Add NonNull<T> as parameter (#3857)

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 * Add support for `Option<*const T>`, `Option<*mut T>` and `NonNull<T>`.
   [#3852](https://github.com/rustwasm/wasm-bindgen/pull/3852)
+  [#3857](https://github.com/rustwasm/wasm-bindgen/pull/3857)
 
 * Allow overriding the URL used for headless tests by setting `WASM_BINDGEN_TEST_ADDRESS`.
   [#3861](https://github.com/rustwasm/wasm-bindgen/pull/3861)

crates/cli-support/src/js/binding.rs

@@ -497,6 +497,11 @@ impl<'a, 'b> JsBuilder<'a, 'b> {
         self.prelude("}");
     }
 
+    fn assert_non_null(&mut self, arg: &str) {
+        self.cx.expose_assert_non_null();
+        self.prelude(&format!("_assertNonNull({});", arg));
+    }
+
     fn assert_optional_bigint(&mut self, arg: &str) {
         if !self.cx.config.debug {
             return;
@@ -1218,6 +1223,12 @@ fn instruction(
             js.push(format!("{0} === {1} ? undefined : {0}", val, hole));
         }
 
+        Instruction::I32FromNonNull => {
+            let val = js.pop();
+            js.assert_non_null(&val);
+            js.push(val);
+        }
+
         Instruction::I32FromOptionNonNull => {
             let val = js.pop();
             js.cx.expose_is_like_none();

crates/cli-support/src/js/mod.rs

@@ -2103,6 +2103,19 @@ impl<'a> Context<'a> {
         );
     }
 
+    fn expose_assert_non_null(&mut self) {
+        if !self.should_write_global("assert_non_null") {
+            return;
+        }
+        self.global(
+            "
+            function _assertNonNull(n) {
+                if (typeof(n) !== 'number' || n === 0) throw new Error(`expected a number argument that is not 0, found ${n}`);
+            }
+            ",
+        );
+    }
+
     fn expose_make_mut_closure(&mut self) -> Result<(), Error> {
         if !self.should_write_global("make_mut_closure") {
             return Ok(());

crates/cli-support/src/wit/incoming.rs

@@ -156,7 +156,11 @@ impl InstructionBuilder<'_, '_> {
             // Largely synthetic and can't show up
             Descriptor::ClampedU8 => unreachable!(),
 
-            Descriptor::NonNull => unimplemented!("converting `NonNull<T>` from Wasm to Rust is not implemented"),
+            Descriptor::NonNull => self.instruction(
+                &[AdapterType::NonNull],
+                Instruction::I32FromNonNull,
+                &[AdapterType::I32],
+            ),
         }
         Ok(())
     }

crates/cli-support/src/wit/standard.rs

@@ -311,6 +311,7 @@ pub enum Instruction {
     },
     I32FromOptionNonNull,
     OptionNonNullFromI32,
+    I32FromNonNull,
 }
 
 impl AdapterType {

guide/src/reference/types/non-null.md

@@ -2,7 +2,7 @@
 
 | `T` parameter | `&T` parameter | `&mut T` parameter | `T` return value | `Option<T>` parameter | `Option<T>` return value | JavaScript representation |
 |:---:|:---:|:---:|:---:|:---:|:---:|:---:|
-| No | No | No | Yes | Yes | Yes | A JavaScript number value |
+| Yes | No | No | Yes | Yes | Yes | A JavaScript number value |
 
 ## Example Rust Usage
 

src/convert/impls.rs

@@ -294,12 +294,20 @@ impl<T> OptionIntoWasmAbi for NonNull<T> {
     }
 }
 
-impl<T> FromWasmAbi for Option<NonNull<T>> {
+impl<T> FromWasmAbi for NonNull<T> {
     type Abi = u32;
 
     #[inline]
     unsafe fn from_abi(js: Self::Abi) -> Self {
-        NonNull::new(js as *mut T)
+        // SAFETY: Checked in bindings.
+        NonNull::new_unchecked(js as *mut T)
+    }
+}
+
+impl<T> OptionFromWasmAbi for NonNull<T> {
+    #[inline]
+    fn is_none(js: &u32) -> bool {
+        *js == 0
     }
 }
 

tests/wasm/simple.js

@@ -139,6 +139,9 @@ exports.test_raw_pointers = function() {
 };
 
 exports.test_non_null = function() {
+  assert.strictEqual(wasm.simple_nonnull_work(wasm.simple_return_non_null()), 42);
+  assert.throws(() => wasm.simple_nonnull_work(0), /expected a number argument that is not 0/);
+
   assert.strictEqual(wasm.simple_option_nonnull_work(0), undefined);
   assert.strictEqual(wasm.simple_option_nonnull_work(null), undefined);
   assert.strictEqual(wasm.simple_option_nonnull_work(undefined), undefined);

tests/wasm/simple.rs

@@ -113,6 +113,11 @@ pub fn simple_return_option_non_null(value: u32) -> Option<NonNull<u32>> {
     Some(NonNull::from(Box::leak(Box::new(value))))
 }
 
+#[wasm_bindgen]
+pub unsafe fn simple_nonnull_work(a: NonNull<u32>) -> u32 {
+    *Box::from_raw(a.as_ptr())
+}
+
 #[wasm_bindgen]
 pub unsafe fn simple_option_nonnull_work(a: Option<NonNull<u32>>) -> Option<u32> {
     a.map(|ptr| *Box::from_raw(ptr.as_ptr()))