fix(seo): answer failed renders with 503 and shorten package page state

A page whose API call failed now answers 503 with Retry-After and noindex. A package page
embeds its newest versions, and the browser fetches the rest after it loads.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: Enes Yağız

src/backend/PkgDiff.API/Controllers/PackageController.cs

@@ -15,6 +15,7 @@ namespace PkgDiff.API.Controllers;
 public class PackageController : ControllerBase
 {
     private const int MaxConcurrentAnalyses = 10;
+    private const int MaxVersionLimit = 100;
 
     private const int MaxConcurrentAnalysesPerAddress = 2;
     private static readonly System.Collections.Concurrent.ConcurrentDictionary<string, int> AnalysesPerAddress = new();
@@ -198,7 +199,11 @@ private async Task<bool> MayQueueScrapeAsync()
 
     [HttpGet("{registry}/{packageId}")]
     [ValidatePackageRoute]
-    public async Task<ActionResult<PackageMetadata>> GetPackageMetadata(string registry, string packageId)
+    public async Task<ActionResult<PackageMetadata>> GetPackageMetadata(
+        string registry,
+        string packageId,
+        [FromQuery] int? versionLimit = null,
+        [FromQuery] string? includeVersion = null)
     {
         try
         {
@@ -222,6 +227,16 @@ public async Task<ActionResult<PackageMetadata>> GetPackageMetadata(string regis
                 }
             }
 
+            if (versionLimit.HasValue)
+            {
+                var limit = Math.Clamp(versionLimit.Value, 1, MaxVersionLimit);
+                metadata.Versions = metadata.Versions
+                    .Where((version, index) => index < limit
+                        || version.Version == metadata.LatestVersion
+                        || string.Equals(version.Version, includeVersion, StringComparison.OrdinalIgnoreCase))
+                    .ToList();
+            }
+
             return Ok(metadata);
         }
         catch (ArgumentException ex)
@@ -379,6 +394,7 @@ public async Task<IActionResult> ExportDiffToPdf([FromBody] AnalyzeRequest reque
         ProjectUrl = metadata.ProjectUrl,
         GitHubRepositoryUrl = metadata.GitHubRepositoryUrl,
         Versions = metadata.Versions,
+        TotalVersions = metadata.Versions.Count,
         Trust = trust
     };
 }

src/backend/PkgDiff.Shared/DTOs/AnalysisModels.cs

@@ -69,6 +69,7 @@ public class PackageMetadata
     public string? GitHubRepositoryUrl { get; set; }
     public string? SourceDirectory { get; set; }
     public List<VersionSummary> Versions { get; set; } = new();
+    public int TotalVersions { get; set; }
     public PackageTrust? Trust { get; set; }
 }
 

src/frontend/src/app/core/models/package.models.ts

@@ -38,6 +38,7 @@ export interface PackageMetadata {
   gitHubRepositoryUrl: string | null;
   sourceDirectory?: string | null;
   versions: VersionSummary[];
+  totalVersions?: number;
   trust?: PackageTrust | null;
 }
 

src/frontend/src/app/core/services/http-status.service.ts

@@ -1,6 +1,8 @@
 import { Injectable, RESPONSE_INIT, inject } from '@angular/core';
 
-// Lets a server render answer a missing page with a real 404 instead of a 200
+const RETRY_AFTER_SECONDS = '120';
+
+// Lets a server render answer a missing or failed page with its real status instead of a 200
 @Injectable({ providedIn: 'root' })
 export class HttpStatusService {
   private response = inject(RESPONSE_INIT, { optional: true });
@@ -10,4 +12,13 @@ export class HttpStatusService {
       this.response.status = 404;
     }
   }
+
+  serviceUnavailable(): void {
+    if (this.response) {
+      const headers = new Headers(this.response.headers);
+      headers.set('Retry-After', RETRY_AFTER_SECONDS);
+      this.response.status = 503;
+      this.response.headers = headers;
+    }
+  }
 }

src/frontend/src/app/core/services/package.service.ts

@@ -15,8 +15,12 @@ export class PackageService {
     return this.api.get<RegistryInfo[]>('Package/registries');
   }
 
