Add an unsafe method view_mut_raw (#1850)

* adding .vscode folder to .gitignore

* Adding view_mut_raw to generated arrays

* test populating rust vector from JS  function

* Uint32Array test, need to make it generic

* Add doc + more test cases

* replacing macro-generated tests with generic test function

it is cleaner, safer and better that way

* improving rustdoc

crates/js-sys/tests/wasm/Array.rs

@@ -1,5 +1,6 @@
 use js_sys::*;
 use std::iter::FromIterator;
+use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 use wasm_bindgen::JsValue;
 use wasm_bindgen_test::*;
@@ -466,3 +467,87 @@ fn array_inheritance() {
     assert!(array.is_instance_of::<Object>());
     let _: &Object = array.as_ref();
 }
+
+#[wasm_bindgen(module = "tests/wasm/Array.js")]
+extern "C" {
+    fn populate_array(arr: JsValue, start: JsValue, len: JsValue) -> JsValue;
+}
+
+fn test_array_view_mut_raw<ElemT: std::cmp::PartialEq + std::fmt::Debug, ArrT>(
+    sut: unsafe fn(*mut ElemT, usize) -> ArrT,
+    u8ToElem: fn(u8) -> ElemT,
+    arrToJsValue: fn(ArrT) -> JsValue,
+) {
+    let start: u8 = 10;
+    let len: usize = 32;
+    let end: u8 = start + len as u8;
+    let mut buffer: Vec<ElemT> = Vec::new();
+    buffer.reserve(len);
+    unsafe {
+        let array: ArrT = sut(buffer.as_mut_ptr(), len);
+        populate_array(
+            arrToJsValue(array),
+            JsValue::from(start),
+            JsValue::from(len as u32),
+        );
+        buffer.set_len(len);
+    }
+    let expected: Vec<ElemT> = (start..end).map(u8ToElem).collect();
+    assert_eq!(buffer, expected)
+}
+
+#[wasm_bindgen_test]
+fn Int8Array_view_mut_raw() {
+    fn u8Toi8_unsafe(x: u8) -> i8 {
+        x as i8
+    }
+    test_array_view_mut_raw(
+        js_sys::Int8Array::view_mut_raw,
+        u8Toi8_unsafe,
+        JsValue::from,
+    );
+}
+
+#[wasm_bindgen_test]
+fn Int16Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Int16Array::view_mut_raw, i16::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Int32Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Int32Array::view_mut_raw, i32::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Uint8Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Uint8Array::view_mut_raw, u8::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Uint8ClampedArray_view_mut_raw() {
+    test_array_view_mut_raw(
+        js_sys::Uint8ClampedArray::view_mut_raw,
+        u8::from,
+        JsValue::from,
+    );
+}
+
+#[wasm_bindgen_test]
+fn Uint16Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Uint16Array::view_mut_raw, u16::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Uint32Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Uint32Array::view_mut_raw, u32::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Float32Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Float32Array::view_mut_raw, f32::from, JsValue::from);
+}
+
+#[wasm_bindgen_test]
+fn Float64Array_view_mut_raw() {
+    test_array_view_mut_raw(js_sys::Float64Array::view_mut_raw, f64::from, JsValue::from);
+}