deprecate no-unsafe-optional-property-assignment. Fix #83

Author: danielnixon

README.md

@@ -72,7 +72,6 @@ Alternatively you can configure individual rules separately (see below).
 |  no-unsafe-type-assertion               | ✅           | ✅    |        |
 |  no-unsafe-readonly-mutable-assignment  | ✅           | ✅    |        |
 |  no-unsafe-mutable-readonly-assignment  |              | ✅    | [Not yet](https://github.com/danielnixon/eslint-plugin-total-functions/issues/99) |
-|  no-unsafe-optional-property-assignment | [Not yet](https://github.com/danielnixon/eslint-plugin-total-functions/issues/83) | ✅    |       |
 |  no-unsafe-enum-assignment              | ✅           | ✅    |        |
 |  no-enums                               | ✅           | ✅    |        |
 |  no-partial-url-constructor             | ✅           | ✅    |        |
@@ -83,6 +82,10 @@ Alternatively you can configure individual rules separately (see below).
 |  no-partial-array-reduce                | ✅           | ✅    |        |
 |  no-hidden-type-assertions              |              | ✅    |        |
 
+### Deprecated rules
+
+* no-unsafe-optional-property-assignment
+
 ### total-functions/require-strict-mode
 
 The world is a very strange place when [strict mode](https://www.typescriptlang.org/tsconfig#strict) is disabled. This rule enforces strict mode and [noUncheckedIndexedAccess](https://devblogs.microsoft.com/typescript/announcing-typescript-4-1-beta/#no-unchecked-indexed-access) mode (which is sadly not included under the strict umbrella).
@@ -143,31 +146,6 @@ The solution is to append `as const` to the RHS:
 
 For examples of assignment that this rule considers valid and invalid, see [no-unsafe-mutable-readonly-assignment.test.ts](https://github.com/danielnixon/eslint-plugin-total-functions/blob/master/src/rules/no-unsafe-mutable-readonly-assignment.test.ts).
 
-### total-functions/no-unsafe-optional-property-assignment
-
-Optional properties (those with a `?` after their name) interact badly with TypeScript's structural type system in a way that can lead to unsoundness. Example:
-
-```ts
-type Foo = { readonly foo: string };
-type Bar = Foo & { readonly bar?: () => unknown };
-
-const thing = { foo: "foo", bar: "bar" };
-const foo: Foo = thing;
-const bar: Bar = foo;
-
-if (bar.bar !== undefined) {
-    bar.bar(); // explodes at runtime
-}
-```
-
-I find this scenario particularly vexing because it doesn't require type assertions, or plain JS with incorrect \*.d.ts typings, or anything 'loose' like that. You can pull it off with otherwise nicely typed, functional TypeScript (strict mode enabled, no interfaces, no classes, everything readonly, everything const, no type assertions, no plain JS, etc).
-
-This rule bans assignment from one type to another, if:
-1. the destination type has an optional property, and
-2. the source type has no matching property (either optional or otherwise).
-
-This rule is excluded from the `recommended` config until [#83](https://github.com/danielnixon/eslint-plugin-total-functions/issues/83) lands.
-
 ### total-functions/no-enums
 
 Enums have a number of issues, including unsoundness issues (which are especially relevant here). This rule bans the declaration of enums entirely. Use an alternative such as a union of strings instead.

src/configs/all.ts

@@ -4,7 +4,6 @@ export = {
     "total-functions/no-unsafe-type-assertion": "error",
     "total-functions/no-unsafe-readonly-mutable-assignment": "error",
     "total-functions/no-unsafe-mutable-readonly-assignment": "error",
-    "total-functions/no-unsafe-optional-property-assignment": "error",
     "total-functions/require-strict-mode": "error",
     "total-functions/no-unsafe-enum-assignment": "error",
     "total-functions/no-enums": "error",

