Change the encoding of wit definitions

crates/wit-component/src/encoding/wit/mod.rs

@@ -0,0 +1,68 @@
+use anyhow::Result;
+use wasm_encoder::{ComponentBuilder, ComponentType};
+use wit_parser::{PackageId, Resolve, WorldId};
+
+mod v1;
+mod v2;
+
+const ENCODE_V2_BY_DEFAULT: bool = false;
+
+fn use_v2_encoding() -> bool {
+    match std::env::var("WIT_COMPONENT_ENCODING_V2") {
+        Ok(s) => s == "1",
+        Err(_) => ENCODE_V2_BY_DEFAULT,
+    }
+}
+
+/// Encodes the given `package` within `resolve` to a binary WebAssembly
+/// representation.
+///
+/// This function is the root of the implementation of serializing a WIT package
+/// into a WebAssembly representation. The wasm representation serves two
+/// purposes:
+///
+/// * One is to be a binary encoding of a WIT document which is ideally more
+///   stable than the WIT textual format itself.
+/// * Another is to provide a clear mapping of all WIT features into the
+///   component model through use of its binary representation.
+///
+/// The `resolve` provided is a set of packages and types and such and the
+/// `package` argument is an ID within the world provided. The documents within
+/// `package` will all be encoded into the binary returned.
+///
+/// The binary returned can be [`decode`d](crate::decode) to recover the WIT
+/// package provided.
+pub fn encode(use_v2: Option<bool>, resolve: &Resolve, package: PackageId) -> Result<Vec<u8>> {
+    if use_v2.unwrap_or_else(use_v2_encoding) {
+        v2::encode(resolve, package)
+    } else {
+        v1::encode(resolve, package)
+    }
+}
+
+/// Exactly like `encode`, except gives an unfinished `ComponentBuilder` in case you need
+/// to append anything else before finishing.
+pub fn encode_component(
+    use_v2: Option<bool>,
+    resolve: &Resolve,
+    package: PackageId,
+) -> Result<ComponentBuilder> {
+    if use_v2.unwrap_or_else(use_v2_encoding) {
+        v2::encode_component(resolve, package)
+    } else {
+        v1::encode_component(resolve, package)
+    }
+}
+
+/// Encodes a `world` as a component type.
+pub fn encode_world(
+    use_v2: Option<bool>,
+    resolve: &Resolve,
+    world_id: WorldId,
+) -> Result<ComponentType> {
+    if use_v2.unwrap_or_else(use_v2_encoding) {
+        v2::encode_world(resolve, world_id)
+    } else {
+        v1::encode_world(resolve, world_id)
+    }
+}

crates/wit-component/src/encoding/wit.rs → crates/wit-component/src/encoding/wit/v1.rs

@@ -1,13 +1,14 @@
-use crate::encoding::types::{FunctionKey, ValtypeEncoder};
+use crate::encoding::{
+    docs::PackageDocs,
+    types::{FunctionKey, ValtypeEncoder},
+};
 use anyhow::Result;
 use indexmap::IndexSet;
 use std::collections::HashMap;
 use std::mem;
 use wasm_encoder::*;
 use wit_parser::*;
 
-use super::docs::PackageDocs;
-
 /// Encodes the given `package` within `resolve` to a binary WebAssembly
 /// representation.
 ///