public bool TryParse <T>(string source, ref int index, [NotNullWhen(true)] out JsonPathExpression?expression, [NotNullWhen(false)] out string?errorMessage)
{
PathExpression <T> node;
var isLocal = source[index] == '@';
if (!JsonPathParser.TryParse(source, ref index, out var path, out errorMessage) &&
// Swallow this error from the path parser and assume the path just ended.
// If it's really a syntax error, the expression parser should catch it.
errorMessage != "Unrecognized JSON Path element.")
{
expression = null !;
return(false);
}
var lastOp = path !.Operators.Last();
if (lastOp is NameOperator name)
{
path.Operators.Remove(name);
if (name.Name == "indexOf")
{
if (source[index] != '(')
{
errorMessage = "Expected '('. 'indexOf' operator requires a parameter.";
expression = null !;
return(false);
}
index++;
if (!JsonParser.TryParse(source, ref index, out var parameter, out errorMessage, true) &&
// Swallow this error from the JSON parser and assume the value just ended.
// If it's really a syntax error, the expression parser should catch it.
errorMessage != "Expected \',\', \']\', or \'}\'.")
{
errorMessage = $"Error parsing parameter for 'indexOf' expression: {errorMessage}.";
expression = null !;
return(false);
}
if (source[index] != ')')
{
errorMessage = "Expected ')'.";
expression = null !;
return(false);
}
index++;
node = new IndexOfExpression <T>(path, isLocal, parameter !);
}
else
{
node = new NameExpression <T>(path, isLocal, name.Name);
}
}
else if (lastOp is LengthOperator length)
{
path.Operators.Remove(length);
node = new LengthExpression <T>(path, isLocal);
}
else if (lastOp is ArrayOperator array)
{
path.Operators.Remove(array);
var query = array.Query as SliceQuery;
var constant = query?.Slices.FirstOrDefault <Slice?>()?.Index;
if (query == null || query.Slices.Count() != 1 || !constant.HasValue)
{
errorMessage = "JSON Path expression indexers only support single constant values.";
expression = null !;
return(false);
}
node = new ArrayIndexExpression <T>(path, isLocal, constant.Value);
}
else
{
throw new NotImplementedException();
}
expression = new PathValueExpression <T>(node);
return(true);
}
public string TryParse <T>(string source, ref int index, out JsonPathExpression expression)
{
expression = null;
PathExpression <T> node;
var isLocal = source[index] == '@';
var error = JsonPathParser.Parse(source, ref index, out JsonPath path);
// Swallow this error from the path parser and assume the path just ended.
// If it's really a syntax error, the expression parser should catch it.
if (error != null && error != "Unrecognized JSON Path element.")
{
return(error);
}
var lastOp = path.Operators.Last();
if (lastOp is NameOperator name)
{
path.Operators.Remove(name);
if (name.Name == "indexOf")
{
if (source[index] != '(')
{
return("Expected '('. 'indexOf' operator requires a parameter.");
}
index++;
error = JsonParser.Parse(source, ref index, out JsonValue parameter, true);
// Swallow this error from the JSON parser and assume the value just ended.
// If it's really a syntax error, the expression parser should catch it.
if (error != null && error != "Expected \',\', \']\', or \'}\'.")
{
return($"Error parsing parameter for 'indexOf' expression: {error}.");
}
if (source[index] != ')')
{
return("Expected ')'.");
}
index++;
node = new IndexOfExpression <T>
{
Path = path,
IsLocal = isLocal,
Parameter = parameter
};
}
else
{
node = new NameExpression <T>
{
Path = path,
IsLocal = isLocal,
Name = name.Name
}
};
}
else if (lastOp is LengthOperator length)
{
path.Operators.Remove(length);
node = new LengthExpression <T>
{
Path = path,
IsLocal = isLocal
};
}
else if (lastOp is ArrayOperator array)
{
path.Operators.Remove(array);
var query = array.Query as SliceQuery;
var constant = query?.Slices.FirstOrDefault()?.Index;
if (query == null || query.Slices.Count() != 1 || !constant.HasValue)
{
return("JSON Path expression indexers only support single constant values.");
}
node = new ArrayIndexExpression <T>
{
Path = path,
IsLocal = isLocal,
Index = constant.Value
};
}
else
{
throw new NotImplementedException();
}
expression = new PathValueExpression <T> {
Path = node
};
return(null);
}