fix(codegen, packages/codegen): remove extraneous space before RestElement in ArrayPattern (#27613)

Fix both Rust and JS codegens.

Both printed an extraneous space before `...` for a `RestElement` as first element of an `ArrayPattern`.

```javascript
// Before
const [ ...rest] = arr;
// After
const [...rest] = arr;
```

[Playground](https://playground.oxc.rs/?options=%7B%22run%22%3A%7B%22lint%22%3Afalse%2C%22formatter%22%3Afalse%2C%22transform%22%3Afalse%2C%22isolatedDeclarations%22%3Afalse%2C%22whitespace%22%3Afalse%2C%22mangle%22%3Afalse%2C%22mangleProps%22%3Afalse%2C%22compress%22%3Afalse%2C%22scope%22%3Atrue%2C%22symbol%22%3Atrue%2C%22cfg%22%3Afalse%7D%2C%22parser%22%3A%7B%22extension%22%3A%22js%22%2C%22allowReturnOutsideFunction%22%3Atrue%2C%22preserveParens%22%3Atrue%2C%22allowV8Intrinsics%22%3Atrue%2C%22semanticErrors%22%3Atrue%7D%2C%22linter%22%3A%7B%7D%2C%22formatter%22%3A%7B%22useTabs%22%3Afalse%2C%22tabWidth%22%3A2%2C%22endOfLine%22%3A%22lf%22%2C%22printWidth%22%3A80%2C%22singleQuote%22%3Afalse%2C%22jsxSingleQuote%22%3Afalse%2C%22quoteProps%22%3A%22as-needed%22%2C%22trailingComma%22%3A%22all%22%2C%22semi%22%3Atrue%2C%22arrowParens%22%3A%22always%22%2C%22bracketSpacing%22%3Atrue%2C%22bracketSameLine%22%3Afalse%2C%22objectWrap%22%3A%22preserve%22%2C%22singleAttributePerLine%22%3Afalse%7D%2C%22transformer%22%3A%7B%22target%22%3A%22es2015%22%2C%22useDefineForClassFields%22%3Atrue%2C%22experimentalDecorators%22%3Atrue%2C%22emitDecoratorMetadata%22%3Atrue%2C%22optimizeEnums%22%3Atrue%2C%22optimizeConstEnums%22%3Atrue%7D%2C%22isolatedDeclarations%22%3A%7B%22stripInternal%22%3Afalse%7D%2C%22codegen%22%3A%7B%22normal%22%3Atrue%2C%22jsdoc%22%3Atrue%2C%22annotation%22%3Atrue%2C%22legal%22%3Atrue%7D%2C%22compress%22%3A%7B%7D%2C%22mangle%22%3A%7B%22topLevel%22%3Atrue%2C%22keepNames%22%3Afalse%7D%2C%22mangleProps%22%3A%7B%22include%22%3A%22_%24%22%2C%22reserved%22%3A%5B%5D%2C%22quoted%22%3Afalse%2C%22debug%22%3Afalse%7D%2C%22controlFlow%22%3A%7B%22verbose%22%3Afalse%7D%2C%22inject%22%3A%7B%22inject%22%3A%7B%7D%7D%2C%22define%22%3A%7B%22define%22%3A%7B%7D%7D%7D&code=const+%5B...x%5D+%3D+y%3B)

crates/oxc_codegen/src/gen.rs

@@ -3205,7 +3205,9 @@ impl Gen for ArrayPattern<'_> {
             }
         }
         if let Some(rest) = &self.rest {
-            p.print_soft_space();
+            if !self.elements.is_empty() {
+                p.print_soft_space();
+            }
             rest.print(p, ctx);
         }
         p.print_ascii_byte(b']');

crates/oxc_codegen/tests/integration/js.rs

@@ -18,6 +18,13 @@ fn cases() {
 #[test]
 fn decl() {
     test_same("const [foo, ...bar] = qux;\n");
+    test_same("const [...bar] = qux;\n");
+    test_same("const [, ...bar] = qux;\n");
+    test_same("const [, , , ...bar] = qux;\n");
+    test_same("function foo([bar, ...qux]) {}\n");
+    test_same("function foo([...bar]) {}\n");
+    test_same("function foo([, ...bar]) {}\n");
+    test_same("function foo([, , , ...bar]) {}\n");
     test_same("const { foo, ...bar } = qux;\n");
     test_minify("const [foo] = bar", "const[foo]=bar;");
     test_minify("const {foo} = bar", "const{foo}=bar;");
@@ -475,6 +482,10 @@ fn r#yield() {
 
 #[test]
 fn arrow() {
+    test_same("([bar, ...qux]) => {};\n");
+    test_same("([...bar]) => {};\n");
+    test_same("([, ...bar]) => {};\n");
+    test_same("([, , , ...bar]) => {};\n");
     test_minify("x => a, b", "x=>a,b;");
     test_minify("x => (a, b)", "x=>(a,b);");
     test_minify("x => (a => b)", "x=>(a=>b);");

packages/codegen/src-js/print/binding_pattern.ts

@@ -171,7 +171,7 @@ export function printPropertyKey(key: ESTree.PropertyKey, state: State): void {
  */
 function printArrayBindingPattern(node: ESTree.ArrayPattern, state: State): void {
   // Oxc stores the rest element separately from the other elements.
-  // A trailing comma is printed before it, and a space always precedes it.
+  // A comma and a space separate it from any elements before it.
   const { elements } = node;
   let { length } = elements;
 
@@ -196,7 +196,7 @@ function printArrayBindingPattern(node: ESTree.ArrayPattern, state: State): void
   }
 
   if (rest !== null) {
-    write(state, " ", CAT_OTHER);
+    if (length > 0) write(state, " ", CAT_OTHER);
     writeWithMap(state, "...", CAT_OTHER, rest.start, rest.end, rest);
     printBindingPattern(rest.argument, state);
     if (TS) {

packages/codegen/test/fixtures/array-pattern-rest.js

@@ -0,0 +1,22 @@
+const [foo, ...a] = arr;
+const [...b] = arr;
+const [, ...c] = arr;
+const [, , , ...d] = arr;
+const [...[e]] = arr;
+const [...{ length }] = arr;
+for (const [...f] of arr);
+
+function f1([bar, ...g]) {}
+function f2([...h]) {}
+function f3([, ...i]) {}
+function f4([, , , ...j]) {}
+
+([bar, ...k]) => {};
+([...l]) => {};
+([, ...m]) => {};
+([, , , ...n]) => {};
+
+[foo, ...o] = arr;
+[...p] = arr;
+[, ...q] = arr;
+[, , , ...r] = arr;