Split out four new crates (#5302)

1 files changed, 38 insertions, 0 deletions

diff --git a/crates/typst-library/src/introspection/metadata.rs b/crates/typst-library/src/introspection/metadata.rs
new file mode 100644
index 00000000..06000174
--- /dev/null
+++ b/crates/typst-library/src/introspection/metadata.rs
@@ -0,0 +1,38 @@
+use crate::diag::SourceResult;
+use crate::engine::Engine;
+use crate::foundations::{elem, Content, Packed, Show, StyleChain, Value};
+use crate::introspection::Locatable;
+
+/// Exposes a value to the query system without producing visible content.
+///
+/// This element can be retrieved with the [`query`] function and from the
+/// command line with
+/// [`typst query`]($reference/introspection/query/#command-line-queries). Its
+/// purpose is to expose an arbitrary value to the introspection system. To
+/// identify a metadata value among others, you can attach a [`label`] to it and
+/// query for that label.
+///
+/// The `metadata` element is especially useful for command line queries because
+/// it allows you to expose arbitrary values to the outside world.
+///
+/// ```example
+/// // Put metadata somewhere.
+/// #metadata("This is a note") <note>
+///
+/// // And find it from anywhere else.
+/// #context {
+///   query(<note>).first().value
+/// }
+/// ```
+#[elem(Show, Locatable)]
+pub struct MetadataElem {
+    /// The value to embed into the document.
+    #[required]
+    pub value: Value,
+}
+
+impl Show for Packed<MetadataElem> {
+    fn show(&self, _: &mut Engine, _styles: StyleChain) -> SourceResult<Content> {
+        Ok(Content::empty())
+    }
+}