diff --git a/web/github_dataviz/analysis_options.yaml b/web/github_dataviz/analysis_options.yaml
new file mode 100644
index 000000000..3f238dcdc
--- /dev/null
+++ b/web/github_dataviz/analysis_options.yaml
@@ -0,0 +1,6 @@
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  rules:
+    avoid_print: false
+    prefer_single_quotes: true
diff --git a/web/github_dataviz/lib/catmull.dart b/web/github_dataviz/lib/catmull.dart
index a1b735763..bfbefd68f 100644
--- a/web/github_dataviz/lib/catmull.dart
+++ b/web/github_dataviz/lib/catmull.dart
@@ -1,8 +1,8 @@
 import 'package:github_dataviz/mathutils.dart';
 
 class ControlPointAndValue {
-  int point;
-  double value;
+  late int point;
+  double? value;
 
   ControlPointAndValue() {
     value = 0;
@@ -37,9 +37,9 @@ class CatmullInterpolator implements Interpolator {
   }
 
   ControlPointAndValue progressiveGet(ControlPointAndValue cpv) {
-    double v = cpv.value;
+    double? v = cpv.value;
     for (int i = cpv.point; i < controlPoints.length - 1; i++) {
-      if (controlPoints[i].x >= v) {
+      if (controlPoints[i].x >= v!) {
         double t = (v - controlPoints[i - 1].x) /
             (controlPoints[i].x - controlPoints[i - 1].x);
         double p0 = controlPoints[i - 2].y;
diff --git a/web/github_dataviz/lib/constants.dart b/web/github_dataviz/lib/constants.dart
index d7e2d3c3e..f5aa3a800 100644
--- a/web/github_dataviz/lib/constants.dart
+++ b/web/github_dataviz/lib/constants.dart
@@ -2,8 +2,8 @@ import 'package:flutter/material.dart';
 import 'dart:ui';
 
 class Constants {
-  static final Color backgroundColor = const Color(0xFF000020);
-  static final Color timelineLineColor = Color(0x60FFFFFF);
-  static final Color milestoneColor = Color(0x40FFFFFF);
-  static final Color milestoneTimelineColor = Colors.white;
+  static const Color backgroundColor = Color(0xFF000020);
+  static const Color timelineLineColor = Color(0x60FFFFFF);
+  static const Color milestoneColor = Color(0x40FFFFFF);
+  static const Color milestoneTimelineColor = Colors.white;
 }
diff --git a/web/github_dataviz/lib/data/contribution_data.dart b/web/github_dataviz/lib/data/contribution_data.dart
index 3c47afced..9ef6abf5e 100644
--- a/web/github_dataviz/lib/data/contribution_data.dart
+++ b/web/github_dataviz/lib/data/contribution_data.dart
@@ -8,7 +8,7 @@ class ContributionData {
 
   static ContributionData fromJson(Map<String, dynamic> jsonMap) {
     ContributionData data = ContributionData(
-        jsonMap["w"], jsonMap["a"], jsonMap["d"], jsonMap["c"]);
+        jsonMap['w'], jsonMap['a'], jsonMap['d'], jsonMap['c']);
     return data;
   }
 }
diff --git a/web/github_dataviz/lib/data/user.dart b/web/github_dataviz/lib/data/user.dart
index 0716e6cbf..7533e51e1 100644
--- a/web/github_dataviz/lib/data/user.dart
+++ b/web/github_dataviz/lib/data/user.dart
@@ -6,7 +6,7 @@ class User {
   User(this.id, this.username, this.avatarUrl);
 
   static User fromJson(Map<String, dynamic> jsonMap) {
-    User user = User(jsonMap["id"], jsonMap["login"], jsonMap["avatar_url"]);
+    User user = User(jsonMap['id'], jsonMap['login'], jsonMap['avatar_url']);
     return user;
   }
 }
diff --git a/web/github_dataviz/lib/data/user_contribution.dart b/web/github_dataviz/lib/data/user_contribution.dart
index cc0be09ce..49611ccce 100644
--- a/web/github_dataviz/lib/data/user_contribution.dart
+++ b/web/github_dataviz/lib/data/user_contribution.dart
@@ -8,11 +8,11 @@ class UserContribution {
   UserContribution(this.user, this.contributions);
 
