ast: make cargo test -p bun_ast link natively

src/ast/lib.rs

@@ -2830,6 +2830,8 @@ pub mod use_directive;
 pub mod lexer_log;
 pub use lexer_log::LexerLog;
 pub mod lexer_tables;
+#[cfg(test)]
+mod native_test_shims;
 pub mod nodes;
 pub mod runtime;
 

src/ast/native_test_shims.rs

@@ -0,0 +1,51 @@
+//! mimalloc symbols the `TapeAlloc::Arena` arm makes this crate's `cargo test`
+//! binary reference; mimalloc is only linked into bun. Never compiled into the
+//! real build.
+
+use core::ffi::c_void;
+
+use bun_alloc::mimalloc::Heap;
+
+/// Nothing here references `mi_heap_new` or `mi_heap_main`, so no arena exists to get here.
+fn no_mimalloc_in_test_binary(symbol: &str) -> ! {
+    unreachable!("{symbol} called, but bun_ast's test binary does not link mimalloc")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_heap_malloc(_heap: *mut Heap, _size: usize) -> *mut c_void {
+    no_mimalloc_in_test_binary("mi_heap_malloc")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_heap_malloc_aligned(
+    _heap: *mut Heap,
+    _size: usize,
+    _alignment: usize,
+) -> *mut c_void {
+    no_mimalloc_in_test_binary("mi_heap_malloc_aligned")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_malloc_usable_size(_p: *const c_void) -> usize {
+    no_mimalloc_in_test_binary("mi_malloc_usable_size")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_is_in_heap_region(_p: *const c_void) -> bool {
+    no_mimalloc_in_test_binary("mi_is_in_heap_region")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_free(_p: *mut c_void) {
+    no_mimalloc_in_test_binary("mi_free")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_free_size(_p: *mut c_void, _size: usize) {
+    no_mimalloc_in_test_binary("mi_free_size")
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn mi_free_size_aligned(_p: *mut c_void, _size: usize, _alignment: usize) {
+    no_mimalloc_in_test_binary("mi_free_size_aligned")
+}

test/internal/rust-ast-cargo-test.test.ts

@@ -0,0 +1,53 @@
+// The Miri lane (scripts/rust-miri.ts) runs bun_ast's tests without linking,
+// so only a host `cargo test -p bun_ast` notices when the test binary
+// references symbols that exist only in the full bun link. The tape tests keep
+// the TapeAlloc::Arena arm live, and src/ast/native_test_shims.rs defines the
+// mimalloc symbols it reaches; without it:
+//   ld.lld: error: undefined symbol: mi_heap_malloc
+// The set differs per profile (bun_alloc's mi_free_checked uses mi_free_size*
+// under debug_assertions and mi_free otherwise), hence both rows; the tests
+// are run, not just linked, because the shims abort if anything reaches them.
+//
+// Unix only: this relies on the linker reporting only references from live
+// code (lld --gc-sections). link.exe reports dead ones too, so a bun_core
+// dependent's test binary there either fails on ~100 unrelated externs or has
+// them forced through; neither says anything about these shims. Remaining
+// prerequisites as in rust-windows-sys-link.test.ts: cargo, and a configured
+// checkout (vendor/lolhtml, build_options.rs), which test-only CI lanes lack.
+import { which } from "bun";
+import { expect, test } from "bun:test";
+import { isWindows } from "harness";
+import { existsSync } from "node:fs";
+import { join } from "node:path";
+
+const cargo = which("cargo");
+const repoRoot = join(import.meta.dir, "..", "..");
+const workspaceResolvable =
+  existsSync(join(repoRoot, "vendor", "lolhtml", "Cargo.toml")) &&
+  existsSync(join(repoRoot, "build", "debug", "codegen", "build_options.rs"));
+
+test.skipIf(isWindows || !cargo || !workspaceResolvable).each([
+  ["dev", []],
+  ["release", ["--release"]],
+] as const)(
+  "cargo test -p bun_ast links and passes without the rest of bun (%s profile)",
+  async (_profile, profileArgs) => {
+    await using proc = Bun.spawn({
+      cmd: [cargo!, "test", "--locked", "-p", "bun_ast", "--lib", ...profileArgs],
+      cwd: repoRoot,
+      env: { ...process.env, CARGO_TERM_COLOR: "never" },
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+    expect(stderr).not.toContain("undefined symbol");
+    // The tape tests are what make the arena arm live; they must have run here, natively.
+    expect(stdout).toMatch(/^test e::json_tape_tests::\w+ \.\.\. ok$/m);
+    expect(stdout).toContain("test result: ok.");
+    expect({ stdout, stderr, exitCode }).toMatchObject({ exitCode: 0 });
+  },
+  // Cold target dir: compiles bun_core and ~30 other crates first, and the
+  // release row ends in a fat-LTO link.
+  180_000,
+);