Is there a way to enforce using tabs instead of spaces?

Question

StyleCop offers to check for consistent use of spaces, but sadly lacks the opposite idea: Force source code to use tabs. Is there some way to add this functionality? It does not have to be StyleCop, other tools are welcome as well.

Answer 1

I'm a tabs-not-spaces person, too, though there are plenty of reasons to use either one and there are other places to get into why you think one is better than the other. :)

I actually wanted the same thing - a rule to check for tab indents - so I wrote it based on the SpacingRules source from StyleCop. It seems to work reasonably well, though I've only used it on a few projects so far. It could probably be optimized or whatever... but it works.

using System;
using System.Text.RegularExpressions;
using Microsoft.StyleCop;
using Microsoft.StyleCop.CSharp;

namespace CustomRules.StyleCop.CSharp
{
  [SourceAnalyzer(typeof(CsParser))]
  public class SpacingRules : SourceAnalyzer
  {
    public SpacingRules()
    {
    }

    public override void AnalyzeDocument(CodeDocument document)
    {
      Param.RequireNotNull(document, "document");

      CsDocument csdocument = (CsDocument)document;
      if (csdocument.RootElement != null && !csdocument.RootElement.Generated)
      {
        this.CheckSpacing(csdocument.Tokens);
      }
    }

    private void CheckSpacing(MasterList<CsToken> tokens)
    {
      Param.AssertNotNull(tokens, "tokens");

      foreach (var token in tokens)
      {
        if (this.Cancel)
        {
          break;
        }

        if (token.Generated)
        {
          continue;
        }

        switch (token.CsTokenType)
        {
          case CsTokenType.WhiteSpace:
            this.CheckWhitespace(token as Whitespace);
            break;

          case CsTokenType.XmlHeader:
            XmlHeader header = (XmlHeader)token;
            foreach (var xmlChild in header.ChildTokens)
            {
              this.CheckTabsInComment(xmlChild);
            }
            break;

          case CsTokenType.SingleLineComment:
          case CsTokenType.MultiLineComment:
            this.CheckTabsInComment(token);
            break;
        }

        switch (token.CsTokenClass)
        {
          case CsTokenClass.ConstructorConstraint:
            this.CheckSpacing(((ConstructorConstraint)token).ChildTokens);
            break;

          case CsTokenClass.GenericType:
            this.CheckGenericSpacing((GenericType)token);
            this.CheckSpacing(((TypeToken)token).ChildTokens);
            break;

          case CsTokenClass.Type:
            this.CheckSpacing(((TypeToken)token).ChildTokens);
            break;
        }
      }
    }

    private void CheckGenericSpacing(GenericType generic)
    {
      Param.AssertNotNull(generic, "generic");
      if (generic.ChildTokens.Count == 0)
      {
        return;
      }

      foreach (var token in generic.ChildTokens)
      {
        if (this.Cancel)
        {
          break;
        }

        if (token.CsTokenClass == CsTokenClass.GenericType)
        {
          this.CheckGenericSpacing(token as GenericType);
        }

        if (!token.Generated && token.CsTokenType == CsTokenType.WhiteSpace)
        {
          this.CheckWhitespace(token as Whitespace);
        }
      }
    }

    private void CheckWhitespace(Whitespace whitespace)
    {
      Param.AssertNotNull(whitespace, "whitespace");

      if (whitespace.Location.StartPoint.IndexOnLine == 0 && Regex.IsMatch(whitespace.Text, "^ +"))
      {
        this.AddViolation(whitespace.FindParentElement(), whitespace.LineNumber, "TabsMustBeUsed");
      }
    }

    private void CheckTabsInComment(CsToken comment)
    {
      Param.AssertNotNull(comment, "comment");

      var lines = comment.Text.Split('\n');
      for (int i = 0; i < lines.Length; i++)
      {
        if (Regex.IsMatch(lines[i], "^ +"))
        {
          this.AddViolation(comment.FindParentElement(), comment.LineNumber + i, "TabsMustBeUsed");
        }
      }
    }
  }
}

Note that you also have to have the embedded XML file "SpacingRules.xml" in the assembly alongside this thing. (Read the StyleCop SDK doc for more on that.)

<?xml version="1.0" encoding="utf-8" ?>
<SourceAnalyzer Name="Custom Spacing Rules">
  <Description>
    Rules which verify the spacing placed between keywords and symbols in the code.
  </Description>
  <Rules>
    <Rule Name="TabsMustBeUsed" CheckId="MY1027">
      <Context>Spaces are not allowed. Use tabs instead.</Context>
      <Description>Verifies that the code does not contain spaces.</Description>
    </Rule>
  </Rules>
</SourceAnalyzer>