Configuration system throws PlatformNotSupportedException on Xamarin Android.

[borrrden]

Description

Configuration system throws PlatformNotSupportedException on Xamarin Android.

Complete minimal example reproducing the issue

3.Should().BeGreaterThan(4); // Probably any failing test?

Expected behavior:

The normal assertion failure process

Actual behavior:

The following Exception is thrown:

System.PlatformNotSupportedException : Operation is not supported on this platform.
 		  at System.Configuration.ConfigurationManager.PrepareConfigSystem () [0x0001a] in <4cd8a957e7664f4a9e27ce43dd1afeb7>:0 
 		  at System.Configuration.ConfigurationManager.GetSection (System.String sectionName) [0x0000a] in <4cd8a957e7664f4a9e27ce43dd1afeb7>:0 
 		  at System.Configuration.ConfigurationManager.get_AppSettings () [0x00000] in <4cd8a957e7664f4a9e27ce43dd1afeb7>:0 
		  at FluentAssertions.Common.AppSettingsConfigurationStore.GetSetting (System.String name) [0x00000] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Common.Configuration.get_ValueFormatterAssembly () [0x00008] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Common.Configuration.DetermineFormatterDetectionMode () [0x00000] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Common.Configuration.get_ValueFormatterDetectionMode () [0x0001e] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Formatting.AttributeBasedFormatter.get_IsScanningEnabled () [0x00005] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Formatting.AttributeBasedFormatter.CanHandle (System.Object value) [0x00000] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Formatting.Formatter+<>c__DisplayClass7_0.<Format>b__0 (FluentAssertions.Formatting.IValueFormatter f) [0x00000] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at System.Linq.Enumerable.TryGetFirst[TSource] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] predicate, System.Boolean& found) [0x0003f] in <15cecf952ca44136ad5b83afa233f6f3>:0 
 		  at System.Linq.Enumerable.First[TSource] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] predicate) [0x00000] in <15cecf952ca44136ad5b83afa233f6f3>:0 
 		  at FluentAssertions.Formatting.Formatter.Format (System.Object value, FluentAssertions.Formatting.FormattingContext context, FluentAssertions.Formatting.FormatChild formatChild) [0x00012] in <d52b982f9eb24747b8fd904dff0631fe>:0 
		  at FluentAssertions.Formatting.Formatter.ToString (System.Object value, System.Boolean useLineBreaks) [0x00054] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.MessageBuilder.<FormatArgumentPlaceholders>b__6_0 (System.Object a) [0x00000] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at System.Linq.Enumerable+SelectArrayIterator`2[TSource,TResult].ToArray () [0x00012] in <15cecf952ca44136ad5b83afa233f6f3>:0 
		  at System.Linq.Enumerable.ToArray[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0001f] in <15cecf952ca44136ad5b83afa233f6f3>:0 
 		  at FluentAssertions.Execution.MessageBuilder.FormatArgumentPlaceholders (System.String failureMessage, System.Object[] failureArgs) [0x00012] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.MessageBuilder.Build (System.String message, System.Object[] messageArgs, System.String reason, FluentAssertions.Execution.ContextDataItems contextData, System.String identifier, System.String fallbackIdentifier) [0x00036] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.AssertionScope+<>c__DisplayClass30_0.<FailWith>b__0 () [0x00055] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.AssertionScope.FailWith (System.Func`1[TResult] failReasonFunc) [0x0001a] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.AssertionScope.FailWith (System.Func`1[TResult] failReasonFunc) [0x00014] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Execution.AssertionScope.FailWith (System.String message, System.Object[] args) [0x00014] in <d52b982f9eb24747b8fd904dff0631fe>:0 
 		  at FluentAssertions.Numeric.NumericAssertions`1[T].BeGreaterThan (T expected, System.String because, System.Object[] becauseArgs) [0x0004c] in <d52b982f9eb24747b8fd904dff0631fe>:0 

Versions

FluentAssertions 5.9.0
Xamarin.Android SDK 9.1.7.0 (HEAD/ba9da7a76)
Emulator 27.3.9-4899998 API 27 (x86)

[dennisdoomen]

Which platform-variant of FA is it picking up? You can determine that from the folder name that points to the DLL from your project.

[borrrden]

I'm not quite sure what that means, but dotPeek tells me it is the .NET Standard 2.0 variant.

[borrrden]

It looks like ConfigurationManager is not supported on Xamarin or UWP

The recommendation from the Xamarin Forms team is to use Xamarin.Essentials.Preferences instead.

[dennisdoomen]

Yeah, strangely it does compile, so something must have changed. We'll need to fix that.

[borrrden]

I imagine it compiles because of the odd Microsoft policy that it is acceptable for things to be part of the .NET Standard, but then throw not supported exceptions on platforms that are not applicable....

[jnyrup]

Some different possibilities.

1. Wrap calls to Configuration.AppSettings in try/catch.
   • Easiest to implement, but still leaves Xamarin users without the ability to set settings.
2. Somehow detect that Configuration.AppSettings is unavailable and avoid invoking it.
   • Much like 1) but avoids the exception control flow
3. Add target frameworks for xamarin/uwp and use the suggested Preferences.
   • Adds more target frameworks to support...
4. Remove references to System.Configuration and expose the three settings as properties on e.g. a static Settings class.
   • pro: Fewer dependencies
   • pro: Will support Xamarin
   • con: Breaking change

[dennisdoomen]

Or we keep the current Configuration abstraction, but introduce an in-memory decorator that intercepts any exceptions while accessing the AppSettingsConfigurationStore and which falls back to local state,

[SteveBush]

A variation on jnyrup suggestions would be in the set the ConfigurationStore to a NullConfigurationStore(); if accessing a setting throws an exception.

pros:

• ConfigurationStore is available to platforms that support it.
• Exception handling only on assignment of ConfigurationStore
• Unblocks Android users :)

cons:

• Unsupported platforms cannot set settings

---

#if NETSTANDARD1_3
    Reflector = new NullReflector();
    ConfigurationStore = new NullConfigurationStore();
#elif NETSTANDARD1_6
    Reflector = new NetStandardReflector();
    ConfigurationStore = new NullConfigurationStore();
#else
    Reflector = new FullFrameworkReflector();
    ConfigurationStore = new AppSettingsConfigurationStore();

// try to use the ConfigurationStore, catch any exceptions 
// and set ConfigurationStore to NullConfigurationStore(); on exception.  

#endif

[dennisdoomen]

That's exactly what I proposed as well ;-)

[akamud]

The fix is exactly what I did for my project.

[dennisdoomen]

@jnyrup why was it moved to 6.0? You're envisioning a breaking change?

[jnyrup]

I put this in the 6.0 milestone to make sure we at latest fix it there.
I haven't really thought about whether it will introduce any breaking changes.

[jnyrup]

Fixed in #1210, which is included in 5.10.0