diff --git a/navigation_and_routing/pubspec.lock b/navigation_and_routing/pubspec.lock
index 7296d7a5a..e4c6e6c34 100644
--- a/navigation_and_routing/pubspec.lock
+++ b/navigation_and_routing/pubspec.lock
@@ -28,7 +28,7 @@ packages:
       name: analyzer
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.1"
+    version: "1.7.2"
   args:
     dependency: transitive
     description:
@@ -42,7 +42,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.6.1"
+    version: "2.7.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -63,7 +63,7 @@ packages:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   cli_util:
     dependency: transitive
     description:
@@ -149,6 +149,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  frontend_server_client:
+    dependency: transitive
+    description:
+      name: frontend_server_client
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.0"
   glob:
     dependency: transitive
     description:
@@ -211,7 +218,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0"
+    version: "1.7.0"
   mime:
     dependency: transitive
     description:
@@ -370,21 +377,21 @@ packages:
       name: test
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.16.8"
+    version: "1.17.9"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.0"
+    version: "0.4.1"
   test_core:
     dependency: transitive
     description:
       name: test_core
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.19"
+    version: "0.3.29"
   typed_data:
     dependency: transitive
     description:
diff --git a/web/_tool/pubspec.lock b/web/_tool/pubspec.lock
index 1789ea7a9..d11b0dce2 100644
--- a/web/_tool/pubspec.lock
+++ b/web/_tool/pubspec.lock
@@ -7,14 +7,14 @@ packages:
       name: args
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.1"
+    version: "2.2.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   lints:
     dependency: "direct dev"
     description:
@@ -35,7 +35,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.4.0"
+    version: "1.7.0"
   path:
     dependency: "direct main"
     description:
diff --git a/web/samples_index/lib/cookbook.dart b/web/samples_index/lib/cookbook.dart
index c42c1dff1..94a6e12c3 100644
--- a/web/samples_index/lib/cookbook.dart
+++ b/web/samples_index/lib/cookbook.dart
@@ -12,7 +12,7 @@ import 'package:html/parser.dart' show parse;
 import 'package:path/path.dart' as path;
 
 class CookbookScraper {
-  WebDriver _driver;
+  late WebDriver _driver;
 
   Future init() async {
     _driver = await createDriver(desired: <String, dynamic>{});
@@ -36,7 +36,12 @@ class CookbookScraper {
     await _driver.get(Uri.parse(url));
     var pageContent = await _driver.pageSource;
     var page = parse(pageContent);
-    var name = page.querySelector('main>.container>header>h1').text;
+    var search = 'main>.container>header>h1';
+    var h1 = page.querySelector(search);
+    if (h1 == null) {
+      throw ('Could not find match for $search on page $url');
+    }
+    var name = h1.text;
     var description = page.querySelectorAll('main>.container>p').first.text;
 
     var urlSegments = Uri.parse(url).pathSegments;
@@ -50,6 +55,7 @@ class CookbookScraper {
       screenshots: [Screenshot(screenshotPath(url), 'Cookbook article')],
       tags: ['cookbook', category],
       source: url,
+      difficulty: 'advanced',
     );
   }
 
diff --git a/web/samples_index/lib/samples_index.dart b/web/samples_index/lib/samples_index.dart
index 6fd6be892..765006e68 100644
--- a/web/samples_index/lib/samples_index.dart
+++ b/web/samples_index/lib/samples_index.dart
@@ -15,8 +15,10 @@ Future<List<Sample>> getSamples() async {
   var cookbookFile = File('lib/src/cookbook.json');
   var contents = await yamlFile.readAsString();
   var cookbookContents = await cookbookFile.readAsString();
-  var index = checkedYamlDecode(contents, (m) => Index.fromJson(m),
+  var index = checkedYamlDecode(
+      contents, (m) => m != null ? Index.fromJson(m) : null,
       sourceUrl: yamlFile.uri);
+  if (index == null) throw('unable to get load from ${yamlFile.uri}');
   var cookbookIndex =
       Index.fromJson(json.decode(cookbookContents) as Map<dynamic, dynamic>);
   return index.samples..addAll(cookbookIndex.samples);
diff --git a/web/samples_index/lib/src/carousel.dart b/web/samples_index/lib/src/carousel.dart
index cb94a4729..b617e983f 100644
--- a/web/samples_index/lib/src/carousel.dart
+++ b/web/samples_index/lib/src/carousel.dart
@@ -7,14 +7,15 @@ import 'dart:html';
 class Carousel {
   final bool withArrowKeyControl;
 
