Files
Luke Sandberg a24462d9e5 Replace wasmer with wasmtime for SWC plugin WASM engine (#91533)
## What?

Replace wasmer with wasmtime as the WASM runtime for SWC plugins.

## Why?

- Wasmer has been a source of build complexity due to conflicting feature flags (`wasmer/default` vs `wasmer/js-default`) and large binary size
- Wasmtime is actively maintained by the Bytecode Alliance with better performance and smaller footprint
- The upstream SWC project already provides `swc_plugin_backend_wasmtime` on crates.io, so we can use it directly instead of maintaining our own implementation

## How?

- Use the upstream `swc_plugin_backend_wasmtime` v9.0.0 crate from crates.io instead of a custom local implementation
- Replace `swc_core/plugin_transform_host_native` (which pulls in wasmer via `__plugin_transform_env_native`) with granular features: `__plugin_transform_host` + `__plugin_transform_host_schema_v1`
- Provide `WasmtimeRuntime` explicitly in both the NAPI bindings and turbopack plugin paths
- Remove all direct `wasmtime`/`wasmtime-wasi` workspace dependencies — the upstream crate manages its own wasmtime version
- Replace wasmer-related release profile size optimizations with equivalent wasmtime ones (`swc_plugin_backend_wasmtime`, `swc_plugin_runner`, `wasmtime`, `wasmtime-internal-cranelift`)
- Pin `vergen = "=9.0.6"` to avoid a `vergen-lib` version conflict with `vergen-gitcl` 1.0.8

## Binary size impact (darwin-arm64, compared against current canary)

| Metric | Canary | Wasmtime (this PR) | Delta |
|---|---|---|---|
| Unstripped dylib | 133.1 MB | 128.2 MB | **-5.0 MB (-3.7%)** |
| Stripped | 91.2 MB | 86.9 MB | **-4.3 MB (-4.8%)** |
| Stripped + gzip (npm) | 30.9 MB | 29.4 MB | **-1.5 MB (-5.0%)** |

<!-- NEXT_JS_LLM_PR -->
2026-04-09 09:34:00 -07:00

137 lines
4.5 KiB
Rust

use std::{
path::{Path, PathBuf},
sync::Arc,
};
use next_custom_transforms::chain_transforms::{TransformOptions, custom_before_pass};
use serde::de::DeserializeOwned;
use swc_core::{
base::Compiler,
common::{Mark, comments::SingleThreadedComments},
ecma::{
ast::noop_pass,
parser::{Syntax, TsSyntax},
},
};
use testing::{NormalizedOutput, Tester};
#[testing::fixture("tests/full/**/input.js")]
fn full(input: PathBuf) {
test(&input, true);
}
#[testing::fixture("tests/loader/**/input.js")]
fn loader(input: PathBuf) {
test(&input, false);
}
fn test(input: &Path, minify: bool) {
let output = input.parent().unwrap().join("output.js");
Tester::new()
.print_errors(|cm, handler| {
let c = Compiler::new(cm.clone());
let fm = cm.load_file(input).expect("failed to load file");
let options = TransformOptions {
lint_codemod_comments: true,
swc: swc_core::base::config::Options {
swcrc: true,
output_path: Some(output.clone()),
config: swc_core::base::config::Config {
is_module: Some(swc_core::base::config::IsModule::Unknown),
jsc: swc_core::base::config::JscConfig {
minify: if minify {
Some(assert_json("{ \"compress\": true, \"mangle\": true }"))
} else {
None
},
syntax: Some(Syntax::Typescript(TsSyntax {
tsx: true,
..Default::default()
})),
external_helpers: true.into(),
..Default::default()
},
..Default::default()
},
..Default::default()
},
disable_next_ssg: false,
pages_dir: None,
is_page_file: false,
is_development: true,
is_server_compiler: false,
server_components: None,
styled_components: Some(assert_json("{}")),
styled_jsx: assert_json("{}"),
remove_console: None,
react_remove_properties: None,
relay: None,
shake_exports: None,
emotion: Some(assert_json("{}")),
modularize_imports: None,
font_loaders: None,
app_dir: None,
server_actions: None,
cjs_require_optimizer: None,
auto_modularize_imports: None,
optimize_barrel_exports: None,
optimize_server_react: None,
prefer_esm: false,
debug_function_name: false,
css_env: None,
track_dynamic_imports: false,
};
let unresolved_mark = Mark::new();
let mut options = options.patch(&fm);
options.swc.unresolved_mark = Some(unresolved_mark);
options.swc.runtime_options = swc_core::base::config::RuntimeOptions::default()
.plugin_runtime(Arc::new(swc_plugin_backend_wasmtime::WasmtimeRuntime));
let comments = SingleThreadedComments::default();
match c.process_js_with_custom_pass(
fm.clone(),
None,
&handler,
&options.swc,
comments.clone(),
|_| {
custom_before_pass(
cm.clone(),
fm.clone(),
&options,
comments.clone(),
Default::default(),
unresolved_mark,
Default::default(),
)
},
|_| noop_pass(),
) {
Ok(v) => {
NormalizedOutput::from(v.code)
.compare_to_file(output)
.unwrap();
}
Err(err) => panic!("Error: {:?}", err),
};
Ok(())
})
.map(|_| ())
.expect("failed");
}
/// Using this, we don't have to break code by adding field.s
fn assert_json<T>(json_str: &str) -> T
where
T: DeserializeOwned,
{
serde_json::from_str(json_str).expect("failed to deserialize")
}