[SR-10241] A way to get raw string without quotes from StringLiteralExprSyntax

[swift-ci]

Previous ID	SR-10241
Radar	None
Original Reporter	kitasuke (JIRA User)
Type	Improvement
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	SwiftSyntax
Labels	Improvement
Assignee	kitasuke (JIRA)
Priority	Medium

md5: 0345f8455f9bcaa284679f0dc943b32a

relates to:

• SR-10469 Unknown syntax for interpolated string literal

Issue Description:

Background
I would like to have a better way to extract raw string without quotes from `StringLiteralExprSyntax`. `StringInterpolationExprSyntax` looks well-organized because its cursor has openQuote, segments and closeQuote to express strings and quotes separately.

My proposal

Can we have quotes in children of StringLiteralExpr like StringInterpolationExpr?
https://github.com/apple/swift/blob/c04a7dec9f739fbe53f3c305a32e8d426972bfd8/utils/gyb_syntax_support/ExprNodes.py#L266:L269

https://github.com/apple/swift/blob/c04a7dec9f739fbe53f3c305a32e8d426972bfd8/utils/gyb_syntax_support/ExprNodes.py#L468:L481

References

Data structures and examples are below.

public struct StringLiteralExprSyntax: ExprSyntax, _SyntaxBase, Hashable {
  enum Cursor: Int {
    case stringLiteral
  }
}

// let foo = "foo"
print(node.stringLiteral.text) // "\"foo\""

public struct StringInterpolationExprSyntax: ExprSyntax, _SyntaxBase, Hashable {
  enum Cursor: Int {
    case openQuote
    case segments
    case closeQuote
  }
}

// let foo = "foo \(bar)"
print((node.segments[0] as! StringSegmentSyntax).content.text) // "foo"

[rintaro]

CC: @nkcsgexi @akyrtzi

[akyrtzi]

Seems good idea to me. The benefit is you will be able to structurally distinguish what kind of quotes (multiline or single) were used, instead of searching the string literal text string in order to distinguish.

If we do this we should probably get rid of 'string_literal' token kind and use 'string_segment' token kind for the non-interpolation case as well.

[swift-ci]

Comment by Yusuke Kita (JIRA)

Exactly.

Can I implement this fix? Seems quite interesting to dive into more details.

[akyrtzi]

Sure! Note that after changing the syntax definition file it would need a change on the C++ parser side.

[swift-ci]

Comment by Yusuke Kita (JIRA)

I have a question about literal expression for this. I'm looking into Parser and wondering whether I should extend 'StringLiteralExpr' or create new one like 'NonInterpolatedStringLiteralExpr'. Which one do you think is better? @akyrtzi

I figured out how 'string_segment' is parsed in 'parseExprStringLiteral' func, but I haven't had conclusion for the interface yet.

[rintaro]

I think we should generalize StringLiteralExpr.
Basically, syntax change would be:

• Remove StringLiteralExpr

• Rename StringInterpolationExpr to StringLiteralExpr

• Rename StringInterpolationSegments to StringLiteralSegment

like:

    Node('StringLiteralExpr', kind='Expr',
         children=[
             Child('OpenQuote', kind='Token',
                   token_choices=[
                       'StringQuoteToken',
                       'MultilineStringQuoteToken',
                   ]),
             Child('Segments', kind='StringLiteralSegments'),
             Child('CloseQuote', kind='Token',
                   token_choices=[
                       'StringQuoteToken',
                       'MultilineStringQuoteToken',
                   ]),
         ]),

We can easily check whether it's interpolated or not by (segments.count == 1 && segments[0] is StringSegmentToken)

[nkcsgexi]

I'm not a big fan of adding `NonInterpolatedStringLiteralExpr` either. The reason is users are likely to have two overrides for either visit or rewrite functions to handle all string literal cases. We should strive to help users reduce code duplication. However, feel free to add a convenient function to `StringLIteralExpr` indicating whether there are interpolations in the node.

[swift-ci]

Comment by Yusuke Kita (JIRA)

What Rintaro suggested makes sense to me. I'll go with `StringLiteralExpr` for the case. Thanks for your feedbacks!