Support TSNamedTupleMember

changelog_unreleased/typescript/pr-8885.md

@@ -0,0 +1,18 @@
+#### Support `Labeled Tuple Elements` ([#8885](https://github.com/prettier/prettier/pull/8885) by [@fisker](https://github.com/fisker))
+
+[`Labeled Tuple Elements`](https://devblogs.microsoft.com/typescript/announcing-typescript-4-0-beta/#labeled-tuple-elements)
+
+_Only works for `babel-ts` parser_
+
+<!-- prettier-ignore -->
+```ts
+// Input
+type Range = [start: number, end: number];
+
+// Prettier stable
+SyntaxError: Unexpected token, expected "," (1:20)
+> 1 | type Range = [start: number, end: number];
+
+// Prettier master
+type Range = [start: number, end: number];
+```

src/language-js/printer-estree.js

@@ -2314,6 +2314,13 @@ function printPathNoParens(path, options, print, args) {
 
       /* istanbul ignore next */
       return "";
+    case "TSNamedTupleMember":
+      return concat([
+        path.call(print, "label"),
+        n.optional ? "?" : "",
+        ": ",
+        path.call(print, "elementType"),
+      ]);
     case "TSTupleType":
     case "TupleTypeAnnotation": {
       const typesField = n.type === "TSTupleType" ? "elementTypes" : "types";

tests/misc/typescript-babel-only/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,57 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`tuple-labeled.ts format 1`] = `
+====================================options=====================================
+parsers: ["babel-ts"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+// https://github.com/babel/babel/pull/11754
+// TODO: move this file to \`test/typescript/tuple\`
+
+type T = [x: A, y?: B, ...z: C];
+
+type T = [A, y: B];
+
+let x: [A: string, ...B: number[]]
+
+type T = [foo: string, bar?: number];
+
+type T = [x?: A, y: B];
+
+type T = [x: A, ...B];
+
+type T = [...B, x: A];
+
+// Invalid label 1
+type T = [x.y: A];
+
+// Invalid label 2
+type T = [x<y>: A];
+
+=====================================output=====================================
+// https://github.com/babel/babel/pull/11754
+// TODO: move this file to \`test/typescript/tuple\`
+
+type T = [x: A, y?: B, ...z: C];
+
+type T = [A, y: B];
+
+let x: [A: string, ...B: number[]];
+
+type T = [foo: string, bar?: number];
+
+type T = [x?: A, y: B];
+
+type T = [x: A, ...B];
+
+type T = [...B, x: A];
+
+// Invalid label 1
+type T = [x.y: A];
+
+// Invalid label 2
+type T = [x<y>: A];
+
+================================================================================
+`;

tests/misc/typescript-babel-only/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, ["babel-ts"]);

tests/misc/typescript-babel-only/tuple-labeled.ts

@@ -0,0 +1,22 @@
+// https://github.com/babel/babel/pull/11754
+// TODO: move this file to `test/typescript/tuple`
+
+type T = [x: A, y?: B, ...z: C];
+
+type T = [A, y: B];
+
+let x: [A: string, ...B: number[]]
+
+type T = [foo: string, bar?: number];
+
+type T = [x?: A, y: B];
+
+type T = [x: A, ...B];
+
+type T = [...B, x: A];
+
+// Invalid label 1
+type T = [x.y: A];
+
+// Invalid label 2
+type T = [x<y>: A];