-  final Element container = querySelector('.slider-container');
+  final Element container = querySelector('.slider-container')!;
   final List<Element> slides = querySelectorAll('.slider-single');
 
-  int currentSlideIndex, lastSlideIndex;
+  late int currentSlideIndex;
+  late int lastSlideIndex;
 
-  Element prevSlide, currentSlide, nextSlide;
+  late Element prevSlide, currentSlide, nextSlide;
 
-  num x0;
+  late num x0;
   bool touched = false;
 
   Carousel.init({this.withArrowKeyControl = false}) {
@@ -90,13 +91,13 @@ class Carousel {
   }
 
   void _touchStartListener(TouchEvent e) {
-    x0 = e.changedTouches.first.client.x;
+    x0 = e.changedTouches!.first.client.x;
     touched = true;
   }
 
   void _touchEndListener(TouchEvent e) {
     if (touched) {
-      int dx = (e.changedTouches.first.client.x - x0) as int;
+      int dx = (e.changedTouches!.first.client.x - x0) as int;
 
       // dx==0 case is ignored
       if (dx > 0 && currentSlideIndex > 0) {
@@ -115,7 +116,7 @@ class Carousel {
 
   void _updateBullets() {
     final bullets =
-        querySelector('.bullet-container').querySelectorAll('.bullet');
+        querySelector('.bullet-container')!.querySelectorAll('.bullet');
     for (var i = 0; i < bullets.length; i++) {
       bullets[i].classes.remove('active');
       if (i == currentSlideIndex) {
@@ -132,18 +133,18 @@ class Carousel {
     if (currentSlideIndex == slides.length - 1) {
       slides[0].classes.add('hidden');
       slides[slides.length - 1].classes.remove('hidden');
-      prevArrow.classes.remove('hidden');
-      nextArrow.classes.add('hidden');
+      prevArrow!.classes.remove('hidden');
+      nextArrow!.classes.add('hidden');
     } else if (currentSlideIndex == 0) {
       slides[slides.length - 1].classes.add('hidden');
       slides[0].classes.remove('hidden');
-      prevArrow.classes.add('hidden');
-      nextArrow.classes.remove('hidden');
+      prevArrow!.classes.add('hidden');
+      nextArrow!.classes.remove('hidden');
     } else {
       slides[slides.length - 1].classes.remove('hidden');
       slides[0].classes.remove('hidden');
-      prevArrow.classes.remove('hidden');
-      nextArrow.classes.remove('hidden');
+      prevArrow!.classes.remove('hidden');
+      nextArrow!.classes.remove('hidden');
     }
   }
 
diff --git a/web/samples_index/lib/src/data.dart b/web/samples_index/lib/src/data.dart
index ed843c590..b5e9008ff 100644
--- a/web/samples_index/lib/src/data.dart
+++ b/web/samples_index/lib/src/data.dart
@@ -34,7 +34,7 @@ class Sample {
   final String name;
 
   /// The author of the sample. Typically "Flutter"
-  final String author;
+  final String? author;
 
   /// Screenshots of the sample or cookbook article. At least 1 screenshot is
   /// required.
@@ -44,14 +44,14 @@ class Sample {
   final String source;
 
   /// A link to this sample running in the browser.
-  final String web;
+  final String? web;
 
   /// 3-5 sentences describing the sample.
   final String description;
 
   /// The difficulty level. Values are either 'beginner', 'intermediate', or
   /// 'advanced'.
-  final String difficulty;
+  final String? difficulty;
 
   /// List of widgets or Flutter APIs used by the sample. e.g. "AnimatedBuilder"
   /// or "ChangeNotifier".
@@ -76,26 +76,26 @@ class Sample {
   final String type;
 
   /// The date this sample was created.
-  final DateTime date;
+  final DateTime? date;
 
   /// The Flutter channel this sample runs on. Either 'stable', 'dev' or
   /// 'master'.
-  final String channel;
+  final String? channel;
 
