[oden] IO: Load Strings

It's useful. The stock JS way is bad.

src/script/io.rs

@@ -82,6 +82,24 @@ impl IoImpl {
 
         Ok(value)
     }
+
+    fn load_string(&self, context: &ContextRef, path: &str) -> ValueResult {
+        let (value, promise) = context.new_promise()?;
+
+        let path = path.to_string();
+        self.thread_pool.execute(Box::new(move || {
+            let path = path;
+
+            let result = resolve_path(&path, &[]).and_then(|p| std::fs::read(p));
+            promise.resolve(move |ctx: &ContextRef| {
+                let result = result?;
+                let string = std::str::from_utf8(&result)?;
+                ctx.new_string(string)
+            });
+        }));
+
+        Ok(value)
+    }
 }
 
 pub struct IoAPI {}
@@ -97,6 +115,13 @@ impl IoAPI {
                 ctx.new_fn(move |ctx: &ContextRef, p: String| io.load(ctx, &p))?,
             )?;
         }
+        {
+            let io = io.clone();
+            builder.export(
+                "load_string",
+                ctx.new_fn(move |ctx: &ContextRef, p: String| io.load_string(ctx, &p))?,
+            )?;
+        }
         builder.build("io-core")?;
         Ok(IoAPI {})
     }