Merge branch 'fix-205' into 'main'

pandoc: Add support for --citeproc

Closes #205

See merge request subplot/subplot!215

2 files changed, 25 insertions, 2 deletions

diff --git a/src/doc.rs b/src/doc.rs
index 2272581..c5bb2c7 100644
--- a/src/doc.rs
+++ b/src/doc.rs
@@ -159,8 +159,7 @@ impl<'a> Document {
         pandoc.set_output(pandoc::OutputKind::Pipe);
 
         // Add external Pandoc filters.
-        let citeproc = std::path::Path::new("pandoc-citeproc");
-        pandoc.add_option(pandoc::PandocOption::Filter(citeproc.to_path_buf()));
+        crate::policy::add_citeproc(&mut pandoc);
 
         event!(Level::TRACE, ?filename, "Invoking Pandoc to parse document");
         let output = match pandoc.execute()? {
diff --git a/src/policy.rs b/src/policy.rs
index e24bf8f..00a18d3 100644
--- a/src/policy.rs
+++ b/src/policy.rs
@@ -1,5 +1,8 @@
 use std::path::{Component, Path, PathBuf};
 
+use pandoc::{InputFormat, InputKind, OutputFormat, OutputKind, Pandoc, PandocOption};
+use tracing::{event, instrument, Level};
+
 /// Get the base directory given the name of the markdown file.
 ///
 /// All relative filename, such as bindings files, are resolved
@@ -14,3 +17,24 @@ pub fn get_basedir_from(filename: &Path) -> PathBuf {
         Some(x) => x.to_path_buf(),
     }
 }
+
+/// Add 'citeproc' to a Pandoc instance.
+///
+/// This attempts to determine if `--citeproc` or `--filter pandoc-citeproc`
+/// is needed, and then does that specific thing.
+#[instrument(skip(pandoc))]
+pub fn add_citeproc(pandoc: &mut Pandoc) {
+    let mut guesser = Pandoc::new();
+    guesser.set_input(InputKind::Pipe("".to_string()));
+    guesser.set_input_format(InputFormat::Markdown, vec![]);
+    guesser.set_output_format(OutputFormat::Markdown, vec![]);
+    guesser.set_output(OutputKind::Pipe);
+    guesser.add_option(PandocOption::Citeproc);
+    if guesser.execute().is_ok() {
+        event!(Level::TRACE, "Discovered --citeproc");
+        pandoc.add_option(PandocOption::Citeproc);
+    } else {
+        event!(Level::TRACE, "Discovered --filter pandoc-citeproc");
+        pandoc.add_option(PandocOption::Filter("pandoc-citeproc".into()));
+    }
+}