Add jsonc/no-floating-decimal rule (#57)

Author: ota-meshi

README.md

@@ -190,6 +190,7 @@ The rules with the following star :star: are included in the config.
 | [jsonc/indent](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/indent.html) | enforce consistent indentation | :wrench: |  |  |  |
 | [jsonc/key-spacing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/key-spacing.html) | enforce consistent spacing between keys and values in object literal properties | :wrench: |  |  |  |
 | [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-floating-decimal](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-floating-decimal.html) | disallow leading or trailing decimal points in numeric literals | :wrench: | :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: |

docs/rules/README.md

@@ -37,6 +37,7 @@ The rules with the following star :star: are included in the `plugin:jsonc/recom
 | [jsonc/indent](./indent.md) | enforce consistent indentation | :wrench: |  |  |  |
 | [jsonc/key-spacing](./key-spacing.md) | enforce consistent spacing between keys and values in object literal properties | :wrench: |  |  |  |
 | [jsonc/no-dupe-keys](./no-dupe-keys.md) | disallow duplicate keys in object literals |  | :star: | :star: | :star: |
+| [jsonc/no-floating-decimal](./no-floating-decimal.md) | disallow leading or trailing decimal points in numeric literals | :wrench: | :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: |

docs/rules/no-floating-decimal.md

@@ -0,0 +1,50 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "jsonc/no-floating-decimal"
+description: "disallow leading or trailing decimal points in numeric literals"
+---
+# jsonc/no-floating-decimal
+
+> disallow leading or trailing decimal points in numeric literals
+
+- :gear: This rule is included in `"plugin:jsonc/recommended-with-json"` and `"plugin:jsonc/recommended-with-jsonc"`.
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
+## :book: Rule Details
+
+This rule is aimed at eliminating floating decimal points and will warn whenever a numeric value has a decimal point but is missing a number either before or after it.
+
+<eslint-code-block fix>
+
+<!-- eslint-skip -->
+
+```json5
+/* eslint jsonc/no-floating-decimal: 'error' */
+{
+    /* ✓ GOOD */
+    "GOOD": 42.0,
+
+    /* ✗ BAD */
+    "BAD": 42.
+}
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+Nothing.
+
+## :couple: Related rules
+
+- [no-floating-decimal]
+
+[no-floating-decimal]: https://eslint.org/docs/rules/no-floating-decimal
+
+## Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/lib/rules/no-floating-decimal.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-jsonc/blob/master/tests/lib/rules/no-floating-decimal.js)
+
+<sup>Taken with ❤️ [from ESLint core](https://eslint.org/docs/rules/no-floating-decimal)</sup>

lib/configs/prettier.ts

@@ -13,6 +13,7 @@ export = {
         "jsonc/comma-style": "off",
         "jsonc/indent": "off",
         "jsonc/key-spacing": "off",
+        "jsonc/no-floating-decimal": "off",
         "jsonc/object-curly-newline": "off",
         "jsonc/object-curly-spacing": "off",
         "jsonc/object-property-newline": "off",

lib/configs/recommended-with-json.ts

@@ -10,6 +10,7 @@ export = {
         "jsonc/no-bigint-literals": "error",
         "jsonc/no-comments": "error",
         "jsonc/no-dupe-keys": "error",
+        "jsonc/no-floating-decimal": "error",
         "jsonc/no-multi-str": "error",
         "jsonc/no-number-props": "error",
         "jsonc/no-numeric-separators": "error",

lib/configs/recommended-with-jsonc.ts

@@ -8,6 +8,7 @@ export = {
         // eslint-plugin-jsonc rules
         "jsonc/no-bigint-literals": "error",
         "jsonc/no-dupe-keys": "error",
+        "jsonc/no-floating-decimal": "error",
         "jsonc/no-multi-str": "error",
         "jsonc/no-number-props": "error",
         "jsonc/no-numeric-separators": "error",

lib/rules/no-floating-decimal.ts

@@ -0,0 +1,21 @@
+import { createRule, defineWrapperListener, getCoreRule } from "../utils"
+const coreRule = getCoreRule("no-floating-decimal")
+
+export default createRule("no-floating-decimal", {
+    meta: {
+        docs: {
+            description:
+                "disallow leading or trailing decimal points in numeric literals",
+            recommended: ["json", "jsonc"],
+            extensionRule: true,
+            layout: 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

@@ -11,6 +11,7 @@ import keySpacing from "../rules/key-spacing"
 import noBigintLiterals from "../rules/no-bigint-literals"
 import noComments from "../rules/no-comments"
 import noDupeKeys from "../rules/no-dupe-keys"
+import noFloatingDecimal from "../rules/no-floating-decimal"
 import noMultiStr from "../rules/no-multi-str"
 import noNumberProps from "../rules/no-number-props"
 import noNumericSeparators from "../rules/no-numeric-separators"
@@ -43,6 +44,7 @@ export const rules = [
     noBigintLiterals,
     noComments,
     noDupeKeys,
+    noFloatingDecimal,
     noMultiStr,
     noNumberProps,
     noNumericSeparators,

tests/lib/rules/no-floating-decimal.ts

@@ -0,0 +1,25 @@
+import { RuleTester } from "eslint"
+import rule from "../../../lib/rules/no-floating-decimal"
+
+const tester = new RuleTester({
+    parser: require.resolve("jsonc-eslint-parser"),
+    parserOptions: {
+        ecmaVersion: 2020,
+    },
+})
+
+tester.run("no-floating-decimal", rule as any, {
+    valid: ["42", "42.0", "0.42"],
+    invalid: [
+        {
+            code: `.42`,
+            output: `0.42`,
+            errors: ["A leading decimal point can be confused with a dot."],
+        },
+        {
+            code: `42.`,
+            output: `42.0`,
+            errors: ["A trailing decimal point can be confused with a dot."],
+        },
+    ],
+})