/// <summary>
/// This method is to get the unique key for a UsingExpressionAst. The key is a base64
/// encoded string based on the text of the UsingExpressionAst.
///
/// This method is used when handling a script block that contains $using for Invoke-Command.
///
/// When run Invoke-Command targeting a machine that runs PSv3 or above, we pass a dictionary
/// to the remote end that contains the key of each UsingExpressionAst and its value. This method
/// is used to generate the key.
/// </summary>
/// <param name="usingAst">A using expression</param>
/// <returns>Base64 encoded string as the key of the UsingExpressionAst</returns>
internal static string GetUsingExpressionKey(Language.UsingExpressionAst usingAst)
{
Diagnostics.Assert(usingAst != null, "Caller makes sure the parameter is not null");
// We cannot call ToLowerInvariant unconditionally, because usingAst might
// contain IndexExpressionAst in its SubExpression, such as
// $using:bar["AAAA"]
// and the index "AAAA" might not get us the same value as "aaaa".
//
// But we do want a unique key to represent the same UsingExpressionAst's as much
// as possible, so as to avoid sending redundant key-value's to remote machine.
// As a workaround, we call ToLowerInvariant when the SubExpression of usingAst
// is a VariableExpressionAst, because:
// (1) Variable name is case insensitive;
// (2) People use $using to refer to a variable most of the time.
string usingAstText = usingAst.ToString();
if (usingAst.SubExpression is Language.VariableExpressionAst)
{
usingAstText = usingAstText.ToLowerInvariant();
}
return(StringToBase64Converter.StringToBase64String(usingAstText));
}
public static VariableExpressionAst ExtractUsingVariable(UsingExpressionAst usingExpressionAst)
{
throw new NotImplementedException(usingExpressionAst.ToString());
}
public static VariableExpressionAst ExtractUsingVariable(UsingExpressionAst usingExpressionAst)
{
throw new NotImplementedException(usingExpressionAst.ToString());
}