refactor(napi/parser): do not compile raw transfer code on WASM (#12271)

Reduce size of `oxc-parser` WASM binary by omitting code for raw transfer. Raw transfer is not supported on WASM.

This also allows removing the workaround to prevent compilation failure on 32-bit systems due to `1 << 32` overflowing `usize`. This code is no longer compiled on 32-bit systems.

Author: overlookmotel

napi/parser/src/lib.rs

@@ -22,13 +22,28 @@ use oxc::{
 use oxc_napi::{Comment, OxcError, convert_utf8_to_utf16, get_source_type};
 
 mod convert;
+mod types;
+pub use types::{EcmaScriptModule, ParseResult, ParserOptions};
+
+// Raw transfer is only supported on 64-bit little-endian systems.
+// Don't include raw transfer code on other platforms (notably WASM32).
+// `raw_transfer_types` still needs to be compiled, as `assert_layouts` refers to those types,
+// but it's all dead code on unsupported platforms, and will be excluded from binary.
+#[cfg(all(target_pointer_width = "64", target_endian = "little"))]
 mod raw_transfer;
 mod raw_transfer_types;
-mod types;
+#[cfg(all(target_pointer_width = "64", target_endian = "little"))]
 pub use raw_transfer::{
     get_buffer_offset, parse_async_raw, parse_sync_raw, raw_transfer_supported,
 };
-pub use types::{EcmaScriptModule, ParseResult, ParserOptions};
+
+// Fallback for 32-bit or big-endian platforms.
+/// Returns `true` if raw transfer is supported on this platform.
+#[cfg(not(all(target_pointer_width = "64", target_endian = "little")))]
+#[napi]
+pub fn raw_transfer_supported() -> bool {
+    false
+}
 
 mod generated {
     // Note: We intentionally don't import `generated/derive_estree.rs`. It's not needed.

napi/parser/src/raw_transfer.rs

@@ -22,10 +22,6 @@ use crate::{
     raw_transfer_types::{EcmaScriptModule, Error, RawTransferData},
 };
 
-// Only 64-bit little-endian platforms are supported at present.
-const IS_SUPPORTED_PLATFORM: bool =
-    cfg!(all(target_pointer_width = "64", target_endian = "little"));
-
 // For raw transfer, use a buffer 4 GiB in size, with 4 GiB alignment.
 // This ensures that all 64-bit pointers have the same value in upper 32 bits,
 // so JS only needs to read the lower 32 bits to get an offset into the buffer.
@@ -34,9 +30,7 @@ const IS_SUPPORTED_PLATFORM: bool =
 // so this enables using `>>` bitshift operator in JS, rather than the more expensive `>>>`,
 // without offsets being interpreted as negative.
 const TWO_GIB: usize = 1 << 31;
-// `1 << 32`.
-// We use `IS_SUPPORTED_PLATFORM as usize * 32` to avoid compilation failure on 32-bit platforms.
-const FOUR_GIB: usize = 1 << (IS_SUPPORTED_PLATFORM as usize * 32);
+const FOUR_GIB: usize = 1 << 32;
 
 const BUFFER_SIZE: usize = TWO_GIB;
 const BUFFER_ALIGN: usize = FOUR_GIB;
@@ -175,11 +169,6 @@ unsafe fn parse_raw_impl(
     source_len: u32,
     options: Option<ParserOptions>,
 ) {
-    assert!(
-        IS_SUPPORTED_PLATFORM,
-        "Raw transfer is only supported on 64-bit little-endian platforms"
-    );
-
     // Check buffer has expected size and alignment
     assert_eq!(buffer.len(), BUFFER_SIZE);
     let buffer_ptr = ptr::from_mut(buffer).cast::<u8>();
@@ -291,9 +280,12 @@ unsafe fn parse_raw_impl(
 }
 
 /// Returns `true` if raw transfer is supported on this platform.
+//
+// This module is only compiled on 64-bit little-endian platforms.
+// Fallback version for unsupported platforms in `lib.rs`.
 #[napi]
 pub fn raw_transfer_supported() -> bool {
-    IS_SUPPORTED_PLATFORM
+    true
 }
 
 /// Returns `true` if `n` is a multiple of `divisor`.

napi/parser/src/raw_transfer_types.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(not(all(target_pointer_width = "64", target_endian = "little")), expect(dead_code))]
+
 use std::sync::Arc;
 
 use rustc_hash::FxHashMap;