Need to evaluate whether any C# 6 features will require changes to the Razor parser

[Eilon]

Please don't close this bug until the C#6 features are finalized (which won't be any time soon). We can use this bug to track potential changes we might need to make to Razor. E.g. imagine a new C# 6 feature has some additional @ signs in it somewhere - we'll likely have to adapt to that.

[yishaigalatzer]

@NTaylorMullen let us verify out var in a functions block, and ?. @Foo.FirstOrDefault()?.Something

[NTaylorMullen]

?. breaks rendering.

[dougbu]

please be more specific about the exact way you're using ?. and what gets broken. also does the breakage vary depending on

• what's on either side of the ?. e.g. (foo as Bar)?.Beez versus foo?.bar ?
• whether you use ?. or ?[ e.g. foo?.bar versus foo?[bar] or foo?[42] ?

[NTaylorMullen]

@DateTime?.Now Generates:

Write(DateTime);
WriteLiteral("?.Now");

When it should generate:

Write(DateTime?.Now);

[Eilon]

Also need to support exception filters:

Today with this code:

try
{
    throw new InvalidOperationException();
}
    catch (Exception e) if (e.Message.Contains("Operation is not valid"))
{
}

You get this error

CompilationFailedException: Compilation for 'c:\users\mattgal\documents\visual studio 2015\Projects\WebApplication1\src\WebApplication1\Views\Home\Index.cshtml' failed:
Expected a "{" but found a "if". Block statements must be enclosed in "{" and "}". You cannot use single-statement control-flow statements in CSHTML pages. For example, the following is not allowed:

@if(isLoggedIn)
<p>Hello, @user</p>

Instead, wrap the contents of the block in "{}":

@if(isLoggedIn) {
<p>Hello, @user</p>
} 

From TFS bug 1099131.

[NTaylorMullen]

I investigated and it looks like the only pieces that aren't working are:

1. Exception Filters
2. Null-Conditional for expressions (works fine in statement blocks)

/cc @DamianEdwards Do you feel strongly one way or the other about exception filters making it?

[Eilon]

Just making sure these are tested:

_Using Static Members_

• Tricky because it could change how we parse @using ... (or maybe not)

using static System.Console;

_Expression-bodied members_

• Tricky because there's an extra > where we might not expect it (or maybe not)

public double Dist => Sqrt(X * X + Y * Y);  

_String interpolation_

• Tricky because all kinds of weird stuff can happen inside a string

$"{p.Name} is {p.Age} years old."  

var @class = "History";
var happiness = 6;
$"I like taking {@class} class? {(happiness > 5).ToString()}."  

[NTaylorMullen]

Status

_Null Conditional Operators_ Breaks by using them in implicit expressions such as @Foo?.Bar, @Foo?[0].

Fixed: 58c0a36200727b449996242ec9976f8f9fd1e612

_Using Static Members_ Breaks in the scenario @Eilon mentioned: @using static System.Console

Fixed: 1879ac642754b5f84e6055580e6fc60e13fa2100

_String Interpolation_ Breaks in the following scenario.

@{
    $"abc{"123\""}.def";
}

Note the \" in combination with the {" from the string interpolation cause the chaos and results in the } being treated as the end of the @{ block.

https://github.com/aspnet/Razor/issues/401

_Exception Filters_ Breaks by using them :trollface:

https://github.com/aspnet/Razor/issues/402

Conclusion

I'm addressing each of these issues (in order mentioned) and associating their fixes with this issue. If needed I can break them into separate issues.

[dougbu]

What about the following features within a c# block?

• new dictionary indexer initialization syntax
• nameof operator (probably works, just confirming)
• await in catch and finally blocks (probably work and very minor since try is unusual in Razor source)

[NTaylorMullen]

@dougbu Yup, all of those work :smile:

[NTaylorMullen]

Investigated string interpolation and the fix for it is relatively complex. Talked to @DamianEdwards about prioritization and it's not a must-have for beta5. Will file two separate issues for exception filters and string interpolation so I can close this issue out in regards to null conditional operators and static usings once I've completed them.

[NTaylorMullen]

58c0a36200727b449996242ec9976f8f9fd1e612 1879ac642754b5f84e6055580e6fc60e13fa2100