   Sample({
-    this.name,
-    this.author,
-    this.screenshots,
-    this.source,
+    required this.name,
+    this.author = 'Flutter',
+    required this.screenshots,
+    required this.source,
     this.web,
-    this.description,
-    this.difficulty,
+    required this.description,
+    this.difficulty = 'beginner',
     this.widgets = const [],
     this.packages = const [],
     this.tags = const [],
     this.platforms = const [],
     this.links = const [],
-    this.type,
+    required this.type,
     this.date,
     this.channel,
   });
diff --git a/web/samples_index/lib/src/data.g.dart b/web/samples_index/lib/src/data.g.dart
index 465cbce68..96508749c 100644
--- a/web/samples_index/lib/src/data.g.dart
+++ b/web/samples_index/lib/src/data.g.dart
@@ -12,9 +12,9 @@ Index _$IndexFromJson(Map json) {
       $checkedConvert(
           json,
           'samples',
-          (v) => (v as List)
-              ?.map((e) => e == null ? null : Sample.fromJson(e as Map))
-              ?.toList()),
+          (v) => (v as List<dynamic>)
+              .map((e) => Sample.fromJson(e as Map))
+              .toList()),
     );
     return val;
   });
@@ -28,35 +28,35 @@ Sample _$SampleFromJson(Map json) {
   return $checkedNew('Sample', json, () {
     final val = Sample(
       name: $checkedConvert(json, 'name', (v) => v as String),
-      author: $checkedConvert(json, 'author', (v) => v as String),
+      author: $checkedConvert(json, 'author', (v) => v as String?),
       screenshots: $checkedConvert(
           json,
           'screenshots',
-          (v) => (v as List)
-              ?.map((e) => e == null ? null : Screenshot.fromJson(e as Map))
-              ?.toList()),
+          (v) => (v as List<dynamic>)
+              .map((e) => Screenshot.fromJson(e as Map))
+              .toList()),
       source: $checkedConvert(json, 'source', (v) => v as String),
-      web: $checkedConvert(json, 'web', (v) => v as String),
+      web: $checkedConvert(json, 'web', (v) => v as String?),
       description: $checkedConvert(json, 'description', (v) => v as String),
-      difficulty: $checkedConvert(json, 'difficulty', (v) => v as String),
+      difficulty: $checkedConvert(json, 'difficulty', (v) => v as String?),
       widgets: $checkedConvert(json, 'widgets',
-          (v) => (v as List)?.map((e) => e as String)?.toList()),
+          (v) => (v as List<dynamic>).map((e) => e as String).toList()),
       packages: $checkedConvert(json, 'packages',
-          (v) => (v as List)?.map((e) => e as String)?.toList()),
-      tags: $checkedConvert(
-          json, 'tags', (v) => (v as List)?.map((e) => e as String)?.toList()),
+          (v) => (v as List<dynamic>).map((e) => e as String).toList()),
+      tags: $checkedConvert(json, 'tags',
+          (v) => (v as List<dynamic>).map((e) => e as String).toList()),
       platforms: $checkedConvert(json, 'platforms',
-          (v) => (v as List)?.map((e) => e as String)?.toList()),
+          (v) => (v as List<dynamic>).map((e) => e as String).toList()),
       links: $checkedConvert(
           json,
           'links',
-          (v) => (v as List)
-              ?.map((e) => e == null ? null : Link.fromJson(e as Map))
-              ?.toList()),
+          (v) => (v as List<dynamic>)
+              .map((e) => Link.fromJson(e as Map))
+              .toList()),
       type: $checkedConvert(json, 'type', (v) => v as String),
       date: $checkedConvert(
           json, 'date', (v) => v == null ? null : DateTime.parse(v as String)),
-      channel: $checkedConvert(json, 'channel', (v) => v as String),
+      channel: $checkedConvert(json, 'channel', (v) => v as String?),
     );
     return val;
   });
diff --git a/web/samples_index/lib/src/samples.yaml b/web/samples_index/lib/src/samples.yaml
index 481077dcf..fc20e56b0 100644
--- a/web/samples_index/lib/src/samples.yaml
+++ b/web/samples_index/lib/src/samples.yaml
@@ -83,6 +83,7 @@ samples:
       - scoped_model
     tags: ['intermediate', 'sample', 'gallery', 'material', 'design', 'vignettes']
     platforms: ['web', 'ios', 'android']
+    links: []
     type: demo
 
