[xen staging] docs-parse-support-md: Cope with buster's pandoc

[patchbot@xxxxxxx]

commit 1a58d8dab52f241d52fec1d992d859b9632c4739
Author:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
AuthorDate: Tue Jun 9 12:26:36 2020 +0100
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Tue Jun 9 14:05:49 2020 +0100

    docs-parse-support-md: Cope with buster's pandoc
    
    Provide the implementation for newer pandoc json.
    
    I have done an adhoc test and this now works on both buster and
    stretch and seems to produce the expected support matrix when run
    using the example rune (which processes unstable and 4.11).
    
    Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Release-acked-by: Paul Durrant <paul@xxxxxxx>
---
 docs/parse-support-md | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/docs/parse-support-md b/docs/parse-support-md
index b9978bfb4d..a397637639 100755
--- a/docs/parse-support-md
+++ b/docs/parse-support-md
@@ -243,6 +243,15 @@ sub r_toplevel ($) {
     $had_unknown = undef;
     $had_feature = undef;
 
+    # Pandoc's JSON output changed some time between 1.17.2 (stretch)
+    # and 2.2.1 (buster).  I can find no documentation about this
+    # change or about the compatibility rules.  (It seems that
+    # processing the parse tree *is* supported upstream: they offer
+    # many libraries to do this inside the pandoc process.)
+    # Empirically, what has changed is just the top level structure.
+    # Also pandoc wants the same structure back that it spat out,
+    # when we ask it to format snippets.
+
     my $blocks;
     if (ref $i eq 'ARRAY') {
        $pandoc_toplevel_constructor = sub {
@@ -256,6 +265,17 @@ sub r_toplevel ($) {
            next unless ref $e eq 'ARRAY';
            r_content $e;
        }
+    } elsif (ref $i eq 'HASH') {
+       my $api_version = $i->{'pandoc-api-version'};
+       $pandoc_toplevel_constructor = sub {
+           my ($blocks) = @_;
+           return {
+                   blocks => $blocks,
+                   meta => { },
+                   'pandoc-api-version' => $api_version,
+                  };
+       };
+       r_content $i->{blocks};
     } else {
        die;
     }
--
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