   static UserContribution fromJson(Map<String, dynamic> jsonMap) {
-    List<ContributionData> contributionList = (jsonMap["weeks"] as List)
+    List<ContributionData> contributionList = (jsonMap['weeks'] as List)
         .map((e) => ContributionData.fromJson(e))
         .toList();
     var userContribution =
-        UserContribution(User.fromJson(jsonMap["author"]), contributionList);
+        UserContribution(User.fromJson(jsonMap['author']), contributionList);
     return userContribution;
   }
 }
diff --git a/web/github_dataviz/lib/data/week_label.dart b/web/github_dataviz/lib/data/week_label.dart
index b4bf6928e..37d1baced 100644
--- a/web/github_dataviz/lib/data/week_label.dart
+++ b/web/github_dataviz/lib/data/week_label.dart
@@ -1,24 +1,23 @@
 import 'package:intl/intl.dart';
 
 class WeekLabel {
-  int weekNum;
+  int? weekNum;
   String label;
 
   WeekLabel(this.weekNum, this.label);
 
-  WeekLabel.forDate(DateTime date, String label) {
-    this.label = label;
+  WeekLabel.forDate(DateTime date, this.label) {
     int year = getYear(date);
     int weekOfYearNum = getWeekNumber(date);
-    this.weekNum = 9 + ((year - 2015) * 52) + weekOfYearNum;
+    weekNum = 9 + ((year - 2015) * 52) + weekOfYearNum;
   }
 
   int getYear(DateTime date) {
-    return int.parse(DateFormat("y").format(date));
+    return int.parse(DateFormat('y').format(date));
   }
 
   int getWeekNumber(DateTime date) {
-    int dayOfYear = int.parse(DateFormat("D").format(date));
+    int dayOfYear = int.parse(DateFormat('D').format(date));
     return ((dayOfYear - date.weekday + 10) / 7).floor();
   }
 }
diff --git a/web/github_dataviz/lib/layered_chart.dart b/web/github_dataviz/lib/layered_chart.dart
index 41ecebde4..ab71d093e 100644
--- a/web/github_dataviz/lib/layered_chart.dart
+++ b/web/github_dataviz/lib/layered_chart.dart
@@ -14,7 +14,9 @@ class LayeredChart extends StatefulWidget {
   final List<WeekLabel> milestones;
   final double animationValue;
 
-  LayeredChart(this.dataToPlot, this.milestones, this.animationValue);
+  const LayeredChart(this.dataToPlot, this.milestones, this.animationValue,
+      {Key? key})
+      : super(key: key);
 
   @override
   State<StatefulWidget> createState() {
@@ -23,14 +25,14 @@ class LayeredChart extends StatefulWidget {
 }
 
 class LayeredChartState extends State<LayeredChart> {
-  List<Path> paths;
-  List<Path> capPaths;
-  List<double> maxValues;
-  double theta;
-  double graphHeight;
-  List<TextPainter> labelPainter;
-  List<TextPainter> milestonePainter;
-  Size lastSize;
+  late List<Path> paths;
+  late List<Path> capPaths;
+  late List<double> maxValues;
+  late double theta;
+  late double graphHeight;
+  late List<TextPainter> labelPainter;
+  late List<TextPainter> milestonePainter;
+  Size? lastSize;
 
