Refactoring provider to convert regular string to interpolated string

[louis-z]

Fixes #48219

The refactoring is offered for regular string literals that

• contain either '{' or '}', and
• are not assigned to a constant

[Youssef1313]

This is less repetitive, and IMO still readable.

Suggested change

	=> isVerbatim
	? text.Substring("@'".Length, text.Length - "@''".Length)
	: text.Substring("'".Length, text.Length - "''".Length);
	=> text[(isVerbatim ? "@'" : "'").Length..];

[davidwengier]

That's not the same result, you're missing ^1 on the end.

Personally I find it confusing that this uses the string length of a literal to work out how many characters to remove, particularly as the literals don't have the right quotation marks in them, nor would the text in question have double quotes. I also don't see why this can't be in the language agnostic layer, since isVerbatim will always be false for VB anyway. I would simply write this as:

private static string GetTextWithoutQuotes(string text, bool isVerbatim)
{
    // Trim off an extra character for the @ symbol for verbatim strings
	var startIndex = isVerbatim ? 2 : 1;
	return text[startIndex..^1];
}

[CyrusNajmabadi]

also, please onl yhave this refactoring if there are no diagnotics on the expr. and probably a good time to ensure that the string is terminated. and pleas have test for thie case "foo{ (i.e. an unterminated literal).

[louis-z]

That's not the same result, you're missing ^1 on the end.

Personally I find it confusing that this uses the string length of a literal to work out how many characters to remove, particularly as the literals don't have the right quotation marks in them, nor would the text in question have double quotes. I also don't see why this can't be in the language agnostic layer, since isVerbatim will always be false for VB anyway. I would simply write this as:

private static string GetTextWithoutQuotes(string text, bool isVerbatim)
{
    // Trim off an extra character for the @ symbol for verbatim strings
	var startIndex = isVerbatim ? 2 : 1;
	return text[startIndex..^1];
}

I agree, this is a better way of doing things.

(The code I used was copied from https://github.com/dotnet/roslyn/blob/master/src/Features/CSharp/Portable/ConvertToInterpolatedString/CSharpConvertConcatenationToInterpolatedStringRefactoringProvider.cs#L25)

[CyrusNajmabadi]

feel free to extract all of this into a helper utilities class they can both call into.

[Youssef1313]

Does something like the following work?

public class C
{
    public void M(string code = @"class Program{}")
    {
    }
}

If it works, add a test for it.
If it doesn't work, then this is an edge case that IMO can be addressed later, but it's up to the team whether they want it in this PR or to be addressed later. (I think it may not be hard to add it if it doesn't currently work)

Just noticed how crap I just wrote 😄
This may be something to check with const interpolated strings if it came with C# 10.

[davidwengier]

That's not the same result, you're missing ^1 on the end.

Personally I find it confusing that this uses the string length of a literal to work out how many characters to remove, particularly as the literals don't have the right quotation marks in them, nor would the text in question have double quotes. I also don't see why this can't be in the language agnostic layer, since isVerbatim will always be false for VB anyway. I would simply write this as:

private static string GetTextWithoutQuotes(string text, bool isVerbatim)
{
    // Trim off an extra character for the @ symbol for verbatim strings
	var startIndex = isVerbatim ? 2 : 1;
	return text[startIndex..^1];
}

[CyrusNajmabadi]

Could you show a picture of the refactoring and lightbulb?

[CyrusNajmabadi]

Suggested change

	var startToken = generator.CreateInterpolatedStringStartToken(isVerbatimStringLiteral)
	.WithLeadingTrivia(literalExpression.GetLeadingTrivia());
	var endToken = generator.CreateInterpolatedStringEndToken()
	.WithTrailingTrivia(literalExpression.GetTrailingTrivia());
	var startToken = generator.CreateInterpolatedStringStartToken(isVerbatimStringLiteral).WithLeadingTrivia(literalExpression.GetLeadingTrivia());
	var endToken = generator.CreateInterpolatedStringEndToken().WithTrailingTrivia(literalExpression.GetTrailingTrivia());

[CyrusNajmabadi]

Very close IMO. Only need some minor changes.

[louis-z]

@CyrusNajmabadi, there are still a few unresolved conversations... Personally I feel they are not showstoppers, but LMK if you feel otherwise and I will attempt to address them.

And thanks again for all your input.

[louis-z]

Hey @CyrusNajmabadi, I noticed some checks had failed. Do I need to do anything else on my end to get the PR merged? Do you need me to rebase?

[CyrusNajmabadi]

rerunning test now. LMK when you're green :)

[louis-z]

Still not green. :(

[louis-z]

Ok @CyrusNajmabadi, we're good to go. 😉

[CyrusNajmabadi]

Awesome!

[CyrusNajmabadi]

thanks!