Share host-aware completion across runtimes

crates/decodal-core/src/module.rs

@@ -1,4 +1,4 @@
-use alloc::string::String;
+use alloc::{string::String, vec::Vec};
 
 use crate::{
     Ast, ExprId, HostValue, SourceForm, SourceId,
@@ -36,6 +36,27 @@ pub enum LoadedImport {
     Value(LoadedValue),
 }
 
+/// An import specifier offered by host-owned language tooling.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ImportCandidate {
+    pub specifier: String,
+    pub detail: Option<String>,
+}
+
+impl ImportCandidate {
+    pub fn new(specifier: impl Into<String>) -> Self {
+        Self {
+            specifier: specifier.into(),
+            detail: None,
+        }
+    }
+
+    pub fn with_detail(mut self, detail: impl Into<String>) -> Self {
+        self.detail = Some(detail.into());
+        self
+    }
+}
+
 impl LoadedImport {
     pub fn source(
         key: impl Into<String>,
@@ -59,6 +80,19 @@ impl LoadedImport {
 
 pub trait ImportLoader {
     fn load(&mut self, current_key: Option<&str>, specifier: &str) -> crate::Result<LoadedImport>;
+
+    /// Returns host-resolvable import specifiers matching an unfinished prefix.
+    ///
+    /// Runtime-only loaders may keep the default implementation. Hosts that
+    /// provide an editor should implement this from the same namespace used by
+    /// [`ImportLoader::load`].
+    fn complete_import(
+        &mut self,
+        _current_key: Option<&str>,
+        _prefix: &str,
+    ) -> crate::Result<Vec<ImportCandidate>> {
+        Ok(Vec::new())
+    }
 }
 
 #[derive(Debug, Clone, Copy, Default)]