From b925f9601b30afd9b0c2a5e7354440a63aba8c60 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Sat, 22 Oct 2022 08:37:30 +0300
Subject: feat: allow arbitrary Pandoc metadata in a .subplot

The "pandoc" key gets added to the metadata given to Pandoc as-is.

Sponsored-by: author
---
 src/ast.rs      | 37 ++++++++++++++++++++++++++++++++++++-
 subplot.md      | 26 ++++++++++++++++++++++++++
 subplot.subplot |  3 +++
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/src/ast.rs b/src/ast.rs
index 7efe836..531208c 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -4,7 +4,8 @@ use pandoc_ast::{Attr, Block, Inline, Map, MetaValue, Pandoc};
 use pulldown_cmark::{CodeBlockKind, Event, Options, Parser, Tag};
 use regex::Regex;
 use serde::Deserialize;
-use std::collections::BTreeMap;
+use serde_yaml::{Mapping, Value};
+use std::collections::{BTreeMap, HashMap};
 use std::path::{Path, PathBuf};
 
 lazy_static! {
@@ -293,6 +294,7 @@ pub struct YamlMetadata {
     documentclass: Option<String>,
     #[serde(default)]
     impls: BTreeMap<String, Vec<PathBuf>>,
+    pandoc: Option<HashMap<String, Value>>,
 }
 
 impl YamlMetadata {
@@ -351,11 +353,44 @@ impl YamlMetadata {
             map.insert("documentclass".into(), meta_string(v));
         }
 
+        if let Some(pandoc) = &self.pandoc {
+            for (key, value) in pandoc.iter() {
+                map.insert(key.to_string(), value_to_pandoc(value));
+            }
+        }
+
         trace!("Created metadata map from parsed YAML");
         map
     }
 }
 
+fn mapping_to_pandoc(mapping: &Mapping) -> MetaValue {
+    let mut map = Map::new();
+    for (key, value) in mapping.iter() {
+        assert!(matches!(key, Value::String(_)));
+        let key = if let MetaValue::MetaString(s) = value_to_pandoc(&key) {
+            s
+        } else {
+            panic!("key not a string: {:?}", key);
+        };
+        map.insert(key, Box::new(value_to_pandoc(value)));
+    }
+
+    MetaValue::MetaMap(map)
+}
+
+fn value_to_pandoc(data: &Value) -> MetaValue {
+    match data {
+        Value::Null => unreachable!("null not OK"),
+        Value::Number(_) => unreachable!("number not OK"),
+        Value::Sequence(_) => unreachable!("sequence not OK"),
+
+        Value::Bool(b) => MetaValue::MetaBool(*b),
+        Value::String(s) => MetaValue::MetaString(s.clone()),
+        Value::Mapping(mapping) => mapping_to_pandoc(mapping),
+    }
+}
+
 fn meta_string(s: &str) -> MetaValue {
     MetaValue::MetaString(s.to_string())
 }
diff --git a/subplot.md b/subplot.md
index 8daf1dd..27da981 100644
--- a/subplot.md
+++ b/subplot.md
@@ -2474,6 +2474,32 @@ and file mtime.html contains "Geoffrey Butler"
 and file mtime.html contains "2020-02-26 07:53"
 ~~~
 
+### Pandoc metadata
+
+~~~scenario
+given file pandoc.subplot
+given file pandoc.md
+and an installed subplot
+when I run subplot docgen pandoc.subplot -o pandoc.html
+when I run cat pandoc.html
+then file pandoc.html exists
+and file pandoc.html contains "<title>The Fabulous Title</title>"
+and file pandoc.html contains "Superlative Subtitle"
+~~~
+
+~~~{#pandoc.subplot .file .yaml .numberLines}
+title: The Fabulous Title
+markdowns:
+- pandoc.md
+pandoc:
+  subtitle: Superlative Subtitle
+~~~
+
+~~~{#pandoc.md .file .markdown .numberLines}
+# Introduction
+This is a test document. That's all.
+~~~
+
 ### Missing bindings file
 
 If a bindings file is missing, the error message should name the
diff --git a/subplot.subplot b/subplot.subplot
index 61ecd4f..d4a9353 100644
--- a/subplot.subplot
+++ b/subplot.subplot
@@ -16,3 +16,6 @@ impls:
 classes:
 - json
 - ignored
+pandoc:
+  documentclass: report
+  subtitle: Yoyo
-- 
cgit v1.2.1