   - name: Add to App
@@ -105,6 +106,7 @@ samples:
       - provider
     tags: ['advanced', 'sample', 'add-to-app', 'android', 'ios', 'native', 'embedding']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: Animations
@@ -133,6 +135,7 @@ samples:
       - flutter/material
     tags: ['intermediate', 'sample', 'animation']
     platforms: ['ios', 'android', 'web']
+    links: []
     type: sample
     web: web/animations
 
@@ -157,6 +160,7 @@ samples:
       - google_maps_webservice
     tags: ['intermediate', 'sample', 'firebase', 'maps']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: Isolate Example
@@ -181,6 +185,7 @@ samples:
       - dart:math
     tags: ['intermediate', 'sample', 'isolates', 'concurrency']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: jsonexample
@@ -209,6 +214,7 @@ samples:
       - built_value_generator
     tags: ['beginner', 'sample']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: Place Tracker
@@ -235,6 +241,7 @@ samples:
       - google_maps_flutter
     tags: ['intermediate', 'sample', 'json', 'serialization']
     platforms: ['android']
+    links: []
     type: sample
 
   - name: Platform Design
@@ -266,6 +273,7 @@ samples:
       - flutter/cupertino
     tags: ['advanced', 'sample', 'ios']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: Platform View Swift
@@ -287,6 +295,7 @@ samples:
       - flutter/services
     tags: ['advanced', 'sample', 'ios']
     platforms: ['ios']
+    links: []
     type: sample
 
   - name: Infinite List
@@ -311,6 +320,7 @@ samples:
       - meta
     tags: ['sample', 'material', 'design', 'android', 'ios']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: IOS App Clip
@@ -331,6 +341,7 @@ samples:
       - device_info
     tags: ['sample', 'Device Info', 'ios']
     platforms: ['ios']
+    links: []
     type: sample
 
   - name: Testing App
@@ -353,6 +364,7 @@ samples:
       - provider
     tags: ['sample', 'material', 'android', 'ios']
     platforms: ['ios', 'android']
+    links: []
     type: sample
 
   - name: Provider Shopper
@@ -376,6 +388,7 @@ samples:
       - provider
     tags: ['intermediate', 'sample', 'provider']
     platforms: ['ios', 'android', 'web']
+    links: []
     type: sample
     web: web/provider_shopper
 
@@ -402,6 +415,7 @@ samples:
       - firebase
     tags: ['intermediate', 'sample', 'firebase']
     platforms: ['ios', 'android', 'web']
+    links: []
     type: sample
     web: web/web_dashboard
 
@@ -423,6 +437,7 @@ samples:
     packages: []
     tags: ['intermediate', 'sample', 'forms']
     platforms: ['ios', 'android', 'web']
+    links: []
     type: sample
     web: web/form_app
 ###################
@@ -433,6 +448,7 @@ samples:
     author: Flutter
     screenshots:
       - url: images/charts1.png
+        alt: Charts screenshot
     source: https://github.com/google/charts
     description: >
       A general-purpose charting library.
@@ -440,6 +456,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['ios', 'android', 'web']
+    links: []
     tags: ['demo', 'charts']
     web: web/charts
     type: demo
@@ -456,6 +473,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['web']
+    links: []
     tags: ['demo', 'flutter create']
     web: web/filipino_cuisine
     type: demo
@@ -472,6 +490,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['web']
+    links: []
     tags: ['demo', 'data', 'visualization']
     web: web/github_dataviz
     type: demo
@@ -488,6 +507,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['web']
+    links: []
     tags: ['demo', 'animation']
     web: web/particle_background
     type: demo
@@ -504,6 +524,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['web']
+    links: []
     tags: ['demo', 'game']
     web: web/slide_puzzle
     type: demo
@@ -520,6 +541,7 @@ samples:
     widgets: []
     packages: []
     platforms: ['web']
+    links: []
     tags: ['demo', 'animation']
     web: https://z.flutter.gallery/#/dice
     type: demo
diff --git a/web/samples_index/lib/src/search.dart b/web/samples_index/lib/src/search.dart
index 3d2ad4fd7..24ebb55ac 100644
--- a/web/samples_index/lib/src/search.dart
+++ b/web/samples_index/lib/src/search.dart
@@ -3,7 +3,7 @@
 // found in the LICENSE file
 
