Experimental test coverage support

CHANGELOG.md

@@ -75,6 +75,9 @@
 * Added importing strings as `JsString` through `#[wasm_bindgen(thread_local, static_string)] static STRING: JsString = "a string literal";`.
   [#4055](https://github.com/rustwasm/wasm-bindgen/pull/4055)
 
+* Added experimental test coverage support for `wasm-bindgen-test-runner`, see the guide for more information.
+  [#4060](https://github.com/rustwasm/wasm-bindgen/pull/4060)
+
 ### Changed
 
 * Stabilize Web Share API.

Cargo.toml

@@ -56,6 +56,11 @@ serde_derive = "1.0"
 wasm-bindgen-test-crate-a = { path = 'tests/crates/a' }
 wasm-bindgen-test-crate-b = { path = 'tests/crates/b' }
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = [
+    'cfg(wasm_bindgen_unstable_test_coverage)',
+] }
+
 [workspace]
 members = [
   "benchmarks",

crates/backend/src/codegen.rs

@@ -220,6 +220,7 @@ impl ToTokens for ast::Struct {
         (quote! {
             #[automatically_derived]
             impl #wasm_bindgen::describe::WasmDescribe for #name {
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 fn describe() {
                     use #wasm_bindgen::__wbindgen_if_not_std;
                     use #wasm_bindgen::describe::*;
@@ -293,6 +294,7 @@ impl ToTokens for ast::Struct {
                 #[doc(hidden)]
                 // `allow_delayed` is whether it's ok to not actually free the `ptr` immediately
                 // if it's still borrowed.
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub unsafe extern "C" fn #free_fn(ptr: u32, allow_delayed: u32) {
                     use #wasm_bindgen::__rt::alloc::rc::Rc;
 
@@ -401,6 +403,7 @@ impl ToTokens for ast::Struct {
             }
 
             impl #wasm_bindgen::describe::WasmDescribeVector for #name {
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 fn describe_vector() {
                     use #wasm_bindgen::describe::*;
                     inform(VECTOR);
@@ -484,6 +487,7 @@ impl ToTokens for ast::StructField {
             const _: () = {
                 #[cfg_attr(all(target_arch = "wasm32", target_os = "unknown"), no_mangle)]
                 #[doc(hidden)]
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub unsafe extern "C" fn #getter(js: u32)
                     -> #wasm_bindgen::convert::WasmRet<<#ty as #wasm_bindgen::convert::IntoWasmAbi>::Abi>
                 {
@@ -525,6 +529,7 @@ impl ToTokens for ast::StructField {
             const _: () = {
                 #[no_mangle]
                 #[doc(hidden)]
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub unsafe extern "C" fn #setter(
                     js: u32,
                     #(#args,)*
@@ -781,6 +786,7 @@ impl TryToTokens for ast::Export {
                     all(target_arch = "wasm32", target_os = "unknown"),
                     export_name = #export_name,
                 )]
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub unsafe extern "C" fn #generated_name(#(#args),*) -> #wasm_bindgen::convert::WasmRet<#projection::Abi> {
                     #start_check
 
@@ -932,6 +938,7 @@ impl ToTokens for ast::ImportType {
                 use #wasm_bindgen::__rt::core;
 
                 impl WasmDescribe for #rust_name {
+                    #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                     fn describe() {
                         #description
                     }
@@ -1222,6 +1229,7 @@ impl ToTokens for ast::StringEnum {
 
             #[automatically_derived]
             impl #wasm_bindgen::describe::WasmDescribe for #enum_name {
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 fn describe() {
                     use #wasm_bindgen::describe::*;
                     inform(STRING_ENUM);
@@ -1563,6 +1571,7 @@ impl ToTokens for ast::Enum {
 
             #[automatically_derived]
             impl #wasm_bindgen::describe::WasmDescribe for #enum_name {
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 fn describe() {
                     use #wasm_bindgen::describe::*;
                     inform(ENUM);
@@ -1599,6 +1608,7 @@ impl ToTokens for ast::Enum {
             }
 
             impl #wasm_bindgen::describe::WasmDescribeVector for #enum_name {
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 fn describe_vector() {
                     use #wasm_bindgen::describe::*;
                     inform(VECTOR);
@@ -1795,6 +1805,7 @@ impl<'a, T: ToTokens> ToTokens for Descriptor<'a, T> {
                 #(#attrs)*
                 #[no_mangle]
                 #[doc(hidden)]
+                #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
                 pub extern "C" fn #name() {
                     use #wasm_bindgen::describe::*;
                     // See definition of `link_mem_intrinsics` for what this is doing

crates/cli/src/bin/wasm-bindgen-test-runner/main.rs

@@ -15,6 +15,7 @@ use anyhow::{anyhow, bail, Context};
 use log::error;
 use std::env;
 use std::fs;
+use std::path::Path;
 use std::path::PathBuf;
 use std::thread;
 use wasm_bindgen_cli_support::Bindgen;
@@ -222,6 +223,8 @@ fn main() -> anyhow::Result<()> {
         b.split_linked_modules(true);
     }
 