   void buildPaths(
       Size size,
@@ -89,7 +91,7 @@ class LayeredChartState extends State<LayeredChart> {
             j.toDouble(), 0, (numPoints - 1).toDouble(), 0, (n - 1).toDouble());
         curve.progressiveGet(cpv);
         curvePoints.add(MathUtils.map(
-            max(0, cpv.value), 0, maxValues[i].toDouble(), 0, graphHeight));
+            max(0, cpv.value!), 0, maxValues[i].toDouble(), 0, graphHeight));
       }
       paths.add(Path());
       capPaths.add(Path());
@@ -136,7 +138,7 @@ class LayeredChartState extends State<LayeredChart> {
     labelPainter = <TextPainter>[];
     for (int i = 0; i < dataToPlot.length; i++) {
       TextSpan span = TextSpan(
-          style: TextStyle(
+          style: const TextStyle(
               color: Color.fromARGB(255, 255, 255, 255), fontSize: 12),
           text: dataToPlot[i].label.toUpperCase());
       TextPainter tp = TextPainter(
@@ -149,7 +151,7 @@ class LayeredChartState extends State<LayeredChart> {
     milestonePainter = <TextPainter>[];
     for (int i = 0; i < milestones.length; i++) {
       TextSpan span = TextSpan(
-          style: TextStyle(
+          style: const TextStyle(
               color: Color.fromARGB(255, 255, 255, 255), fontSize: 10),
           text: milestones[i].label.toUpperCase());
       TextPainter tp = TextPainter(
@@ -174,15 +176,15 @@ class LayeredChartState extends State<LayeredChart> {
 }
 
 class ChartPainter extends CustomPainter {
-  static List<Color> colors = [
+  static List<Color?> colors = [
     Colors.red[900],
-    Color(0xffc4721a),
+    const Color(0xffc4721a),
     Colors.lime[900],
     Colors.green[900],
     Colors.blue[900],
     Colors.purple[900],
   ];
-  static List<Color> capColors = [
+  static List<Color?> capColors = [
     Colors.red[500],
     Colors.amber[500],
     Colors.lime[500],
@@ -196,17 +198,17 @@ class ChartPainter extends CustomPainter {
 
   double margin;
   double graphGap;
-  double capTheta;
+  late double capTheta;
   double capSize;
   int numPoints;
   double amount = 1.0;
 
-  Paint pathPaint;
-  Paint capPaint;
-  Paint textPaint;
-  Paint milestonePaint;
-  Paint linePaint;
-  Paint fillPaint;
+  late Paint pathPaint;
+  late Paint capPaint;
+  late Paint textPaint;
+  late Paint milestonePaint;
+  late Paint linePaint;
+  late Paint fillPaint;
 
   LayeredChartState state;
 
@@ -220,13 +222,13 @@ class ChartPainter extends CustomPainter {
       this.capSize,
       this.numPoints,
       this.amount) {
-    this.capTheta = pi * capDegrees / 180;
+    capTheta = pi * capDegrees / 180;
     pathPaint = Paint();
     pathPaint.style = PaintingStyle.fill;
     capPaint = Paint();
     capPaint.style = PaintingStyle.fill;
     textPaint = Paint();
-    textPaint.color = Color(0xFFFFFFFF);
+    textPaint.color = const Color(0xFFFFFFFF);
     milestonePaint = Paint();
     milestonePaint.color = Constants.milestoneColor;
     milestonePaint.style = PaintingStyle.stroke;
@@ -236,19 +238,19 @@ class ChartPainter extends CustomPainter {
     linePaint.strokeWidth = 0.5;
     fillPaint = Paint();
     fillPaint.style = PaintingStyle.fill;
-    fillPaint.color = Color(0xFF000000);
+    fillPaint.color = const Color(0xFF000000);
   }
 
   @override
   void paint(Canvas canvas, Size size) {
-    if (dataToPlot.length == 0) {
+    if (dataToPlot.isEmpty) {
       return;
     }
 
     if (state.lastSize == null ||
-        size.width != state.lastSize.width ||
-        size.height != state.lastSize.height) {
-      print("Building paths, lastsize = ${state.lastSize}");
+        size.width != state.lastSize!.width ||
+        size.height != state.lastSize!.height) {
+      print('Building paths, lastsize = ${state.lastSize}');
       state.buildPaths(size, dataToPlot, milestones, numPoints, graphGap,
           margin, capTheta, capSize);
     }
@@ -266,7 +268,7 @@ class ChartPainter extends CustomPainter {
     {
       for (int i = 0; i < milestones.length; i++) {
         WeekLabel milestone = milestones[i];
-        double p = (milestone.weekNum.toDouble() / numWeeks) + (1 - amount);
+        double p = (milestone.weekNum!.toDouble() / numWeeks) + (1 - amount);
         if (p < 1) {
           double x1 = MathUtils.map(p, 0, 1, startX, endX);
           double y1 = MathUtils.map(p, 0, 1, startY, endY);
@@ -282,7 +284,7 @@ class ChartPainter extends CustomPainter {
           canvas.translate(textX, textY);
           canvas.skew(tan(capTheta * 1.0), -tan(state.theta));
           canvas.translate(-tp.width / 2, 0);
-          tp.paint(canvas, Offset(0, 0));
+          tp.paint(canvas, const Offset(0, 0));
           canvas.restore();
         }
       }
@@ -302,11 +304,11 @@ class ChartPainter extends CustomPainter {
         canvas.skew(0, -tan(state.theta));
         canvas.drawRect(
             Rect.fromLTWH(-1, -1, tp.width + 2, tp.height + 2), fillPaint);
-        tp.paint(canvas, Offset(0, 0));
+        tp.paint(canvas, const Offset(0, 0));
         canvas.restore();
       }
 