 bool matchesQuery(String query, String sampleAttributes) {
-  if (query == null || query.isEmpty) {
+  if (query.isEmpty) {
     return true;
   }
   var queryWords = query.split(' ')..removeWhere((s) => s.isEmpty);
@@ -68,11 +68,13 @@ String searchQueryFromParams(Map<String, String> params) {
   }
   if (params.containsKey('type')) {
     if (buf.isNotEmpty) buf.write(' ');
-    buf.write('type:' + params['type']);
+    var value = params['type'];
+    if (value != null) buf.write('type:' + value);
   }
   if (params.containsKey('platform')) {
     if (buf.isNotEmpty) buf.write(' ');
-    buf.write('platform:' + params['platform']);
+    var value = params['platform'];
+    if (value != null) buf.write('platform:' + value);
   }
 
   return buf.toString();
diff --git a/web/samples_index/lib/src/templates.dart b/web/samples_index/lib/src/templates.dart
index b9ef3d257..15b139664 100644
--- a/web/samples_index/lib/src/templates.dart
+++ b/web/samples_index/lib/src/templates.dart
@@ -187,7 +187,7 @@ String _descriptionPage(Sample sample) => '''
 
 String _descriptionButtons(Sample sample) {
   var buf = StringBuffer();
-  if (sample?.web?.isNotEmpty == true) {
+  if (sample.web?.isNotEmpty == true) {
     buf.write(
         '''<button class="mdc-button mdc-button--outlined" onclick="window.location.href = '${sample.web}';"><span class="mdc-button__ripple"></span> Launch App</button>''');
   }
diff --git a/web/samples_index/lib/src/util.dart b/web/samples_index/lib/src/util.dart
index a20d1e668..aaf0bfc20 100644
--- a/web/samples_index/lib/src/util.dart
+++ b/web/samples_index/lib/src/util.dart
@@ -23,7 +23,9 @@ String pascalCase(String input) {
 
 String _fixCase(String input, String separator) =>
     input.replaceAllMapped(_upperCase, (match) {
-      var lower = match.group(0).toLowerCase();
+      var group = match.group(0);
+      if (group == null) return input;
+      var lower = group.toLowerCase();
 
       if (match.start > 0) {
         lower = '$separator$lower';
diff --git a/web/samples_index/pubspec.yaml b/web/samples_index/pubspec.yaml
index 2185f65a2..fcb3e970e 100644
--- a/web/samples_index/pubspec.yaml
+++ b/web/samples_index/pubspec.yaml
@@ -4,23 +4,29 @@ homepage: https://github.com/flutter/samples_index
 author: Flutter Team <flutter-dev@googlegroups.com>
 version: 0.0.1
 environment:
-  sdk: ">=2.5.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 dependencies:
-  json_annotation: ^3.0.0
+  json_annotation: ^4.0.1
   path: ^1.6.0
-  yaml: ^2.2.0
-  mdc_web: ^0.5.0-pre
+  yaml: ^3.0.0
+  mdc_web: ^0.6.0
   sass_builder: ^2.1.0
-  checked_yaml: ^1.0.0
-  webdriver: ^2.1.0
-  html: ^0.14.0
+  checked_yaml: ^2.0.1
+  webdriver: ^3.0.0
+  html: ^0.15.0
 dev_dependencies:
-  grinder: ^0.8.3
+  grinder: ^0.9.0
   flutter_lints: ^1.0.0
-  test: ^1.6.0
-  json_serializable: ^3.2.0
-  build: ^1.2.0
-  build_runner: ^1.7.0
-  build_web_compilers: ^2.7.0
-  tuneup: ^0.3.6
-  image: ^2.1.0
+  test: ^1.17.10
+  json_serializable: ^4.0.2
+  build: ^2.0.3
+  build_runner: ^2.0.6
+  build_web_compilers: ^3.0.0
+  tuneup: ^0.3.8
+  image: ^3.0.2
+# waiting for the next material-components-web release.
+# Once released, it will need to be rolled into package:mdc_web.
+#
+# https://github.com/material-components/material-components-web/pull/7158
+dependency_overrides:
+  sass: 1.32.10
\ No newline at end of file
diff --git a/web/samples_index/test/samples_index_test.dart b/web/samples_index/test/samples_index_test.dart
index 2df5f26c2..55d2d5af2 100644
--- a/web/samples_index/test/samples_index_test.dart
+++ b/web/samples_index/test/samples_index_test.dart
@@ -16,15 +16,18 @@ void main() {
       var contents = await file.readAsString();
       expect(contents, isNotEmpty);
 
