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Allow context type annotation on getters/setters #9641

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Mar 6, 2019
Merged

Allow context type annotation on getters/setters #9641

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238598c
Allow context type annotation on getters/setters
matt-tingen Mar 5, 2019
c5cca01
Extract getAccessorsExpectedParamCount
matt-tingen Mar 6, 2019
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14 changes: 12 additions & 2 deletions packages/babel-parser/src/parser/expression.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1552,15 +1552,25 @@ export default class ExpressionParser extends LValParser {
checkGetterSetterParams(method: N.ObjectMethod | N.ClassMethod): void {
const paramCount = method.kind === "get" ? 0 : 1;
const start = method.start;
if (method.params.length !== paramCount) {
// Allow `this` type annotation in TypeScript
if (
method.params.length === paramCount + 1 &&
method.params[0].type === "Identifier" &&
method.params[0].name === "this"
) {
this.expectPlugin("typescript");
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When the first parameter is this the new implementation doesn't check the parameters count because the } else if (method.params.length !== paramCount) { branch is skipped: (EDIT: I was wrong)

//get prop(this: {}, foo, bar) {}

If we parsed this as a function parameter, then this plugin is already enabled (no need to assert). I would prefer to have as few as possible TypeScript-specific logic in the parser/* files. WDYT about extractions method.kind === "get" ? 0 : 1 to a new getAccessorsExpectedParamCount(method) function and overwrite it in the typescript plugin?

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method.params.length === paramCount + 1 wouldn't be true in that case I guess?

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Oh right 🤦‍♂️

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@nicolo-ribaudo I have pushed a change for getGetterSetterExpectedParamCount. Thanks for suggesting the separation. I hadn't noticed I had the first usage of this.expectPlugin("typescript").

At first, it felt a little odd that the error messages directly reference the required number of params despite that number being abstracted away. I considered extracting a checkGetterSetterExpectedParamCount method instead, but didn't find a good way to do so without duplicating logic in the TypeScript plugin. However, I found that there's less of a dissonance if I look at it as the error messages being based on target language and getGetterSetterExpectedParamCount being based on the source language, so I'm on board now 😄

} else if (method.params.length !== paramCount) {
if (method.kind === "get") {
this.raise(start, "getter must not have any formal parameters");
} else {
this.raise(start, "setter must have exactly one formal parameter");
}
}

if (method.kind === "set" && method.params[0].type === "RestElement") {
if (
method.kind === "set" &&
method.params[method.params.length - 1].type === "RestElement"
) {
this.raise(
start,
"setter function argument must not be a rest parameter",
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6 changes: 6 additions & 0 deletions packages/babel-parser/test/fixtures/typescript/function/getter-setter/input.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
const g = {
get m(this: {}) {}
};
const s = {
set m(this: {}, value) {}
};