-      linePaint.color = capColors[i];
+      linePaint.color = capColors[i]!;
       canvas.drawLine(Offset(startX, startY), Offset(endX, endY), linePaint);
 
       Path clipPath = Path();
@@ -317,8 +319,8 @@ class ChartPainter extends CustomPainter {
       clipPath.close();
       canvas.clipPath(clipPath);
 
-      pathPaint.color = colors[i];
-      capPaint.color = capColors[i];
+      pathPaint.color = colors[i]!;
+      capPaint.color = capColors[i]!;
       double offsetX = MathUtils.map(1 - amount, 0, 1, startX, endX);
       double offsetY = MathUtils.map(1 - amount, 0, 1, startY, endY);
       canvas.translate(offsetX - startX, offsetY - startY);
diff --git a/web/github_dataviz/lib/main.dart b/web/github_dataviz/lib/main.dart
index 747e23b73..df11cb109 100644
--- a/web/github_dataviz/lib/main.dart
+++ b/web/github_dataviz/lib/main.dart
@@ -19,21 +19,23 @@ import 'package:github_dataviz/mathutils.dart';
 import 'package:github_dataviz/timeline.dart';
 
 class MainLayout extends StatefulWidget {
+  const MainLayout({Key? key}) : super(key: key);
+
   @override
   _MainLayoutState createState() => _MainLayoutState();
 }
 
 class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
-  AnimationController _animation;
-  List<UserContribution> contributions;
-  List<StatForWeek> starsByWeek;
-  List<StatForWeek> forksByWeek;
-  List<StatForWeek> pushesByWeek;
-  List<StatForWeek> issueCommentsByWeek;
-  List<StatForWeek> pullRequestActivityByWeek;
-  List<WeekLabel> weekLabels;
-
-  static final double earlyInterpolatorFraction = 0.8;
+  AnimationController? _animation;
+  List<UserContribution>? contributions;
+  List<StatForWeek>? starsByWeek;
+  List<StatForWeek>? forksByWeek;
+  List<StatForWeek>? pushesByWeek;
+  List<StatForWeek>? issueCommentsByWeek;
+  List<StatForWeek>? pullRequestActivityByWeek;
+  late List<WeekLabel> weekLabels;
+
+  static const double earlyInterpolatorFraction = 0.8;
   static final EarlyInterpolator interpolator =
       EarlyInterpolator(earlyInterpolatorFraction);
   double animationValue = 1.0;
@@ -47,14 +49,14 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
     createAnimation(0);
 
     weekLabels = <WeekLabel>[];
-    weekLabels.add(WeekLabel.forDate(DateTime(2019, 2, 26), "v1.2"));
-    weekLabels.add(WeekLabel.forDate(DateTime(2018, 12, 4), "v1.0"));
+    weekLabels.add(WeekLabel.forDate(DateTime(2019, 2, 26), 'v1.2'));
+    weekLabels.add(WeekLabel.forDate(DateTime(2018, 12, 4), 'v1.0'));
 //    weekLabels.add(WeekLabel.forDate(new DateTime(2018, 9, 19), "Preview 2"));
-    weekLabels.add(WeekLabel.forDate(DateTime(2018, 6, 21), "Preview 1"));
+    weekLabels.add(WeekLabel.forDate(DateTime(2018, 6, 21), 'Preview 1'));
 //    weekLabels.add(WeekLabel.forDate(new DateTime(2018, 5, 7), "Beta 3"));
-    weekLabels.add(WeekLabel.forDate(DateTime(2018, 2, 27), "Beta 1"));
-    weekLabels.add(WeekLabel.forDate(DateTime(2017, 5, 1), "Alpha"));
-    weekLabels.add(WeekLabel(48, "Repo Made Public"));
+    weekLabels.add(WeekLabel.forDate(DateTime(2018, 2, 27), 'Beta 1'));
+    weekLabels.add(WeekLabel.forDate(DateTime(2017, 5, 1), 'Alpha'));
+    weekLabels.add(WeekLabel(48, 'Repo Made Public'));
 