-      var index = checkedYamlDecode(contents, (m) => Index.fromJson(m),
+      var index = checkedYamlDecode(contents, (m) => m != null ? Index.fromJson(m) : null,
           sourceUrl: file.uri);
+      if (index == null) {
+        throw('unable to load YAML from $file');
+      }
       expect(index.samples, isNotEmpty);
 
       var sample = index.samples.first;
       expect(sample, isNotNull);
       expect(sample.name, 'Kittens');
       expect(sample.screenshots, hasLength(2));
-      expect(sample.source, 'http://github.com/johnpryan/kittens');
+      expect(sample.source, 'https://github.com/johnpryan/kittens');
       expect(sample.description, 'A sample kitten app');
       expect(sample.difficulty, 'beginner');
       expect(sample.widgets, hasLength(2));
@@ -36,7 +39,7 @@ void main() {
       expect(sample.platforms, hasLength(3));
       expect(sample.links, hasLength(2));
       expect(sample.links[1].text, 'author');
-      expect(sample.links[1].href, 'http://jpryan.me');
+      expect(sample.links[1].href, 'https://jpryan.me');
       expect(sample.type, 'sample');
       expect(sample.date, DateTime.parse('2019-12-15T02:59:43.1Z'));
       expect(sample.channel, 'stable');
@@ -49,8 +52,11 @@ void main() {
       var contents = await file.readAsString();
       expect(contents, isNotEmpty);
 
-      var index = checkedYamlDecode(contents, (m) => Index.fromJson(m),
+      var index = checkedYamlDecode(contents, (m) => m != null ? Index.fromJson(m) : null,
           sourceUrl: file.uri);
+      if (index == null) {
+        throw('unable to load YAML from $file');
+      }
       var sample = index.samples.first;
       expect(
           sample.searchAttributes.split(' '),
diff --git a/web/samples_index/test/yaml/single.yaml b/web/samples_index/test/yaml/single.yaml
index 3affccb27..f981a8ece 100644
--- a/web/samples_index/test/yaml/single.yaml
+++ b/web/samples_index/test/yaml/single.yaml
@@ -5,7 +5,7 @@ samples:
         alt: a kitten
       - url: https://placekitten.com/400/400
         alt: another kitten
-    source: http://github.com/johnpryan/kittens
+    source: https://github.com/johnpryan/kittens
     description: A sample kitten app
     difficulty: beginner
     widgets:
@@ -20,7 +20,7 @@ samples:
       - text: inspiration
         href: https://apps.apple.com/us/app/neko-atsume-kitty-collector/id923917775
       - text: author
-        href: http://jpryan.me
+        href: https://jpryan.me
     type: sample # sample, app, or cookbook
     date: 2019-12-15T02:59:43.1Z
     channel: stable
diff --git a/web/samples_index/tool/grind.dart b/web/samples_index/tool/grind.dart
index 4456d0c5d..aa4e02cf5 100644
--- a/web/samples_index/tool/grind.dart
+++ b/web/samples_index/tool/grind.dart
@@ -104,12 +104,11 @@ Future<void> _createThumbnails(Directory directory) async {
       continue;
     }
 
-    var file = entity as File;
-    var pathPrefix = path.dirname(file.path);
+    var pathPrefix = path.dirname(entity.path);
     var thumbnailFile = File(path.join(pathPrefix, filename + '_thumb.png'));
 
-    var img = image.decodeImage(await file.readAsBytes());
-    var resized = image.copyResize(img, width: 640);
+    var img = image.decodeImage(await entity.readAsBytes());
+    var resized = image.copyResize(img!, width: 640);
     filesToWrite.add(thumbnailFile.writeAsBytes(image.encodePng(resized)));
   }
 
diff --git a/web/samples_index/web/description.dart b/web/samples_index/web/description.dart
index cc623d816..f75861e8a 100644
--- a/web/samples_index/web/description.dart
+++ b/web/samples_index/web/description.dart
@@ -3,8 +3,6 @@ import 'dart:html';
 import 'package:mdc_web/mdc_web.dart';
 import 'package:samples_index/src/carousel.dart';
 
