XML (version 3.1-1)

xmlStructuredStop: Condition/error handler functions for XML parsing

Description

These functions provide basic error handling for the XML parser in R. They also illustrate the basics which will allow others to provide customized error handlers that make more use of the information provided in each error reported. The xmlStructuredStop function provides a simple R-level handler for errors raised by the XML parser. It collects the information provided by the XML parser and raises an R error. This is only used if NULL is specified for the error argument of xmlTreeParse, xmlTreeParse and htmlTreeParse.

The default is to use the function returned by a call to xmlErrorCumulator as the error handler. This, as the name suggests, cumulates errors. The idea is to catch each error and let the parser continue and then report them all. As each error is encountered, it is collected by the function. If immediate is TRUE, the error is also reported on the console. When the parsing is complete and has failed, this function is invoked again with a zero-length character vector as the message (first argument) and then it raises an error. This function will then raise an R condition of class class.

Usage

xmlStructuredStop(msg, code, domain, line, col, level, filename, 
                    class = "XMLError") 
xmlErrorCumulator(class = "XMLParserErrorList", immediate = TRUE)

Value

• This calls stop and so does not return a value.

concept

error handling

References

libxml2 and its error handling facilities (http://xmlsoft.org

See Also

xmlTreeParse xmlInternalTreeParse htmlTreeParse

Examples

tryCatch( xmlTreeParse("<a><b></a>", asText = TRUE, error = NULL),
                 XMLError = function(e) {
                    cat("There was an error in the XML at line", 
                          e$line, "column", e$col, "",
                         e$message, "")
                })