How deal with input strings containing the default escape character `\`

[mysupply-jlm]

Hi! Thanks for reporting this bug!

Please fill in the relevant information from this template so that we can help you best.

Smart.Format version: 3.5.3

Framework version: net8.0
Microsoft Visual Studio Professional 2022, Version 17.12.4

• Please provide a working source code example to reproduce the bug:

            // This will throw the exception 'Unrecognized escape sequence "\M" in literal.')
            Dictionary<string, string> keyValuePairs = new Dictionary<string, string>();

            string value = @"localhost\MSSQL2019";
            string updated = Smart.Format(value, keyValuePairs);

• What is the current result?
  Two excaped backslash is reduced to one excaped backslash.
  One excaped backslash is seen as a escape charater, and will throw the exception 'Unrecognized escape sequence "\M" in literal.'

• What is the expected result?
  That Smart.Format did not change the value / can handle a text string with a backslash.

• Please post full exception details if applicable (message, stacktrace, inner exceptions)

   at SmartFormat.Core.Parsing.EscapedLiteral.UnEscapeCharLiterals(Char escapingSequenceStart, ReadOnlySpan`1 input, Boolean includeFormatterOptionChars, Span`1 resultBuffer)
   at SmartFormat.Core.Parsing.LiteralText.AsSpan()
   at SmartFormat.Core.Parsing.LiteralText.ToString()
   at SmartFormat.Evaluator.WriteFormat(FormattingInfo formattingInfo)
   at SmartFormat.SmartFormatter.ExecuteFormattingAction(SmartFormatter formatter, IFormatProvider provider, Format formatParsed, IList`1 args, IOutput output, Action`1 doWork)
   at SmartFormat.SmartFormatter.FormatInto(IOutput output, IFormatProvider provider, Format formatParsed, IList`1 args)
   at SmartFormat.SmartFormatter.Format(IFormatProvider provider, Format formatParsed, IList`1 args)
   at SmartFormat.SmartFormatter.Format(IFormatProvider provider, String format, IList`1 args)
   at SmartFormat.SmartFormatter.Format(String format, Object[] args)
   at SmartFormat.Smart.Format(String format, Object arg0)
   at TaskSchedulerServer.UnitTest.TaskScheduler.Utilities.ConfigurationResultUtilTest.ThisWillFail() in ....

• Did you find a workaround? yes/no
  No.

• Is there a version in which it worked?
  Don't know

• Can you help us by writing an unit test?

This illustrate the problem, that two excaped backslash is reduced to one excaped backslash

[Fact]
 public void ValueShouldNotHaveBeenUpdated()
 {            
     IDictionary<string, string> keyValuePairs = new Dictionary<string, string>();

     string value = @"localhost\\MSSQL2019";
     string updated = Smart.Format(value, keyValuePairs);

     Assert.Equal(value, updated);

     /*
     Assert.Equal() Failure: Strings differ
                           ↓ (pos 10)
     Expected: "localhost\\\\MSSQL2019"
     Actual:   "localhost\\MSSQL2019"
                           ↑ (pos 10)
      */
 }       

This demonstrate who Smart.Format, first reduce the two excaped backslash to one, and then see excaped backslash, as a escape charater.

[Fact]
public void ThisWillFail()
{
    try
    {
        IDictionary<string, string> keyValuePairs = new Dictionary<string, string>();
        keyValuePairs["key"] = "value";

        string server = "localhost\\\\MSSQL2019";
        // Server value is 'localhost\\MSSQL2019' - Note the double backslash.

        // This will replace the double backslash, with one backslash
        server = Smart.Format(server, keyValuePairs);
        // Server value is now 'localhost\MSSQL2019' only one backslash

        // If I now try to use the server value, with one backslash,
        // it will throw an exception: 'Unrecognized escape sequence "\M" in literal.'
        server = Smart.Format(server, keyValuePairs);
    }
    catch (Exception ex)
    {
        Assert.Fail(ex.Message);
    }
}

Jacob Mogensen
mySupply ApS
Denmark

[mysupply-jlm]

Is this issue kind of the same problem as Issue 200?

Jacob Mogensen
mySupply ApS
Denmark

[axunonb]

The exception is causes by a disallowed escape sequence -\M in particular.

There are 2 alternatives so resolve this issue, especially when the input string is not under your control:

1. Disable conversion of character string literals:

Smart.Default.Settings.Parser.ConvertCharacterStringLiterals = false;
var result = Smart.Format(@"abc\MSD");
// result is ""abc\MSD"

2. Choose another escape character (is must not interfere with other reserved characters like {}[] and others

Smart.Default.Settings.Parser.CharLiteralEscapeChar = '^';
var result = Smart.Format(@"abc\MSD");
// result is ""abc\MSD"

See also this section in the Wiki..

Please let us know what would have helped you to resolve the issue by yourself?
Any suggestions are welcome.