Add jsonc/no-undefined-value rule (#8)

Author: ota-meshi

README.md

@@ -137,6 +137,7 @@ The rules with the following star :star: are included in the config.
 |:--------|:------------|:-------:|:----:|:-----:|:-----:|
 | [jsonc/no-comments](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-comments.html) | disallow comments |  | :star: |  |  |
 | [jsonc/no-template-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-template-literals.html) | disallow template literals | :wrench: | :star: | :star: | :star: |
+| [jsonc/no-undefined-value](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-undefined-value.html) | disallow `undefined` |  | :star: | :star: | :star: |
 | [jsonc/valid-json-number](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/valid-json-number.html) | disallow invalid number for JSON | :wrench: | :star: | :star: |  |
 
 ## Extension Rules

docs/rules/README.md

@@ -15,6 +15,7 @@ The rules with the following star :star: are included in the `plugin:jsonc/recom
 |:--------|:------------|:-------:|:----:|:-----:|:-----:|
 | [jsonc/no-comments](./no-comments.md) | disallow comments |  | :star: |  |  |
 | [jsonc/no-template-literals](./no-template-literals.md) | disallow template literals | :wrench: | :star: | :star: | :star: |
+| [jsonc/no-undefined-value](./no-undefined-value.md) | disallow `undefined` |  | :star: | :star: | :star: |
 | [jsonc/valid-json-number](./valid-json-number.md) | disallow invalid number for JSON | :wrench: | :star: | :star: |  |
 
 ## Extension Rules

docs/rules/no-undefined-value.md

@@ -0,0 +1,38 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "jsonc/no-undefined-value"
+description: "disallow `undefined`"
+---
+# jsonc/no-undefined-value
+
+> disallow `undefined`
+
+- :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 reports the use of `undefined`.
+
+JSON, JSONC and JSON5 do not allow `undefined`.
+
+<eslint-code-block>
+
+```json5
+/* eslint jsonc/no-undefined-value: 'error' */
+{
+    /* ✗ BAD */
+    "BAD": undefined
+}
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/lib/rules/no-undefined-value.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/tests/lib/rules/no-undefined-value.js)

lib/configs/recommended-with-json.ts

@@ -11,6 +11,7 @@ export = {
         "jsonc/no-dupe-keys": "error",
         "jsonc/no-multi-str": "error",
         "jsonc/no-template-literals": "error",
+        "jsonc/no-undefined-value": "error",
         "jsonc/no-useless-escape": "error",
         "jsonc/quote-props": "error",
         "jsonc/quotes": "error",

lib/configs/recommended-with-json5.ts

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

lib/configs/recommended-with-jsonc.ts

@@ -9,6 +9,7 @@ export = {
         "jsonc/no-dupe-keys": "error",
         "jsonc/no-multi-str": "error",
         "jsonc/no-template-literals": "error",
+        "jsonc/no-undefined-value": "error",
         "jsonc/no-useless-escape": "error",
         "jsonc/quote-props": "error",
         "jsonc/quotes": "error",

lib/rules/no-undefined-value.ts

@@ -0,0 +1,31 @@
+import type { JSONIdentifier } from "../parser/ast"
+import { createRule } from "../utils"
+import { isUndefinedIdentifier } from "../utils/ast"
+
+export default createRule("no-undefined-value", {
+    meta: {
+        docs: {
+            description: "disallow `undefined`",
+            recommended: ["json", "jsonc", "json5"],
+            extensionRule: false,
+        },
+        schema: [],
+        messages: {
+            unexpected: "`undefined` is not allowed.",
+        },
+        type: "problem",
+    },
+    create(context) {
+        return {
+            JSONIdentifier(node: JSONIdentifier) {
+                if (!isUndefinedIdentifier(node)) {
+                    return
+                }
+                context.report({
+                    loc: node.loc,
+                    messageId: "unexpected",
+                })
+            },
+        }
+    },
+})

lib/utils/ast.ts

@@ -53,6 +53,15 @@ export function isNumberIdentifier(
     )
 }
 
+/**
+ * Checks if given node is JSONUndefinedIdentifier
+ */
+export function isUndefinedIdentifier(
+    node: JSONIdentifier,
+): node is JSONUndefinedIdentifier {
+    return isExpression(node) && node.name === "undefined"
+}
+
 export type JSONValue =
     | string
     | number

lib/utils/rules.ts

@@ -11,6 +11,7 @@ import noDupeKeys from "../rules/no-dupe-keys"
 import noMultiStr from "../rules/no-multi-str"
 import noOctalEscape from "../rules/no-octal-escape"
 import noTemplateLiterals from "../rules/no-template-literals"
+import noUndefinedValue from "../rules/no-undefined-value"
 import noUselessEscape from "../rules/no-useless-escape"
 import objectCurlyNewline from "../rules/object-curly-newline"
 import objectCurlySpacing from "../rules/object-curly-spacing"
@@ -33,6 +34,7 @@ export const rules = [
     noMultiStr,
     noOctalEscape,
     noTemplateLiterals,
+    noUndefinedValue,
     noUselessEscape,
     objectCurlyNewline,
     objectCurlySpacing,

tests/lib/rules/no-undefined-value.ts

@@ -0,0 +1,38 @@
+import { RuleTester } from "eslint"
+import rule from "../../../lib/rules/no-undefined-value"
+
+const tester = new RuleTester({
+    parser: require.resolve("../../../lib/parser/json-eslint-parser"),
+})
+
+tester.run("no-undefined-value", rule as any, {
+    valid: ["null", "[1,,2]", "{undefined:1}"],
+    invalid: [
+        {
+            code: "undefined",
+            errors: ["`undefined` is not allowed."],
+        },
+        {
+            code: `[
+                undefined,
+                {
+                    undefined: undefined
+                }
+            ]`,
+            errors: [
+                {
+                    message: "`undefined` is not allowed.",
+                    line: 2,
+                    column: 17,
+                    endColumn: 26,
+                },
+                {
+                    message: "`undefined` is not allowed.",
+                    line: 4,
+                    column: 32,
+                    endColumn: 41,
+                },
+            ],
+        },
+    ],
+})