fix(deadcode): account for impure paths inside for statements (#834)

* fix(deadcode): account for impure paths inside for statements * add env test
babel · May 10, 2018 · 5f60189 · 5f60189
1 parent 37ccf8c
commit 5f60189
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Showing 4 changed files with 25 additions and 1 deletion.
diff --git a/packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/loops/actual.js b/packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/loops/actual.js
@@ -19,6 +19,10 @@ for (; true; ) {
 for (; false; ) {
   baz();
 }
+for (var j; false; ) {
+  blah();
+}
+for (0; false; ) {}
 
 // do_while
 do {

diff --git a/packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/loops/expected.js b/packages/babel-plugin-minify-dead-code-elimination/__tests__/fixtures/loops/expected.js
@@ -16,6 +16,8 @@ for (;;) {
   bar();
 }
 
+var j;
+
 // do_while
 do {
   foo();

diff --git a/packages/babel-plugin-minify-dead-code-elimination/src/index.js b/packages/babel-plugin-minify-dead-code-elimination/src/index.js
@@ -678,7 +678,12 @@ module.exports = ({ types: t, traverse }) => {
         if (result.value) {
           test.remove();
         } else {
-          path.remove();
+          const init = path.get("init");
+          if (init.node && !init.isPure()) {
+            path.replaceWith(init);
+          } else {
+            path.remove();
+          }
         }
       }
     },

diff --git a/packages/babel-preset-minify/__tests__/minify-env-tests.js b/packages/babel-preset-minify/__tests__/minify-env-tests.js
@@ -183,4 +183,17 @@ describe("preset along with env", () => {
     })();
   `
   );
+
+  thePlugin(
+    "should fix issue#824 simplify + deadcode",
+    `
+      let foo;
+      while (0) {}
+      console.log(foo);
+    `,
+    `
+      var foo;
+      console.log(foo);
+    `
+  );
 });