feat: Add sort-keys rule

README.md

@@ -161,6 +161,7 @@ export default [
   like integers but are too large, and
   [subnormal numbers](https://en.wikipedia.org/wiki/Subnormal_number).
 - `no-unnormalized-keys` - warns on keys containing [unnormalized characters](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/normalize#description). You can optionally specify the normalization form via `{ form: "form_name" }`, where `form_name` can be any of `"NFC"`, `"NFD"`, `"NFKC"`, or `"NFKD"`.
+- `sort-keys` - warns when keys are not in the specified order. Based on the ESLint [`sort-keys`](https://eslint.org/docs/latest/rules/sort-keys) rule.
 - `top-level-interop` - warns when the top-level item in the document is neither an array nor an object. This can be enabled to ensure maximal interoperability with the oldest JSON parsers.
 
 ## Configuration Comments

package.json

@@ -65,7 +65,8 @@
   "dependencies": {
     "@eslint/core": "^0.10.0",
     "@eslint/plugin-kit": "^0.2.5",
-    "@humanwhocodes/momoa": "^3.3.4"
+    "@humanwhocodes/momoa": "^3.3.4",
+    "natural-compare": "^1.4.0"
   },
   "devDependencies": {
     "@types/eslint": "^8.56.10",

src/index.js

@@ -13,6 +13,7 @@ import noDuplicateKeys from "./rules/no-duplicate-keys.js";
 import noEmptyKeys from "./rules/no-empty-keys.js";
 import noUnsafeValues from "./rules/no-unsafe-values.js";
 import noUnnormalizedKeys from "./rules/no-unnormalized-keys.js";
+import sortKeys from "./rules/sort-keys.js";
 import topLevelInterop from "./rules/top-level-interop.js";
 
 //-----------------------------------------------------------------------------
@@ -34,6 +35,7 @@ const plugin = {
 		"no-empty-keys": noEmptyKeys,
 		"no-unsafe-values": noUnsafeValues,
 		"no-unnormalized-keys": noUnnormalizedKeys,
+		"sort-keys": sortKeys,
 		"top-level-interop": topLevelInterop,
 	},
 	configs: {

src/rules/sort-keys.js

@@ -0,0 +1,178 @@
+/**
+ * @fileoverview Rule to require JSON object keys to be sorted. Copied largely from https://github.com/eslint/eslint/blob/main/lib/rules/sort-keys.js
+ * @author Robin Thomas
+ */
+
+import naturalCompare from "natural-compare";
+
+const hasNonWhitespace = /\S/u;
+
+const comparators = {
+	ascending: {
+		alphanumeric: {
+			sensitive: (a, b) => a <= b,
+			insensitive: (a, b) => a.toLowerCase() <= b.toLowerCase(),
+		},
+		natural: {
+			sensitive: (a, b) => naturalCompare(a, b) <= 0,
+			insensitive: (a, b) =>
+				naturalCompare(a.toLowerCase(), b.toLowerCase()) <= 0,
+		},
+	},
+	descending: {
+		alphanumeric: {
+			sensitive: (a, b) =>
+				comparators.ascending.alphanumeric.sensitive(b, a),
+			insensitive: (a, b) =>
+				comparators.ascending.alphanumeric.insensitive(b, a),
+		},
+		natural: {
+			sensitive: (a, b) => comparators.ascending.natural.sensitive(b, a),
+			insensitive: (a, b) =>
+				comparators.ascending.natural.insensitive(b, a),
+		},
+	},
+};
+
+function getKey(member) {
+	return member.name.type === `Identifier`
+		? member.name.name
+		: member.name.value;
+}
+
+export default {
+	meta: {
+		type: /** @type {const} */ ("suggestion"),
+
+		defaultOptions: [
+			"asc",
+			{
+				allowLineSeparatedGroups: false,
+				caseSensitive: true,
+				minKeys: 2,
+				natural: false,
+			},
+		],
+
+		docs: {
+			description: `Require JSON object keys to be sorted`,
+		},
+
+		messages: {
+			sortKeys:
+				"Expected object keys to be in {{sortName}} case-{{sensitivity}} {{direction}} order. '{{thisName}}' should be before '{{prevName}}'.",
+		},
+
+		schema: [
+			{
+				enum: ["asc", "desc"],
+			},
+			{
+				type: "object",
+				properties: {
+					caseSensitive: {
+						type: "boolean",
+					},
+					natural: {
+						type: "boolean",
+					},
+					minKeys: {
+						type: "integer",
+						minimum: 2,
+					},
+					allowLineSeparatedGroups: {
+						type: "boolean",
+					},
+				},
+				additionalProperties: false,
+			},
+		],
+	},
+
+	create(context) {
+		const [
+			directionShort,
+			{ allowLineSeparatedGroups, caseSensitive, natural, minKeys },
+		] = context.options;
+
+		const direction = directionShort === "asc" ? "ascending" : "descending";
+		const sortName = natural ? "natural" : "alphanumeric";
+		const sensitivity = caseSensitive ? "sensitive" : "insensitive";
+		const isValidOrder = comparators[direction][sortName][sensitivity];
+
+		// Note that @humanwhocodes/momoa doesn't include comments in the object.members tree, so we can't just see if a member is preceded by a comment
+		const commentLineNums = new Set();
+		for (const comment of context.sourceCode.comments) {
+			for (
+				let lineNum = comment.loc.start.line;
+				lineNum <= comment.loc.end.line;
+				lineNum += 1
+			) {
+				commentLineNums.add(lineNum);
+			}
+		}
+
+		// Note that there can be comments *inside* members, e.g. `{"foo: /* comment *\/ "bar"}`, but these are ignored when calculating line-separated groups
+		function isLineSeparated(prevMember, member) {
+			const prevMemberEndLine = prevMember.loc.end.line;
+			const thisStartLine = member.loc.start.line;
+			if (thisStartLine - prevMemberEndLine < 2) {
+				return false;
+			}
+
+			for (
+				let lineNum = prevMemberEndLine + 1;
+				lineNum < thisStartLine;
+				lineNum += 1
+			) {
+				if (
+					!commentLineNums.has(lineNum) &&
+					!hasNonWhitespace.test(
+						context.sourceCode.lines[lineNum - 1],
+					)
+				) {
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		return {
+			Object(node) {
+				let prevMember;
+				let prevName;
+
+				if (node.members.length < minKeys) {
+					return;
+				}
+
+				for (const member of node.members) {
+					const thisName = getKey(member);
+
+					if (
+						prevMember &&
+						!isValidOrder(prevName, thisName) &&
+						(!allowLineSeparatedGroups ||
+							!isLineSeparated(prevMember, member))
+					) {
+						context.report({
+							loc: member.name.loc,
+							messageId: "sortKeys",
+							data: {
+								thisName,
+								prevName,
+								direction,
+								sensitivity,
+								sortName,
+							},
+						});
+					}
+
+					prevMember = member;
+					prevName = thisName;
+				}
+			},
+		};
+	},
+};