Fix wasm_js feature combined with a backend override on Wasm

.github/workflows/build.yml

@@ -271,15 +271,19 @@ jobs:
           RUSTFLAGS: -Dwarnings --cfg getrandom_backend="unsupported"
         run: cargo build --target riscv32i-unknown-none-elf
 
-  unsupported:
-    name: Runtime error
+  wasm_override:
+    name: Web WASM override (${{ matrix.backend }})
     runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        backend: [unsupported, custom]
+    env:
+      RUSTFLAGS: -Dwarnings --cfg getrandom_backend="${{ matrix.backend }}"
     steps:
       - uses: actions/checkout@v7
       - uses: dtolnay/rust-toolchain@stable
         with:
           targets: wasm32-unknown-unknown
       - uses: Swatinem/rust-cache@v2
-      - env:
-          RUSTFLAGS: -Dwarnings --cfg getrandom_backend="unsupported"
-        run: cargo build --target wasm32-unknown-unknown
+      - run: cargo build --target wasm32-unknown-unknown
+      - run: cargo build --target wasm32-unknown-unknown --features wasm_js

CHANGELOG.md

@@ -10,6 +10,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Deprecation warning for `libc::INT_MAX` [#868]
+- Compilation error on WASM targets when `wasm_js` crate feature and
+  `getrandom_backend` configuration flag are used simultaneously ([#875])
 
 ### Changed
 - Bumped `r-efi` dependency to v7 ([#869])
@@ -22,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#869]: https://github.com/rust-random/getrandom/pull/869
 [#870]: https://github.com/rust-random/getrandom/pull/870
 [#871]: https://github.com/rust-random/getrandom/pull/871
+[#875]: https://github.com/rust-random/getrandom/pull/875
 
 ## [0.4.3] - 2026-06-17
 ### Added

src/error.rs

@@ -179,6 +179,11 @@ impl Error {
             Error::WINDOWS_RTL_GEN_RANDOM => "RtlGenRandom: Windows system function failure",
             #[cfg(all(
                 feature = "wasm_js",
+                not(any(
+                    getrandom_backend = "unsupported",
+                    getrandom_backend = "custom",
+                    getrandom_backend = "extern_impl",
+                )),
                 target_arch = "wasm32",
                 any(target_os = "unknown", target_os = "none")
             ))]