✨ Introduce the ability to abort requests from specificed hostnames (disallowedHostnames)

packages/cli-command/src/flags.js

@@ -56,6 +56,15 @@ export const allowedHostnames = {
   short: 'h'
 };
 
+export const disallowedHostnames = {
+  name: 'disallowed-hostname',
+  description: 'Disallowed hostnames to abort in asset discovery',
+  percyrc: 'discovery.disallowedHostnames',
+  type: 'hostname',
+  multiple: true,
+  group: 'Percy'
+};
+
 export const networkIdleTimeout = {
   name: 'network-idle-timeout',
   description: 'Asset discovery network idle timeout',
@@ -95,6 +104,7 @@ export const PERCY = [
 
 export const DISCOVERY = [
   allowedHostnames,
+  disallowedHostnames,
   networkIdleTimeout,
   disableCache,
   debug

packages/cli-command/test/flags.test.js

@@ -64,6 +64,7 @@ describe('Built-in flags:', () => {
         -c, --config <file>                Config file path
         -d, --dry-run                      Print snapshot names only
         -h, --allowed-hostname <hostname>  Allowed hostnames to capture in asset discovery
+        --disallowed-hostname <hostname>   Disallowed hostnames to abort in asset discovery
         -t, --network-idle-timeout <ms>    Asset discovery network idle timeout
         --disable-cache                    Disable asset discovery caches
         --debug                            Debug asset discovery and do not upload snapshots

packages/cli-exec/README.md

@@ -32,6 +32,7 @@ Percy options:
   -c, --config <file>                Config file path
   -d, --dry-run                      Print snapshot names only
   -h, --allowed-hostname <hostname>  Allowed hostnames to capture in asset discovery
+  --disallowed-hostname <hostname>   Disallowed hostnames to abort in asset discovery
   -t, --network-idle-timeout <ms>    Asset discovery network idle timeout
   --disable-cache                    Disable asset discovery caches
   --debug                            Debug asset discovery and do not upload snapshots
@@ -62,6 +63,7 @@ Percy options:
   -c, --config <file>                Config file path
   -d, --dry-run                      Print snapshot names only
   -h, --allowed-hostname <hostname>  Allowed hostnames to capture in asset discovery
+  --disallowed-hostname <hostname>   Disallowed hostnames to abort in asset discovery
   -t, --network-idle-timeout <ms>    Asset discovery network idle timeout
   --disable-cache                    Disable asset discovery caches
   --debug                            Debug asset discovery and do not upload snapshots

packages/cli-snapshot/README.md

@@ -29,6 +29,7 @@ Percy options:
   -c, --config <file>                Config file path
   -d, --dry-run                      Print snapshot names only
   -h, --allowed-hostname <hostname>  Allowed hostnames to capture in asset discovery
+  --disallowed-hostname <hostname>   Disallowed hostnames to abort in asset discovery
   -t, --network-idle-timeout <ms>    Asset discovery network idle timeout
   --disable-cache                    Disable asset discovery caches
   --debug                            Debug asset discovery and do not upload snapshots

packages/core/README.md

@@ -49,6 +49,7 @@ The following options can also be defined within a Percy config file
   - `enableJavaScript` — Enable JavaScript for screenshots (**default** `false`)
 - `discovery` — Asset discovery options
   - `allowedHostnames` — Array of allowed hostnames to capture assets from
+  - `disallowedHostnames` — Array of hostnames where requests will be aborted
   - `requestHeaders` — Request headers used when discovering snapshot assets
   - `authorization` — Basic auth `username` and `password` for protected snapshot assets
   - `disableCache` — Disable asset caching (**default** `false`)
@@ -192,7 +193,7 @@ depending on the provided properties ([see alternate syntaxes below](#alternate-
 - `name` — Snapshot name
 - `domSnapshot` — Snapshot DOM string
 - `discovery` - Limited snapshot specific discovery options
-  - `allowedHostnames`, `requestHeaders`, `authorization`, `disableCache`, `userAgent`
+  - `allowedHostnames`, `disallowedHostnames`, `requestHeaders`, `authorization`, `disableCache`, `userAgent`
 
 Common snapshot options are also accepted and will override instance snapshot options. [See instance
 options](#options) for common snapshot and discovery options.

packages/core/src/config.js

@@ -46,6 +46,20 @@ export const configSchema = {
           }]
         }
       },
+      disallowedHostnames: {
+        type: 'array',
+        default: [],
+        items: {
+          type: 'string',
+          allOf: [{
+            not: { pattern: '[^/]/' },
+            error: 'must not include a pathname'
+          }, {
+            not: { pattern: '^([a-zA-Z]+:)?//' },
+            error: 'must not include a protocol'
+          }]
+        }
+      },
       networkIdleTimeout: {
         type: 'integer',
         default: 100,
@@ -124,6 +138,7 @@ export const snapshotSchema = {
           additionalProperties: false,
           properties: {
             allowedHostnames: { $ref: '/config/discovery#/properties/allowedHostnames' },
+            disallowedHostnames: { $ref: '/config/discovery#/properties/disallowedHostnames' },
             requestHeaders: { $ref: '/config/discovery#/properties/requestHeaders' },
             authorization: { $ref: '/config/discovery#/properties/authorization' },
             disableCache: { $ref: '/config/discovery#/properties/disableCache' },

packages/core/src/discovery.js

@@ -5,7 +5,7 @@ const MAX_RESOURCE_SIZE = 15 * (1024 ** 2); // 15MB
 const ALLOWED_STATUSES = [200, 201, 301, 302, 304, 307, 308];
 const ALLOWED_RESOURCES = ['Document', 'Stylesheet', 'Image', 'Media', 'Font', 'Other'];
 
