Modify warning message on display package page when missing readme

src/AccountDeleter/EmptyFeatureFlagService.cs

@@ -296,6 +296,11 @@ public bool IsDisplayUploadWarningV2Enabled(User user)
             throw new NotImplementedException();
         }
 
+        public bool IsDisplayPackageReadmeWarningEnabled(User user)
+        {
+            throw new NotImplementedException();
+        }
+
         public bool IsFrameworkFilteringEnabled(User user) {
             throw new NotImplementedException();
         }

src/Bootstrap/less/theme/page-display-package.less

@@ -423,6 +423,10 @@
       margin-bottom: -1px;
     }
 
+    .nav-tabs > li.active > a.body-warning-tab > {
+      background-color: #fff4ce;
+    }
+
     .nav-tabs > li > a {
       border-left: 0px;
       border-right: 0px;

src/GitHubVulnerabilities2Db/Fakes/FakeFeatureFlagService.cs

@@ -135,6 +135,11 @@ public bool IsDisplayUploadWarningV2Enabled(User user)
             throw new NotImplementedException();
         }
 
+        public bool IsDisplayPackageReadmeWarningEnabled(User user)
+        {
+            throw new NotImplementedException();
+        }
+
         public bool IsODataDatabaseReadOnlyEnabled()
         {
             throw new NotImplementedException();

src/NuGetGallery.Services/Configuration/FeatureFlagService.cs

@@ -48,6 +48,7 @@ public class FeatureFlagService : IFeatureFlagService
         private const string MarkdigMdRenderingFlightName = GalleryPrefix + "MarkdigMdRendering";
         private const string MarkdigMdSyntaxHighlightFlightName = GalleryPrefix + "MarkdigMdSyntaxHighlight";
         private const string DisplayUploadWarningV2FlightName = GalleryPrefix + "DisplayUploadWarningV2";
+        private const string DisplayPackageReadmeWarningFlightName = GalleryPrefix + "DisplayPackageReadmeWarning";
         private const string DeletePackageApiFlightName = GalleryPrefix + "DeletePackageApi";
         private const string ImageAllowlistFlightName = GalleryPrefix + "ImageAllowlist";
         private const string DisplayBannerFlightName = GalleryPrefix + "Banner";
@@ -348,6 +349,11 @@ public bool IsDisplayUploadWarningV2Enabled(User user)
             return _client.IsEnabled(DisplayUploadWarningV2FlightName, user, defaultValue: false);
         }
 
+        public bool IsDisplayPackageReadmeWarningEnabled(User user)
+        {
+            return _client.IsEnabled(DisplayPackageReadmeWarningFlightName, user, defaultValue: false);
+        }
+
         public bool IsDeletePackageApiEnabled(User user)
         {
             return _client.IsEnabled(DeletePackageApiFlightName, user, defaultValue: false);

src/NuGetGallery.Services/Configuration/IFeatureFlagService.cs

@@ -273,6 +273,11 @@ public interface IFeatureFlagService
         /// </summary>
         bool IsDisplayUploadWarningV2Enabled(User user);
 
+        /// <summary>
+        /// Whether the new warning of the missing readme is displayed to package authors
+        /// </summary>
+        bool IsDisplayPackageReadmeWarningEnabled(User user);
+
         /// <summary>
         /// Whether or not the user can delete a package through the API.
         /// </summary>

src/NuGetGallery/App_Data/Files/Content/flags.json

@@ -120,6 +120,12 @@
       "SiteAdmins": false,
       "Accounts": [],
       "Domains": []
+    },
+    "NuGetGallery.DisplayPackageReadmeWarning": {
+      "All": true,
+      "SiteAdmins": false,
+      "Accounts": [],
+      "Domains": []
     }
   }
 }

src/NuGetGallery/Controllers/PackagesController.cs

@@ -941,6 +941,8 @@ public virtual async Task<ActionResult> DisplayPackage(string id, string version
                 packageRenames,
                 readme);
 
