initial no direct mutation state identification

packages/@romejs/diagnostics/categories.ts

@@ -111,6 +111,7 @@ type LintDiagnosticCategory =
   | 'lint/noDebugger'
   | 'lint/noDelete'
   | 'lint/noDeleteVars'
+  | 'lint/noDirectMutationState'
   | 'lint/noDupeArgs'
   | 'lint/noDuplicateCase'
   | 'lint/noDuplicateGroupNamesInRegularExpressions'

packages/@romejs/diagnostics/descriptions.ts

@@ -346,6 +346,10 @@ export const descriptions = createMessages({
       category: 'lint/noChildrenProp',
       message: 'children should not be passed as a prop',
     },
+    NO_DIRECT_MUTATION_STATE: {
+      category: 'lint/noDirectMutationState',
+      message: 'Cannot directly mutate state, try using setState or spreading',
+    },
     PREFER_BLOCK_STATEMENT: {
       category: 'lint/preferBlockStatements',
       message: 'Block statements are preferred in this position',

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

@@ -26,6 +26,7 @@ import noCondAssign from './regular/noCondAssign';
 import noDebugger from './regular/noDebugger';
 import noDelete from './regular/noDelete';
 import noDeleteVars from './regular/noDeleteVars';
+import noDirectMutationState from './react/noDirectMutationState';
 import noDupeArgs from './regular/noDupeArgs';
 import noDuplicateCase from './regular/noDuplicateCase';
 import noDuplicateGroupNamesInRegularExpressions from './regular/noDuplicateGroupNamesInRegularExpressions';
@@ -79,6 +80,7 @@ export const lintTransforms = [
   noDebugger,
   noDelete,
   noDeleteVars,
+  noDirectMutationState,
   noDupeArgs,
   noDuplicateCase,
   noDuplicateGroupNamesInRegularExpressions,

packages/@romejs/js-compiler/lint/rules/react/noDirectMutationState.ts

@@ -0,0 +1,41 @@
+/**
+ * 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';
+import {descriptions} from '@romejs/diagnostics';
+
+export default {
+  name: 'noDirectMutationState',
+  enter(path: Path): AnyNode {
+    const {node} = path;
+
+    if (
+      node.type === 'ClassDeclaration'
+    ) {
+      for (let bodyNode of node.meta.body) {
+        if (bodyNode.type === 'ClassMethod') {
+          for (let bodyBodyNode of bodyNode.body.body) {
+            if (
+              bodyBodyNode.type === 'ExpressionStatement' &&
+              bodyBodyNode.expression.type === 'AssignmentExpression' &&
+              bodyBodyNode.expression.left.type === 'MemberExpression' &&
+              bodyBodyNode.expression.left.object.type === 'MemberExpression' &&
+              bodyBodyNode.expression.left.object.object.type === 'ThisExpression' &&
+              bodyBodyNode.expression.left.object.property.value.type === 'Identifier' &&
+              bodyBodyNode.expression.left.object.property.value.name === 'state'
+            ) {
+                path.context.addNodeDiagnostic(node, descriptions.LINT.NO_DIRECT_MUTATION_STATE);
+            }
+          }
+        }
+      }
+    }
+
+    return node;
+  },
+};