+    let coverage = coverage_args(&tmpdir);
+
     b.debug(debug)
         .input_module(module, wasm)
         .keep_debug(false)
@@ -256,6 +259,7 @@ fn main() -> anyhow::Result<()> {
                 &tests,
                 test_mode,
                 std::env::var("WASM_BINDGEN_TEST_NO_ORIGIN_ISOLATION").is_err(),
+                coverage,
             )
             .context("failed to spawn server")?;
             let addr = srv.server_addr();
@@ -282,3 +286,28 @@ fn main() -> anyhow::Result<()> {
     }
     Ok(())
 }
+
+fn coverage_args(tmpdir: &Path) -> PathBuf {
+    fn generated(tmpdir: &Path, prefix: &str) -> String {
+        let res = format!(
+            "{prefix}{}.profraw",
+            tmpdir.file_name().and_then(|s| s.to_str()).unwrap()
+        );
+        res
+    }
+
+    let prefix = env::var_os("WASM_BINDGEN_UNSTABLE_TEST_PROFRAW_PREFIX")
+        .map(|s| s.to_str().unwrap().to_string())
+        .unwrap_or_default();
+
+    match env::var_os("WASM_BINDGEN_UNSTABLE_TEST_PROFRAW_OUT") {
+        Some(s) => {
+            let mut buf = PathBuf::from(s);
+            if buf.is_dir() {
+                buf.push(generated(tmpdir, &prefix));
+            }
+            buf
+        }
+        None => PathBuf::from(generated(tmpdir, &prefix)),
+    }
+}

crates/cli/src/bin/wasm-bindgen-test-runner/server.rs

@@ -1,8 +1,9 @@
 use std::borrow::Cow;
 use std::ffi::OsString;
 use std::fs;
+use std::io::{Read, Write};
 use std::net::SocketAddr;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use anyhow::{anyhow, Context, Error};
 use rouille::{Request, Response, Server};
@@ -18,9 +19,24 @@ pub(crate) fn spawn(
     tests: &[String],
     test_mode: TestMode,
     isolate_origin: bool,
+    coverage: PathBuf,
 ) -> Result<Server<impl Fn(&Request) -> Response + Send + Sync>, Error> {
     let mut js_to_execute = String::new();
 
+    let cov_import = if test_mode.no_modules() {
+        "let __wbgtest_cov_dump = wasm_bindgen.__wbgtest_cov_dump;"
+    } else {
+        "__wbgtest_cov_dump,"
+    };
+    let cov_dump = r#"
+        // Dump the coverage data collected during the tests
+        const coverage = __wbgtest_cov_dump();
+        await fetch("/__wasm_bindgen/coverage", {
+            method: "POST",
+            body: coverage
+        });
+    "#;
+
     let wbg_import_script = if test_mode.no_modules() {
         String::from(
             r#"
@@ -30,6 +46,7 @@ pub(crate) fn spawn(
             let __wbgtest_console_info = wasm_bindgen.__wbgtest_console_info;
             let __wbgtest_console_warn = wasm_bindgen.__wbgtest_console_warn;
             let __wbgtest_console_error = wasm_bindgen.__wbgtest_console_error;
+            {cov_import}
             let init = wasm_bindgen;
             "#,
         )
@@ -43,6 +60,7 @@ pub(crate) fn spawn(
                 __wbgtest_console_info,
                 __wbgtest_console_warn,
                 __wbgtest_console_error,
+                {cov_import}
                 default as init,
             }} from './{}';
             "#,
@@ -116,6 +134,7 @@ pub(crate) fn spawn(
 
                 cx.args({1:?});
                 await cx.run(tests.map(s => wasm[s]));
+                {cov_dump}
             }}
 
             port.onmessage = function(e) {{
@@ -250,6 +269,7 @@ pub(crate) fn spawn(
                 cx.args({1:?});
 
                 await cx.run(test.map(s => wasm[s]));
+                {cov_dump}
             }}
 
             const tests = [];
@@ -300,6 +320,16 @@ pub(crate) fn spawn(
             }
 
             return response;
+        } else if request.url() == "/__wasm_bindgen/coverage" {
+            return if let Err(e) = handle_coverage_dump(&coverage, request) {
+                let s: &str = &format!("Failed to dump coverage: {e}");
+                log::error!("{s}");
+                let mut ret = Response::text(s);
+                ret.status_code = 500;
+                ret
+            } else {
+                Response::empty_204()
+            };
         }
 
         // Otherwise we need to find the asset here. It may either be in our
@@ -351,6 +381,21 @@ pub(crate) fn spawn(
     }
 }
 
