From aeea4cd40e2ac66ff596a205ba7bfc95aa376128 Mon Sep 17 00:00:00 2001
From: Alexander T <alexander.tarasyuk@outlook.com>
Date: Thu, 12 Sep 2019 13:05:04 +0300
Subject: [PATCH] feat(eslint-plugin): [no-magic-numbers] add
 ignoreReadonlyClassProperties option (#938)

---
 .../docs/rules/no-magic-numbers.md            | 28 ++++++++++++
 .../src/rules/no-magic-numbers.ts             | 25 +++++++++++
 .../tests/rules/no-magic-numbers.test.ts      | 44 +++++++++++++++++++
 .../eslint-plugin/typings/eslint-rules.d.ts   |  1 +
 4 files changed, 98 insertions(+)

diff --git a/packages/eslint-plugin/docs/rules/no-magic-numbers.md b/packages/eslint-plugin/docs/rules/no-magic-numbers.md
index cf647833887..215890a2e83 100644
--- a/packages/eslint-plugin/docs/rules/no-magic-numbers.md
+++ b/packages/eslint-plugin/docs/rules/no-magic-numbers.md
@@ -41,6 +41,34 @@ Examples of **correct** code for the `{ "ignoreNumericLiteralTypes": true }` opt
 type SmallPrimes = 2 | 3 | 5 | 7 | 11;
 ```
 
+### ignoreReadonlyClassProperties
+
+Examples of **incorrect** code for the `{ "ignoreReadonlyClassProperties": false }` option:
+
+```ts
+/*eslint @typescript-eslint/no-magic-numbers: ["error", { "ignoreReadonlyClassProperties": false }]*/
+
+class Foo {
+  readonly A = 1;
+  readonly B = 2;
+  public static readonly C = 1;
+  static readonly D = 1;
+}
+```
+
+Examples of **correct** code for the `{ "ignoreReadonlyClassProperties": true }` option:
+
+```ts
+/*eslint @typescript-eslint/no-magic-numbers: ["error", { "ignoreReadonlyClassProperties": true }]*/
+
+class Foo {
+  readonly A = 1;
+  readonly B = 2;
+  public static readonly C = 1;
+  static readonly D = 1;
+}
+```
+
 ### ignoreEnums
 
 A boolean to specify if enums used in Typescript are considered okay. `false` by default.
diff --git a/packages/eslint-plugin/src/rules/no-magic-numbers.ts b/packages/eslint-plugin/src/rules/no-magic-numbers.ts
index 005bae9eb0a..01a2505498f 100644
--- a/packages/eslint-plugin/src/rules/no-magic-numbers.ts
+++ b/packages/eslint-plugin/src/rules/no-magic-numbers.ts
@@ -33,6 +33,9 @@ export default util.createRule<Options, MessageIds>({
           ignoreEnums: {
             type: 'boolean',
           },
+          ignoreReadonlyClassProperties: {
+            type: 'boolean',
+          },
         },
       },
     ],
@@ -46,6 +49,7 @@ export default util.createRule<Options, MessageIds>({
       detectObjects: false,
       ignoreNumericLiteralTypes: false,
       ignoreEnums: false,
+      ignoreReadonlyClassProperties: false,
     },
   ],
   create(context, [options]) {
@@ -149,6 +153,20 @@ export default util.createRule<Options, MessageIds>({
       return false;
     }
 
+    /**
+     * Checks if the node parent is a readonly class property
+     * @param node the node to be validated.
+     * @returns true if the node parent is a readonly class property
+     * @private
+     */
+    function isParentTSReadonlyClassProperty(node: TSESTree.Node): boolean {
+      return (
+        !!node.parent &&
+        node.parent.type === AST_NODE_TYPES.ClassProperty &&
+        !!node.parent.readonly
+      );
+    }
+
     return {
       Literal(node): void {
         // Check if the node is a TypeScript enum declaration
@@ -156,6 +174,13 @@ export default util.createRule<Options, MessageIds>({
           return;
         }
 
+        if (
+          options.ignoreReadonlyClassProperties &&
+          isParentTSReadonlyClassProperty(node)
+        ) {
+          return;
+        }
+
         // Check TypeScript specific nodes for Numeric Literal
         if (
           options.ignoreNumericLiteralTypes &&
diff --git a/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts b/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts
index 09b6c35d0b4..1ab26cfa704 100644
--- a/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-magic-numbers.test.ts
@@ -41,6 +41,17 @@ ruleTester.run('no-magic-numbers', rule, {
       code: 'enum foo { SECOND = 1000, NUM = "0123456789" }',
       options: [{ ignoreEnums: true }],
     },
+    {
+      code: `
+class Foo {
+  readonly A = 1;
+  readonly B = 2;
+  public static readonly C = 1;
+  static readonly D = 1;
+}
+      `,
+      options: [{ ignoreReadonlyClassProperties: true }],
+    },
   ],
 
   invalid: [
@@ -166,5 +177,38 @@ ruleTester.run('no-magic-numbers', rule, {
         },
       ],
     },
+    {
+      code: `
+class Foo {
+  readonly A = 1;
+  readonly B = 2;
+  public static readonly C = 1;
+  static readonly D = 1;
+}
+      `,
+      options: [{ ignoreReadonlyClassProperties: false }],
+      errors: [
+        {
+          messageId: 'noMagic',
+          line: 3,
+          column: 16,
+        },
+        {
+          messageId: 'noMagic',
+          line: 4,
+          column: 16,
+        },
+        {
+          messageId: 'noMagic',
+          line: 5,
+          column: 30,
+        },
+        {
+          messageId: 'noMagic',
+          line: 6,
+          column: 23,
+        },
+      ],
+    },
   ],
 });
diff --git a/packages/eslint-plugin/typings/eslint-rules.d.ts b/packages/eslint-plugin/typings/eslint-rules.d.ts
index de6545f744d..120b11433cb 100644
--- a/packages/eslint-plugin/typings/eslint-rules.d.ts
+++ b/packages/eslint-plugin/typings/eslint-rules.d.ts
@@ -199,6 +199,7 @@ declare module 'eslint/lib/rules/no-magic-numbers' {
         detectObjects?: boolean;
         ignoreNumericLiteralTypes?: boolean;
         ignoreEnums?: boolean;
+        ignoreReadonlyClassProperties?: boolean;
       },
     ],
     {