/// <summary>
/// Checks a string to determine whether it is using an incorrect empty string notation.
/// </summary>
/// <param name="text">The string to check.</param>
/// <param name="parentElement">The parent element.</param>
private void CheckEmptyString(Token text, Element parentElement)
{
Param.AssertNotNull(text, "text");
Param.AssertNotNull(parentElement, "parentElement");
Debug.Assert(text.TokenType == TokenType.String, "The token must be a string.");
if (string.Equals(text.Text, "\"\"", StringComparison.Ordinal) ||
string.Equals(text.Text, "@\"\"", StringComparison.Ordinal))
{
// Look at the previous token. If it is the 'case' keyword, then do not throw this
// exception. It is illegal to write case: String.Empty and instead case: "" must be written.
Token previousToken = text.FindPreviousToken();
if (previousToken == null || (previousToken.TokenType != TokenType.Case && !IsConstVariableDeclaration(previousToken)))
{
this.Violation(
Rules.UseStringEmptyForEmptyStrings,
new ViolationContext(parentElement, text.LineNumber),
(c, o) =>
{
// Fix the violation.
CsDocument document = text.Document;
// Create a member access expression which represents "string.Empty".
var stringEmpty = document.CreateMemberAccessExpression(document.CreateLiteralExpression("string"), document.CreateLiteralExpression("Empty"));
// The parent of the token should be a literal expression.
if (text.Parent != null && text.Parent.Is(ExpressionType.Literal))
{
document.Replace(text.Parent, stringEmpty);
}
else
{
Debug.Fail("Unhandled situation");
}
});
}
}
}
/// <summary>
/// Determines whether the statement is declaring a const field or variable.
/// </summary>
/// <param name="assignmentOperator">The assignment operator for the variable declaration.</param>
/// <returns>Returns true if the statement is declaring a const, false otherwise.</returns>
private static bool IsConstVariableDeclaration(Token assignmentOperator)
{
Param.Ignore(assignmentOperator);
if (assignmentOperator != null && assignmentOperator.Text == "=")
{
// Work backwards until we find the keyword const, or have moved past the beginning of the statement.
Token token = assignmentOperator.FindPreviousToken();
while (token != null)
{
if (token.TokenType == TokenType.CloseParenthesis ||
token.TokenType == TokenType.OpenParenthesis ||
token.TokenType == TokenType.OpenCurlyBracket ||
token.TokenType == TokenType.CloseCurlyBracket ||
token.TokenType == TokenType.Semicolon)
{
break;
}
else if (token.TokenType == TokenType.Const)
{
return true;
}
token = token.FindPreviousToken();
}
}
return false;
}