     loadGitHubData();
   }
@@ -66,10 +68,10 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
       duration: const Duration(milliseconds: 14400),
       vsync: this,
     )..repeat();
-    _animation.addListener(() {
+    _animation!.addListener(() {
       setState(() {
         if (!timelineOverride) {
-          animationValue = _animation.value;
+          animationValue = _animation!.value;
           interpolatedAnimationValue = interpolator.get(animationValue);
         }
       });
@@ -82,7 +84,7 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
     List<DataSeries> dataToPlot = [];
     if (contributions != null) {
       List<int> series = [];
-      for (UserContribution userContrib in contributions) {
+      for (UserContribution userContrib in contributions!) {
         for (int i = 0; i < userContrib.contributions.length; i++) {
           ContributionData data = userContrib.contributions[i];
           if (series.length > i) {
@@ -92,32 +94,32 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
           }
         }
       }
-      dataToPlot.add(DataSeries("Added Lines", series));
+      dataToPlot.add(DataSeries('Added Lines', series));
     }
 
     if (starsByWeek != null) {
       dataToPlot
-          .add(DataSeries("Stars", starsByWeek.map((e) => e.stat).toList()));
+          .add(DataSeries('Stars', starsByWeek!.map((e) => e.stat).toList()));
     }
 
     if (forksByWeek != null) {
       dataToPlot
-          .add(DataSeries("Forks", forksByWeek.map((e) => e.stat).toList()));
+          .add(DataSeries('Forks', forksByWeek!.map((e) => e.stat).toList()));
     }
 
     if (pushesByWeek != null) {
       dataToPlot
-          .add(DataSeries("Pushes", pushesByWeek.map((e) => e.stat).toList()));
+          .add(DataSeries('Pushes', pushesByWeek!.map((e) => e.stat).toList()));
     }
 
     if (issueCommentsByWeek != null) {
       dataToPlot.add(DataSeries(
-          "Issue Comments", issueCommentsByWeek.map((e) => e.stat).toList()));
+          'Issue Comments', issueCommentsByWeek!.map((e) => e.stat).toList()));
     }
 
     if (pullRequestActivityByWeek != null) {
-      dataToPlot.add(DataSeries("Pull Request Activity",
-          pullRequestActivityByWeek.map((e) => e.stat).toList()));
+      dataToPlot.add(DataSeries('Pull Request Activity',
+          pullRequestActivityByWeek!.map((e) => e.stat).toList()));
     }
 
     LayeredChart layeredChart =
@@ -126,15 +128,13 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
     const double timelinePadding = 60.0;
 
     var timeline = Timeline(
-      numWeeks: dataToPlot != null && dataToPlot.length > 0
-          ? dataToPlot.last.series.length
-          : 0,
+      numWeeks: dataToPlot.isNotEmpty ? dataToPlot.last.series.length : 0,
       animationValue: interpolatedAnimationValue,
       weekLabels: weekLabels,
       mouseDownCallback: (double xFraction) {
         setState(() {
           timelineOverride = true;
-          _animation.stop();
+          _animation?.stop();
           interpolatedAnimationValue = xFraction;
         });
       },
@@ -176,53 +176,55 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
 
   @override
   void dispose() {
-    _animation.dispose();
+    _animation?.dispose();
     super.dispose();
   }
 
