chore; fixes parsing to avoid unnecessary allocations

Signed-off-by: Vincent Biret <[email protected]>

Author: baywet

src/Microsoft.OpenApi/Reader/V2/OpenApiDocumentDeserializer.cs

@@ -104,7 +104,7 @@ internal static partial class OpenApiV2Deserializer
                 }
             },
             {"security", (o, n, _) => o.SecurityRequirements = n.CreateList(LoadSecurityRequirement, o)},
-            {"tags", (o, n, _) => o.Tags = new HashSet<OpenApiTag>(n.CreateList(LoadTag, o), OpenApiTagComparer.Instance)},
+            {"tags", (o, n, _) => { if (n.CreateList(LoadTag, o) is {Count:> 0} tags) {o.Tags = new HashSet<OpenApiTag>(tags, OpenApiTagComparer.Instance); } } },
             {"externalDocs", (o, n, _) => o.ExternalDocs = LoadExternalDocs(n, o)}
         };
 

src/Microsoft.OpenApi/Reader/V3/OpenApiDocumentDeserializer.cs

@@ -27,7 +27,7 @@ internal static partial class OpenApiV3Deserializer
             {"servers", (o, n, _) => o.Servers = n.CreateList(LoadServer, o)},
             {"paths", (o, n, _) => o.Paths = LoadPaths(n, o)},
             {"components", (o, n, _) => o.Components = LoadComponents(n, o)},
-            {"tags", (o, n, _) => o.Tags = new HashSet<OpenApiTag>(n.CreateList(LoadTag, o), OpenApiTagComparer.Instance) },
+            {"tags", (o, n, _) => { if (n.CreateList(LoadTag, o) is {Count:> 0} tags) {o.Tags = new HashSet<OpenApiTag>(tags, OpenApiTagComparer.Instance); } } },
             {"externalDocs", (o, n, _) => o.ExternalDocs = LoadExternalDocs(n, o)},
             {"security", (o, n, _) => o.SecurityRequirements = n.CreateList(LoadSecurityRequirement, o)}
         };

src/Microsoft.OpenApi/Reader/V31/OpenApiDocumentDeserializer.cs

@@ -25,7 +25,7 @@ internal static partial class OpenApiV31Deserializer
             {"paths", (o, n, _) => o.Paths = LoadPaths(n, o)},
             {"webhooks", (o, n, _) => o.Webhooks = n.CreateMap(LoadPathItem, o)},
             {"components", (o, n, _) => o.Components = LoadComponents(n, o)},
-            {"tags", (o, n, _) => o.Tags = new HashSet<OpenApiTag>(n.CreateList(LoadTag, o), OpenApiTagComparer.Instance) },
+            {"tags", (o, n, _) => { if (n.CreateList(LoadTag, o) is {Count:> 0} tags) {o.Tags = new HashSet<OpenApiTag>(tags, OpenApiTagComparer.Instance); } } },
             {"externalDocs", (o, n, _) => o.ExternalDocs = LoadExternalDocs(n, o)},
             {"security", (o, n, _) => o.SecurityRequirements = n.CreateList(LoadSecurityRequirement, o)}
         };