Nemesis.TextParsers 2.9.1

• .NETStandard 2.0

  • System.Memory (>= 4.5.5)

• .NETStandard 2.1

  • System.Runtime.CompilerServices.Unsafe (>= 6.0.0)

• net6.0

  • No dependencies.

• net7.0

  • No dependencies.

# Release 2.9.1 - Source code generator for enum types

## What's Changed
* Implement source code generator for enum by @MichalBrylka in https://github.com/nemesissoft/Nemesis.TextParsers/pull/16

**Full Changelog**: https://github.com/nemesissoft/Nemesis.TextParsers/compare/v2.7.2...2.9.1

## Code generator for enum types
With this feature it is enough to annotate enum with 2 attributes:
```csharp
[Auto.AutoEnumTransformer(
   //1. optionally pass parser settings
   CaseInsensitive = true, AllowParsingNumerics = true,
   //2. TransformerClassName can be left blank. In that case the name of enum is used with "Transformer" suffix
   TransformerClassName = "MonthCodeGenTransformer",
   //3. optionally pass namespace to generate the transformer class within. If not provided the namespace of the enum will be used
   TransformerClassNamespace = "ABC"
)]
//4. decorate enum with TransformerAttribute that points to automatically generated transformer
[Transformer(typeof(ABC.MonthCodeGenTransformer))]
public enum Month : byte
{
   None = 0,
   January = 1, February = 2, March = 3,
   April = 4, May = 5, June = 6,
   July = 7, August = 8, September = 9,
   October = 10, November = 11, December = 12
}
```
This in turn generates the following parser using best practices (some lines are ommited for brevity):

<details>
<summary>Source code for generated parser</summary>

```csharp
public sealed class MonthCodeGenTransformer : TransformerBase<Nemesis.TextParsers.CodeGen.Sample.Month>
{
   public override string Format(Nemesis.TextParsers.CodeGen.Sample.Month element) => element switch
   {
       Nemesis.TextParsers.CodeGen.Sample.Month.None => nameof(Nemesis.TextParsers.CodeGen.Sample.Month.None),
       Nemesis.TextParsers.CodeGen.Sample.Month.January => nameof(Nemesis.TextParsers.CodeGen.Sample.Month.January),
       
       // ...

       Nemesis.TextParsers.CodeGen.Sample.Month.December => nameof(Nemesis.TextParsers.CodeGen.Sample.Month.December),
       _ => element.ToString("G"),
   };

   protected override Nemesis.TextParsers.CodeGen.Sample.Month ParseCore(in ReadOnlySpan<char> input) =>
       input.IsWhiteSpace() ? default : (Nemesis.TextParsers.CodeGen.Sample.Month)ParseElement(input);

   private static byte ParseElement(ReadOnlySpan<char> input)
   {
       if (input.IsEmpty || input.IsWhiteSpace()) return default;
       input = input.Trim();
       if (IsNumeric(input) && byte.TryParse(input
#if NETFRAMEWORK
   .ToString() //legacy frameworks do not support parsing from ReadOnlySpan<char>
#endif
           , out var number))
           return number;
       else
           return ParseName(input);


       static bool IsNumeric(ReadOnlySpan<char> input) =>
           input.Length > 0 && input[0] is var first &&
           (char.IsDigit(first) || first is '-' or '+');    
   }

   private static byte ParseName(ReadOnlySpan<char> input)
   {    
       if (IsEqual(input, nameof(Nemesis.TextParsers.CodeGen.Sample.Month.None)))
           return (byte)Nemesis.TextParsers.CodeGen.Sample.Month.None;            

       else if (IsEqual(input, nameof(Nemesis.TextParsers.CodeGen.Sample.Month.January)))
           return (byte)Nemesis.TextParsers.CodeGen.Sample.Month.January;            

       else if (IsEqual(input, nameof(Nemesis.TextParsers.CodeGen.Sample.Month.February)))
           return (byte)Nemesis.TextParsers.CodeGen.Sample.Month.February;            

       // ...         

       else if (IsEqual(input, nameof(Nemesis.TextParsers.CodeGen.Sample.Month.December)))
           return (byte)Nemesis.TextParsers.CodeGen.Sample.Month.December;            

       else throw new FormatException(@$"Enum of type 'Nemesis.TextParsers.CodeGen.Sample.Month' cannot be parsed from '{input.ToString()}'.
Valid values are: [None or January or February or March or April or May or June or July or August or September or October or November or December] or number within byte range.
Ignore case option on.");        

       static bool IsEqual(ReadOnlySpan<char> input, string label) =>
           MemoryExtensions.Equals(input, label.AsSpan(), StringComparison.OrdinalIgnoreCase);
   }
}
```

</details>