Fixed incorrect node url being returned when no suitable domain exist…

src/Umbraco.Core/Routing/DomainUtilities.cs

@@ -190,7 +190,7 @@ public static DomainAndUri SelectDomain(IEnumerable<Domain> domains, Uri uri, st
             }
 
             // look for domains that would be the base of the uri
-            var baseDomains = SelectByBase(considerForBaseDomains, uri);
+            var baseDomains = SelectByBase(considerForBaseDomains, uri, culture);
             if (baseDomains.Count > 0) // found, return
                 return baseDomains.First();
 
@@ -199,10 +199,6 @@ public static DomainAndUri SelectDomain(IEnumerable<Domain> domains, Uri uri, st
             if (filter != null)
             {
                 var domainAndUri = filter(cultureDomains ?? domainsAndUris, uri, culture, defaultCulture);
-                // if still nothing, pick the first one?
-                // no: move that constraint to the filter, but check
-                if (domainAndUri == null)
-                    throw new InvalidOperationException("The filter returned null.");
                 return domainAndUri;
             }
 
@@ -212,12 +208,15 @@ public static DomainAndUri SelectDomain(IEnumerable<Domain> domains, Uri uri, st
         private static bool IsBaseOf(DomainAndUri domain, Uri uri)
             => domain.Uri.EndPathWithSlash().IsBaseOf(uri);
 
-        private static IReadOnlyCollection<DomainAndUri> SelectByBase(IReadOnlyCollection<DomainAndUri> domainsAndUris, Uri uri)
+        private static bool MatchesCulture(DomainAndUri domain, string culture)
+            => culture == null || domain.Culture == culture;
+
+        private static IReadOnlyCollection<DomainAndUri> SelectByBase(IReadOnlyCollection<DomainAndUri> domainsAndUris, Uri uri, string culture)
         {
             // look for domains that would be the base of the uri
             // ie current is www.example.com/foo/bar, look for domain www.example.com
             var currentWithSlash = uri.EndPathWithSlash();
-            var baseDomains = domainsAndUris.Where(d => IsBaseOf(d, currentWithSlash)).ToList();
+            var baseDomains = domainsAndUris.Where(d => IsBaseOf(d, currentWithSlash) && MatchesCulture(d, culture)).ToList();
 
             // if none matches, try again without the port
             // ie current is www.example.com:1234/foo/bar, look for domain www.example.com

src/Umbraco.Core/Routing/SiteDomainMapper.cs

@@ -336,8 +336,7 @@ private DomainAndUri MapDomain(IReadOnlyCollection<DomainAndUri> domainAndUris,
             if (qualifiedSites == null)
             {
                 return domainAndUris.FirstOrDefault(x => x.Culture.InvariantEquals(culture))
-                    ?? domainAndUris.FirstOrDefault(x => x.Culture.InvariantEquals(defaultCulture))
-                    ?? domainAndUris.First();
+                    ?? domainAndUris.FirstOrDefault(x => x.Culture.InvariantEquals(defaultCulture));
             }
 
             // find a site that contains the current authority
@@ -350,18 +349,7 @@ private DomainAndUri MapDomain(IReadOnlyCollection<DomainAndUri> domainAndUris,
                 : domainAndUris.FirstOrDefault(d => currentSite.Value.Contains(d.Uri.GetLeftPart(UriPartial.Authority)));
 
             // no match means that either current does not belong to a site, or the site it belongs to
-            // does not contain any of domainAndUris. Yet we have to return something. here, it becomes
-            // a bit arbitrary.
-
-            // look through sites in order and pick the first domainAndUri that belongs to a site
-            ret = ret ?? qualifiedSites
-                .Where(site => site.Key != currentSite.Key)
-                .Select(site => domainAndUris.FirstOrDefault(domainAndUri => site.Value.Contains(domainAndUri.Uri.GetLeftPart(UriPartial.Authority))))
-                .FirstOrDefault(domainAndUri => domainAndUri != null);
-
-            // random, really
-            ret = ret ?? domainAndUris.FirstOrDefault(x => x.Culture.InvariantEquals(culture)) ?? domainAndUris.First();
-
+            // does not contain any of domainAndUris.
             return ret;
         }
 

src/Umbraco.Core/Routing/UrlProviderExtensions.cs

@@ -247,6 +247,13 @@ private static async Task<Attempt<UrlInfo>> DetectCollisionAsync(ILogger logger,
                 return Attempt.Succeed(urlInfo);
             }
 
+            // collisions with a different culture of the same content can never be routed.
+            if (!culture.InvariantEquals(pcr.Culture))
+            {
+                var urlInfo = UrlInfo.Message(textService.Localize("content", "routeErrorCannotRoute"), culture);
+                return Attempt.Succeed(urlInfo);
+            }
+
             // no collision
             return Attempt<UrlInfo>.Fail();
         }

src/Umbraco.Tests.UnitTests/Umbraco.Core/Routing/SiteDomainMapperTests.cs

@@ -191,9 +191,7 @@ public void MapDomainWithScheme()
             siteDomainMapper.AddSite("site3", "domain3.com", "domain3.net", "domain3.org");
             siteDomainMapper.AddSite("site4", "https://domain4.com", "https://domain4.net", "https://domain4.org");
 
-            // this works, but it's purely by chance / arbitrary
-            // don't use the www in tests here!
-            var current = new Uri("https://www.domain1.com/foo/bar");
+            var current = new Uri("https://domain1.com/foo/bar");
             Domain[] domains = new[]
                 {
                     new Domain(1, "domain2.com", -1, s_cultureFr, false),