dotnet/roslyn

InterpolatedStringExpression inserts a space on its own.

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#39,923 opened on Nov 21, 2019

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Area-AnalyzersBughelp wanted

Description

Version Used: 3.3.1 Steps to Reproduce:

Dim Workspace As New AdhocWorkspace()

Dim generator As SyntaxGenerator = SyntaxGenerator.GetGenerator(Workspace, LanguageNames.VisualBasic)

Dim InterpolationBroken As SyntaxNode = VisualBasic.SyntaxFactory.InterpolatedStringExpression(New SyntaxList(Of VisualBasic.Syntax.InterpolatedStringContentSyntax)({
                                                                                                                                                                             VisualBasic.SyntaxFactory.Interpolation(generator.IdentifierName("uApp.AccentColor.ToString")),
                                                                                                                                                                             VisualBasic.SyntaxFactory.Interpolation(VisualBasic.SyntaxFactory.ParseExpression("If(uApp.ThemeIsDark,""Dark"","""")"))}))

Dim InterpolationWorking As SyntaxNode = VisualBasic.SyntaxFactory.InterpolatedStringExpression(New SyntaxList(Of VisualBasic.Syntax.InterpolatedStringContentSyntax)({
                                                                                                                                                                              VisualBasic.SyntaxFactory.Interpolation(generator.IdentifierName("uApp.AccentColor.ToString")),
                                                                                                                                                                              VisualBasic.SyntaxFactory.InterpolatedStringText(VisualBasic.SyntaxFactory.InterpolatedStringTextToken("", "")),
                                                                                                                                                                              VisualBasic.SyntaxFactory.Interpolation(VisualBasic.SyntaxFactory.ParseExpression("If(uApp.ThemeIsDark,""Dark"","""")"))}))

Dim txtoutputBroken = generator.CompilationUnit(generator.ExpressionStatement(InterpolationBroken)).NormalizeWhitespace

Dim txtoutputWorking = generator.CompilationUnit(generator.ExpressionStatement(InterpolationWorking)).NormalizeWhitespace

Expected Behavior: Output Stirng should be $"{uApp.AccentColor.ToString}{If(uApp.ThemeIsDark, "Dark", "")}" No added space between the Interpolations

Actual Behavior: Current output string is $"{uApp.AccentColor.ToString} {If(uApp.ThemeIsDark, "Dark", "")}" With a space between the Interpolations

I had to manually add a InterpolatedStringText with a empty string to make the space between the two Interpolations not appear. I don't understand why it is adding the space by default, messing up the formatting of the output string.

Contributor guide

Tech stack
csharp
Domain
developer experiencetooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic knowledge of Roslyn APIUnderstanding of VB interpolated strings
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Investigate the NormalizeWhitespace method in the Roslyn codebase, specifically how it handles InterpolatedStringExpression containing multiple Interpolation nodes. The bug suggests that a space is incorrectly inserted between interpolations. Look at the formatting logic in the Visual Basic syntax formatting classes, likely in the SyntaxNormalizer or whitespace normalizer. Check if there is a missing check for adjacent interpolations that should not have whitespace. The fix would likely be a small change in the formatting rules.