[duplicate-code] Duplicate Code: IndentedStringBuilder Duplicated Across MSTest Source Generator Projects

[Evangelink]

🔍 Duplicate Code Detected: IndentedStringBuilder Duplicated Across Source Generators

Analysis of commit 3e056b0

Assignee: @copilot

Summary

The IndentedStringBuilder helper class — a StringBuilder wrapper that tracks an indentation level for source-code generation — is duplicated in two separate Roslyn source-generator projects: MSTest.SourceGeneration and MSTest.AotReflection.SourceGeneration. Both files implement the same core concept (append text with automatic indentation, open/close curly-brace blocks) with slightly different APIs but identical intent.

Duplication Details

Pattern: IndentedStringBuilder helper class

• Severity: Low-Medium
• Occurrences: 2 instances
• Locations:
  • src/Analyzers/MSTest.SourceGeneration/Helpers/IndentedStringBuilder.cs (83 lines)
  • src/Analyzers/MSTest.AotReflection.SourceGeneration/Helpers/IndentedStringBuilder.cs (92 lines)
• Code Sample (shared indent-tracking pattern):

// MSTest.SourceGeneration version uses IndentationLevel property:
public int IndentationLevel { get; internal set; }
public void Append(string value) { MaybeAppendIndent(); ... }
public void AppendLine(string value) { MaybeAppendIndent(); ... }
public IDisposable AppendBlock(string header) { AppendLine(header); AppendLine("{"); IndentationLevel++; ... }

// MSTest.AotReflection.SourceGeneration version uses _indent field:
private int _indent;
public IndentedStringBuilder Append(string value) { EnsureIndent(); ... return this; }
public IndentedStringBuilder AppendLine(string value) { EnsureIndent(); ... return this; }
public IDisposable Block(string? header = null) { ... _indent++; return new BlockScope(this); }

Both files share:

• Same concept of a StringBuilder wrapper tracking indentation
• Same nested IDisposable scope class to close {...} blocks automatically
• Same _needsIndent boolean to lazily insert indentation on the first write per line
• Same 4-space indent unit

Differences:

• Namespace (...SourceGeneration.Helpers vs MSTest.AotReflection.SourceGeneration.Helpers)
• The AotReflection version has a fluent (builder-style) API returning this; the SourceGeneration version returns void
• The AotReflection version uses _builder.AppendLine() (platform newline); the SourceGeneration version uses Constants.NewLine
• The inner scope class is named DisposableAction vs BlockScope
• The AotReflection version's comment explicitly notes it is a private PoC copy to avoid pulling in the SourceGeneration helper

Impact Analysis

• Maintainability: Any improvement to indentation handling (e.g., different indent widths, CR/LF normalization, performance optimization) must be applied to both files separately.
• Bug Risk: The APIs differ slightly, which can cause inconsistencies in generated code formatting between the two generators.
• Code Bloat: ~80 lines duplicated across the two source-generator projects.

Refactoring Recommendations

1. Unify into a shared Analyzers helper project:

   • Move a single IndentedStringBuilder with both void and fluent overloads to src/Analyzers/MSTest.Analyzers/Helpers/ (or a new shared analyzer helpers project)
   • Reference it from both MSTest.SourceGeneration and MSTest.AotReflection.SourceGeneration

2. Source-link via linked file:

   • Add the SourceGeneration version as a linked file in the AotReflection project:
     <Compile Include="../MSTest.SourceGeneration/Helpers/IndentedStringBuilder.cs" Link="Helpers/IndentedStringBuilder.cs" />
   • Standardize the API between the two projects first

3. Align APIs before consolidating:

   • Decide on fluent vs void return style and on Constants.NewLine vs Environment.NewLine
   • Estimated effort: 1–2 hours

Implementation Checklist

• Review duplication findings
• Align API (fluent vs void, newline handling)
• Extract to a shared location or use linked file
• Update both source generators to use the shared helper
• Verify generated source output is unchanged

Analysis Metadata

• Analyzed Files: 2
• Duplicated Lines: ~75 lines of shared logic
• Detection Method: Semantic code analysis + diff comparison
• Commit: 3e056b0
• Analysis Date: 2026-06-10

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Duplicate Code Detector workflow.{ai_credits_suffix} · [◷]( · ◷)

Add this agentic workflows to your repo

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/duplicate-code-detector.md@main

• expires on Jun 12, 2026, 5:55 AM UTC

[copilot-swe-agent]

The agent encountered an error and was unable to start working on this issue: Please try again later, or contact support if the problem persists. (Request id: 2028:2BF05B:2C0E0:A7FCD:6A28FC66)