Fix bug with holes in array literals (#7911)

prettier · Mar 31, 2020 · 18bf01e · 18bf01e
1 parent bd31256
commit 18bf01e
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diff --git a/changelog_unreleased/javascript/pr-7911.md b/changelog_unreleased/javascript/pr-7911.md
@@ -0,0 +1,16 @@
+#### Fix bug with holes in array literals ([#7911](https://github.com/prettier/prettier/pull/7911) by [@bakkot](https://github.com/bakkot))
+
+<!-- prettier-ignore -->
+```jsx
+// Input
+new Test()
+  .test()
+  .test([, 0])
+  .test();
+
+// Prettier stable
+[error] in.js: TypeError: Cannot read property 'type' of null
+
+// Prettier master
+new Test().test().test([, 0]).test();
+```
diff --git a/src/language-js/utils.js b/src/language-js/utils.js
@@ -958,7 +958,7 @@ function isSimpleCallArgument(node, depth) {
     );
   }
   if (node.type === "ArrayExpression") {
-    return node.elements.every(isChildSimple);
+    return node.elements.every((x) => x == null || isChildSimple(x));
   }
   if (
     node.type === "CallExpression" ||

diff --git a/tests/arrays/__snapshots__/jsfmt.spec.js.snap b/tests/arrays/__snapshots__/jsfmt.spec.js.snap
@@ -18,6 +18,23 @@ const b =
 ================================================================================
 `;
 
+exports[`holes-in-args.js 1`] = `
+====================================options=====================================
+parsers: ["flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+new Test()
+  .test()
+  .test([, 0])
+  .test();
+
+=====================================output=====================================
+new Test().test().test([, 0]).test();
+
+================================================================================
+`;
+
 exports[`last.js 1`] = `
 ====================================options=====================================
 parsers: ["flow", "typescript"]

diff --git a/tests/arrays/holes-in-args.js b/tests/arrays/holes-in-args.js
@@ -0,0 +1,4 @@
+new Test()
+  .test()
+  .test([, 0])
+  .test();