Problem with nested entities in xml2

[HanOostdijk]

When I try to handle DTD entities in xml2 my R session (both in RGui and RStudio) consistently aborts. In RStudio (1.2.1114) a dialog window appears with R Session Aborted , R encountered a fatal error, The session was terminated,Start New Session.

I enclose a session where I

• define a DTD and a XML example file
• read the XML with the package XML that works as expected: the field field1 contains 'Han Oostdijk Quantitative Consultancy' i.e. the resolved entity hoqc with the nested entity author defined in the DTD.
• do the same with package xml2. I have commented out the line c1 = xml2::xml_find_all(w2,"//field1") because this is the line that causes the abortion of the R session.
• use package xml2 but replace the line in the XML with the entity hoqc by <field1>a none-entity</field1>. This works as expected: results in the string 'a none-entity'.
• use package xml2 but replace the line in the XML with the entity hoqc by <field1>&author;</field1>. This works as expected: results in the string 'Han Oostdijk'.

My conclusion: xml2 can not handle nested entities where XML has no problems (?)

getwd()
#> [1] "D:/data/R/default_working_directory"
dtd_info <- c(
  '<!ENTITY author "Han Oostdijk">',
  '<!ENTITY hoqc "&author; Quantitative Consultancy">',
  "<!ELEMENT records (record+)>",
  "<!ELEMENT record (field1)>",
  "<!ELEMENT field1 (#PCDATA)>"
)
xml_data <- c(
  '<?xml version="1.0" encoding="UTF-8"?>',
  '<!DOCTYPE records SYSTEM "records.dtd">',
  "<records>",
  "<record>",
  "<field1>&hoqc;</field1>",
  "</record>",
  "</records>"
)
writeLines(dtd_info, "records.dtd")
xml_data1 <- paste(xml_data, collapse = "\n")
# read with package XML
w1 <- XML::xmlParse(xml_data1, options = c(XML::DTDVALID))
print(w1)
#> <?xml version="1.0" encoding="UTF-8"?>
#> <!DOCTYPE records SYSTEM "records.dtd">
#> <records>
#>   <record>
#>     <field1>&hoqc;</field1>
#>   </record>
#> </records>
#> 
unlist(XML::xpathApply(w1, "//field1", XML::xmlValue))
#> [1] "Han Oostdijk Quantitative Consultancy"
# read with package xml2
w2 <- xml2::read_xml(xml_data1, options = c("DTDVALID"))
print(w2)
#> {xml_document}
#> <records>
#> [1] <record>\n<field1>&hoqc;</field1>\n</record>
######## next line will cause abort of session
# c1 = xml2::xml_find_all(w2,"//field1")
######## previous line will cause abort of session
# replace '&hoqc;' by 'a none-entity'
xml_data2 <- xml_data
xml_data2[5] <- "<field1>a none-entity</field1>"
xml_data2 <- paste(xml_data2, collapse = "\n")
w3 <- xml2::read_xml(xml_data2, options = c("DTDVALID"))
print(w3)
#> {xml_document}
#> <records>
#> [1] <record>\n<field1>a none-entity</field1>\n</record>
c2 <- xml2::xml_find_all(w3, "//field1")
purrr::map_chr(c2, xml2::xml_text)
#> [1] "a none-entity"
# replace '&hoqc;' by '&author;'
xml_data3 <- xml_data
xml_data3[5] <- "<field1>&author;</field1>"
xml_data3 <- paste(xml_data3, collapse = "\n")
w4 <- xml2::read_xml(xml_data3, options = c("DTDVALID"))
print(w4)
#> {xml_document}
#> <records>
#> [1] <record>\n<field1>&author;</field1>\n</record>
c3 <- xml2::xml_find_all(w4, "//field1")
purrr::map_chr(c3, xml2::xml_text)
#> [1] "Han Oostdijk"

^{Created on 2018-11-26 by the reprex package (v0.2.1)}

Session info

devtools::session_info()
#> - Session info ----------------------------------------------------------
#>  setting  value                       
#>  version  R version 3.5.0 (2018-04-23)
#>  os       Windows 10 x64              
#>  system   x86_64, mingw32             
#>  ui       RTerm                       
#>  language (EN)                        
#>  collate  English_United States.1252  
#>  ctype    English_United States.1252  
#>  tz       Europe/Berlin               
#>  date     2018-11-26                  
#> 
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#>  XML           3.98-1.16  2018-08-19 [1] CRAN (R 3.5.1)             
#>  xml2          1.2.0.9000 2018-11-17 [1] Github (r-lib/xml2@de9781d)
#>  yaml          2.2.0      2018-07-25 [1] CRAN (R 3.5.1)             
#> 
#> [1] D:/tools/R/Packages
#> [2] D:/tools/R/R-3.5.0/library