perf(webidl): optimize dictionary converters

ext/webidl/00_webidl.js

@@ -671,11 +671,19 @@
  }
  }
 
- return function (V, opts = {}) {
+ return new Function(
+ "makeException",
+ "type",
+ "defaultValues",
+ "allMembers",
+ `return function (V, opts = {}) {
  const typeV = type(V);
+ let useDefault = false;
  switch (typeV) {
  case "Undefined":
  case "Null":
+ useDefault = true;
+ break;
  case "Object":
  break;
  default:
@@ -685,43 +693,16 @@
  opts,
  );
  }
- const esDict = V;
-
- const idlDict = ObjectAssign({}, defaultValues);
 
- // NOTE: fast path Null and Undefined.
- if ((V === undefined || V === null) && !hasRequiredKey) {
- return idlDict;
+ return {
+ ${
+ allMembers.map((member, idx) =>
+ `${member.key}: (useDefault || V.${member.key} === undefined) ? defaultValues.${member.key} : allMembers[${idx}].converter(V.${member.key}, opts)`
+ ).join(",\n")
  }
-
- for (const member of allMembers) {
- const key = member.key;
-
- let esMemberValue;
- if (typeV === "Undefined" || typeV === "Null") {
- esMemberValue = undefined;
- } else {
- esMemberValue = esDict[key];
- }
-
- if (esMemberValue !== undefined) {
- const context = `'${key}' of '${name}'${
- opts.context ? ` (${opts.context})` : ""
- }`;
- const converter = member.converter;
- const idlMemberValue = converter(esMemberValue, { ...opts, context });
- idlDict[key] = idlMemberValue;
- } else if (member.required) {
- throw makeException(
- TypeError,
- `can not be converted to '${name}' because '${key}' is required in '${name}'.`,
- opts,
- );
- }
- }
-
- return idlDict;
- };
+ };
+ };`,
+ )(makeException, type, defaultValues, allMembers);
  }
 
  // https://heycam.github.io/webidl/#es-enumeration

ext/webidl/Cargo.toml

@@ -15,3 +15,10 @@ path = "lib.rs"
 
 [dependencies]
 deno_core = { version = "0.158.0", path = "../../core" }
+
+[dev-dependencies]
+deno_bench_util = { version = "0.70.0", path = "../../bench_util" }
+
+[[bench]]
+name = "dict"
+harness = false

ext/webidl/benches/dict.js

@@ -0,0 +1,33 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+const { createDictionaryConverter, converters } = globalThis.__bootstrap.webidl;
+
+const TextDecodeOptions = createDictionaryConverter(
+ "TextDecodeOptions",
+ [
+ {
+ key: "stream",
+ converter: converters.boolean,
+ defaultValue: false,
+ },
+ ],
+);
+
+// Sanity check
+{
+ const o = TextDecodeOptions(undefined);
+ if (o.stream !== false) {
+ throw new Error("Unexpected stream value");
+ }
+}
+
+function handwrittenConverter(V) {
+ const defaultValue = { stream: false };
+ if (V === undefined || V === null) {
+ return defaultValue;
+ }
+ if (V.stream !== undefined) {
+ defaultValue.stream = !!V.stream;
+ }
+ return defaultValue;
+}

ext/webidl/benches/dict.rs

@@ -0,0 +1,41 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use deno_bench_util::bench_js_sync;
+use deno_bench_util::bench_or_profile;
+use deno_bench_util::bencher::{benchmark_group, Bencher};
+
+use deno_core::Extension;
+
+fn setup() -> Vec<Extension> {
+ vec![
+ deno_webidl::init(),
+ Extension::builder()
+ .js(vec![("setup", include_str!("dict.js"))])
+ .build(),
+ ]
+}
+
+fn converter_undefined(b: &mut Bencher) {
+ bench_js_sync(b, r#"TextDecodeOptions(undefined);"#, setup);
+}
+
+fn handwritten_baseline_undefined(b: &mut Bencher) {
+ bench_js_sync(b, r#"handwrittenConverter(undefined)"#, setup);
+}
+
+fn converter_object(b: &mut Bencher) {
+ bench_js_sync(b, r#"TextDecodeOptions({});"#, setup);
+}
+
+fn handwritten_baseline_object(b: &mut Bencher) {
+ bench_js_sync(b, r#"handwrittenConverter({})"#, setup);
+}
+
+benchmark_group!(
+ benches,
+ converter_undefined,
+ handwritten_baseline_undefined,
+ converter_object,
+ handwritten_baseline_object,
+);
+bench_or_profile!(benches);