docbook reader: fix nesting of chapters and sections (#5864)

* Set dbBook to true when traversing a chapter too.
  Currently, a `<title/>` in a chapter and in a `<section/>` below that
  chapter have the same level if they're not inside a `<book/>`.

  This can happen in a multi-file book project. Also see the example at
  https://tdg.docbook.org/tdg/4.5/chapter.html

  Co-authored-by: Félix Baylac-Jacqué <felix@alternativebit.fr>

* Add docbook-chapter test

  This tests nested `<section/>` and makes sure `<title/>` in the first
  `<section/>` below `<chapter/>` is one level deeper than the `<chapter/>`'s
  `<title/>`, also when not inside a `<book/>`.

  Co-authored-by: Félix Baylac-Jacqué <felix@alternativebit.fr>

3 files changed, 49 insertions, 0 deletions

diff --git a/test/Tests/Old.hs b/test/Tests/Old.hs
index d0a1e0e4f..45e40a830 100644
--- a/test/Tests/Old.hs
+++ b/test/Tests/Old.hs
@@ -86,6 +86,8 @@ tests pandocPath =
     , test' "reader" ["-r", "docbook", "-w", "native", "-s"]
       "docbook-reader.docbook" "docbook-reader.native"
     , test' "reader" ["-r", "docbook", "-w", "native", "-s"]
+      "docbook-chapter.docbook" "docbook-chapter.native"
+    , test' "reader" ["-r", "docbook", "-w", "native", "-s"]
       "docbook-xref.docbook" "docbook-xref.native"
     ]
   , testGroup "docbook5"
diff --git a/test/docbook-chapter.docbook b/test/docbook-chapter.docbook
new file mode 100644
index 000000000..68bb60e02
--- /dev/null
+++ b/test/docbook-chapter.docbook
@@ -0,0 +1,30 @@
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
+<!-- This matches the example from
+https://tdg.docbook.org/tdg/4.5/section.html, sans sectioninfo and subtitle, as
+they're currently not supported -->
+<chapter><title>Test Chapter</title>
+<para>This chapter uses recursive sections.</para>
+<section>
+<title>Like a Sect1</title>
+<para>This section is like a Sect1.</para>
+<section><title>Like a Sect2</title>
+<para>This section is like a Sect2.</para>
+<section><title>Like a Sect3</title>
+<para>This section is like a Sect3.</para>
+<section><title>Like a Sect4</title>
+<para>This section is like a Sect4.</para>
+<section><title>Like a Sect5</title>
+<para>This section is like a Sect5.</para>
+<section><title>Would be like a Sect6</title>
+<para>This section would be like a Sect6, if there was one.</para>
+<section><title>Would be like a Sect7</title>
+<para>This section would be like a Sect7, if there was one.</para>
+</section>
+</section>
+</section>
+</section>
+</section>
+</section>
+</section>
+</chapter>
diff --git a/test/docbook-chapter.native b/test/docbook-chapter.native
new file mode 100644
index 000000000..396b6a21a
--- /dev/null
+++ b/test/docbook-chapter.native
@@ -0,0 +1,17 @@
+Pandoc (Meta {unMeta = fromList []})
+[Header 1 ("",[],[]) [Str "Test",Space,Str "Chapter"]
+,Para [Str "This",Space,Str "chapter",Space,Str "uses",Space,Str "recursive",Space,Str "sections."]
+,Header 2 ("",[],[]) [Str "Like",Space,Str "a",Space,Str "Sect1"]
+,Para [Str "This",Space,Str "section",Space,Str "is",Space,Str "like",Space,Str "a",Space,Str "Sect1."]
+,Header 3 ("",[],[]) [Str "Like",Space,Str "a",Space,Str "Sect2"]
+,Para [Str "This",Space,Str "section",Space,Str "is",Space,Str "like",Space,Str "a",Space,Str "Sect2."]
+,Header 4 ("",[],[]) [Str "Like",Space,Str "a",Space,Str "Sect3"]
+,Para [Str "This",Space,Str "section",Space,Str "is",Space,Str "like",Space,Str "a",Space,Str "Sect3."]
+,Header 5 ("",[],[]) [Str "Like",Space,Str "a",Space,Str "Sect4"]
+,Para [Str "This",Space,Str "section",Space,Str "is",Space,Str "like",Space,Str "a",Space,Str "Sect4."]
+,Header 6 ("",[],[]) [Str "Like",Space,Str "a",Space,Str "Sect5"]
+,Para [Str "This",Space,Str "section",Space,Str "is",Space,Str "like",Space,Str "a",Space,Str "Sect5."]
+,Header 7 ("",[],[]) [Str "Would",Space,Str "be",Space,Str "like",Space,Str "a",Space,Str "Sect6"]
+,Para [Str "This",Space,Str "section",Space,Str "would",Space,Str "be",Space,Str "like",Space,Str "a",Space,Str "Sect6,",Space,Str "if",Space,Str "there",Space,Str "was",Space,Str "one."]
+,Header 8 ("",[],[]) [Str "Would",Space,Str "be",Space,Str "like",Space,Str "a",Space,Str "Sect7"]
+,Para [Str "This",Space,Str "section",Space,Str "would",Space,Str "be",Space,Str "like",Space,Str "a",Space,Str "Sect7,",Space,Str "if",Space,Str "there",Space,Str "was",Space,Str "one."]]