fix: "try" methods should never throw

src/TimeZoneConverter/TZConvert.cs

@@ -124,6 +124,12 @@ public static string IanaToWindows(string ianaTimeZoneName)
     /// <returns><c>true</c> if successful, <c>false</c> otherwise.</returns>
     public static bool TryIanaToWindows(string ianaTimeZoneName, [MaybeNullWhen(false)] out string windowsTimeZoneId)
     {
+        if (string.IsNullOrWhiteSpace(ianaTimeZoneName))
+        {
+            windowsTimeZoneId = null;
+            return false;
+        }
+
         return IanaMap.TryGetValue(ianaTimeZoneName, out windowsTimeZoneId!);
     }
 
@@ -337,6 +343,12 @@ public static TimeZoneInfo GetTimeZoneInfo(string windowsOrIanaTimeZoneId)
     public static bool TryGetTimeZoneInfo(string windowsOrIanaTimeZoneId,
         [MaybeNullWhen(false)] out TimeZoneInfo timeZoneInfo)
     {
+        if (string.IsNullOrWhiteSpace(windowsOrIanaTimeZoneId))
+        {
+            timeZoneInfo = null;
+            return false;
+        }
+
         if (string.Equals(windowsOrIanaTimeZoneId, "UTC", StringComparison.OrdinalIgnoreCase))
         {
             timeZoneInfo = TimeZoneInfo.Utc;
@@ -395,6 +407,11 @@ public static IList<string> IanaToRails(string ianaTimeZoneName)
     /// <returns><c>true</c> if successful, <c>false</c> otherwise.</returns>
     public static bool TryIanaToRails(string ianaTimeZoneName, out IList<string> railsTimeZoneNames)
     {
+        if (string.IsNullOrWhiteSpace(ianaTimeZoneName))
+        {
+            railsTimeZoneNames = Array.Empty<string>();
+            return false;
+        }
 
         // in the case of an Etc/GMT+/-n zone, use the Rails fixed-offset zone.  For example, `Etc/GMT-6` -> `+06:00` or `Etc/GMT+3` -> `-03:00`
         if (ianaTimeZoneName.StartsWith("Etc/GMT", StringComparison.OrdinalIgnoreCase))
@@ -466,6 +483,12 @@ public static string RailsToIana(string railsTimeZoneName)
     /// <returns><c>true</c> if successful, <c>false</c> otherwise.</returns>
     public static bool TryRailsToIana(string railsTimeZoneName, [MaybeNullWhen(false)] out string ianaTimeZoneName)
     {
+        if (string.IsNullOrWhiteSpace(railsTimeZoneName))
+        {
+            ianaTimeZoneName = null;
+            return false;
+        }
+
         return RailsMap.TryGetValue(railsTimeZoneName, out ianaTimeZoneName);
     }
 

test/TimeZoneConverter.Tests/MiscTests.cs

@@ -0,0 +1,73 @@
+using Xunit.Abstractions;
+
+namespace TimeZoneConverter.Tests;
+
+public class MiscTests()
+{
+#pragma warning disable CS8625
+
+    [Fact]
+    public void No_Exception_From_TryGetTimeZoneInfo()
+    {
+        Assert.False(TZConvert.TryGetTimeZoneInfo(null, out var _));
+        Assert.False(TZConvert.TryGetTimeZoneInfo("", out var _));
+        Assert.False(TZConvert.TryGetTimeZoneInfo(" ", out var _));
+        Assert.False(TZConvert.TryGetTimeZoneInfo("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryIanaToRails()
+    {
+        Assert.False(TZConvert.TryIanaToRails(null, out var _));
+        Assert.False(TZConvert.TryIanaToRails("", out var _));
+        Assert.False(TZConvert.TryIanaToRails(" ", out var _));
+        Assert.False(TZConvert.TryIanaToRails("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryIanaToWindows()
+    {
+        Assert.False(TZConvert.TryIanaToWindows(null, out var _));
+        Assert.False(TZConvert.TryIanaToWindows("", out var _));
+        Assert.False(TZConvert.TryIanaToWindows(" ", out var _));
+        Assert.False(TZConvert.TryIanaToWindows("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryRailsToIana()
+    {
+        Assert.False(TZConvert.TryRailsToIana(null, out var _));
+        Assert.False(TZConvert.TryRailsToIana("", out var _));
+        Assert.False(TZConvert.TryRailsToIana(" ", out var _));
+        Assert.False(TZConvert.TryRailsToIana("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryRailsToWindows()
+    {
+        Assert.False(TZConvert.TryRailsToWindows(null, out var _));
+        Assert.False(TZConvert.TryRailsToWindows("", out var _));
+        Assert.False(TZConvert.TryRailsToWindows(" ", out var _));
+        Assert.False(TZConvert.TryRailsToWindows("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryWindowsToIana()
+    {
+        Assert.False(TZConvert.TryWindowsToIana(null, out var _));
+        Assert.False(TZConvert.TryWindowsToIana("", out var _));
+        Assert.False(TZConvert.TryWindowsToIana(" ", out var _));
+        Assert.False(TZConvert.TryWindowsToIana("blah", out var _));
+    }
+
+    [Fact]
+    public void No_Exception_From_TryWindowsToRails()
+    {
+        Assert.False(TZConvert.TryWindowsToRails(null, out var _));
+        Assert.False(TZConvert.TryWindowsToRails("", out var _));
+        Assert.False(TZConvert.TryWindowsToRails(" ", out var _));
+        Assert.False(TZConvert.TryWindowsToRails("blah", out var _));
+    }
+
+#pragma warning restore CS8625
+}