Add jsonc/no-sparse-arrays rule

Author: ota-meshi

README.md

@@ -154,6 +154,7 @@ The rules with the following star :star: are included in the config.
 | [jsonc/no-dupe-keys](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-dupe-keys.html) | disallow duplicate keys in object literals |  | :star: | :star: | :star: |
 | [jsonc/no-multi-str](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-multi-str.html) | disallow multiline strings |  | :star: | :star: |  |
 | [jsonc/no-octal-escape](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-octal-escape.html) | disallow octal escape sequences in string literals |  |  |  |  |
+| [jsonc/no-sparse-arrays](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-sparse-arrays.html) | disallow sparse arrays |  | :star: | :star: | :star: |
 | [jsonc/no-useless-escape](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-useless-escape.html) | disallow unnecessary escape usage |  | :star: | :star: | :star: |
 | [jsonc/object-curly-newline](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/object-curly-newline.html) | enforce consistent line breaks inside braces | :wrench: |  |  |  |
 | [jsonc/object-curly-spacing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/object-curly-spacing.html) | enforce consistent spacing inside braces | :wrench: |  |  |  |

docs/rules/README.md

@@ -32,6 +32,7 @@ The rules with the following star :star: are included in the `plugin:jsonc/recom
 | [jsonc/no-dupe-keys](./no-dupe-keys.md) | disallow duplicate keys in object literals |  | :star: | :star: | :star: |
 | [jsonc/no-multi-str](./no-multi-str.md) | disallow multiline strings |  | :star: | :star: |  |
 | [jsonc/no-octal-escape](./no-octal-escape.md) | disallow octal escape sequences in string literals |  |  |  |  |
+| [jsonc/no-sparse-arrays](./no-sparse-arrays.md) | disallow sparse arrays |  | :star: | :star: | :star: |
 | [jsonc/no-useless-escape](./no-useless-escape.md) | disallow unnecessary escape usage |  | :star: | :star: | :star: |
 | [jsonc/object-curly-newline](./object-curly-newline.md) | enforce consistent line breaks inside braces | :wrench: |  |  |  |
 | [jsonc/object-curly-spacing](./object-curly-spacing.md) | enforce consistent spacing inside braces | :wrench: |  |  |  |

docs/rules/no-sparse-arrays.md

@@ -0,0 +1,51 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "jsonc/no-sparse-arrays"
+description: "disallow sparse arrays"
+---
+# jsonc/no-sparse-arrays
+
+> disallow sparse arrays
+
+- :gear: This rule is included in all of `"plugin:jsonc/recommended-with-json"`, `"plugin:jsonc/recommended-with-json5"` and `"plugin:jsonc/recommended-with-jsonc"`.
+
+## :book: Rule Details
+
+This rule disallows sparse array literals which have "holes" where commas are not preceded by elements. It does not apply to a trailing comma following the last element.
+
+JSON, JSONC and JSON5 do not allow arrays contain empty slots.
+
+<eslint-code-block>
+
+```json5
+/* eslint jsonc/no-sparse-arrays: 'error' */
+{
+    /* ✓ GOOD */
+    "GOOD": [1, 2, 3, 4],
+    "GOOD": [1, 2, 3, 4,],
+
+    /* ✗ BAD */
+    "BAD": [1, , , 4],
+    "BAD": [, 2, 3, 4]
+}
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :couple: Related rules
+
+- [no-sparse-arrays]
+
+[no-sparse-arrays]: https://eslint.org/docs/rules/no-sparse-arrays
+
+## Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/lib/rules/no-sparse-arrays.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/tests/lib/rules/no-sparse-arrays.js)
+
+<sup>Taken with ❤️ [from ESLint core](https://eslint.org/docs/rules/no-sparse-arrays)</sup>