   Future loadGitHubData() async {
     String contributorsJsonStr =
-        (await http.get("assets/github_data/contributors.json")).body;
+        (await http.get(Uri.parse('assets/github_data/contributors.json')))
+            .body;
     List jsonObjs = jsonDecode(contributorsJsonStr) as List;
     List<UserContribution> contributionList =
         jsonObjs.map((e) => UserContribution.fromJson(e)).toList();
     print(
-        "Loaded ${contributionList.length} code contributions to /flutter/flutter repo.");
+        'Loaded ${contributionList.length} code contributions to /flutter/flutter repo.');
 
     int numWeeksTotal = contributionList[0].contributions.length;
 
     String starsByWeekStr =
-        (await http.get("assets/github_data/stars.tsv")).body;
+        (await http.get(Uri.parse('assets/github_data/stars.tsv'))).body;
     List<StatForWeek> starsByWeekLoaded =
         summarizeWeeksFromTSV(starsByWeekStr, numWeeksTotal);
 
     String forksByWeekStr =
-        (await http.get("assets/github_data/forks.tsv")).body;
+        (await http.get(Uri.parse('assets/github_data/forks.tsv'))).body;
     List<StatForWeek> forksByWeekLoaded =
         summarizeWeeksFromTSV(forksByWeekStr, numWeeksTotal);
 
     String commitsByWeekStr =
-        (await http.get("assets/github_data/commits.tsv")).body;
+        (await http.get(Uri.parse('assets/github_data/commits.tsv'))).body;
     List<StatForWeek> commitsByWeekLoaded =
         summarizeWeeksFromTSV(commitsByWeekStr, numWeeksTotal);
 
     String commentsByWeekStr =
-        (await http.get("assets/github_data/comments.tsv")).body;
+        (await http.get(Uri.parse('assets/github_data/comments.tsv'))).body;
     List<StatForWeek> commentsByWeekLoaded =
         summarizeWeeksFromTSV(commentsByWeekStr, numWeeksTotal);
 
     String pullRequestActivityByWeekStr =
-        (await http.get("assets/github_data/pull_requests.tsv")).body;
+        (await http.get(Uri.parse('assets/github_data/pull_requests.tsv')))
+            .body;
     List<StatForWeek> pullRequestActivityByWeekLoaded =
         summarizeWeeksFromTSV(pullRequestActivityByWeekStr, numWeeksTotal);
 
     setState(() {
-      this.contributions = contributionList;
-      this.starsByWeek = starsByWeekLoaded;
-      this.forksByWeek = forksByWeekLoaded;
-      this.pushesByWeek = commitsByWeekLoaded;
-      this.issueCommentsByWeek = commentsByWeekLoaded;
-      this.pullRequestActivityByWeek = pullRequestActivityByWeekLoaded;
+      contributions = contributionList;
+      starsByWeek = starsByWeekLoaded;
+      forksByWeek = forksByWeekLoaded;
+      pushesByWeek = commitsByWeekLoaded;
+      issueCommentsByWeek = commentsByWeekLoaded;
+      pullRequestActivityByWeek = pullRequestActivityByWeekLoaded;
     });
   }
 
@@ -230,18 +232,18 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
       String statByWeekStr, int numWeeksTotal) {
     List<StatForWeek> loadedStats = [];
     HashMap<int, StatForWeek> statMap = HashMap();
-    statByWeekStr.split("\n").forEach((s) {
-      List<String> split = s.split("\t");
+    statByWeekStr.split('\n').forEach((s) {
+      List<String> split = s.split('\t');
       if (split.length == 2) {
         int weekNum = int.parse(split[0]);
         statMap[weekNum] = StatForWeek(weekNum, int.parse(split[1]));
       }
     });
-    print("Loaded ${statMap.length} weeks.");
+    print('Loaded ${statMap.length} weeks.');
 
     // Convert into a list by week, but fill in empty weeks with 0
     for (int i = 0; i < numWeeksTotal; i++) {
-      StatForWeek starsForWeek = statMap[i];
+      StatForWeek? starsForWeek = statMap[i];
       if (starsForWeek == null) {
         loadedStats.add(StatForWeek(i, 0));
       } else {
@@ -253,5 +255,5 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
 }
 
 void main() {
-  runApp(Center(child: MainLayout()));
+  runApp(const Center(child: MainLayout()));
 }
diff --git a/web/github_dataviz/lib/timeline.dart b/web/github_dataviz/lib/timeline.dart
index 482588ac9..6576afe95 100644
--- a/web/github_dataviz/lib/timeline.dart
+++ b/web/github_dataviz/lib/timeline.dart
@@ -14,17 +14,19 @@ class Timeline extends StatefulWidget {
   final double animationValue;
   final List<WeekLabel> weekLabels;
 