+fn handle_coverage_dump(profraw_path: &Path, request: &Request) -> anyhow::Result<()> {
+    // This is run after all tests are done and dumps the data received in the request
+    // into a single profraw file
+    let mut profraw = std::fs::File::create(profraw_path)?;
+    let mut data = Vec::new();
+    if let Some(mut r_data) = request.data() {
+        r_data.read_to_end(&mut data)?;
+    }
+    // Warnings about empty data should have already been handled by
+    // the client
+
+    profraw.write_all(&data)?;
+    Ok(())
+}
+
 /*
  * Set the Cross-Origin-Opener-Policy and Cross-Origin_Embedder-Policy headers
  * on the Server response to enable worker context sharing, as described in:

crates/macro/Cargo.toml

@@ -31,3 +31,8 @@ trybuild = "1.0"
 wasm-bindgen = { path = "../.." }
 wasm-bindgen-futures = { path = "../futures" }
 web-sys = { path = "../web-sys", features = ["Worker"] }
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = [
+    'cfg(wasm_bindgen_unstable_test_coverage)',
+] }

crates/macro/src/lib.rs

@@ -1,11 +1,20 @@
 #![doc(html_root_url = "https://docs.rs/wasm-bindgen-macro/0.2")]
+#![cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    feature(allow_internal_unstable),
+    allow(internal_features)
+)]
 
 extern crate proc_macro;
 
 use proc_macro::TokenStream;
 use quote::quote;
 
 #[proc_macro_attribute]
+#[cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    allow_internal_unstable(coverage_attribute)
+)]
 pub fn wasm_bindgen(attr: TokenStream, input: TokenStream) -> TokenStream {
     match wasm_bindgen_macro_support::expand(attr.into(), input.into()) {
         Ok(tokens) => {
@@ -32,6 +41,10 @@ pub fn wasm_bindgen(attr: TokenStream, input: TokenStream) -> TokenStream {
 /// let worker = Worker::new(&wasm_bindgen::link_to!(module = "/src/worker.js"));
 /// ```
 #[proc_macro]
+#[cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    allow_internal_unstable(coverage_attribute)
+)]
 pub fn link_to(input: TokenStream) -> TokenStream {
     match wasm_bindgen_macro_support::expand_link_to(input.into()) {
         Ok(tokens) => {
@@ -48,6 +61,10 @@ pub fn link_to(input: TokenStream) -> TokenStream {
 }
 
 #[proc_macro_attribute]
+#[cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    allow_internal_unstable(coverage_attribute)
+)]
 pub fn __wasm_bindgen_class_marker(attr: TokenStream, input: TokenStream) -> TokenStream {
     match wasm_bindgen_macro_support::expand_class_marker(attr.into(), input.into()) {
         Ok(tokens) => {

crates/test-macro/Cargo.toml

@@ -20,3 +20,8 @@ syn = { version = "2.0", default-features = false, features = [ "parsing", "proc
 [dev-dependencies]
 wasm-bindgen-test = { path = "../test" }
 trybuild = "1.0"
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = [
+    'cfg(wasm_bindgen_unstable_test_coverage)',
+] }

crates/test-macro/src/lib.rs

@@ -1,6 +1,12 @@
 //! See the README for `wasm-bindgen-test` for a bit more info about what's
 //! going on here.
 
+#![cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    feature(allow_internal_unstable),
+    allow(internal_features)
+)]
+
 extern crate proc_macro;
 
 use proc_macro2::*;
@@ -12,6 +18,10 @@ use std::sync::atomic::*;
 static CNT: AtomicUsize = AtomicUsize::new(0);
 
 #[proc_macro_attribute]
+#[cfg_attr(
+    wasm_bindgen_unstable_test_coverage,
+    allow_internal_unstable(coverage_attribute)
+)]
 pub fn wasm_bindgen_test(
     attr: proc_macro::TokenStream,
     body: proc_macro::TokenStream,
@@ -102,6 +112,7 @@ pub fn wasm_bindgen_test(
     tokens.extend(
         quote! {
             #[no_mangle]
+            #[cfg_attr(wasm_bindgen_unstable_test_coverage, coverage(off))]
             pub extern "C" fn #name(cx: &#wasm_bindgen_path::__rt::Context) {
                 let test_name = ::core::concat!(::core::module_path!(), "::", ::core::stringify!(#ident));
                 #test_body

crates/test/Cargo.toml

@@ -18,5 +18,13 @@ wasm-bindgen-futures = { path = '../futures', version = '0.4.42' }
 wasm-bindgen-test-macro = { path = '../test-macro', version = '=0.3.42' }
 gg-alloc = { version = "1.0", optional = true }
 
+[target.'cfg(all(target_arch = "wasm32", wasm_bindgen_unstable_test_coverage))'.dependencies]
+minicov = "0.3"
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = [
+    'cfg(wasm_bindgen_unstable_test_coverage)',
+] }
+
 [lib]
 test = false