lib/configs/recommended-with-json.ts

@@ -10,6 +10,7 @@ export = {
         "jsonc/no-comments": "error",
         "jsonc/no-dupe-keys": "error",
         "jsonc/no-multi-str": "error",
+        "jsonc/no-sparse-arrays": "error",
         "jsonc/no-template-literals": "error",
         "jsonc/no-undefined-value": "error",
         "jsonc/no-useless-escape": "error",

lib/configs/recommended-with-json5.ts

@@ -7,6 +7,7 @@ export = {
     rules: {
         // eslint-plugin-jsonc rules
         "jsonc/no-dupe-keys": "error",
+        "jsonc/no-sparse-arrays": "error",
         "jsonc/no-template-literals": "error",
         "jsonc/no-undefined-value": "error",
         "jsonc/no-useless-escape": "error",

lib/configs/recommended-with-jsonc.ts

@@ -8,6 +8,7 @@ export = {
         // eslint-plugin-jsonc rules
         "jsonc/no-dupe-keys": "error",
         "jsonc/no-multi-str": "error",
+        "jsonc/no-sparse-arrays": "error",
         "jsonc/no-template-literals": "error",
         "jsonc/no-undefined-value": "error",
         "jsonc/no-useless-escape": "error",

lib/rules/no-sparse-arrays.ts

@@ -0,0 +1,19 @@
+import coreRule from "eslint/lib/rules/no-sparse-arrays"
+import { createRule, defineWrapperListener } from "../utils"
+
+export default createRule("no-sparse-arrays", {
+    meta: {
+        docs: {
+            description: "disallow sparse arrays",
+            recommended: ["json", "jsonc", "json5"],
+            extensionRule: true,
+        },
+        fixable: coreRule.meta!.fixable,
+        schema: coreRule.meta!.schema!,
+        messages: coreRule.meta!.messages!,
+        type: coreRule.meta!.type!,
+    },
+    create(context) {
+        return defineWrapperListener(coreRule, context, context.options)
+    },
+})

lib/utils/rules.ts

@@ -10,6 +10,7 @@ import noComments from "../rules/no-comments"
 import noDupeKeys from "../rules/no-dupe-keys"
 import noMultiStr from "../rules/no-multi-str"
 import noOctalEscape from "../rules/no-octal-escape"
+import noSparseArrays from "../rules/no-sparse-arrays"
 import noTemplateLiterals from "../rules/no-template-literals"
 import noUndefinedValue from "../rules/no-undefined-value"
 import noUselessEscape from "../rules/no-useless-escape"
@@ -33,6 +34,7 @@ export const rules = [
     noDupeKeys,
     noMultiStr,
     noOctalEscape,
+    noSparseArrays,
     noTemplateLiterals,
     noUndefinedValue,
     noUselessEscape,

tests/lib/rules/no-sparse-arrays.ts

@@ -0,0 +1,20 @@
+import { RuleTester } from "eslint"
+import rule from "../../../lib/rules/no-sparse-arrays"
+
+const tester = new RuleTester({
+    parser: require.resolve("../../../lib/parser/json-eslint-parser"),
+})
+
+tester.run("no-sparse-arrays", rule as any, {
+    valid: ["[1,2,3,4]", "[1,2,3,4,]"],
+    invalid: [
+        {
+            code: "[1,,,4]",
+            errors: ["Unexpected comma in middle of array."],
+        },
+        {
+            code: "[,2,3,4]",
+            errors: ["Unexpected comma in middle of array."],
+        },
+    ],
+})

tools/new-rule.ts

@@ -32,10 +32,10 @@ export default createRule("${ruleId}", {
             description: "...",
             recommended: true,
         },
-        fixable: coreRule.meta?.fixable,
-        schema: coreRule.meta?.schema!,
-        messages: coreRule.meta?.messages!,
-        type: coreRule.meta?.type!,
+        fixable: coreRule.meta!.fixable,
+        schema: coreRule.meta!.schema!,
+        messages: coreRule.meta!.messages!,
+        type: coreRule.meta!.type!,
     },
     create(context) {
         return defineWrapperListener(coreRule, context, context.options)