-InputElement searchInput;
-
 void main() {
   querySelectorAll('.mdc-card__primary-action').forEach((el) => MDCRipple(el));
 
diff --git a/web/samples_index/web/main.dart b/web/samples_index/web/main.dart
index 90ef493e1..05d4f7f45 100644
--- a/web/samples_index/web/main.dart
+++ b/web/samples_index/web/main.dart
@@ -4,8 +4,8 @@ import 'package:mdc_web/mdc_web.dart';
 import 'package:samples_index/browser.dart';
 
 /// The Material text input for searching
-MDCTextField searchBar;
-MDCChipSet chipSet;
+late final MDCTextField searchBar;
+late final MDCChipSet chipSet;
 
 /// The current set of query parameters that determine how the cards are
 /// filtered. e.g. {'search': 'kittens', 'platform': 'ios'}
@@ -16,9 +16,9 @@ const platformKey = 'platform';
 
 void main() {
   // Initialize Material components
-  MDCFloatingLabel(querySelector('.mdc-floating-label'));
-  searchBar = MDCTextField(querySelector('#search-bar'));
-  MDCRipple(querySelector('#clear-button'));
+  MDCFloatingLabel(querySelector('.mdc-floating-label')!);
+  searchBar = MDCTextField(querySelector('#search-bar')!);
+  MDCRipple(querySelector('#clear-button')!);
 
   // Listen for hash changes
   window.onHashChange.listen((_) {
@@ -33,7 +33,7 @@ void main() {
   querySelectorAll('.mdc-card__primary-action').forEach((el) => MDCRipple(el)
     // Navigate to the description page when tapped
     ..listen('click', (e) {
-      window.location.href = el.attributes['href'];
+      window.location.href = el.attributes['href']!;
     }));
 
   // Filter cards on each keypress
@@ -44,12 +44,12 @@ void main() {
 
   // Update the URL only when the user is done typing in the search bar
   searchBar.listen('change', (e) {
-    queryParams[searchKey] = searchBar.value;
+    queryParams[searchKey] = searchBar.value!;
     updateHash();
   });
 
   // Update the hash, cards, and text input when the clear button is pressed
-  querySelector('#clear-button').onClick.listen((e) {
+  querySelector('#clear-button')!.onClick.listen((e) {
     queryParams.remove('search');
     updateHash();
     setSearchBarText();
@@ -57,10 +57,10 @@ void main() {
   });
 
   // Initialize chips
-  chipSet = MDCChipSet(querySelector('.mdc-chip-set'));
+  chipSet = MDCChipSet(querySelector('.mdc-chip-set')!);
   chipSet.listen('MDCChip:selection', (e) {
     // Get the query parameters for this chip
-    var selectedChipIndex = chipSet.chips.indexWhere((chip) => chip.selected);
+    var selectedChipIndex = chipSet.chips.indexWhere((chip) => chip.selected!);
     var chipParams = paramsForChip(selectedChipIndex);
 
     // Overwrite query parameters with new ones
@@ -89,7 +89,7 @@ void setSearchBarText() {
 
 void setSelectedChips() {
   var type = queryParams.containsKey(typeKey) ? queryParams[typeKey] : '';
-  if (type.isNotEmpty) {
+  if (type!.isNotEmpty) {
     if (type == 'sample') {
       chipSet.chips[1].selected = true;
     }
@@ -101,7 +101,7 @@ void setSelectedChips() {
   // Apply the platform from the hash in the URL
   var platform =
       queryParams.containsKey(platformKey) ? queryParams[platformKey] : '';
-  if (platform.isNotEmpty) {
+  if (platform!.isNotEmpty) {
     if (platform == 'web') {
       chipSet.chips[3].selected = true;
     }
@@ -113,7 +113,7 @@ void setSelectedChips() {
 
 void handleSearch() {
   var search = searchBar.value;
-  queryParams[searchKey] = search;
+  queryParams[searchKey] = search!;
   filterCards();
 }
 
@@ -139,7 +139,7 @@ void filterCards() {
   var elements = querySelectorAll('[search-attrs]');
   for (var element in elements) {
     var searchAttributes = element.attributes['search-attrs'];
-    if (matchesQuery(searchQuery, searchAttributes)) {
+    if (matchesQuery(searchQuery, searchAttributes!)) {
       element.hidden = false;
     } else {
       element.hidden = true;