feat: add new enforce option to lines-between-class-members (#17462)

* feat: add new \`enforce\` option (`lines-between-class-members`) * test: add cases for enforce with exceptAfterSingleLine option * docs: add `enforce` option * docs: fix example * fix: update schema to make enforce option required * refactor: remove redundant if condition * refactor: remove redundant if condition * docs: add suggestions Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com> * test: add cases where multiple config objects match a pair --------- Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>
eslint · Sep 2, 2023 · acb7df3 · acb7df3
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diff --git a/docs/src/rules/lines-between-class-members.md b/docs/src/rules/lines-between-class-members.md
@@ -69,14 +69,19 @@ class MyClass {
 
 ### Options
 
-This rule has a string option and an object option.
+This rule has two options, first option can be string or object, second option is object.
 
-String option:
+First option can be string `"always"` or `"never"` or an object with a property named `enforce`:
 
 * `"always"`(default) require an empty line after class members
 * `"never"` disallows an empty line after class members
+* `Object`: An object with a property named `enforce`. The enforce property should be an array of objects, each specifying the configuration for enforcing empty lines between specific pairs of class members.
+    * **enforce**: You can supply any number of configurations. If a member pair matches multiple configurations, the last matched configuration will be used. If a member pair does not match any configurations, it will be ignored. Each object should have the following properties:
+        * **blankLine**: Can be set to either `"always"` or `"never"`, indicating whether a blank line should be required or disallowed between the specified members.
+        * **prev**: Specifies the type of the preceding class member. It can be `"method"` for class methods, `"field"` for class fields, or `"*"` for any class member.
+        * **next**: Specifies the type of the following class member. It follows the same options as `prev`.
 
-Object option:
+Second option is an object with a property named `exceptAfterSingleLine`:
 
 * `"exceptAfterSingleLine": false`(default) **do not** skip checking empty lines after single-line class members
 * `"exceptAfterSingleLine": true` skip checking empty lines after single-line class members
@@ -129,6 +134,146 @@ class Foo{
 
 :::
 
+Examples of **incorrect** code for this rule with the array of configurations option:
+
+::: incorrect
+
+```js
+// disallows blank lines between methods
+/*eslint lines-between-class-members: [
+    "error",
+    {
+      enforce: [
+        { blankLine: "never", prev: "method", next: "method" }
+      ]
+    },
+]*/
+
+class MyClass {
+  constructor(height, width) {
+      this.height = height;
+      this.width = width;
+  }
+
+  fieldA = 'Field A';
+  #fieldB = 'Field B';
+
+  method1() {}
+
+  get area() {
+    return this.method1();
+  }
+
+  method2() {}
+}
+```
+
+:::
+
+::: incorrect
+
+```js
+// requires blank lines around fields, disallows blank lines between methods
+/*eslint lines-between-class-members: [
+    "error",
+    {
+      enforce: [
+        { blankLine: "always", prev: "*", next: "field" },
+        { blankLine: "always", prev: "field", next: "*" },
+        { blankLine: "never", prev: "method", next: "method" }
+      ]
+    },
+]*/
+
+class MyClass {
+  constructor(height, width) {
+      this.height = height;
+      this.width = width;
+  }
+  fieldA = 'Field A';
+  #fieldB = 'Field B';
+  method1() {}
+
+  get area() {
+    return this.method1();
+  }
+
+  method2() {}
+}
+```
+
+:::
+
+Examples of **correct** code for this rule with the array of configurations option:
+
+::: correct
+
+```js
+// disallows blank lines between methods
+/*eslint lines-between-class-members: [
+    "error",
+    {
+      enforce: [
+        { blankLine: "never", prev: "method", next: "method" }
+      ]
+    },
+]*/
+
+class MyClass {
+  constructor(height, width) {
+      this.height = height;
+      this.width = width;
+  }
+
+  fieldA = 'Field A';
+
+  #fieldB = 'Field B';
+
+  method1() {}
+  get area() {
+    return this.method1();
+  }
+  method2() {}
+}
+```
+
+:::
+
+::: correct
+
+```js
+// requires blank lines around fields, disallows blank lines between methods
+/*eslint lines-between-class-members: [
+    "error",
+    {
+      enforce: [
+        { blankLine: "always", prev: "*", next: "field" },
+        { blankLine: "always", prev: "field", next: "*" },
+        { blankLine: "never", prev: "method", next: "method" }
+      ]
+    },
+]*/
+
+class MyClass {
+  constructor(height, width) {
+      this.height = height;
+      this.width = width;
+  }
+
+  fieldA = 'Field A';
+
+  #fieldB = 'Field B';
+
+  method1() {}
+  get area() {
+    return this.method1();
+  }
+  method2() {}
+}
+```
+
+:::
+
 Examples of **correct** code for this rule with the object option:
 
 ::: correct
@@ -148,6 +293,40 @@ class Foo{
 
 :::
 
