fix(JavaScript): bug when arrow fn as function parameter with newline (#6301)

CHANGELOG.unreleased.md

@@ -339,6 +339,35 @@ Previously, even if the line length is shorter than print-width is Prettier brea
 </template>
 ```
 
+#### JavaScript: Fix breaks indentation and idempotency when an arrow function that args include object pattern is passed to a function as parameter. ([#6301] by [@sosukesuzuki])
+
+Previously, Prettier collapses strangely, when an arrow function that args include object pattern is passed to a function as parameter. Also, it breaks idempotency. Please see [#6294](https://github.com/prettier/prettier/issues/6294) for detail.
+
+<!-- prettier-ignore -->
+```js
+// Input
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+// Output (Prettier stable)
+foo(({ a,
+  b }) => {});
+
+// Output (Prettier master)
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+```
+
 [#5910]: https://github.com/prettier/prettier/pull/5910
 [#6186]: https://github.com/prettier/prettier/pull/6186
 [#6206]: https://github.com/prettier/prettier/pull/6206
@@ -350,6 +379,7 @@ Previously, even if the line length is shorter than print-width is Prettier brea
 [#6289]: https://github.com/prettier/prettier/pull/6289
 [#6332]: https://github.com/prettier/prettier/pull/6332
 [#6284]: https://github.com/prettier/prettier/pull/6284
+[#6301]: https://github.com/prettier/prettier/pull/6301
 [@duailibe]: https://github.com/duailibe
 [@gavinjoyce]: https://github.com/gavinjoyce
 [@sosukesuzuki]: https://github.com/sosukesuzuki

src/language-js/printer-estree.js

@@ -4056,6 +4056,32 @@ function printArgumentsList(path, options, print) {
     ]);
   }
 
+  // func(
+  //   ({
+  //     a,
+
+  //     b
+  //   }) => {}
+  // );
+  function hasEmptyLineInObjectArgInArrowFunction(arg) {
+    return (
+      arg &&
+      arg.type === "ArrowFunctionExpression" &&
+      arg.params &&
+      arg.params.some(
+        param =>
+          param.type &&
+          param.type === "ObjectPattern" &&
+          param.properties &&
+          param.properties.some(
+            (property, i, properties) =>
+              i < properties.length - 1 &&
+              isNextLineEmpty(options.originalText, property, options)
+          )
+      )
+    );
+  }
+
   let anyArgEmptyLine = false;
   let hasEmptyLineFollowingFirstArg = false;
   const lastArgIndex = args.length - 1;
@@ -4076,6 +4102,8 @@ function printArgumentsList(path, options, print) {
       parts.push(",", line);
     }
 
+    anyArgEmptyLine = hasEmptyLineInObjectArgInArrowFunction(arg);
+
     return concat(parts);
   }, "arguments");
 

tests/arrows/__snapshots__/jsfmt.spec.js.snap

@@ -286,6 +286,61 @@ fooooooooooooooooooooooooooooooooooooooooooooooooooo(action => next =>
     dispatch(action),
 );
 
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => {}
+);
+
+foo(
+  a,
+  ({
+    a,
+
+    b
+  }) => {}
+)
+
+foo(
+  ({
+    a,
+
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => a
+);
+
 =====================================output=====================================
 Seq(typeDef.interface.groups).forEach(group =>
   Seq(group.members).forEach((member, memberName) =>
@@ -376,6 +431,39 @@ fooooooooooooooooooooooooooooooooooooooooooooooooooo(action => next =>
   dispatch(action)
 );
 
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(({ a, b }) => {});
+
+foo(({ a, b }) => {});
+
+foo(
+  a,
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+
+    b
+  }) => a
+);
+
+foo(({ a, b }) => a);
+
+foo(({ a, b }) => a);
+
 ================================================================================
 `;
 
@@ -467,6 +555,61 @@ fooooooooooooooooooooooooooooooooooooooooooooooooooo(action => next =>
     dispatch(action),
 );
 
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => {}
+);
+
+foo(
+  a,
+  ({
+    a,
+
+    b
+  }) => {}
+)
+
+foo(
+  ({
+    a,
+
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => a
+);
+
 =====================================output=====================================
 Seq(typeDef.interface.groups).forEach((group) =>
   Seq(group.members).forEach((member, memberName) =>
@@ -557,6 +700,39 @@ fooooooooooooooooooooooooooooooooooooooooooooooooooo((action) => (next) =>
   dispatch(action)
 );
 
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(({ a, b }) => {});
+
+foo(({ a, b }) => {});
+
+foo(
+  a,
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+
+    b
+  }) => a
+);
+
+foo(({ a, b }) => a);
+
+foo(({ a, b }) => a);
+
 ================================================================================
 `;
 

tests/arrows/call.js

@@ -78,3 +78,58 @@ jest.mock(
 fooooooooooooooooooooooooooooooooooooooooooooooooooo(action => next =>
     dispatch(action),
 );
+
+foo(
+  ({
+    a,
+
+    b
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => {}
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => {}
+);
+
+foo(
+  a,
+  ({
+    a,
+
+    b
+  }) => {}
+)
+
+foo(
+  ({
+    a,
+
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+  }) => a
+);
+
+foo(
+  ({
+    a,
+    b
+
+  }) => a
+);