-  getPackageMetadata(registry: string, packageId: string): Observable<PackageMetadata> {
-    return this.api.get<PackageMetadata>(`Package/${registry}/${encodeURIComponent(packageId)}`);
+  getPackageMetadata(
+    registry: string,
+    packageId: string,
+    versions?: { versionLimit: number; includeVersion?: string },
+  ): Observable<PackageMetadata> {
+    return this.api.get<PackageMetadata>(`Package/${registry}/${encodeURIComponent(packageId)}`, versions);
   }
 
   analyze(request: AnalyzeRequest): Observable<AnalysisResult> {

src/frontend/src/app/core/services/seo.service.ts

@@ -84,6 +84,16 @@ export class SeoService {
     this.clearPageData();
   }
 
+  // The page failed to load; the next successful updateMeta makes it indexable again
+  setUnavailable(): void {
+    this.setNoIndex();
+    this.clearPageData();
+  }
+
+  setNoIndex(): void {
+    this.meta.updateTag({ name: 'robots', content: 'noindex, follow' });
+  }
+
   setStructuredData(data: StructuredData): void {
     this.setJsonLd('page', data);
   }
@@ -128,7 +138,7 @@ export class SeoService {
   }
 
   setPackage(metadata: PackageMetadata, registry: string, version?: string): void {
-    const versionCount = metadata.versions.length;
+    const versionCount = metadata.totalVersions ?? metadata.versions.length;
     const latestVersion = metadata.latestVersion;
 
     let description = metadata.packageId;

src/frontend/src/app/features/contributors/contributors.ts

@@ -5,6 +5,7 @@ import { RouterModule } from '@angular/router';
 import { LucideAngularModule, Github, Users, RefreshCw } from 'lucide-angular';
 import { ApiService } from '../../core/services/api';
 import { SeoService } from '../../core/services/seo.service';
+import { HttpStatusService } from '../../core/services/http-status.service';
 
 interface ContributorDto {
     gitHubUsername: string;
@@ -23,6 +24,7 @@ interface ContributorDto {
 export class ContributorsComponent {
     private api = inject(ApiService);
     private seo = inject(SeoService);
+    private httpStatus = inject(HttpStatusService);
     private destroyRef = inject(DestroyRef);
 
     readonly GithubIcon = Github;
@@ -63,7 +65,11 @@ export class ContributorsComponent {
                 this.contributors.set(data);
                 this.loading.set(false);
             },
-            error: () => this.loading.set(false),
+            error: () => {
+                this.httpStatus.serviceUnavailable();
+                this.seo.setNoIndex();
+                this.loading.set(false);
+            },
         });
     }
 

src/frontend/src/app/features/package/components/releases-tab/releases-tab.html

@@ -3,7 +3,7 @@
     <h3 class="text-sm font-bold uppercase tracking-widest text-gray-400">Release History</h3>
     <span
       class="px-2 py-0.5 text-[10px] font-bold bg-gray-100 dark:bg-gray-800 text-gray-500 dark:text-gray-400 rounded-full">
-      {{ versions().length }} total
+      {{ totalCount() ?? versions().length }} total
     </span>
   </div>
   @if (selectedVersion()) {

src/frontend/src/app/features/package/components/releases-tab/releases-tab.ts

@@ -20,6 +20,7 @@ export class ReleasesTabComponent {
   registry = input<string>('nuget');
   gitHubUrl = input<string | null>(null);
   selectedVersion = input<string | undefined>(undefined);
+  totalCount = input<number | null>(null);
 
   readonly GithubIcon = Github;
   readonly ExternalLinkIcon = ExternalLink;

src/frontend/src/app/features/package/package.html

@@ -195,7 +195,8 @@ <h1 class="text-2xl md:text-3xl font-bold tracking-tight break-words min-w-0">{{
 
   @if (activeTab() === 'releases') {
   <app-releases-tab [versions]="mappedVersions()" [packageId]="metadata()!.packageId" [registry]="registry()"
-    [gitHubUrl]="metadata()!.gitHubRepositoryUrl" [selectedVersion]="version()" />
+    [gitHubUrl]="metadata()!.gitHubRepositoryUrl" [selectedVersion]="version()"
+    [totalCount]="version() ? null : (metadata()!.totalVersions ?? null)" />
   }
   @if (activeTab() === 'diff') {
   <app-diff-tab [versions]="mappedVersions()" [packageId]="metadata()!.packageId" [registry]="registry()" [trust]="trust()"