try build emscripten without flags

.github/workflows/ci.yml

@@ -423,7 +423,13 @@ jobs:
         run: PATH="$PATH:/c/Users/runneradmin/.cargo/bin" nox -s test-examples
 
   test-emscripten:
+    name: emscripten (${{ matrix.rust-version }} Rust)
+    strategy:
+      fail-fast: true
+      matrix:
+        rust-version: [stable, nightly]
     runs-on: ubuntu-latest
+    continue-on-error: ${{ matrix.rust-version == 'nightly' }}
     steps:
       - uses: actions/checkout@v6
       - uses: astral-sh/setup-uv@v7
@@ -433,8 +439,9 @@ jobs:
       - run: |
           uvx nox -s install-pyodide-emscripten
           echo "ORIG_PATH=$PATH" >> $GITHUB_ENV
-      - uses: dtolnay/rust-toolchain@nightly
+      - uses: dtolnay/rust-toolchain@master
         with:
+          toolchain: ${{ matrix.rust-version }}
           components: rust-src
           targets: wasm32-unknown-emscripten
       - uses: mymindstorm/setup-emsdk@v14

noxfile.py

@@ -1,11 +1,11 @@
 import os
-from contextlib import ExitStack
-from inspect import cleandoc as heredoc
-from glob import glob
-from pathlib import Path
 import shutil
 import sys
 import tempfile
+from contextlib import ExitStack
+from glob import glob
+from inspect import cleandoc as heredoc
+from pathlib import Path
 
 import nox
 import nox.command
@@ -264,15 +264,6 @@ def install_pyodide_emscripten(session: nox.Session):
 def test_examples_emscripten(session: nox.Session):
     session.install(".", "build")
 
-    session.run(
-        "rustup",
-        "component",
-        "add",
-        "rust-src",
-        "--toolchain",
-        "nightly",
-        external=True,
-    )
     examples_dir = Path("examples").absolute()
     test_crates = [
         examples_dir / "html-py-ever",
@@ -297,7 +288,6 @@ def test_examples_emscripten(session: nox.Session):
         for example in test_crates:
             env = os.environ.copy()
             env.update(
-                RUSTUP_TOOLCHAIN="nightly",
                 PYTHONPATH=str(EMSCRIPTEN_DIR),
                 _PYTHON_SYSCONFIGDATA_NAME="_sysconfigdata__emscripten_wasm32-emscripten",
                 _PYTHON_HOST_PLATFORM=f"emscripten_{emscripten_version_joined}_wasm32",

setuptools_rust/build.py

@@ -1,30 +1,30 @@
 from __future__ import annotations
 
 import json
+import logging
 import os
 import platform
 import shutil
 import subprocess
 import sys
 import sysconfig
-import logging
 import warnings
-from setuptools.errors import (
-    CompileError,
-    ExecError,
-    FileError,
-    PlatformError,
-)
-from sysconfig import get_config_var
 from pathlib import Path
+from sysconfig import get_config_var
 from typing import Dict, List, Literal, NamedTuple, Optional, Set, Tuple, cast
 
 from setuptools import Distribution
 from setuptools.command.build_ext import build_ext as CommandBuildExt
 from setuptools.command.build_ext import get_abi3_suffix
 from setuptools.command.install_scripts import install_scripts as CommandInstallScripts
+from setuptools.errors import (
+    CompileError,
+    ExecError,
+    FileError,
+    PlatformError,
+)
 
-from ._utils import check_subprocess_output, format_called_process_error, Env
+from ._utils import Env, check_subprocess_output, format_called_process_error
 from .command import RustCommand
 from .extension import Binding, RustBin, RustExtension, Strip
 from .rustc_info import (
@@ -40,7 +40,9 @@
     from setuptools.command.bdist_wheel import bdist_wheel as CommandBdistWheel
 except ImportError:  # old version of setuptools
     try:
-        from wheel.bdist_wheel import bdist_wheel as CommandBdistWheel  # type: ignore[no-redef]
+        from wheel.bdist_wheel import (
+            bdist_wheel as CommandBdistWheel,  # type: ignore[no-redef]
+        )
     except ImportError:
         from setuptools import Command as CommandBdistWheel  # type: ignore[assignment]
 
@@ -54,6 +56,16 @@ def _check_cargo_supports_crate_type_option(env: Optional[Env]) -> bool:
     return version.major > 1 or (version.major == 1 and version.minor >= 64)  # type: ignore
 
 
+def _rustc_passes_side_module_automatically(env: Optional[Env]) -> bool:
+    version = get_rust_version(env)
+
+    if version is None:
+        return False
+
+    # Rust 1.95.0 and above automatically pass `-C link-args=-sSIDE_MODULE=2` for wasm32-emscripten targets when building cdylibs
+    return version.major > 1 or (version.major == 1 and version.minor >= 95)  # type: ignore
+
+
 class build_rust(RustCommand):
     """Command for building Rust crates via cargo."""
 
@@ -212,11 +224,13 @@ def build_extension(
                 # the cdylib, see https://github.com/rust-lang/cargo/issues/10143
                 rustflags.append("-Ctarget-feature=-crt-static")
 
-            elif (rustc_cfgs.get("target_arch"), rustc_cfgs.get("target_os")) == (
-                "wasm32",
-                "emscripten",
+            elif (
+                rustc_cfgs.get("target_arch") == "wasm32"
+                and rustc_cfgs.get("target_os") == "emscripten"
             ):
-                rustc_args.extend(["-C", "link-args=-sSIDE_MODULE=2 -sWASM_BIGINT"])
+                rustc_args.extend(["-C", "symbol-mangling-version=v0"])
+                if not _rustc_passes_side_module_automatically(ext.env):
+                    rustc_args.extend(["-C", "link-args=-sSIDE_MODULE=2"])
 
             if use_cargo_crate_type and "--crate-type" not in cargo_args:
                 cargo_args.extend(["--crate-type", "cdylib"])