+::: correct
+
+```js
+/*eslint lines-between-class-members: [
+    "error",
+    {
+      enforce: [
+        { blankLine: "always", prev: "*", next: "method" },
+        { blankLine: "always", prev: "method", next: "*" },
+        { blankLine: "always", prev: "field", next: "field" }
+      ]
+    },
+    { exceptAfterSingleLine: true }
+]*/
+
+class MyClass {
+  constructor(height, width) {
+      this.height = height;
+      this.width = width;
+  }
+
+  fieldA = 'Field A';
+  #fieldB = 'Field B';
+  method1() {}
+  get area() {
+    return this.method1();
+  }
+
+  method2() {}
+}
+```
+
+:::
+
 ## When Not To Use It
 
 If you don't want to enforce empty lines between class members, you can disable this rule.

diff --git a/lib/rules/lines-between-class-members.js b/lib/rules/lines-between-class-members.js
@@ -10,6 +10,21 @@
 
 const astUtils = require("./utils/ast-utils");
 
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/**
+ * Types of class members.
+ * Those have `test` method to check it matches to the given class member.
+ * @private
+ */
+const ClassMemberTypes = {
+    "*": { test: () => true },
+    field: { test: node => node.type === "PropertyDefinition" },
+    method: { test: node => node.type === "MethodDefinition" }
+};
+
 //------------------------------------------------------------------------------
 // Rule Definition
 //------------------------------------------------------------------------------
@@ -29,7 +44,32 @@ module.exports = {
 
         schema: [
             {
-                enum: ["always", "never"]
+                anyOf: [
+                    {
+                        type: "object",
+                        properties: {
+                            enforce: {
+                                type: "array",
+                                items: {
+                                    type: "object",
+                                    properties: {
+                                        blankLine: { enum: ["always", "never"] },
+                                        prev: { enum: ["method", "field", "*"] },
+                                        next: { enum: ["method", "field", "*"] }
+                                    },
+                                    additionalProperties: false,
+                                    required: ["blankLine", "prev", "next"]
+                                },
+                                minItems: 1
+                            }
+                        },
+                        additionalProperties: false,
+                        required: ["enforce"]
+                    },
+                    {
+                        enum: ["always", "never"]
+                    }
+                ]
             },
             {
                 type: "object",
@@ -55,6 +95,7 @@ module.exports = {
         options[0] = context.options[0] || "always";
         options[1] = context.options[1] || { exceptAfterSingleLine: false };
 
+        const configureList = typeof options[0] === "object" ? options[0].enforce : [{ blankLine: options[0], prev: "*", next: "*" }];
         const sourceCode = context.sourceCode;
 
         /**
@@ -144,6 +185,38 @@ module.exports = {
             return sourceCode.getTokensBetween(before, after, { includeComments: true }).length !== 0;
         }
 
+        /**
+         * Checks whether the given node matches the given type.
+         * @param {ASTNode} node The class member node to check.
+         * @param {string} type The class member type to check.
+         * @returns {boolean} `true` if the class member node matched the type.
+         * @private
+         */
+        function match(node, type) {
+            return ClassMemberTypes[type].test(node);
+        }
+
+        /**
+         * Finds the last matched configuration from the configureList.
+         * @param {ASTNode} prevNode The previous node to match.
+         * @param {ASTNode} nextNode The current node to match.
+         * @returns {string|null} Padding type or `null` if no matches were found.
+         * @private
+         */
+        function getPaddingType(prevNode, nextNode) {
+            for (let i = configureList.length - 1; i >= 0; --i) {
+                const configure = configureList[i];
+                const matched =
+                    match(prevNode, configure.prev) &&
+                    match(nextNode, configure.next);
+
+                if (matched) {
+                    return configure.blankLine;
+                }
+            }
+            return null;
+        }
+
         return {
             ClassBody(node) {
                 const body = node.body;
@@ -158,22 +231,34 @@ module.exports = {
                     const isPadded = afterPadding.loc.start.line - beforePadding.loc.end.line > 1;
                     const hasTokenInPadding = hasTokenOrCommentBetween(beforePadding, afterPadding);
                     const curLineLastToken = findLastConsecutiveTokenAfter(curLast, nextFirst, 0);
+                    const paddingType = getPaddingType(body[i], body[i + 1]);
+
+                    if (paddingType === "never" && isPadded) {
+                        context.report({
+                            node: body[i + 1],
+                            messageId: "never",
 
-                    if ((options[0] === "always" && !skip && !isPadded) ||
-                        (options[0] === "never" && isPadded)) {
+                            fix(fixer) {
+                                if (hasTokenInPadding) {
+                                    return null;
+                                }
+                                return fixer.replaceTextRange([beforePadding.range[1], afterPadding.range[0]], "\n");
+                            }
+                        });
+                    } else if (paddingType === "always" && !skip && !isPadded) {
                         context.report({
                             node: body[i + 1],
-                            messageId: isPadded ? "never" : "always",
+                            messageId: "always",
+
                             fix(fixer) {
                                 if (hasTokenInPadding) {
                                     return null;
                                 }
-                                return isPadded
-                                    ? fixer.replaceTextRange([beforePadding.range[1], afterPadding.range[0]], "\n")
-                                    : fixer.insertTextAfter(curLineLastToken, "\n");
+                                return fixer.insertTextAfter(curLineLastToken, "\n");
                             }
                         });
                     }
+
                 }
             }
         };