feat: add memory registry (#1709)

crates/tinymist-package/src/registry.rs

@@ -10,6 +10,9 @@ pub use typst::syntax::package::PackageSpec;
 mod dummy;
 pub use dummy::*;
 
+mod memory;
+pub use memory::*;
+
 #[cfg(feature = "browser")]
 mod browser;
 #[cfg(feature = "browser")]

crates/tinymist-package/src/registry/memory.rs

@@ -0,0 +1,36 @@
+//! Package registry implementation in memory, which could be used in no-std
+//! environments, for example, in a typst plugin.
+
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+use super::{PackageError, PackageRegistry, PackageSpec};
+
+/// Creates a memory package registry from the builder.
+#[derive(Default, Debug)]
+pub struct MemoryRegistry(HashMap<PackageSpec, Arc<Path>>);
+
+impl MemoryRegistry {
+    /// Adds a memory package.
+    pub fn add_memory_package(&mut self, spec: PackageSpec) -> Arc<Path> {
+        let package_root: Arc<Path> = PathBuf::from("/internal-packages")
+            .join(spec.name.as_str())
+            .join(spec.version.to_string())
+            .into();
+
+        self.0.insert(spec, package_root.clone());
+
+        package_root
+    }
+}
+
+impl PackageRegistry for MemoryRegistry {
+    /// Resolves a package.
+    fn resolve(&self, spec: &PackageSpec) -> Result<Arc<Path>, PackageError> {
+        self.0
+            .get(spec)
+            .cloned()
+            .ok_or_else(|| PackageError::NotFound(spec.clone()))
+    }
+}