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Improving wasm loading logic #1996

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merged 2 commits into from
Feb 11, 2020
Merged

Improving wasm loading logic #1996

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a5e3454
Improving wasm loading logic
Pauan Feb 10, 2020
b111305
Adding in note to the book about the new loading functionality
Pauan Feb 11, 2020
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96 changes: 50 additions & 46 deletions crates/cli-support/src/js/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -433,20 +433,20 @@ impl<'a> Context<'a> {
let default_module_path = match self.config.mode {
OutputMode::Web => {
"\
if (typeof module === 'undefined') {
module = import.meta.url.replace(/\\.js$/, '_bg.wasm');
if (typeof input === 'undefined') {
input = import.meta.url.replace(/\\.js$/, '_bg.wasm');
}"
}
OutputMode::NoModules { .. } => {
"\
if (typeof module === 'undefined') {
if (typeof input === 'undefined') {
let src;
if (self.document === undefined) {
src = self.location.href;
} else {
src = self.document.currentScript.src;
}
module = src.replace(/\\.js$/, '_bg.wasm');
input = src.replace(/\\.js$/, '_bg.wasm');
}"
}
_ => "",
Expand Down Expand Up @@ -503,54 +503,58 @@ impl<'a> Context<'a> {

let js = format!(
"\
function init(module{init_memory_arg}) {{
{default_module_path}
let result;
const imports = {{}};
{imports_init}
if ((typeof URL === 'function' && module instanceof URL) || typeof module === 'string' || (typeof Request === 'function' && module instanceof Request)) {{
async function load(module, imports) {{
if (typeof Response === 'function' && module instanceof Response) {{
{init_memory2}
const response = fetch(module);
if (typeof WebAssembly.instantiateStreaming === 'function') {{
result = WebAssembly.instantiateStreaming(response, imports)
.catch(e => {{
return response
.then(r => {{
if (r.headers.get('Content-Type') != 'application/wasm') {{
console.warn(\"`WebAssembly.instantiateStreaming` failed \
because your server does not serve wasm with \
`application/wasm` MIME type. Falling back to \
`WebAssembly.instantiate` which is slower. Original \
error:\\n\", e);
return r.arrayBuffer();
}} else {{
throw e;
}}
}})
.then(bytes => WebAssembly.instantiate(bytes, imports));
}});
}} else {{
result = response
.then(r => r.arrayBuffer())
.then(bytes => WebAssembly.instantiate(bytes, imports));
try {{
return await WebAssembly.instantiateStreaming(module, imports);

}} catch (e) {{
if (module.headers.get('Content-Type') != 'application/wasm') {{
console.warn(\"`WebAssembly.instantiateStreaming` failed \
because your server does not serve wasm with \
`application/wasm` MIME type. Falling back to \
`WebAssembly.instantiate` which is slower. Original \
error:\\n\", e);

}} else {{
throw e;
}}
}}
}}

const bytes = await module.arrayBuffer();
return await WebAssembly.instantiate(bytes, imports);

}} else {{
{init_memory1}
result = WebAssembly.instantiate(module, imports)
.then(result => {{
if (result instanceof WebAssembly.Instance) {{
return {{ instance: result, module }};
}} else {{
return result;
}}
}});
const instance = await WebAssembly.instantiate(module, imports);

if (instance instanceof WebAssembly.Instance) {{
return {{ instance, module }};

}} else {{
return instance;
}}
}}
return result.then(({{instance, module}}) => {{
wasm = instance.exports;
init.__wbindgen_wasm_module = module;
{start}
return wasm;
}});
}}

async function init(input{init_memory_arg}) {{
{default_module_path}
const imports = {{}};
{imports_init}

if (typeof input === 'string' || (typeof Request === 'function' && input instanceof Request) || (typeof URL === 'function' && input instanceof URL)) {{
input = fetch(input);
}}

const {{ instance, module }} = await load(await input, imports);

wasm = instance.exports;
init.__wbindgen_wasm_module = module;
{start}
return wasm;
}}
",
init_memory_arg = init_memory_arg,
Expand Down
19 changes: 16 additions & 3 deletions examples/without-a-bundler/index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,25 @@
// default export to inform it where the wasm file is located on the
// server, and then we wait on the returned promise to wait for the
// wasm to be loaded.
//
// It may look like this: `await init('./pkg/without_a_bundler_bg.wasm');`,
// but there is also a handy default inside `init` function, which uses
// `import.meta` to locate the wasm file relatively to js file
// `import.meta` to locate the wasm file relatively to js file.
//
// Note that instead of a string you can also pass in any of the
// following things:
//
// * `WebAssembly.Module`
//
// * `ArrayBuffer`
//
// * `Response`
//
// * `Promise` which returns any of the above, e.g. `fetch("./path/to/wasm")`
//
// This gives you complete control over how the module is loaded
// and compiled.
//
// Note that instead of a string here you can also pass in an instance
// of `WebAssembly.Module` which allows you to compile your own module.
// Also note that the promise, when resolved, yields the wasm module's
// exports which is the same as importing the `*_bg` module in other
// modes
Expand Down