add ensure-volta-extends rule

Check that the volta/extends file exists and has a volta config.

Author: Kelly Selden

README.md

@@ -54,6 +54,7 @@ eslint . --ext js,json
 | Rule ID | Description |
 |:--------|:------------|
 | [json-files/ensure-repository-directory](./docs/rules/ensure-repository-directory.md) | ensure repository/directory in package.json |
+| [json-files/ensure-volta-extends](./docs/rules/ensure-volta-extends.md) | ensure volta-extends in package.json |
 | [json-files/eol-last](./docs/rules/eol-last.md) | require or disallow newline at the end of package.json |
 | [json-files/no-branch-in-dependencies](./docs/rules/no-branch-in-dependencies.md) | prevent branches in package.json dependencies |
 | [json-files/require-engines](./docs/rules/require-engines.md) | require the engines field in package.json |

docs/rules/ensure-volta-extends.md

@@ -0,0 +1,46 @@
+# Ensure volta/extends in package.json (ensure-repository-directory)
+
+Check that the volta/extends file exists and has a volta config.
+
+
+## Rule Details
+
+This rule aims to ensure the volta/extends file exists and has a volta config.
+
+Examples of **incorrect** code for this rule:
+
+```json
+{
+  "volta": {
+    "extends": "wrong-package/bad-copy-paste"
+  }
+}
+```
+
+Examples of **correct** code for this rule:
+
+```json
+{
+  "volta": {
+    "extends": "correct-path"
+  }
+}
+```
+
+```json
+{
+  "volta": {}
+}
+```
+
+### Options
+
+
+
+## When Not To Use It
+
+Extending is optional. If you aren't using it, you may not want this rule.
+
+## Further Reading
+
+https://volta.sh

lib/rules/ensure-volta-extends.js

@@ -0,0 +1,87 @@
+'use strict';
+
+const path = require('path');
+const fs = require('fs');
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'ensure volta/extends in package.json'
+    },
+    schema: [
+    ]
+  },
+
+  create(context) {
+    let filename = context.getFilename();
+    if (path.basename(filename) !== 'package.json') {
+      return {};
+    }
+
+    return {
+      AssignmentExpression(node) {
+        let json = node.right;
+        let property = json.properties.find(p => p.key.value === 'volta');
+        if (!property) {
+          return;
+        }
+        let repository = property.value;
+        if (repository.type !== 'ObjectExpression') {
+          return;
+        }
+        property = repository.properties.find(p => p.key.value === 'extends');
+        if (!property) {
+          return;
+        }
+        let _extends = property.value;
+        if (_extends.type !== 'Literal') {
+          return;
+        }
+        let value = _extends.value;
+        let dirname = path.dirname(filename);
+        let filePath = path.resolve(dirname, value);
+
+        let text;
+
+        try {
+          text = fs.readFileSync(filePath);
+        } catch (err) {
+          if (err.code === 'ENOENT') {
+            context.report({
+              node: _extends,
+              message: `volta/extends '${value}' does not exist.`
+            });
+
+            return;
+          }
+
+          throw err;
+        }
+
+        json;
+
+        try {
+          json = JSON.parse(text);
+        } catch (err) {
+          if (err.message === 'Unexpected end of JSON input') {
+            context.report({
+              node: _extends,
+              message: `volta/extends '${value}' is not JSON.`
+            });
+
+            return;
+          }
+
+          throw err;
+        }
+
+        if (!('volta' in json)) {
+          context.report({
+            node: _extends,
+            message: `volta/extends '${value}' does not have a volta config.`
+          });
+        }
+      }
+    };
+  }
+};

tests/fixtures/volta/no-volta.json

@@ -0,0 +1 @@
+{}

tests/fixtures/volta/not-json.js

@@ -0,0 +1,3 @@
+{
+  "volta": {}
+}

tests/fixtures/volta/with-volta.json

@@ -0,0 +1,57 @@
+'use strict';
+
+const { RuleTester } = require('eslint');
+const rule = require('../../../lib/rules/ensure-volta-extends');
+const preprocess = require('../../helpers/preprocess');
+const path = require('path');
+
+new RuleTester().run('ensure-volta-extends', rule, preprocess({
+  valid: [
+    {
+      code: '{}',
+      filename: path.join(__dirname, 'package.json')
+    },
+    {
+      code: '{ "volta": "" }',
+      filename: path.join(__dirname, 'package.json')
+    },
+    {
+      code: '{ "volta": {} }',
+      filename: path.join(__dirname, 'package.json')
+    },
+    {
+      code: '{ "volta": { "extends": {} } }',
+      filename: path.join(__dirname, 'package.json')
+    },
+    {
+      code: '{ "volta": { "extends": "../../fixtures/volta/with-volta.json" } }',
+      filename: path.join(__dirname, 'package.json')
+    }
+  ],
+  invalid: [
+    {
+      code: '{ "volta": { "extends": "wrong/dir" } }',
+      filename: path.join(__dirname, 'package.json'),
+      errors: [{
+        message: 'volta/extends \'wrong/dir\' does not exist.',
+        type: 'Literal'
+      }]
+    },
+    {
+      code: '{ "volta": { "extends": "../../fixtures/volta/not-json.js" } }',
+      filename: path.join(__dirname, 'package.json'),
+      errors: [{
+        message: 'volta/extends \'../../fixtures/volta/not-json.js\' is not JSON.',
+        type: 'Literal'
+      }]
+    },
+    {
+      code: '{ "volta": { "extends": "../../fixtures/volta/no-volta.json" } }',
+      filename: path.join(__dirname, 'package.json'),
+      errors: [{
+        message: 'volta/extends \'../../fixtures/volta/no-volta.json\' does not have a volta config.',
+        type: 'Literal'
+      }]
+    }
+  ]
+}));