feat(eslint-plugin): [prefer-literal-enum-member] add allowBitwiseExp…

…ressions option (#3515)
typescript-eslint · Jun 13, 2021 · 288092a · 288092a
1 parent 9e343fd
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diff --git a/packages/eslint-plugin/docs/rules/prefer-literal-enum-member.md b/packages/eslint-plugin/docs/rules/prefer-literal-enum-member.md
@@ -21,6 +21,10 @@ The answer is that `Foo.c` will be `1` at runtime. The [playground](https://www.
 
 This rule is meant to prevent unexpected results in code by requiring the use of literal values as enum members to prevent unexpected runtime behavior. Template literals, arrays, objects, constructors, and all other expression types can end up using a variable from its scope or the parent scope, which can result in the same unexpected behavior at runtime.
 
+## Options
+
+- `allowBitwiseExpressions` set to `true` will allow you to use bitwise expressions in enum initializer (Default: `false`).
+
 Examples of **incorrect** code for this rule:
 
 ```ts
@@ -46,6 +50,37 @@ enum Valid {
 }
 ```
 
+### `allowBitwiseExpressions`
+
+Examples of **incorrect** code for the `{ "allowBitwiseExpressions": true }` option:
+
+```ts
+const x = 1;
+enum Foo {
+  A = x << 0,
+  B = x >> 0,
+  C = x >>> 0,
+  D = x | 0,
+  E = x & 0,
+  F = x ^ 0,
+  G = ~x,
+}
+```
+
+Examples of **correct** code for the `{ "allowBitwiseExpressions": true }` option:
+
+```ts
+enum Foo {
+  A = 1 << 0,
+  B = 1 >> 0,
+  C = 1 >>> 0,
+  D = 1 | 0,
+  E = 1 & 0,
+  F = 1 ^ 0,
+  G = ~1,
+}
+```
+
 ## When Not To Use It
 
 If you want use anything other than simple literals as an enum value.
diff --git a/packages/eslint-plugin/src/rules/prefer-literal-enum-member.ts b/packages/eslint-plugin/src/rules/prefer-literal-enum-member.ts
@@ -15,10 +15,24 @@ export default createRule({
     messages: {
       notLiteral: `Explicit enum value must only be a literal value (string, number, boolean, etc).`,
     },
-    schema: [],
+    schema: [
+      {
+        type: 'object',
+        properties: {
+          allowBitwiseExpressions: {
+            type: 'boolean',
+          },
+        },
+        additionalProperties: false,
+      },
+    ],
   },
-  defaultOptions: [],
-  create(context) {
+  defaultOptions: [
+    {
+      allowBitwiseExpressions: false,
+    },
+  ],
+  create(context, [{ allowBitwiseExpressions }]) {
     return {
       TSEnumMember(node): void {
         // If there is no initializer, then this node is just the name of the member, so ignore.
@@ -39,8 +53,21 @@ export default createRule({
         // -1 and +1
         if (
           node.initializer.type === AST_NODE_TYPES.UnaryExpression &&
-          ['+', '-'].includes(node.initializer.operator) &&
-          node.initializer.argument.type === AST_NODE_TYPES.Literal
+          node.initializer.argument.type === AST_NODE_TYPES.Literal &&
+          (['+', '-'].includes(node.initializer.operator) ||
+            (allowBitwiseExpressions && node.initializer.operator === '~'))
+        ) {
+          return;
+        }
+
+        if (
+          allowBitwiseExpressions &&
+          node.initializer.type === AST_NODE_TYPES.BinaryExpression &&
+          ['|', '&', '^', '<<', '>>', '>>>'].includes(
+            node.initializer.operator,
+          ) &&
+          node.initializer.left.type === AST_NODE_TYPES.Literal &&
+          node.initializer.right.type === AST_NODE_TYPES.Literal
         ) {
           return;
         }

diff --git a/packages/eslint-plugin/tests/rules/prefer-literal-enum-member.test.ts b/packages/eslint-plugin/tests/rules/prefer-literal-enum-member.test.ts
@@ -62,6 +62,20 @@ enum ValidKeyWithComputedSyntaxButNoComputedKey {
   ['a'],
 }
     `,
+    {
+      code: `
+enum Foo {
+  A = 1 << 0,
+  B = 1 >> 0,
+  C = 1 >>> 0,
+  D = 1 | 0,
+  E = 1 & 0,
+  F = 1 ^ 0,
+  G = ~1,
+}
+      `,
+      options: [{ allowBitwiseExpressions: true }],
+    },
   ],
   invalid: [
     {
@@ -255,5 +269,108 @@ enum InvalidSpread {
         },
       ],
     },
+    {
+      code: `
+enum Foo {
+  A = 1 << 0,
+  B = 1 >> 0,
+  C = 1 >>> 0,
+  D = 1 | 0,
+  E = 1 & 0,
+  F = 1 ^ 0,
+  G = ~1,
+}
+      `,
+      options: [{ allowBitwiseExpressions: false }],
+      errors: [
+        {
+          messageId: 'notLiteral',
+          line: 3,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 4,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 5,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 6,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 7,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 8,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 9,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: `
+const x = 1;
+enum Foo {
+  A = x << 0,
+  B = x >> 0,
+  C = x >>> 0,
+  D = x | 0,
+  E = x & 0,
+  F = x ^ 0,
+  G = ~x,
+}
+      `,
+      options: [{ allowBitwiseExpressions: true }],
+      errors: [
+        {
+          messageId: 'notLiteral',
+          line: 4,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 5,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 6,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 7,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 8,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 9,
+          column: 3,
+        },
+        {
+          messageId: 'notLiteral',
+          line: 10,
+          column: 3,
+        },
+      ],
+    },
   ],
 });