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Memoize call expressions in optional chains in loose mode #11261

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merged 4 commits into from Mar 20, 2020
Merged

Memoize call expressions in optional chains in loose mode #11261

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b5cf146
Memoize in loose mode when callee is a CallExpression
oliverdunk Feb 23, 2020
6c1269e
Handle more complex OptionalCallExpressions where memoization is needed
oliverdunk Mar 15, 2020
d4d6ec8
Convert calls to Function#call when member needs memoization
oliverdunk Mar 19, 2020
9098d0a
Only update call context for member expressions
oliverdunk Mar 19, 2020
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19 changes: 15 additions & 4 deletions packages/babel-plugin-proposal-optional-chaining/src/index.js
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Expand Up @@ -7,6 +7,16 @@ export default declare((api, options) => {

const { loose = false } = options;

function isSimpleMemberExpression(expression) {
return (
t.isIdentifier(expression) ||
t.isSuper(expression) ||
(t.isMemberExpression(expression) &&
!expression.computed &&
isSimpleMemberExpression(expression.object))
);
}

return {
name: "proposal-optional-chaining",
inherits: syntaxOptionalChaining,
Expand Down Expand Up @@ -50,9 +60,10 @@ export default declare((api, options) => {

let ref;
let check;
if (loose && isCall) {
if (loose && isCall && isSimpleMemberExpression(chain)) {
// If we are using a loose transform (avoiding a Function#call) and we are at the call,
// we can avoid a needless memoize.
// we can avoid a needless memoize. We only do this if the callee is a simple member
// expression, to avoid multiple calls to nested call expressions.
check = ref = chain;
} else {
ref = scope.maybeGenerateMemoised(chain);
Expand All @@ -72,12 +83,12 @@ export default declare((api, options) => {

// Ensure call expressions have the proper `this`
// `foo.bar()` has context `foo`.
if (isCall && t.isMemberExpression(chain)) {
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if (isCall && isSimpleMemberExpression(chain)) {
if (loose) {
// To avoid a Function#call, we can instead re-grab the property from the context object.
// `a.?b.?()` translates roughly to `_a.b != null && _a.b()`
node.callee = chain;
} else {
} else if (chain.object) {
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// Otherwise, we need to memoize the context object, and change the call into a Function#call.
// `a.?b.?()` translates roughly to `(_b = _a.b) != null && _b.call(_a)`
const { object } = chain;
Expand Down
8 changes: 8 additions & 0 deletions ...ages/babel-plugin-proposal-optional-chaining/test/fixtures/general/memoize-loose/input.js
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Expand Up @@ -7,6 +7,14 @@ function test(foo) {

foo?.bar()

foo.get(bar)?.()

foo.bar()?.()
foo[bar]()?.()

foo.bar().baz?.()
foo[bar]().baz?.()

foo.bar?.(foo.bar, false)

foo?.bar?.(foo.bar, true)
Expand Down
15 changes: 10 additions & 5 deletions ...ges/babel-plugin-proposal-optional-chaining/test/fixtures/general/memoize-loose/output.js
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@@ -1,14 +1,19 @@
function test(foo) {
var _foo$bar, _foo$bar2, _foo$bar3, _foo$bar4, _foo$bar5;
var _foo$bar, _foo$get, _foo$bar2, _foo$bar3, _foo$bar$baz, _foo$bar$baz2, _foo$bar4, _foo$bar5, _foo$bar6, _foo$bar7;

foo == null ? void 0 : foo.bar;
foo == null ? void 0 : (_foo$bar = foo.bar) == null ? void 0 : _foo$bar.baz;
foo == null ? void 0 : foo(foo);
foo == null ? void 0 : foo.bar();
(_foo$get = foo.get(bar)) == null ? void 0 : _foo$get();
(_foo$bar2 = foo.bar()) == null ? void 0 : _foo$bar2();
(_foo$bar3 = foo[bar]()) == null ? void 0 : _foo$bar3();
(_foo$bar$baz = foo.bar().baz) == null ? void 0 : _foo$bar$baz();
(_foo$bar$baz2 = foo[bar]().baz) == null ? void 0 : _foo$bar$baz2();
foo.bar == null ? void 0 : foo.bar(foo.bar, false);
foo == null ? void 0 : foo.bar == null ? void 0 : foo.bar(foo.bar, true);
(_foo$bar2 = foo.bar) == null ? void 0 : _foo$bar2.baz(foo.bar, false);
foo == null ? void 0 : (_foo$bar3 = foo.bar) == null ? void 0 : _foo$bar3.baz(foo.bar, true);
(_foo$bar4 = foo.bar) == null ? void 0 : _foo$bar4.baz == null ? void 0 : _foo$bar4.baz(foo.bar, false);
foo == null ? void 0 : (_foo$bar5 = foo.bar) == null ? void 0 : _foo$bar5.baz == null ? void 0 : _foo$bar5.baz(foo.bar, true);
(_foo$bar4 = foo.bar) == null ? void 0 : _foo$bar4.baz(foo.bar, false);
foo == null ? void 0 : (_foo$bar5 = foo.bar) == null ? void 0 : _foo$bar5.baz(foo.bar, true);
(_foo$bar6 = foo.bar) == null ? void 0 : _foo$bar6.baz == null ? void 0 : _foo$bar6.baz(foo.bar, false);
foo == null ? void 0 : (_foo$bar7 = foo.bar) == null ? void 0 : _foo$bar7.baz == null ? void 0 : _foo$bar7.baz(foo.bar, true);
}