-export function createRequestHandler(network, { disableCache, getResource }) {
+export function createRequestHandler(network, { disableCache, disallowedHostnames, getResource }) {
   let log = logger('core:discovery');
 
   return async request => {
@@ -19,6 +19,9 @@ export function createRequestHandler(network, { disableCache, getResource }) {
       if (resource?.root) {
         log.debug('- Serving root resource', meta);
         await request.respond(resource);
+      } else if (hostnameMatches(disallowedHostnames, url)) {
+        log.debug('- Skipping disallowed hostname', meta);
+        await request.abort(true);
       } else if (resource && !disableCache) {
         log.debug('- Resource cache hit', meta);
         await request.respond(resource);

packages/core/src/snapshot.js

@@ -179,6 +179,7 @@ export function getSnapshotConfig(percy, options) {
     // only specific discovery options are used per-snapshot
     discovery: {
       allowedHostnames: percy.config.discovery.allowedHostnames,
+      disallowedHostnames: percy.config.discovery.disallowedHostnames,
       networkIdleTimeout: percy.config.discovery.networkIdleTimeout,
       requestHeaders: percy.config.discovery.requestHeaders,
       authorization: percy.config.discovery.authorization,
@@ -194,6 +195,8 @@ export function getSnapshotConfig(percy, options) {
       case 'execute': // shorthand for execute.beforeSnapshot
         return (Array.isArray(next) || typeof next !== 'object')
           ? [path.concat('beforeSnapshot'), next] : [path];
+      case 'discovery.disallowedHostnames': // prevent disallowing the root hostname
+        return [path, (prev ?? []).concat(next).filter(h => !hostnameMatches(h, options.url))];
     }
 
     // ensure additional snapshots have complete names
@@ -238,6 +241,7 @@ function debugSnapshotConfig(snapshot, showInfo) {
   debugProp(snapshot, 'execute.afterResize');
   debugProp(snapshot, 'execute.beforeSnapshot');
   debugProp(snapshot, 'discovery.allowedHostnames');
+  debugProp(snapshot, 'discovery.disallowedHostnames');
   debugProp(snapshot, 'discovery.requestHeaders', JSON.stringify);
   debugProp(snapshot, 'discovery.authorization', JSON.stringify);
   debugProp(snapshot, 'discovery.disableCache');
@@ -331,6 +335,7 @@ export async function* discoverSnapshotResources(percy, snapshot, callback) {
       enableJavaScript: snapshot.enableJavaScript,
       disableCache: snapshot.discovery.disableCache,
       allowedHostnames: snapshot.discovery.allowedHostnames,
+      disallowedHostnames: snapshot.discovery.disallowedHostnames,
       getResource: u => resources.get(u) || cache.get(u),
       saveResource: r => resources.set(r.url, r) && cache.set(r.url, r)
     }

packages/core/test/discovery.test.js

@@ -1035,6 +1035,97 @@ describe('Discovery', () => {
       );
     });
 
+    it('does not capture resources from disallowed hostnames', async () => {
+      // stop current instance to create a new one
+      await percy.stop();
+
+      percy = await Percy.start({
+        token: 'PERCY_TOKEN',
+        discovery: {
+          disallowedHostnames: ['ex.localhost']
+        }
+      });
+
+      logger.loglevel('debug');
+
+      await percy.snapshot({
+        name: 'test snapshot',
+        url: 'http://localhost:8000',
+        domSnapshot: testExternalDOM,
+        widths: [1000]
+      });
+
+      await percy.idle();
+
+      expect(logger.stderr).toEqual(jasmine.arrayContaining([
+        '[percy:core:snapshot] - discovery.disallowedHostnames: ex.localhost'
+      ]));
+
+      expect(logger.stderr).toEqual(jasmine.arrayContaining([
+        '[percy:core:discovery] Handling request: http://ex.localhost:8001/img.gif',
+        '[percy:core:discovery] - Skipping disallowed hostname'
+      ]));
+
+      expect(captured[0]).toEqual([
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': jasmine.stringMatching(/^\/percy\.\d+\.log$/)
+          })
+        }),
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': 'http://localhost:8000/'
+          })
+        }),
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': 'http://localhost:8000/style.css'
+          })
+        })
+      ]);
+    });
+
+    it('ignores root resource URL when passed to disallowedHostnames', async () => {
+      // stop current instance to create a new one
+      await percy.stop();
+
+      percy = await Percy.start({
+        token: 'PERCY_TOKEN',
+        discovery: {
+          disallowedHostnames: ['localhost']
+        }
+      });
+
+      logger.loglevel('debug');
+
+      await percy.snapshot({
+        name: 'test snapshot',
+        url: 'http://localhost:8000',
+        domSnapshot: testExternalDOM,
+        widths: [1000]
+      });
+
+      await percy.idle();
+
+      expect(captured[0]).toEqual([
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': jasmine.stringMatching(/^\/percy\.\d+\.log$/)
+          })
+        }),
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': 'http://localhost:8000/'
+          })
+        }),
+        jasmine.objectContaining({
+          attributes: jasmine.objectContaining({
+            'resource-url': 'http://localhost:8000/style.css'
+          })
+        })
+      ]);
+    });
+
     it('does not hang waiting for embedded isolated pages', async () => {
       server.reply('/', () => [200, {
         'Content-Type': 'text/html',