Add host-configurable language service

crates/decodal-core/src/environment.rs

@@ -0,0 +1,34 @@
+use crate::{Engine, ImportLoader, Result};
+
+/// Host-owned configuration shared by runtime and language tooling.
+///
+/// Implementations create the import loader and install global bindings on a
+/// fresh engine. Calling [`HostEnvironment::create_engine`] therefore gives
+/// every consumer the same Decodal execution environment.
+pub trait HostEnvironment {
+    type Loader: ImportLoader;
+
+    fn create_loader(&self) -> Self::Loader;
+
+    fn configure_engine(&self, _engine: &mut Engine<Self::Loader>) -> Result<()> {
+        Ok(())
+    }
+
+    fn create_engine(&self) -> Result<Engine<Self::Loader>> {
+        let mut engine = Engine::new(self.create_loader());
+        self.configure_engine(&mut engine)?;
+        Ok(engine)
+    }
+}
+
+impl<T: HostEnvironment + ?Sized> HostEnvironment for &T {
+    type Loader = T::Loader;
+
+    fn create_loader(&self) -> Self::Loader {
+        T::create_loader(*self)
+    }
+
+    fn configure_engine(&self, engine: &mut Engine<Self::Loader>) -> Result<()> {
+        T::configure_engine(*self, engine)
+    }
+}

crates/decodal-core/src/lib.rs

@@ -6,6 +6,7 @@ pub mod ast;
 pub mod constraints;
 pub mod diagnostic;
 pub mod embedding;
+pub mod environment;
 pub mod eval;
 mod lexer;
 pub mod module;
@@ -20,6 +21,7 @@ pub use constraints::normalize_constraints;
 pub use decodal_derive::Decodal;
 pub use diagnostic::{Diagnostic, DiagnosticKind, Result};
 pub use embedding::{HostField, HostValue};
+pub use environment::HostEnvironment;
 pub use eval::{Engine, format_diagnostic_with};
 pub use module::{EmptyLoader, ImportLoader, LoadedImport, LoadedSource, LoadedValue, Module};
 pub use parser::{ParseOutput, Parser, SourceForm, parse_source, parse_source_with_source_id};