fix(eslint-plugin): [prefer-readonly] add handling for destructuring assignments

a-tarasyuk · bradzacher · commit e011e90d2b97 · 2019-09-06T17:11:19.000-07:00
diff --git a/packages/eslint-plugin/src/rules/prefer-readonly.ts b/packages/eslint-plugin/src/rules/prefer-readonly.ts
@@ -68,7 +68,7 @@ export default util.createRule<Options, MessageIds>({
         return;
       }
 
-      if (ts.isDeleteExpression(parent)) {
+      if (ts.isDeleteExpression(parent) || isDestructuringAssignment(node)) {
         classScope.addVariableModification(node);
         return;
       }
@@ -108,6 +108,35 @@ export default util.createRule<Options, MessageIds>({
       }
     }
 
+    function isDestructuringAssignment(
+      node: ts.PropertyAccessExpression,
+    ): boolean {
+      let current: ts.Node = node.parent;
+
+      while (current) {
+        const parent = current.parent;
+
+        if (
+          ts.isObjectLiteralExpression(parent) ||
+          ts.isArrayLiteralExpression(parent) ||
+          ts.isSpreadAssignment(parent) ||
+          (ts.isSpreadElement(parent) &&
+            ts.isArrayLiteralExpression(parent.parent))
+        ) {
+          current = parent;
+        } else if (ts.isBinaryExpression(parent)) {
+          return (
+            parent.left === current &&
+            parent.operatorToken.kind === ts.SyntaxKind.EqualsToken
+          );
+        } else {
+          break;
+        }
+      }
+
+      return false;
+    }
+
     function isConstructor(node: TSESTree.Node): boolean {
       return (
         node.type === AST_NODE_TYPES.MethodDefinition &&
diff --git a/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts b/packages/eslint-plugin/tests/rules/prefer-readonly.test.ts
@@ -220,6 +220,54 @@ ruleTester.run('prefer-readonly', rule, {
         this['computed'] = 1;
       }
     }`,
+    {
+      code: `
+class Foo {
+  private value: number = 0
+
+  bar(newValue: { value: number }) {
+    ({ value: this.value } = newValue);
+    return this.value;
+  }
+}
+      `,
+    },
+    {
+      code: `
+class Foo {
+  private value: Record<string, number> = {};
+
+  bar(newValue: Record<string, number>) {
+    ({ ...this.value } = newValue);
+    return this.value;
+  }
+}
+      `,
+    },
+    {
+      code: `
+class Foo {
+  private value: number[] = []
+
+  bar(newValue: number[]) {
+    [...this.value] = newValue;
+    return this.value;
+  }
+}
+      `,
+    },
+    {
+      code: `
+class Foo {
+  private value: number = 0;
+
+  bar(newValue: number[]) {
+    [this.value] = newValue;
+    return this.value;
+  }
+}
+      `,
+    },
   ],
   invalid: [
     {
