Common pitfalls

• the trait bound ToV8<'_>/FromV8<'_> is not satisfied
• use of undeclared crate or module deno_core

the trait bound ToV8<'_>/FromV8<'_> is not satisfied

Function argument and return types for js(func), js(prop), etc., must implement specific traits for data to be able to pass to/from JavaScript.

By default, arguments must implement ToV8, and return types must implement FromV8.

If you would like to serialize data using serde instead, you can opt into this behavior by rewriting a type T as serde<T>:

  #[js(interface)]
  impl Foo {
      #[js(func)]
-     fn bar(&self, baz: Baz) {}
+     fn bar(&self, baz: serde<Baz>) {}
  }

See Specifying types for additional information on data conversion.

use of undeclared crate or module deno_core

The #[js] macro generates code that references the deno_core crate, but it does not generate a use deno_core statement. Instead, it assume that deno_core is in scope where the macro is used.

If your crate directly depends on deno_core, then the macro will work without extra steps. If your crate does not directly depend on deno_core, for example, if you are using deno_runtime instead, then you can manually introduce deno_core into scope:

+ use deno_runtime::deno_core;

  #[js(global_this)]
  struct Global;