src/configs/recommended.ts

@@ -3,8 +3,6 @@ export = {
   rules: {
     "total-functions/no-unsafe-type-assertion": "error",
     "total-functions/no-unsafe-readonly-mutable-assignment": "error",
-    // TODO this is too noisy until https://github.com/danielnixon/eslint-plugin-total-functions/issues/83 lands
-    // "total-functions/no-unsafe-optional-property-assignment": "error",
     "total-functions/require-strict-mode": "error",
     "total-functions/no-unsafe-enum-assignment": "error",
     "total-functions/no-enums": "error",

src/rules/index.ts

@@ -1,7 +1,6 @@
 import noUnsafeTypeAssertion from "./no-unsafe-type-assertion";
 import noUnsafeReadonlyMutableAssignment from "./no-unsafe-readonly-mutable-assignment";
 import noUnsafeMutableReadonlyAssignment from "./no-unsafe-mutable-readonly-assignment";
-import noUnsafeOptionalPropertyAssignment from "./no-unsafe-optional-property-assignment";
 import requireStrictMode from "./require-strict-mode";
 import noUnsafeEnumAssignment from "./no-unsafe-enum-assignment";
 import noEnums from "./no-enums";
@@ -18,7 +17,6 @@ export default {
   "no-unsafe-type-assertion": noUnsafeTypeAssertion,
   "no-unsafe-readonly-mutable-assignment": noUnsafeReadonlyMutableAssignment,
   "no-unsafe-mutable-readonly-assignment": noUnsafeMutableReadonlyAssignment,
-  "no-unsafe-optional-property-assignment": noUnsafeOptionalPropertyAssignment,
   "no-unsafe-enum-assignment": noUnsafeEnumAssignment,
   "no-enums": noEnums,
   "no-partial-url-constructor": noPartialUrlConstructor,

src/rules/no-unsafe-optional-property-assignment.test.ts

@@ -1,32 +1,4 @@
-import { isSymbolFlagSet } from "tsutils";
-import { Symbol, SymbolFlags } from "typescript";
 import { createRule } from "./common";
-import {
-  createNoUnsafeAssignmentRule,
-  UnsafeIndexAssignmentFunc,
-  UnsafePropertyAssignmentFunc,
-} from "./unsafe-assignment-rule";
-
-// eslint-disable-next-line functional/functional-parameters
-const unsafeIndexAssignmentFunc: UnsafeIndexAssignmentFunc = (): boolean =>
-  false;
-
-const unsafePropertyAssignmentFunc: UnsafePropertyAssignmentFunc = (
-  // eslint-disable-next-line functional/prefer-immutable-types, @typescript-eslint/ban-types
-  destinationProperty: Symbol,
-  // eslint-disable-next-line functional/prefer-immutable-types, @typescript-eslint/ban-types
-  sourceProperty: Symbol | undefined
-): boolean => {
-  const destinationPropIsOptional = isSymbolFlagSet(
-    destinationProperty,
-    SymbolFlags.Optional
-  );
-
-  return destinationPropIsOptional && sourceProperty === undefined;
-};
-
-const message =
-  "Assigning to an optional property when there is no such property in the source type (optional or otherwise) is unsafe.";
 
 /**
  * An ESLint rule to ban unsafe assignment to optional properties.
@@ -40,20 +12,12 @@ const noUnsafeOptionalPropertyAssignment = createRule({
       description: "Bans unsafe assignment to optional properties.",
       recommended: "error",
     },
-    messages: {
-      errorStringCallExpression: message,
-      errorStringAssignmentExpression: message,
-      errorStringVariableDeclaration: message,
-      errorStringArrowFunctionExpression: message,
-      errorStringTSAsExpression: message,
-      errorStringTSTypeAssertion: message,
-    },
+    messages: {},
     schema: [],
+    deprecated: true,
   },
-  create: createNoUnsafeAssignmentRule(
-    unsafePropertyAssignmentFunc,
-    unsafeIndexAssignmentFunc
-  ),
+  // eslint-disable-next-line functional/functional-parameters
+  create: () => ({}),
   defaultOptions: [],
 } as const);