feat(eslint-plugin): [member-ordering] add support for grouping readonly fields (#6349)

* feat(eslint-plugin): [member-ordering] add support for grouping readonly fields

* refactor: inline readonly assertions

* chore: remove comments

* test: add more tests for readonly TSAbstractPropertyDefinition and TSPropertySignature

* feat: add support for readonly signatures

---------

Co-authored-by: Josh Goldberg <[email protected]>

Author: IronGeek

packages/eslint-plugin/docs/rules/member-ordering.md

@@ -58,7 +58,7 @@ The supported member attributes are, in order:
 
 - **Accessibility** (`'public' | 'protected' | 'private' | '#private'`)
 - **Decoration** (`'decorated'`): Whether the member has an explicit accessibility decorator
-- **Kind** (`'call-signature' | 'constructor' | 'field' | 'get' | 'method' | 'set' | 'signature'`)
+- **Kind** (`'call-signature' | 'constructor' | 'field' | 'readonly-field' | 'get' | 'method' | 'set' | 'signature' | 'readonly-signature'`)
 
 Member attributes may be joined with a `'-'` to combine into more specific groups.
 For example, `'public-field'` would come before `'private-field'`.
@@ -1014,37 +1014,60 @@ The most explicit and granular form is the following:
 [
   // Index signature
   "signature",
+  "readonly-signature",
 
   // Fields
   "public-static-field",
+  "public-static-readonly-field",
   "protected-static-field",
+  "protected-static-readonly-field",
   "private-static-field",
+  "private-static-readonly-field",
   "#private-static-field",
+  "#private-static-readonly-field",
 
   "public-decorated-field",
+  "public-decorated-readonly-field",
   "protected-decorated-field",
+  "protected-decorated-readonly-field",
   "private-decorated-field",
+  "private-decorated-readonly-field",
 
   "public-instance-field",
+  "public-instance-readonly-field",
   "protected-instance-field",
+  "protected-instance-readonly-field",
   "private-instance-field",
+  "private-instance-readonly-field",
   "#private-instance-field",
+  "#private-instance-readonly-field",
 
   "public-abstract-field",
+  "public-abstract-readonly-field",
   "protected-abstract-field",
+  "protected-abstract-readonly-field",
 
   "public-field",
+  "public-readonly-field",
   "protected-field",
+  "protected-readonly-field",
   "private-field",
+  "private-readonly-field"
   "#private-field",
+  "#private-readonly-field"
 
   "static-field",
+  "static-readonly-field",
   "instance-field",
+  "instance-readonly-field"
   "abstract-field",
+  "abstract-readonly-field",
 
