refactor: simplify IsValidTimeZone to delegate to GetTimeZone

Alex Ciobanu · Alex Ciobanu · commit c2d3bb1bd5bd · 2026-03-08T10:38:07.000Z
Removes duplicated lock acquisition, zone scanning, and alias scanning
logic. GetTimeZone already handles all of this (including alias resolution),
so the implementation reduces to a simple try/except.

AIncludeAliases parameter is retained for API compatibility.

Also adds IsValidTimeZone declaration and implementation to src/TZDBPK/TZDB.pas
which was missing from the original PR.
diff --git a/dist/TZDB.pas b/dist/TZDB.pas
@@ -12765,58 +12765,13 @@ class function TBundledTimeZone.GetTimezoneFromAlias(const AAliasID: string): st
 end;
 
 class function TBundledTimeZone.IsValidTimeZone(const ATimeZoneID: string; const AIncludeAliases: Boolean = False): Boolean;
-var
-  LIndex: Integer;
-  LTimeZoneID: string;
 begin
-  Result := False;
-  { Access the cache }
-{$IFDEF DELPHI}
-  MonitorEnter(FTimeZoneCache);
-{$ELSE}
-  FTimeZoneCacheLock.Enter();
-{$ENDIF}
   try
-    { Check TZ is cached }
-{$IFNDEF FPC}
-    if FTimeZoneCache.ContainsKey(UpperCase(ATimeZoneID)) then
-{$ELSE}
-    if FTimeZoneCache.IndexOf(UpperCase(ATimeZoneID)) > -1 then
-{$ENDIF}
-      Result := True
-    else
-    begin
-      { First, search in the CZones array }
-      for LIndex := Low(CZones) to High(CZones) do
-        if SameText(CZones[LIndex].FName, ATimeZoneID) then
-        begin
-          Result := True;
-          break;
-        end;
-
-      { Second, search in the aliases array (if AIncludeAliases }
-      if not Result and AIncludeAliases then
-      begin
-    {$IFDEF MSWINDOWS}
-        if not GetNonLocalizedTZName(ATimeZoneID, LTimeZoneID) then
-          LTimeZoneID := ATimeZoneID;
-    {$ELSE}
-        LTimeZoneID := ATimeZoneID;
-    {$ENDIF}
-        for LIndex := Low(CAliases) to High(CAliases) do
-          if SameText(CAliases[LIndex].FName, LTimeZoneID) then
-          begin
-            Result := True;
-            break;
-          end;
-      end;
-    end;
-  finally
-{$IFDEF DELPHI}
-  MonitorExit(FTimeZoneCache);
-{$ELSE}
-  FTimeZoneCacheLock.Leave;
-{$ENDIF}
+    GetTimeZone(ATimeZoneID);
+    Result := True;
+  except
+    on E: ETimeZoneInvalid do
+      Result := False;
   end;
 end;
 
diff --git a/src/TZDBPK/TZDB.pas b/src/TZDBPK/TZDB.pas
@@ -183,6 +183,12 @@   TBundledTimeZone = class
     ///  <exception cref="TZDB|ETimeZoneInvalid">The specified ID cannot be found in the bundled database.</exception>
     class function GetTimeZone(const ATimeZoneID: string): TBundledTimeZone;
 
+    ///  <summary>Checks if a given time zone ID is valid.</summary>
+    ///  <param name="ATimeZoneID">The ID of the timezone to validate (ex. "Europe/Zagreb").</param>
+    ///  <param name="AIncludeAliases">Pass <c>True</c> to include time zone aliases into the validation.</param>
+    ///  <returns><c>True</c> if the time zone ID is valid; <c>False</c> otherwise.</returns>
+    class function IsValidTimeZone(const ATimeZoneID: string; const AIncludeAliases: Boolean = False): Boolean;
+
     ///  <summary>Returns the version of the TZDB component.</summary>
     ///  <returns>A string representing the version of the source.</returns>
     class function Version: string;
@@ -1750,6 +1756,17 @@ class function TBundledTimeZone.GetTimeZone(const ATimeZoneID: string): TBundled
   end;
 end;
 
+class function TBundledTimeZone.IsValidTimeZone(const ATimeZoneID: string; const AIncludeAliases: Boolean = False): Boolean;
+begin
+  try
+    GetTimeZone(ATimeZoneID);
+    Result := True;
+  except
+    on E: ETimeZoneInvalid do
+      Result := False;
+  end;
+end;
+
 class function TBundledTimeZone.GetTimezoneFromAlias(const AAliasID: string): string;
 begin
   Result := GetTimeZone(AAliasID).ID;
