DocBook: in InsetInfo, ensure that no db:date is inserted within a db:date.

autotests/export/docbook/insetinfo.lyx

@@ -91,6 +91,17 @@ Test:
  InsetInfo
 \end_layout
 
+\begin_layout Date
+
+\lang japanese-cjk
+\begin_inset Info
+type  "moddate"
+arg   "long"
+\end_inset
+
+
+\end_layout
+
 \begin_layout Standard
 
 \lang spanish

autotests/export/docbook/insetinfo.xml

@@ -2,6 +2,9 @@
 <!-- This DocBook file was created by LyX 2.4.0~RC1.devel
   See https://www.lyx.org/ for more information -->
 <article xml:lang="en-US" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.2">
+<info>
 <title>Test: InsetInfo</title>
+<date>2023-10-08</date>
+</info>
 <para>Véase la <emphasis><phrase role="localized">User's Guide</phrase></emphasis> o <emphasis><phrase role="localized">Additional Features</phrase></emphasis> para más detalles.</para>
 </article>

src/Paragraph.cpp

@@ -3669,6 +3669,7 @@ std::tuple<std::vector<docstring>, std::vector<docstring>, std::vector<docstring
             }
         }
     }
+	rp.lastid = id();
 
     // State variables for the main loop.
     auto xs = new XMLStream(os); // XMLStream has no copy constructor: to create a new object, the only solution

src/insets/InsetInfo.cpp

@@ -1726,8 +1726,19 @@ void InsetInfo::docbook(XMLStream & xs, OutputParams const & rp) const
 			break;
 		}
 
+		// A db:date cannot be nested within a db:date. This case typically happens when the document class defines a
+		// Date layout. In this case, avoid outputting a new db:date. This means that InsetInfo cannot add a role on top
+		// of the previous db:date, hence add it as a comment. (Another solution would be an XML processing instruction,
+		// but this case is not common enough.) Adding the role to the already output tag might have consequences for
+		// some document classes where the layout already has a role or uses the same role for another purpose.
+		const bool isWithinDate = buffer().getParFromID(rp.lastid).top().paragraph().layout().docbooktag() == "date";
+
+		if (!isWithinDate)
 			xml::openTag(xs, "date", "role=\"" + role + "\"", "inline");
+		else
+			xs << XMLStream::ESCAPE_NONE << from_ascii(std::string("<!-- ") + role + " -->");
 		xs << qstring_to_ucs4(parseDate(buffer(), params_).toString(Qt::ISODate));
+		if (!isWithinDate)
 			xml::closeTag(xs, "date", "inline");
 		break;
 	}
@@ -1752,8 +1763,16 @@ void InsetInfo::docbook(XMLStream & xs, OutputParams const & rp) const
 		}
 
 		// DocBook has no specific element for time, so use a date.
-		xml::openTag(xs, "date", "(role=\"" + role + "\"", "inline");
+		// See the discussion above (DATE_INFO, MODDATE_INFO, and FIXDATE_INFO) for a discussion about the choices that
+		// have been made.
+		const bool isWithinDate = buffer().getParFromID(rp.lastid).top().paragraph().layout().docbooktag() == "date";
+
+		if (!isWithinDate)
+			xml::openTag(xs, "date", "role=\"" + role + "\"", "inline");
+		else
+			xs << XMLStream::ESCAPE_NONE << from_ascii(std::string("<!-- ") + role + " -->");
 		xs << qstring_to_ucs4(parseTime(buffer(), params_).toString(Qt::ISODate));
+		if (!isWithinDate)
 			xml::closeTag(xs, "date", "inline");
 		break;
 	}