   "decorated-field",
+  "decorated-readonly-field",
 
   "field",
+  "readonly-field",
 
   // Static initialization
   "static-initialization",
@@ -1290,6 +1313,22 @@ The third grouping option is to ignore both scope and accessibility.
 ]
 ```
 
+### Member Group Types (Readonly Fields)
+
+It is possible to group fields by their `readonly` modifiers.
+
+```jsonc
+[
+  // Index signature
+  "readonly-signature",
+  "signature",
+
+  // Fields
+  "readonly-field", // = ["public-static-readonly-field", "protected-static-readonly-field", "private-static-readonly-field", "public-instance-readonly-field", "protected-instance-readonly-field", "private-instance-readonly-field", "public-abstract-readonly-field", "protected-abstract-readonly-field"]
+  "field" // = ["public-static-field", "protected-static-field", "private-static-field", "public-instance-field", "protected-instance-field", "private-instance-field", "public-abstract-field", "protected-abstract-field"]
+]
+```
+
 ### Grouping Different Member Types at the Same Rank
 
 It is also possible to group different member types at the same rank.

packages/eslint-plugin/src/rules/member-ordering.ts

@@ -9,19 +9,30 @@ export type MessageIds =
   | 'incorrectOrder'
   | 'incorrectRequiredMembersOrder';
 
+type ReadonlyType = 'readonly-field' | 'readonly-signature';
+
 type MemberKind =
   | 'call-signature'
   | 'constructor'
+  | ReadonlyType
   | 'field'
   | 'get'
   | 'method'
   | 'set'
   | 'signature'
   | 'static-initialization';
 
-type DecoratedMemberKind = 'field' | 'method' | 'get' | 'set';
+type DecoratedMemberKind =
+  | Exclude<ReadonlyType, 'readonly-signature'>
+  | 'field'
+  | 'method'
+  | 'get'
+  | 'set';
 
-type NonCallableMemberKind = Exclude<MemberKind, 'constructor' | 'signature'>;
+type NonCallableMemberKind = Exclude<
+  MemberKind,
+  'constructor' | 'signature' | 'readonly-signature'
+>;
 
 type MemberScope = 'static' | 'instance' | 'abstract';
 
@@ -31,7 +42,7 @@ type BaseMemberType =
   | MemberKind
   | `${Accessibility}-${Exclude<
       MemberKind,
-      'signature' | 'static-initialization'
+      'signature' | 'readonly-signature' | 'static-initialization'
     >}`
   | `${Accessibility}-decorated-${DecoratedMemberKind}`
   | `decorated-${DecoratedMemberKind}`
@@ -258,7 +269,9 @@ export const defaultOrder: MemberType[] = [
 const allMemberTypes = Array.from(
   (
     [
+      'readonly-signature',
       'signature',
+      'readonly-field',
       'field',
       'method',
       'call-signature',
@@ -273,6 +286,7 @@ const allMemberTypes = Array.from(
     (['public', 'protected', 'private', '#private'] as const).forEach(
       accessibility => {
         if (
+          type !== 'readonly-signature' &&
           type !== 'signature' &&
           type !== 'static-initialization' &&
           type !== 'call-signature' &&
@@ -284,7 +298,8 @@ const allMemberTypes = Array.from(
         // Only class instance fields, methods, get and set can have decorators attached to them
         if (
           accessibility !== '#private' &&
-          (type === 'field' ||
+          (type === 'readonly-field' ||
+            type === 'field' ||
             type === 'method' ||
             type === 'get' ||
             type === 'set')
@@ -295,6 +310,7 @@ const allMemberTypes = Array.from(
 
         if (
           type !== 'constructor' &&
+          type !== 'readonly-signature' &&
           type !== 'signature' &&
           type !== 'call-signature'
         ) {
@@ -340,15 +356,17 @@ function getNodeType(node: Member): MemberKind | null {
     case AST_NODE_TYPES.TSConstructSignatureDeclaration:
       return 'constructor';
     case AST_NODE_TYPES.TSAbstractPropertyDefinition:
-      return 'field';
+      return node.readonly ? 'readonly-field' : 'field';
     case AST_NODE_TYPES.PropertyDefinition:
       return node.value && functionExpressions.includes(node.value.type)
         ? 'method'
+        : node.readonly
+        ? 'readonly-field'
         : 'field';
     case AST_NODE_TYPES.TSPropertySignature:
-      return 'field';
+      return node.readonly ? 'readonly-field' : 'field';
     case AST_NODE_TYPES.TSIndexSignature:
-      return 'signature';
+      return node.readonly ? 'readonly-signature' : 'signature';
     case AST_NODE_TYPES.StaticBlock:
       return 'static-initialization';
     default:
@@ -514,27 +532,50 @@ function getRank(
     const decorated = 'decorators' in node && node.decorators!.length > 0;
     if (
       decorated &&
-      (type === 'field' ||
+      (type === 'readonly-field' ||
+        type === 'field' ||
         type === 'method' ||
         type === 'get' ||
         type === 'set')
     ) {
       memberGroups.push(`${accessibility}-decorated-${type}`);
       memberGroups.push(`decorated-${type}`);
+
+      if (type === 'readonly-field') {
+        memberGroups.push(`${accessibility}-decorated-field`);
+        memberGroups.push(`decorated-field`);
+      }
     }
 
-    if (type !== 'signature' && type !== 'static-initialization') {
+    if (
+      type !== 'readonly-signature' &&
+      type !== 'signature' &&
+      type !== 'static-initialization'
+    ) {
       if (type !== 'constructor') {
         // Constructors have no scope
         memberGroups.push(`${accessibility}-${scope}-${type}`);
         memberGroups.push(`${scope}-${type}`);
+
+        if (type === 'readonly-field') {
+          memberGroups.push(`${accessibility}-${scope}-field`);
+          memberGroups.push(`${scope}-field`);
+        }
       }
 
       memberGroups.push(`${accessibility}-${type}`);
+      if (type === 'readonly-field') {
+        memberGroups.push(`${accessibility}-field`);
+      }
     }
   }
 
   memberGroups.push(type);
+  if (type === 'readonly-signature') {
+    memberGroups.push('signature');
+  } else if (type === 'readonly-field') {
+    memberGroups.push('field');
+  }
 
   // ...then get the rank order for those member groups based on the node
   return getRankOrder(memberGroups, orderConfig);
@@ -621,15 +662,43 @@ export default util.createRule<Options, MessageIds>({
           interfaces: {
             oneOf: [
               neverConfig,
-              arrayConfig(['signature', 'field', 'method', 'constructor']),
-              objectConfig(['signature', 'field', 'method', 'constructor']),
+              arrayConfig([
+                'readonly-signature',
+                'signature',
+                'readonly-field',
+                'field',
+                'method',
+                'constructor',
+              ]),
+              objectConfig([
+                'readonly-signature',
+                'signature',
+                'readonly-field',
+                'field',
+                'method',
+                'constructor',
+              ]),
             ],
           },
           typeLiterals: {
             oneOf: [
               neverConfig,
-              arrayConfig(['signature', 'field', 'method', 'constructor']),
-              objectConfig(['signature', 'field', 'method', 'constructor']),
+              arrayConfig([
+                'readonly-signature',
+                'signature',
+                'readonly-field',
+                'field',
+                'method',
+                'constructor',
+              ]),
+              objectConfig([
+                'readonly-signature',
+                'signature',
+                'readonly-field',
+                'field',
+                'method',
+                'constructor',
+              ]),
             ],
           },
         },