Exception in VS2017 Community

[davegi]

As soon as the 'Generating mapping code" context menu gains focus:

System.NullReferenceException : Object reference not set to an instance of an object. at MappingGenerator.MappingGenerator.<MapTypes>d__4.MoveNext() at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() at Microsoft.CodeAnalysis.SyntaxList1.CreateNode(IEnumerable1 nodes) at Microsoft.CodeAnalysis.CSharp.CodeGeneration.CSharpSyntaxGenerator.AsStatementList(IEnumerable1 nodes) at Microsoft.CodeAnalysis.CSharp.CodeGeneration.CSharpSyntaxGenerator.CreateBlock(IEnumerable1 statements) at Microsoft.CodeAnalysis.CSharp.CodeGeneration.CSharpSyntaxGenerator.MethodDeclaration(String name,IEnumerable1 parameters,IEnumerable1 typeParameters,SyntaxNode returnType,Accessibility accessibility,DeclarationModifiers modifiers,IEnumerable1 statements) at Microsoft.CodeAnalysis.Editing.SyntaxGenerator.MethodDeclaration(IMethodSymbol method,String name,IEnumerable1 statements) at async MappingGenerator.MappingGeneratorCodeFixProvider.GenerateMappingMethodBody(<Unknown Parameters>) at async Microsoft.CodeAnalysis.CodeActions.CodeAction.GetChangedSolutionAsync(<Unknown Parameters>) at async Microsoft.CodeAnalysis.CodeActions.CodeAction.ComputeOperationsAsync(<Unknown Parameters>) at async Microsoft.CodeAnalysis.CodeActions.CodeAction.ComputePreviewOperationsAsync(<Unknown Parameters>) at async Microsoft.CodeAnalysis.CodeActions.CodeAction.GetPreviewOperationsAsync(<Unknown Parameters>) at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedAction.GetPreviewResultAsync(<Unknown Parameters>) at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedActionWithNestedFlavors.<>c__DisplayClass11_0.<GetPreviewAsync>b__0(<Unknown Parameters>) at async Microsoft.CodeAnalysis.Extensions.IExtensionManagerExtensions.PerformFunctionAsync[T](<Unknown Parameters>)

[cezarypiatek]

It's really hard to diagnose without example. Please provide code where you are trying to apply generator. (Source and target class definitions and mapping method)

[davegi]

Yeah...I figured it would be but was hopeful that the ST would be enough:-).

The Quick Action "Implementation of mapping method can be generated" appears on the first line of the following .ctor:

public SegmentedString(Option<string> @string) : this(string.Empty, @string, string.Empty) { }

Option is a type defined in the library lang-ext.

As mentioned, as soon as the MG menu item gains focus in the Quick Action context menu...boom...VS displays the extension error bar; "MappingGeneratorCodeFixProvider encountered an error and has been disabled", w/ the link for the ST, and buttons to re-enable.

Hope this is more helpful.

[cezarypiatek]

@davegi you forgot about SegmentedString class definition.

[davegi]

Sorry...I realize that you asked for the class definition but I read .ctor...here's the definition:
`

[Pure]
public class SegmentedString {
    private readonly string @string = string.Empty;
    private readonly string begin = string.Empty;
    private readonly string middle = string.Empty;
    private readonly string end = string.Empty;

    public SegmentedString(Option<string> @string)
        : this(string.Empty, @string, string.Empty) {
    }

    public SegmentedString(Option<string> begin, Option<string> middle, Option<string> end) {
        this.begin = begin.IfNone(string.Empty);
        this.middle = middle.IfNone(string.Empty);
        this.end = end.IfNone(string.Empty);

        this.@string = this.begin + this.middle + this.end;
    }

    public Option<SegmentedString> Begin => Option<SegmentedString>.Some(Option<string>.Some(this.begin));

    public Option<SegmentedString> Middle => Option<SegmentedString>.Some(Option<string>.Some(this.middle));

    public Option<SegmentedString> End => Option<SegmentedString>.Some(Option<string>.Some(this.end));

    public static implicit operator SegmentedString(Option<string> @string) => new SegmentedString(string.Empty, @string, string.Empty);

    public static implicit operator SegmentedString(string @string) => new SegmentedString(string.Empty, Option<string>.Some(@string), string.Empty);

    public static implicit operator SegmentedString((Option<string> begin, Option<string> middle, Option<string> end) @string) => new SegmentedString(@string.begin, @string.middle, @string.end);

    public static implicit operator SegmentedString(Option<ValueTuple<string, string, string>> @string) => @string;

    public static implicit operator string(SegmentedString segmentedStringEx) => segmentedStringEx.ToString();

    public override string ToString() => this.@string;
}

`
And the method in question is:

public SegmentedString(Option<string> @string) : this(string.Empty, @string, string.Empty) { }

[cezarypiatek]

Thanks, I will investigate it later.

[cezarypiatek]

It looks like the readonly properties are the culprit. This issue has been fixed on develop branch and new version should be release in few days.

By the way, currently MappingGenerator maps only properties, but not fields. I will take this option under advisement.