Fixed imports with late binding and this

CHANGELOG.md

@@ -66,6 +66,9 @@
 * Fixed calls to `JsCast::instanceof()` not respecting JavaScript namespaces.
   [#4241](https://github.com/rustwasm/wasm-bindgen/pull/4241)
 
+* Fixed imports for functions using `this` and late binding.
+  [#4225](https://github.com/rustwasm/wasm-bindgen/pull/4225)
+
 --------------------------------------------------------------------------------
 
 ## [0.2.95](https://github.com/rustwasm/wasm-bindgen/compare/0.2.94...0.2.95)

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

@@ -3062,6 +3062,21 @@ __wbg_set_wasm(wasm);"
             }
         }
 
+        if let JsImportName::Global { .. } | JsImportName::VendorPrefixed { .. } = js.name {
+            // We generally cannot import globals directly, because users can
+            // change most globals at runtime.
+            //
+            // An obvious example of this when the object literally changes
+            // (e.g. binding `foo.bar`), but polyfills can also change the
+            // object or fundtion.
+            //
+            // Late binding is another issue. The function might not even be
+            // defined when the Wasm module is instantiated. In such cases,
+            // there is an observable difference between a direct import and a
+            // JS shim calling the function.
+            return Ok(false);
+        }
+
         self.expose_not_defined();
         let name = self.import_name(js)?;
         let js = format!(

crates/cli/tests/reference/import.js

@@ -0,0 +1,95 @@
+let wasm;
+export function __wbg_set_wasm(val) {
+    wasm = val;
+}
+
+
+const heap = new Array(128).fill(undefined);
+
+heap.push(undefined, null, true, false);
+
+let heap_next = heap.length;
+
+function addHeapObject(obj) {
+    if (heap_next === heap.length) heap.push(heap.length + 1);
+    const idx = heap_next;
+    heap_next = heap[idx];
+
+    heap[idx] = obj;
+    return idx;
+}
+
+function handleError(f, args) {
+    try {
+        return f.apply(this, args);
+    } catch (e) {
+        wasm.__wbindgen_exn_store(addHeapObject(e));
+    }
+}
+
+const lTextDecoder = typeof TextDecoder === 'undefined' ? (0, module.require)('util').TextDecoder : TextDecoder;
+
+let cachedTextDecoder = new lTextDecoder('utf-8', { ignoreBOM: true, fatal: true });
+
+cachedTextDecoder.decode();
+
+let cachedUint8ArrayMemory0 = null;
+
+function getUint8ArrayMemory0() {
+    if (cachedUint8ArrayMemory0 === null || cachedUint8ArrayMemory0.byteLength === 0) {
+        cachedUint8ArrayMemory0 = new Uint8Array(wasm.memory.buffer);
+    }
+    return cachedUint8ArrayMemory0;
+}
+
+function getStringFromWasm0(ptr, len) {
+    ptr = ptr >>> 0;
+    return cachedTextDecoder.decode(getUint8ArrayMemory0().subarray(ptr, ptr + len));
+}
+
+function getObject(idx) { return heap[idx]; }
+
+function dropObject(idx) {
+    if (idx < 132) return;
+    heap[idx] = heap_next;
+    heap_next = idx;
+}
+
+function takeObject(idx) {
+    const ret = getObject(idx);
+    dropObject(idx);
+    return ret;
+}
+
+export function exported() {
+    const ret = wasm.exported();
+    if (ret[1]) {
+        throw takeObject(ret[0]);
+    }
+}
+
+export function __wbg_add_dd5307a7ca6818d5(arg0, arg1) {
+    const ret = add(arg0, arg1);
+    return ret;
+};
+
+export function __wbg_barfromfoo_d097f3ec35aab47c() {
+    bar_from_foo();
+};
+
+export function __wbg_catchme_a7bca7f3d5a5f319() { return handleError(function () {
+    catch_me();
+}, arguments) };
+
+export function __wbg_nocatch_62552fa42a58590b() {
+    no_catch();
+};
+
+export function __wbg_reload_90d82b22b83c1d99() {
+    window.location.reload();
+};
+
+export function __wbg_write_d258674ff6f0ea8d(arg0, arg1) {
+    window.document.write(getStringFromWasm0(arg0, arg1));
+};
+

crates/cli/tests/reference/import.rs

@@ -0,0 +1,34 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    // Both `catch_me` and `no_catch` should be defined in the JS and invoke
+    // their respective JS function inside a JS shim function. This is
+    // important, because these 2 function may not be defined when the WASM
+    // module is instantiated.
+    #[wasm_bindgen(catch)]
+    fn catch_me() -> Result<(), JsValue>;
+    fn no_catch();
+
+    // Reload needs to be passed the right `this` parameter in JS.
+    #[wasm_bindgen(js_namespace = ["window", "location"])]
+    fn reload();
+    #[wasm_bindgen(js_namespace = ["window", "document"])]
+    fn write(s: &str);
+
+    // module import
+    #[wasm_bindgen(module = "./foo.js")]
+    fn bar_from_foo();
+    #[wasm_bindgen(inline_js = "export function add(a,b) { return a + b; }")]
+    fn add(a: f64, b: f64) -> f64;
+}
+
+#[wasm_bindgen]
+pub fn exported() -> Result<(), JsValue> {
+    bar_from_foo();
+    let _ = add(1.0, 2.0);
+    reload();
+    write("");
+    no_catch();
+    catch_me()
+}