-  final MouseDownCallback mouseDownCallback;
-  final MouseMoveCallback mouseMoveCallback;
-  final MouseUpCallback mouseUpCallback;
-
-  Timeline(
-      {@required this.numWeeks,
-      @required this.animationValue,
-      @required this.weekLabels,
+  final MouseDownCallback? mouseDownCallback;
+  final MouseMoveCallback? mouseMoveCallback;
+  final MouseUpCallback? mouseUpCallback;
+
+  const Timeline(
+      {required this.numWeeks,
+      required this.animationValue,
+      required this.weekLabels,
       this.mouseDownCallback,
       this.mouseMoveCallback,
-      this.mouseUpCallback});
+      this.mouseUpCallback,
+      Key? key})
+      : super(key: key);
 
   @override
   State<StatefulWidget> createState() {
@@ -39,17 +41,17 @@ class TimelineState extends State<Timeline> {
   void initState() {
     super.initState();
     for (int year = 2015; year < 2020; year++) {
-      String yearLabel = "$year";
+      String yearLabel = '$year';
       labelPainters[yearLabel] =
           _makeTextPainter(Constants.timelineLineColor, yearLabel);
     }
 
-    widget.weekLabels.forEach((WeekLabel weekLabel) {
+    for (var weekLabel in widget.weekLabels) {
       labelPainters[weekLabel.label] =
           _makeTextPainter(Constants.milestoneTimelineColor, weekLabel.label);
-      labelPainters[weekLabel.label + "_red"] =
+      labelPainters[weekLabel.label + '_red'] =
           _makeTextPainter(Colors.redAccent, weekLabel.label);
-    });
+    }
   }
 
   @override
@@ -57,19 +59,22 @@ class TimelineState extends State<Timeline> {
     return GestureDetector(
       behavior: HitTestBehavior.translucent,
       onHorizontalDragDown: (DragDownDetails details) {
-        if (widget.mouseDownCallback != null) {
-          widget.mouseDownCallback(
+        final mouseDownCallback = widget.mouseDownCallback;
+        if (mouseDownCallback != null) {
+          mouseDownCallback(
               _getClampedXFractionLocalCoords(context, details.globalPosition));
         }
       },
       onHorizontalDragEnd: (DragEndDetails details) {
-        if (widget.mouseUpCallback != null) {
-          widget.mouseUpCallback();
+        final mouseUpCallback = widget.mouseUpCallback;
+        if (mouseUpCallback != null) {
+          mouseUpCallback();
         }
       },
       onHorizontalDragUpdate: (DragUpdateDetails details) {
-        if (widget.mouseMoveCallback != null) {
-          widget.mouseMoveCallback(
+        final mouseMoveCallback = widget.mouseMoveCallback;
+        if (mouseMoveCallback != null) {
+          mouseMoveCallback(
               _getClampedXFractionLocalCoords(context, details.globalPosition));
         }
       },
@@ -95,17 +100,17 @@ class TimelineState extends State<Timeline> {
 
   double _getClampedXFractionLocalCoords(
       BuildContext context, Offset globalOffset) {
-    final RenderBox box = context.findRenderObject();
+    final RenderBox box = context.findRenderObject() as RenderBox;
     final Offset localOffset = box.globalToLocal(globalOffset);
-    return MathUtils.clamp(localOffset.dx / context.size.width, 0, 1);
+    return MathUtils.clamp(localOffset.dx / context.size!.width, 0, 1);
   }
 }
 
 class TimelinePainter extends CustomPainter {
   TimelineState state;
 
-  Paint mainLinePaint;
-  Paint milestoneLinePaint;
+  late Paint mainLinePaint;
+  late Paint milestoneLinePaint;
 
   Color lineColor = Colors.white;
 
