core(plugins): allow supportedModes in category

lighthouse-core/config/config-plugin.js

@@ -23,6 +23,24 @@ function isObjectOfUnknownProperties(val) {
   return typeof val === 'object' && val !== null && !Array.isArray(val);
 }
 
+/**
+ * @param {unknown} str
+ * @return {str is LH.Gatherer.GatherMode}
+ */
+function objectIsGatherMode(str) {
+  if (typeof str !== 'string') return false;
+  return str === 'navigation' || str === 'timespan' || str === 'snapshot';
+}
+
+/**
+ * @param {unknown} arr
+ * @return {arr is Array<LH.Gatherer.GatherMode>}
+ */
+function isArrayOfGatherModes(arr) {
+  if (!Array.isArray(arr)) return false;
+  return arr.every(objectIsGatherMode);
+}
+
 /**
  * Asserts that obj has no own properties, throwing a nice error message if it does.
  * Plugin and object name are included for nicer logging.
@@ -124,6 +142,7 @@ class ConfigPlugin {
       description,
       manualDescription,
       auditRefs: auditRefsJson,
+      supportedModes,
       ...invalidRest
     } = categoryJson;
 
@@ -138,13 +157,20 @@ class ConfigPlugin {
     if (!i18n.isStringOrIcuMessage(manualDescription) && manualDescription !== undefined) {
       throw new Error(`${pluginName} has an invalid category manualDescription.`);
     }
+    if (!isArrayOfGatherModes(supportedModes) && supportedModes !== undefined) {
+      throw new Error(
+        `${pluginName} supportedModes must be an array, ` +
+        `valid array values are "navigation", "timespan", and "snapshot".`
+      );
+    }
     const auditRefs = ConfigPlugin._parseAuditRefsList(auditRefsJson, pluginName);
 
     return {
       title,
       auditRefs,
       description: description,
       manualDescription: manualDescription,
+      supportedModes,
     };
   }
 

lighthouse-core/test/config/__snapshots__/config-plugin-test.js.snap

@@ -23,6 +23,9 @@ Object {
       ],
       "description": "A nice plugin for nice testing",
       "manualDescription": undefined,
+      "supportedModes": Array [
+        "navigation",
+      ],
       "title": "Nice Plugin",
     },
   },

lighthouse-core/test/config/config-plugin-test.js

@@ -39,6 +39,7 @@ const nicePlugin = {
       {id: 'nice-audit', weight: 1, group: 'group-a'},
       {id: 'installable-manifest', weight: 220},
     ],
+    supportedModes: ['navigation'],
   },
 };
 
@@ -115,6 +116,7 @@ describe('ConfigPlugin', () => {
       auditRefs: [
         {id: 'evil-audit', weight: 0, group: undefined},
       ],
+      supportedModes: ['navigation'],
     };
 
     const evilPlugin = {
@@ -242,13 +244,34 @@ describe('ConfigPlugin', () => {
       assert.ok(pluginJson);
     });
 
+    it('accepts a category with no supportedModes', () => {
+      const pluginClone = deepClone(nicePlugin);
+      delete pluginClone.category.supportedModes;
+      const pluginJson = ConfigPlugin.parsePlugin(pluginClone, nicePluginName);
+      assert.ok(pluginJson);
+    });
+
     it('throws if category has an invalid manualDescription', () => {
       const pluginClone = deepClone(nicePlugin);
       pluginClone.category.manualDescription = 55;
       assert.throws(() => ConfigPlugin.parsePlugin(pluginClone, nicePluginName),
         /^Error: lighthouse-plugin-nice-plugin has an invalid category manualDescription/);
     });
 
+    it('throws if supported modes is not an array', () => {
+      const pluginClone = deepClone(nicePlugin);
+      pluginClone.category.supportedModes = 55;
+      assert.throws(() => ConfigPlugin.parsePlugin(pluginClone, nicePluginName),
+        /^Error: lighthouse-plugin-nice-plugin supportedModes must be an array/);
+    });
+
+    it('throws if supported modes is not an array of valid gather modes', () => {
+      const pluginClone = deepClone(nicePlugin);
+      pluginClone.category.supportedModes = ['invalid-mode'];
+      assert.throws(() => ConfigPlugin.parsePlugin(pluginClone, nicePluginName),
+        /^Error: lighthouse-plugin-nice-plugin supportedModes must be an array/);
+    });
+
     describe('`category.auditRefs`', () => {
       it('correctly passes through the contained auditRefs', () => {
         const pluginJson = ConfigPlugin.parsePlugin(nicePlugin, nicePluginName);