feat(interface-types) Make serde optional behind a feature flag.

Cargo.toml

@@ -10,4 +10,11 @@ edition = "2018"
 [dependencies]
 nom = "5.1"
 wast = "8.0"
-serde = { version = "1.0", features = ["derive"] }
+
+# `serde` is useful only to simplify the users' life. It is not
+# required by WIT itself, is is used to transform WIT values like
+# `record`s to Rust sum types.
+serde = { version = "1.0", features = ["derive"], optional = true }
+
+[features]
+default = ["serde"]

src/interpreter/instructions/records.rs

@@ -214,6 +214,7 @@ mod tests {
             ])],
     );
 
+    #[cfg(feature = "serde")]
     #[test]
     #[allow(non_snake_case, unused)]
     fn test_record_lift__to_rust_struct() {

src/interpreter/wasm/mod.rs

@@ -2,6 +2,8 @@
 //! types, and traits —basically this is the part a runtime should
 //! take a look to use the `wasmer-interface-types` crate—.
 
+#[cfg(feature = "serde")]
 mod serde;
+
 pub mod structures;
 pub mod values;

src/interpreter/wasm/values.rs

@@ -2,9 +2,11 @@
 
 pub use crate::ast::{InterfaceType, RecordType};
 use crate::errors::WasmValueNativeCastError;
-pub use crate::interpreter::wasm::serde::*;
 use std::{convert::TryFrom, slice::Iter};
 
+#[cfg(feature = "serde")]
+pub use crate::interpreter::wasm::serde::*;
+
 /// A WIT value.
 #[derive(Debug, Clone, PartialEq)]
 pub enum InterfaceValue {