@@ -164,7 +169,7 @@ class TimelinePainter extends CustomPainter {
             var mappedValue =
                 MathUtils.clampedMap(currTimeXDiff, 0, 0.025, 0, 1);
             var lerpedColor = Color.lerp(Constants.milestoneTimelineColor,
-                Constants.timelineLineColor, mappedValue);
+                Constants.timelineLineColor, mappedValue)!;
             mainLinePaint.color = lerpedColor;
           } else {
             mainLinePaint.color = Constants.timelineLineColor;
@@ -174,8 +179,8 @@ class TimelinePainter extends CustomPainter {
         }
 
         if (isYear) {
-          var yearLabel = "$yearNumber";
-          state.labelPainters[yearLabel]
+          var yearLabel = '$yearNumber';
+          state.labelPainters[yearLabel]!
               .paint(canvas, Offset(currX, size.height - labelHeight));
           yearNumber++;
         }
@@ -185,17 +190,17 @@ class TimelinePainter extends CustomPainter {
     {
       for (int i = 0; i < weekLabels.length; i++) {
         WeekLabel weekLabel = weekLabels[i];
-        double currX = (weekLabel.weekNum / numWeeks.toDouble()) * size.width;
+        double currX = (weekLabel.weekNum! / numWeeks.toDouble()) * size.width;
         var timelineXDiff = (currTimeX - currX) / size.width;
         double maxTimelineDiff = 0.08;
-        TextPainter textPainter = state.labelPainters[weekLabel.label];
+        TextPainter textPainter = state.labelPainters[weekLabel.label]!;
         if (timelineXDiff > 0 &&
             timelineXDiff < maxTimelineDiff &&
             animationValue < 1) {
           var mappedValue =
               MathUtils.clampedMap(timelineXDiff, 0, maxTimelineDiff, 0, 1);
           var lerpedColor = Color.lerp(
-              Colors.redAccent, Constants.milestoneTimelineColor, mappedValue);
+              Colors.redAccent, Constants.milestoneTimelineColor, mappedValue)!;
           milestoneLinePaint.strokeWidth =
               MathUtils.clampedMap(timelineXDiff, 0, maxTimelineDiff, 6, 1);
           milestoneLinePaint.color = lerpedColor;
diff --git a/web/github_dataviz/pubspec.lock b/web/github_dataviz/pubspec.lock
index 1731edffb..ef7a33c02 100644
--- a/web/github_dataviz/pubspec.lock
+++ b/web/github_dataviz/pubspec.lock
@@ -1,13 +1,20 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
+  async:
+    dependency: transitive
+    description:
+      name: async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.8.2"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   charcode:
     dependency: transitive
     description:
@@ -15,6 +22,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.3.1"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
@@ -27,27 +41,41 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_lints:
+    dependency: "direct dev"
+    description:
+      name: flutter_lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.4"
   http:
     dependency: "direct main"
     description:
       name: http
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.2"
+    version: "0.13.4"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.4"
+    version: "4.0.0"
   intl:
     dependency: "direct main"
     description:
       name: intl
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.16.1"
+    version: "0.17.0"
+  lints:
+    dependency: transitive
+    description:
+      name: lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   meta:
     dependency: transitive
     description:
@@ -62,13 +90,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
-  pedantic:
-    dependency: transitive
-    description:
-      name: pedantic
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.11.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -110,4 +131,4 @@ packages:
     source: hosted
     version: "2.1.0"
 sdks:
-  dart: ">=2.12.0 <3.0.0"
+  dart: ">=2.14.0 <3.0.0"
diff --git a/web/github_dataviz/pubspec.yaml b/web/github_dataviz/pubspec.yaml
index c57ca6e89..da76ef5a4 100644
--- a/web/github_dataviz/pubspec.yaml
+++ b/web/github_dataviz/pubspec.yaml
@@ -1,13 +1,17 @@
 name: github_dataviz
 
 environment:
-  sdk: ">=2.2.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
     sdk: flutter
-  intl: ^0.16.0
-  http: ^0.12.0
+  intl: ^0.17.0
+  http: ^0.13.4
+
+dev_dependencies:
+  flutter_lints: ^1.0.4
+
 flutter:
   assets:
     - preview.png