feat: split variable declarations in for loop (#37)

j4k0xb · Jan 2, 2024 · b8d32a4 · b8d32a4
1 parent 38f0165
commit b8d32a4
Show file tree

Hide file tree

Showing 2 changed files with 64 additions and 16 deletions.
diff --git a/packages/webcrack/src/unminify/test/split-variable-declarations.test.ts b/packages/webcrack/src/unminify/test/split-variable-declarations.test.ts
@@ -22,11 +22,42 @@ test('split exported variable declarations', () =>
     export const c = 3;
   `));
 
-test('dont split in for loop', () =>
+test('split var in for loop initializer', () =>
   expectJS(`
-    for (let i = 0, j = 1; i < 10; i++, j++) var a, b;
+    for (var i = 0, j = 1;;) {}
   `).toMatchInlineSnapshot(`
-    for (let i = 0, j = 1; i < 10; i++, j++) {
+    var i = 0;
+    var j = 1;
+    for (;;) {}
+  `));
+
+test('ignore let in for loop initializer', () => {
+  expectJS(`
+    let i;
+    for (let i = 0, j = 1;;) {}
+  `).toMatchInlineSnapshot(`
+    let i;
+    for (let i = 0, j = 1;;) {}
+  `);
+
+  expectJS(`
+    for (let i = 0, j = 1;;) {
+      setTimeout(() => console.log(i));
+      if (++i > 3) break;
+    }
+  `).toMatchInlineSnapshot(`
+    for (let i = 0, j = 1;;) {
+      setTimeout(() => console.log(i));
+      if (++i > 3) break;
+    }
+  `);
+});
+
+test('ignore for loop with test or update', () =>
+  expectJS(`
+    for (var i = 0, j = 1; i < 10; i++, j++) var a, b;
+  `).toMatchInlineSnapshot(`
+    for (var i = 0, j = 1; i < 10; i++, j++) {
       var a;
       var b;
     }

diff --git a/packages/webcrack/src/unminify/transforms/split-variable-declarations.ts b/packages/webcrack/src/unminify/transforms/split-variable-declarations.ts
@@ -7,23 +7,40 @@ export default {
   visitor: () => ({
     VariableDeclaration: {
       exit(path) {
-        if (path.node.declarations.length > 1 && path.key !== 'init') {
-          if (path.parentPath.isExportNamedDeclaration()) {
-            path.parentPath.replaceWithMultiple(
-              path.node.declarations.map((declaration) =>
-                t.exportNamedDeclaration(
+        if (path.node.declarations.length > 1) {
+          // E.g. for (var i = 0, j = 1;;)
+          if (path.key === 'init' && path.parentPath.isForStatement()) {
+            if (
+              !path.parentPath.node.test &&
+              !path.parentPath.node.update &&
+              path.node.kind === 'var'
+            ) {
+              path.parentPath.insertBefore(
+                path.node.declarations.map((declaration) =>
                   t.variableDeclaration(path.node.kind, [declaration]),
                 ),
-              ),
-            );
+              );
+              path.remove();
+              this.changes++;
+            }
           } else {
-            path.replaceWithMultiple(
-              path.node.declarations.map((declaration) =>
-                t.variableDeclaration(path.node.kind, [declaration]),
-              ),
-            );
+            if (path.parentPath.isExportNamedDeclaration()) {
+              path.parentPath.replaceWithMultiple(
+                path.node.declarations.map((declaration) =>
+                  t.exportNamedDeclaration(
+                    t.variableDeclaration(path.node.kind, [declaration]),
+                  ),
+                ),
+              );
+            } else {
+              path.replaceWithMultiple(
+                path.node.declarations.map((declaration) =>
+                  t.variableDeclaration(path.node.kind, [declaration]),
+                ),
+              );
+            }
+            this.changes++;
           }
-          this.changes++;
         }
       },
     },