No cond assign eslint implementation

packages/@romejs/js-compiler/__rtests__/lint.ts

@@ -171,6 +171,44 @@ test('disallows comparing negative zero', async t => {
   t.looksLike(res2.diagnostics, []);
 });
 
+test('no cond assign', async t => {
+  const forLoop = await testLint(
+    `for (let i = 1; i = 10; i++) {
+      console.log('foo')
+    }`,
+    LINT_ENABLED_FORMAT_DISABLED_CONFIG,
+  );
+
+  t.snapshot(forLoop);
+
+  const ifCondition = await testLint(
+    `if(foo = 'bar') {
+      console.log('foo')
+    }`,
+    LINT_ENABLED_FORMAT_DISABLED_CONFIG,
+  );
+
+  t.snapshot(ifCondition);
+
+  const whileLoop = await testLint(
+    `while (foo = 'bar' {
+      console.log('foo')
+    }`,
+    LINT_ENABLED_FORMAT_DISABLED_CONFIG,
+  );
+
+  t.snapshot(whileLoop);
+
+  const DoWhileLoop = await testLint(
+    `do {
+      console.log('foo)
+    } while (foo = 'bar')`,
+    LINT_ENABLED_FORMAT_DISABLED_CONFIG,
+  );
+
+  t.snapshot(DoWhileLoop);
+});
+
 test('no label var', async t => {
   const badLabel = await testLint(
     `

packages/@romejs/js-compiler/transforms/lint/index.ts

@@ -6,31 +6,39 @@
  */
 
 import defaultExportSameBasename from './defaultExportSameBasename';
-import undeclaredVariables from './undeclaredVariables';
-import unusedVariables from './unusedVariables';
+import disallowVar from './disallowVar';
 import emptyBlocks from './emptyBlocks';
 import sparseArray from './sparseArray';
 import noCompareNegZero from './noCompareNegZero';
 import unsafeNegation from './unsafeNegation';
 import noAsyncPromiseExecutor from './noAsyncPromiseExecutor';
-import noLabelVar from './noLabelVar';
+import noCompareNegZero from './noCompareNegZero';
+import noCondAssign from './noCondAssign';
 import noDuplicateKeys from './noDuplicateKeys';
+import noLabelVar from './noLabelVar';
+import undeclaredVariables from './undeclaredVariables';
+import unsafeNegation from './unsafeNegation';
+import unusedVariables from './unusedVariables';
 import disallowVar from './disallowVar';
 import noUnsafeFinally from './noUnsafeFinally';
 import noDeleteVars from './noDeleteVars';
 import noTemplateCurlyInString from './noTemplateCurlyInString';
 
 export const lintTransforms = [
-  undeclaredVariables,
   defaultExportSameBasename,
-  unusedVariables,
+  disallowVar,
   emptyBlocks,
   sparseArray,
   noCompareNegZero,
   unsafeNegation,
   noAsyncPromiseExecutor,
-  noLabelVar,
+  noCompareNegZero,
+  noCondAssign,
   noDuplicateKeys,
+  noLabelVar,
+  undeclaredVariables,
+  unsafeNegation,
+  unusedVariables,
   disallowVar,
   noUnsafeFinally,
   noDeleteVars,

packages/@romejs/js-compiler/transforms/lint/noCondAssign.ts

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {Path} from '@romejs/js-compiler';
+import {AnyNode} from '@romejs/js-ast';
+
+export default {
+  name: 'noCondAssign',
+  enter(path: Path): AnyNode {
+    const {node} = path;
+
+    if (
+      (node.type === 'IfStatement' ||
+        node.type === 'ForStatement' ||
+        node.type === 'WhileStatement' ||
+        node.type === 'DoWhileStatement') &&
+      node.test &&
+      node.test.type === 'AssignmentExpression'
+    ) {
+      path.context.addNodeDiagnostic(node, {
+        category: 'lint/noCondAssign',
+        message: 'Cannot assign variable in loop condition',
+      });
+    }
+    return node;
+  },
+};

packages/@romejs/js-generator/Buffer.ts

@@ -203,9 +203,13 @@ export default class Buffer {
   }
 
   flush(): void {
-    let item;
-    while ((item = this._queue.pop())) {
-      this._append(...item);
+    while (true) {
+      const item = this._queue.pop();
+      if (item === undefined) {
+        break;
+      } else {
+        this._append(...item);
+      }
     }
   }