIASES
+        : COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY;
+      issues.push(this._toIssue(summary, type));
+    }
+
+    return issues;
+  }
+}
+
+module.exports = MDNCompatibility;
diff --git a/devtools/server/actors/compatibility/lib/moz.build b/devtools/server/actors/compatibility/lib/moz.build
new file mode 100644
index 0000000000..f28d8fe482
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/moz.build
@@ -0,0 +1,11 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+XPCSHELL_TESTS_MANIFESTS += ["test/xpcshell/xpcshell.ini"]
+
+DevToolsModules(
+    "MDNCompatibility.js",
+)
diff --git a/devtools/server/actors/compatibility/lib/test/xpcshell/.eslintrc.js b/devtools/server/actors/compatibility/lib/test/xpcshell/.eslintrc.js
new file mode 100644
index 0000000000..65efbdee13
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/test/xpcshell/.eslintrc.js
@@ -0,0 +1,6 @@
+"use strict";
+
+module.exports = {
+  // Extend from the common devtools xpcshell eslintrc config.
+  extends: "../../../../../../.eslintrc.xpcshell.js",
+};
diff --git a/devtools/server/actors/compatibility/lib/test/xpcshell/head.js b/devtools/server/actors/compatibility/lib/test/xpcshell/head.js
new file mode 100644
index 0000000000..733c0400da
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/test/xpcshell/head.js
@@ -0,0 +1,10 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* eslint no-unused-vars: [2, {"vars": "local"}] */
+
+const { require } = ChromeUtils.importESModule(
+  "resource://devtools/shared/loader/Loader.sys.mjs"
+);
diff --git a/devtools/server/actors/compatibility/lib/test/xpcshell/test_mdn-compatibility.js b/devtools/server/actors/compatibility/lib/test/xpcshell/test_mdn-compatibility.js
new file mode 100644
index 0000000000..e411feb3b0
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/test/xpcshell/test_mdn-compatibility.js
@@ -0,0 +1,193 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test for the MDN compatibility diagnosis module.
+
+const {
+  COMPATIBILITY_ISSUE_TYPE,
+} = require("resource://devtools/shared/constants.js");
+const MDNCompatibility = require("resource://devtools/server/actors/compatibility/lib/MDNCompatibility.js");
+const cssPropertiesCompatData = require("resource://devtools/shared/compatibility/dataset/css-properties.json");
+
+const mdnCompatibility = new MDNCompatibility(cssPropertiesCompatData);
+
+const FIREFOX_1 = {
+  id: "firefox",
+  version: "1",
+};
+
+const FIREFOX_60 = {
+  id: "firefox",
+  version: "60",
+};
+
+const FIREFOX_69 = {
+  id: "firefox",
+  version: "69",
+};
+
+const FIREFOX_ANDROID_1 = {
+  id: "firefox_android",
+  version: "1",
+};
+
+const SAFARI_13 = {
+  id: "safari",
+  version: "13",
+};
+
+const TEST_DATA = [
+  {
+    description: "Test for a supported property",
+    declarations: [{ name: "background-color" }],
+    browsers: [FIREFOX_69],
+    expectedIssues: [],
+  },
+  {
+    description: "Test for some supported properties",
+    declarations: [{ name: "background-color" }, { name: "color" }],
+    browsers: [FIREFOX_69],
+    expectedIssues: [],
+  },
+  {
+    description: "Test for an unsupported property",
+    declarations: [{ name: "grid-column" }],
+    browsers: [FIREFOX_1],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY,
+        property: "grid-column",
+        url: "https://developer.mozilla.org/docs/Web/CSS/grid-column",
+        specUrl: "https://drafts.csswg.org/css-grid/#placement-shorthands",
+        deprecated: false,
+        experimental: false,
+        unsupportedBrowsers: [FIREFOX_1],
+      },
+    ],
+  },
+  {
+    description: "Test for an unknown property",
+    declarations: [{ name: "unknown-property" }],
+    browsers: [FIREFOX_69],
+    expectedIssues: [],
+  },
+  {
+    description: "Test for a deprecated property",
+    declarations: [{ name: "clip" }],
+    browsers: [FIREFOX_69],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY,
+        property: "clip",
+        url: "https://developer.mozilla.org/docs/Web/CSS/clip",
+        specUrl: "https://drafts.fxtf.org/css-masking/#clip-property",
