fix: numeric separators were removed from BigInt literals (#6796)

CHANGELOG.unreleased.md

@@ -1351,6 +1351,20 @@ $ prettier --stdin-filepath does/not/exist.js < test.js
 test;
 ```
 
+#### JavaScript: Numeric separators were removed from BigInt literals ([#6796] by [@thorn0])
+
+<!-- prettier-ignore -->
+```js
+// Input
+const bigints = [200_000n, 0x0000_000An, 0b0111_1111n];
+
+// Output (Prettier stable)
+const bigints = [200000n, 0x0000000an, 0b01111111n];
+
+// Output (Prettier master)
+const bigints = [200_000n, 0x0000_000an, 0b0111_1111n];
+```
+
 [#5682]: https://github.com/prettier/prettier/pull/5682
 [#6657]: https://github.com/prettier/prettier/pull/6657
 [#5910]: https://github.com/prettier/prettier/pull/5910
@@ -1398,6 +1412,7 @@ test;
 [#6728]: https://github.com/prettier/prettier/pull/6728
 [#6708]: https://github.com/prettier/prettier/pull/6708
 [#6687]: https://github.com/prettier/prettier/pull/6687
+[#6796]: https://github.com/prettier/prettier/pull/6796
 [@brainkim]: https://github.com/brainkim
 [@duailibe]: https://github.com/duailibe
 [@gavinjoyce]: https://github.com/gavinjoyce

src/language-js/printer-estree.js

@@ -1610,15 +1610,8 @@ function printPathNoParens(path, options, print, args) {
     case "NumericLiteral": // Babel 6 Literal split
       return printNumber(n.extra.raw);
     case "BigIntLiteral":
-      return concat([
-        printNumber(
-          n.extra
-            ? n.extra.rawValue
-            : // TypeScript
-              n.value
-        ),
-        "n"
-      ]);
+      // babel: n.extra.raw, typescript: n.raw
+      return (n.extra ? n.extra.raw : n.raw).toLowerCase();
     case "BooleanLiteral": // Babel 6 Literal split
     case "StringLiteral": // Babel 6 Literal split
     case "Literal": {

tests/big-int/__snapshots__/jsfmt.spec.js.snap

@@ -14,6 +14,9 @@ printWidth: 80
 0XFFF123n
 0b101011101n
 0B101011101n
+200_000n
+0x0000_000An
+0b0111_1111n
 
 =====================================output=====================================
 100n;
@@ -24,6 +27,9 @@ printWidth: 80
 0xfff123n;
 0b101011101n;
 0b101011101n;
+200_000n;
+0x0000_000an;
+0b0111_1111n;
 
 ================================================================================
 `;

tests/big-int/literal.js

@@ -6,3 +6,6 @@
 0XFFF123n
 0b101011101n
 0B101011101n
+200_000n
+0x0000_000An
+0b0111_1111n