Make rustworkx build and run with pyiodide (#1447)

* Pyodide: force only one thread

* Add .cargo/config.toml

* Unstable feature that makes rayon work

* Newline

* Document pyodide

* Add release note for pyodide

* Fix separator

* Consolidate the bare minimum of flags

* Add emscripten-wasm-eh flag

* Solve nit

* Remove flags forcing emscripten builds from requiring nightly

Author: IvanIsCoding

.cargo/config.toml

@@ -9,3 +9,6 @@ rustflags = [
   "-C", "link-arg=-undefined",
   "-C", "link-arg=dynamic_lookup",
 ]
+
+[unstable]
+build-std = ["std", "panic_abort"]

Cargo.toml

@@ -75,5 +75,5 @@ default-features = false
 features = ["multi_thread"]
 
 [profile.release]
-lto = 'fat'
+lto = "fat"
 codegen-units = 1

docs/source/install.rst

@@ -113,6 +113,10 @@ source.
      - i686 or x86_64
      - :ref:`tier-4`
      -
+   * - Pyodide 
+     - WASM (Emscripten)
+     - :ref:`tier-experimental`
+     -
 
 
 .. _manylinux 2014: https://peps.python.org/pep-0599/>
@@ -166,6 +170,18 @@ functioning Python environment and may require a C/C++ compiler or additional
 programs to build dependencies from source as part of the installation process.
 Support for these platforms are best effort only.
 
+.. _tier-experimental:
+
+Tier Experimental
+-----------------
+
+Tier Experimental platforms are not tested upstream as part of the development process.
+Pre-compiled binaries are built by the external community in separate repositories. Not all of rustworkx might compile for
+platforms of this tier and features can be removed. Often, platforms in this tier use unstable features
+from the Rust compiler and might break at any time. Support for these platforms are best effort only.
+
+Currently, the only platform in this tier is Pyodide, which is a port of Python that can run in the browser and on Node.js.
+
 Using rustworkx
 ===============
 

releasenotes/notes/pyodide-support-2172f2313b06f10d.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    `rustworkx` now has experimental support for `Pyodide <https://pyodide.org/en/stable/>`__.
+    Pyodide is a Python distribution for WebAssembly that runs in the browser.
+    This is the first release that compiles with Pyodide and will allow users to run `rustworkx`
+    in web applications. Because Pyodide wheels are not available in PyPI,
+    we are working with the Pyodide team to publish them in the Pyodide package index.

src/lib.rs

@@ -710,5 +710,21 @@ fn rustworkx(py: Python<'_>, m: &Bound<PyModule>) -> PyResult<()> {
     m.add_class::<Type>()?;
     m.add_class::<KeySpec>()?;
     m.add_wrapped(wrap_pymodule!(generators::generators))?;
+    #[cfg(target_os = "emscripten")]
+    setup_rayon_for_pyodide();
     Ok(())
 }
+
+#[cfg(target_os = "emscripten")]
+static PYODIDE_INIT: std::sync::Once = std::sync::Once::new();
+
+#[cfg(target_os = "emscripten")]
+pub fn setup_rayon_for_pyodide() {
+    PYODIDE_INIT.call_once(|| {
+        rayon::ThreadPoolBuilder::new()
+            .num_threads(1)
+            .use_current_thread()
+            .build_global()
+            .expect("failing setting up threads for pyodide");
+    });
+}