Merge pull request #2997 from quantified-uncertainty/array-extra-comm…

…a-bug

Fix incorrect extra commas on empty lists

.changeset/wet-tigers-type.md

@@ -0,0 +1,5 @@
+---
+"@quri/prettier-plugin-squiggle": patch
+---
+
+Fix incorrect extra commas on empty lists

packages/prettier-plugin/src/printer.ts

@@ -203,9 +203,16 @@ export function createSquigglePrinter(
         case "Array":
           return group([
             "[",
-            indent([softline, join([",", line], path.map(print, "elements"))]),
-            ifBreak(",", ""), // trailing comma
-            softline,
+            node.elements.length
+              ? [
+                  indent([
+                    softline,
+                    join([",", line], path.map(print, "elements")),
+                  ]),
+                  ifBreak(",", ""), // trailing comma is there's at least one element
+                  softline,
+                ]
+              : "",
             "]",
           ]);
         case "Call":

packages/prettier-plugin/test/arrays.test.ts

@@ -34,4 +34,15 @@ describe("arrays", () => {
 ]`
     );
   });
+
+  test("don't break empty arrays", async () => {
+    expect(
+      await format(
+        "asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf = []"
+      )
+    ).toBe(
+      `asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf = []
+`
+    );
+  });
 });