+        deprecated: true,
+        experimental: false,
+        unsupportedBrowsers: [],
+      },
+    ],
+  },
+  {
+    description: "Test for a property having some issues",
+    declarations: [{ name: "ruby-align" }],
+    browsers: [FIREFOX_1],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY,
+        property: "ruby-align",
+        url: "https://developer.mozilla.org/docs/Web/CSS/ruby-align",
+        specUrl: "https://drafts.csswg.org/css-ruby/#ruby-align-property",
+        deprecated: false,
+        experimental: true,
+        unsupportedBrowsers: [FIREFOX_1],
+      },
+    ],
+  },
+  {
+    description:
+      "Test for an aliased property not supported in all browsers with prefix needed",
+    declarations: [{ name: "-moz-user-select" }],
+    browsers: [FIREFOX_69, SAFARI_13],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY_ALIASES,
+        property: "user-select",
+        aliases: ["-moz-user-select"],
+        url: "https://developer.mozilla.org/docs/Web/CSS/user-select",
+        specUrl: "https://drafts.csswg.org/css-ui/#content-selection",
+        deprecated: false,
+        experimental: false,
+        prefixNeeded: true,
+        unsupportedBrowsers: [SAFARI_13],
+      },
+    ],
+  },
+  {
+    description:
+      "Test for an aliased property not supported in all browsers without prefix needed",
+    declarations: [
+      { name: "-moz-user-select" },
+      { name: "-webkit-user-select" },
+    ],
+    browsers: [FIREFOX_ANDROID_1, FIREFOX_69, SAFARI_13],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY_ALIASES,
+        property: "user-select",
+        aliases: ["-moz-user-select", "-webkit-user-select"],
+        url: "https://developer.mozilla.org/docs/Web/CSS/user-select",
+        specUrl: "https://drafts.csswg.org/css-ui/#content-selection",
+        deprecated: false,
+        experimental: false,
+        prefixNeeded: false,
+        unsupportedBrowsers: [FIREFOX_ANDROID_1],
+      },
+    ],
+  },
+  {
+    description: "Test for aliased properties supported in all browsers",
+    declarations: [
+      { name: "-moz-user-select" },
+      { name: "-webkit-user-select" },
+    ],
+    browsers: [FIREFOX_69, SAFARI_13],
+    expectedIssues: [],
+  },
+  {
+    description: "Test for a property defined with prefix",
+    declarations: [{ name: "-moz-user-input" }],
+    browsers: [FIREFOX_1, FIREFOX_60, FIREFOX_69],
+    expectedIssues: [
+      {
+        type: COMPATIBILITY_ISSUE_TYPE.CSS_PROPERTY,
+        property: "-moz-user-input",
+        url: "https://developer.mozilla.org/docs/Web/CSS/-moz-user-input",
+        specUrl: undefined,
+        deprecated: true,
+        experimental: false,
+        unsupportedBrowsers: [],
+      },
+    ],
+  },
+];
+
+add_task(() => {
+  for (const {
+    description,
+    declarations,
+    browsers,
+    expectedIssues,
+  } of TEST_DATA) {
+    info(description);
+    const issues = mdnCompatibility.getCSSDeclarationBlockIssues(
+      declarations,
+      browsers
+    );
+    deepEqual(
+      issues,
+      expectedIssues,
+      "CSS declaration compatibility data matches expectations"
+    );
+  }
+});
diff --git a/devtools/server/actors/compatibility/lib/test/xpcshell/xpcshell.ini b/devtools/server/actors/compatibility/lib/test/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..490afa9504
--- /dev/null
+++ b/devtools/server/actors/compatibility/lib/test/xpcshell/xpcshell.ini
@@ -0,0 +1,7 @@
+[DEFAULT]
+tags = devtools
+head = head.js
+firefox-appdir = browser
+skip-if = toolkit == 'android'
+
+[test_mdn-compatibility.js]
diff --git a/devtools/server/actors/compatibility/moz.build b/devtools/server/actors/compatibility/moz.build
new file mode 100644
index 0000000000..010b027d37
--- /dev/null
+++ b/devtools/server/actors/compatibility/moz.build
@@ -0,0 +1,16 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+DIRS += [
+    "lib",
+]
+
+DevToolsModules(
+    "compatibility.js",
+)
+
+with Files("**"):
+    BUG_COMPONENT = ("DevTools", "Inspector: Compatibility")