+            var canDisplayReadmeWarning = _featureFlagService.IsDisplayPackageReadmeWarningEnabled(currentUser) && !model.HasEmbeddedReadmeFile && model.ReadMeHtml == null;
+
             model.ValidatingTooLong = _validationService.IsValidatingTooLong(package);
             model.PackageValidationIssues = _validationService.GetLatestPackageValidationIssues(package);
             model.SymbolsPackageValidationIssues = _validationService.GetLatestPackageValidationIssues(model.LatestSymbolsPackage);
@@ -956,6 +958,7 @@ public virtual async Task<ActionResult> DisplayPackage(string id, string version
             model.IsDisplayTargetFrameworkEnabled = _featureFlagService.IsDisplayTargetFrameworkEnabled(currentUser);
             model.IsComputeTargetFrameworkEnabled = _featureFlagService.IsComputeTargetFrameworkEnabled();
             model.IsMarkdigMdSyntaxHighlightEnabled = _featureFlagService.IsMarkdigMdSyntaxHighlightEnabled();
+            model.CanDisplayReadmeWarning = canDisplayReadmeWarning;
 
             if (model.IsComputeTargetFrameworkEnabled || model.IsDisplayTargetFrameworkEnabled)
             {

src/NuGetGallery/ViewModels/DisplayPackageViewModel.cs

@@ -44,6 +44,7 @@ public class DisplayPackageViewModel : ListPackageItemViewModel
         public bool IsPackageDependentsEnabled { get; set; }
         public bool IsRecentPackagesNoIndexEnabled { get; set; }
         public bool IsMarkdigMdSyntaxHighlightEnabled { get; set; }
+        public bool CanDisplayReadmeWarning { get; set; }
         public NuGetPackageGitHubInformation GitHubDependenciesInformation { get; set; }
         public bool HasEmbeddedIcon { get; set; }
         public bool HasEmbeddedReadmeFile { get; set; }

src/NuGetGallery/Views/Packages/DisplayPackage.cshtml

@@ -530,12 +530,19 @@
                                role="tab"
                                data-toggle="tab"
                                id="readme-body-tab"
-                               class="body-tab"
+                               class="body-@(Model.CanDisplayReadmeWarning && Model.CanDisplayPrivateMetadata? "warning-" : "")tab"
                                aria-controls="readme-tab"
                                aria-expanded="@(activeBodyTab == "readme" ? "true" : "false")"
                                aria-selected="@(activeBodyTab == "readme" ? "true" : "false")"
                                tabindex="@(activeBodyTab == "readme" ? "0" : "-1")">
-                                <i class="ms-Icon ms-Icon--Dictionary" aria-hidden="true"></i>
+                                @if (Model.CanDisplayReadmeWarning && Model.CanDisplayPrivateMetadata)
+                                {
+                                    <i class="ms-Icon ms-Icon--Warning" aria-hidden="true"></i>
+                                } 
+                                else
+                                {
+                                    <i class="ms-Icon ms-Icon--Dictionary" aria-hidden="true"></i>
+                                }
                                 README
                             </a>
                         </li>
@@ -670,7 +677,11 @@
                         }
                         else
                         {
-                            if (Model.CanDisplayPrivateMetadata)
+                            if (Model.CanDisplayPrivateMetadata && Model.CanDisplayReadmeWarning)
+                            {
+                                @ViewHelpers.AlertWarning(@<text>Your package is missing a README. Please update your package to <a href='https://aka.ms/nuget-include-readme'>include a README</a> or <a href=@Url.ManagePackage(Model)>add a README here</a>.</text>);
+                            }
+                            else if (Model.CanDisplayPrivateMetadata)
                             {
                                 @ViewHelpers.AlertWarning(@<text>The package description is shown below. Please update your package to <a href='https://docs.microsoft.com/nuget/nuget-org/package-readme-on-nuget-org'>include a README</a>.</text>);
                             }

src/VerifyMicrosoftPackage/Fakes/FakeFeatureFlagService.cs

@@ -127,6 +127,8 @@ public class FakeFeatureFlagService : IFeatureFlagService
 
         public bool IsDisplayUploadWarningV2Enabled(User user) => throw new NotImplementedException();
 
+        public bool IsDisplayPackageReadmeWarningEnabled(User user) => throw new NotImplementedException();
+
         public bool IsFrameworkFilteringEnabled(User user) => throw new NotImplementedException();
     }
 }