Better error message when the creation of the instantiation expression fails #2421
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src/AutoMapper/ConstructorMap.cs
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| public Expression NewExpression(Expression instanceParameter) | ||
| { | ||
| var parameters = CtorParams.Select(map => | ||
| try |
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I don't think we need the extra try/catch. Some exceptions are really bugs and need no user friendly messages.
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| namespace AutoMapper.QueryableExtensions | ||
| { | ||
| public class BuilderException : Exception |
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I don't think we need a new exception type here. AutoMapperMappingException should do. Just pass it the types so it's easy to understand what's going on.
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Uses now AutoMapperMappingException
| { | ||
| cfg.CreateMap<EntitySource, EntityDestination>(); | ||
| }); | ||
| var exception = Assert.Throws<BuilderException>(() => config.ExpressionBuilder.GetMapExpression<EntitySource, EntityDestination>()); |
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ProjectTo is the API, so the test should call that. GetMapExpression is just an internal thing.
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ProjectTo is now used by unit test.
src/AutoMapper/ConstructorMap.cs
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| result = matchingExpressionConverter?.GetExpressionResolutionResult(result, map) | ||
| ?? throw new Exception("Can't resolve this to Queryable Expression"); | ||
| result = matchingExpressionConverter?.GetExpressionResolutionResult(result, map) | ||
| ?? throw new AutoMapperMappingException($"Unable to generate the instantiation expression for the constructor {Ctor}: no expression could be mapped for constructor parameter '{map.Parameter}'.", null, TypeMap.Types, null, null); |
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The last two nulls are not needed.
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While defining a new mapping between two classes, I was getting a mysterious
Can't resolve this to Queryable Expressionerror message. The message was not meaningful enough so I had to debug AutoMapper to understand what the problem was. I simply had to tell AutoMapper which constructor had to be used...This PR intends to generate a more explanatory error message.