Support for multiple bib files in a bibliography (#296)

assets/files/works_too.bib

@@ -0,0 +1,10 @@
+@article{keshav2007read,
+  title     = {How to read a paper},
+  author    = {Keshav, Srinivasan},
+  journal   = {ACM SIGCOMM Computer Communication Review},
+  volume    = {37},
+  number    = {3},
+  pages     = {83--84},
+  year      = {2007},
+  publisher = {ACM New York, NY, USA}
+}

library/src/meta/bibliography.rs

@@ -48,13 +48,17 @@ pub struct BibliographyElem {
     /// Path to a Hayagriva `.yml` or BibLaTeX `.bib` file.
     #[required]
     #[parse(
-        let Spanned { v: path, span } =
-            args.expect::<Spanned<EcoString>>("path to bibliography file")?;
-        let path: EcoString = vm.locate(&path).at(span)?.to_string_lossy().into();
-        let _ = load(vm.world(), &path).at(span)?;
-        path
+        let Spanned { v: mut paths, span } =
+            args.expect::<Spanned<BibPaths>>("path to bibliography file")?;
+        for path in &mut paths.0 {
+            // resolve paths
+            *path = vm.locate(&path).at(span)?.to_string_lossy().into();
+        }
+        // check that parsing works
+        let _ = load(vm.world(), &paths).at(span)?;
+        paths
     )]
-    pub path: EcoString,
+    pub path: BibPaths,
 
     /// The title of the bibliography.
     ///
@@ -70,6 +74,22 @@ pub struct BibliographyElem {
     pub style: BibliographyStyle,
 }
 
+
+/// A list of bib file paths.
+#[derive(Debug, Default, Clone, Hash)]
+pub struct BibPaths(Vec<EcoString>);
+
+cast_from_value! {
+    BibPaths,
+    v: EcoString => Self(vec![v]),
+    v: Array => Self(v.into_iter().map(Value::cast).collect::<StrResult<_>>()?),
+}
+
+cast_to_value! {
+    v: BibPaths => v.0.into()
+}
+
+
 impl BibliographyElem {
     /// Find the document's bibliography.
     pub fn find(introspector: Tracked<Introspector>) -> StrResult<Self> {
@@ -534,22 +554,53 @@ fn create(
 
 /// Load bibliography entries from a path.
 #[comemo::memoize]
-fn load(world: Tracked<dyn World>, path: &str) -> StrResult<EcoVec<hayagriva::Entry>> {
-    let path = Path::new(path);
-    let buffer = world.file(path)?;
-    let src = std::str::from_utf8(&buffer).map_err(|_| "file is not valid utf-8")?;
+fn load(
+    world: Tracked<dyn World>,
+    paths: &BibPaths,
+) -> StrResult<EcoVec<hayagriva::Entry>> {
+    let mut result = EcoVec::new();
+
+    // We might have multiple bib/yaml files
+    for path in &paths.0 {
+        let buffer = world.file(Path::new(path.as_str()))?;
+        let src = std::str::from_utf8(&buffer).map_err(|_| "file is not valid utf-8")?;
+        let entries = parse_bib(path, src)?;
+        result.extend(entries);
+    }
+
+    // Biblatex only checks for duplicate keys within files
+    // -> We have to do this between files again
+    let mut keys = result.iter().map(|r| r.key()).collect::<Vec<_>>();
+    keys.sort_unstable();
+    // Waiting for `slice_partition_dedup` #54279
+    let mut duplicates = Vec::new();
+    for pair in keys.windows(2) {
+        if pair[0] == pair[1] {
+            duplicates.push(pair[0]);
+        }
+    }
+
+    if !duplicates.is_empty() {
+        Err(eco_format!("duplicate bibliography keys: {}", duplicates.join(", ")))
+    } else {
+        Ok(result)
+    }
+}
+
+/// Parse a bibliography file (bib/yml)
+fn parse_bib(path_str: &str, src: &str) -> StrResult<Vec<hayagriva::Entry>> {
+    let path = Path::new(path_str);
     let ext = path.extension().and_then(OsStr::to_str).unwrap_or_default();
-    let entries = match ext.to_lowercase().as_str() {
-        "yml" => hayagriva::io::from_yaml_str(src).map_err(format_hayagriva_error)?,
+    match ext.to_lowercase().as_str() {
+        "yml" => hayagriva::io::from_yaml_str(src).map_err(format_hayagriva_error),
         "bib" => hayagriva::io::from_biblatex_str(src).map_err(|err| {
             err.into_iter()
                 .next()
-                .map(|error| format_biblatex_error(src, error))
-                .unwrap_or_else(|| "failed to parse biblatex file".into())
-        })?,
-        _ => return Err("unknown bibliography format".into()),
-    };
-    Ok(entries.into_iter().collect())
+                .map(|error| format_biblatex_error(path_str, src, error))
+                .unwrap_or_else(|| eco_format!("failed to parse {path_str}"))
+        }),
+        _ => Err("unknown bibliography format".into()),
+    }
 }
 
 /// Format a Hayagriva loading error.
@@ -558,13 +609,13 @@ fn format_hayagriva_error(error: YamlBibliographyError) -> EcoString {
 }
 
 /// Format a BibLaTeX loading error.
-fn format_biblatex_error(src: &str, error: BibLaTeXError) -> EcoString {
+fn format_biblatex_error(path: &str, src: &str, error: BibLaTeXError) -> EcoString {
     let (span, msg) = match error {
         BibLaTeXError::Parse(error) => (error.span, error.kind.to_string()),
         BibLaTeXError::Type(error) => (error.span, error.kind.to_string()),
     };
     let line = src.get(..span.start).unwrap_or_default().lines().count();
-    eco_format!("failed to parse biblatex file: {msg} in line {line}")
+    eco_format!("parsing failed at {path}:{line}: {msg}")
 }
 
 /// Hayagriva only supports strings, but we have a content supplement. To deal

tests/typ/meta/bibliography.typ

@@ -1,7 +1,7 @@
 // Test citations and bibliographies.
 
 ---
-// Error: 15-25 failed to parse biblatex file: wrong number of digits in line 5
+// Error: 15-25 parsing failed at ../assets/files/bad.bib:5: wrong number of digits
 #bibliography("/bad.bib")
 
 ---
@@ -27,3 +27,13 @@ As described by @netwok],
 the net-work is a creature of its own.
 This is close to piratery! @arrgh
 And quark! @quark
+
+---
+// Error: 15-43 duplicate bibliography keys: arrgh, distress, glacier-melt, issue201, mcintosh_anxiety, netwok, psychology25, quark, restful, sharing, tolkien54
+#bibliography(("/works.bib", "/works.bib"))
+
+---
+#set page(width: 200pt)
+= Multiple Bibs
+Now we have multiple bibliographies containing #cite("glacier-melt", "keshav2007read")
+#bibliography(("/works.bib", "/works_too.bib"))