new rule exports-valid

Author: mightyiam

src/rules/exports-valid.js

@@ -0,0 +1,72 @@
+const isPlainObj = require('is-plain-obj');
+const {isObject, isString} = require('../validators/type');
+const LintIssue = require('../LintIssue');
+const {exists} = require('../validators/property');
+
+const lintId = 'exports-valid';
+const nodeName = 'exports';
+const ruleType = 'standard';
+
+const getKeyType = (key) => {
+  if (key.startsWith('/')) return 'invalid';
+
+  return key.startsWith('.') ? 'entry' : 'condition';
+};
+
+const isValidPath = (value) => {
+  if (typeof value !== 'string') return false;
+
+  if (['', '.', './', '..', '../'].includes(value)) return false;
+
+  if (value.includes('../')) return false;
+
+  if (value.startsWith('/')) return false;
+
+  return true;
+};
+
+const traverse = (exports, path = []) => {
+  const fails = [];
+
+  if (typeof exports === 'string') {
+    if (!isValidPath(exports)) {
+      fails.push([path, 'String value should be a valid export path']);
+    }
+  } else if (isPlainObj(exports)) {
+    // eslint-disable-next-line no-restricted-syntax
+    for (const [key, value] of Object.entries(exports)) {
+      if (getKeyType(key) === 'invalid') {
+        fails.push([path, 'Key should not be relative path or "condition"']);
+      } else {
+        fails.push(...traverse(value));
+      }
+    }
+  } else {
+    fails.push([path, 'Value should be string or object']);
+  }
+
+  if (Array.isArray(exports)) {
+    fails.push([path, 'Array']);
+  }
+
+  return fails.map(([arrayOfKeys, message]) => [arrayOfKeys.join('.'), message]);
+};
+
+const lint = (packageJsonData, severity) => {
+  if (!exists(packageJsonData, nodeName)) return true;
+
+  const fails = traverse(packageJsonData[nodeName]);
+
+  if (fails.length > 0) {
+    const failsListString = fails.map(([path, message]) => `\`${path}\`: ${message}`);
+
+    return new LintIssue(lintId, severity, nodeName, `Invalid paths: ${failsListString}`);
+  }
+
+  return true;
+};
+
+module.exports = {
+  lint,
+  ruleType,
+};

test/unit/rules/exports-valid.test.js

@@ -0,0 +1,109 @@
+const ruleModule = require('../../../src/rules/exports-valid');
+
+const {lint, ruleType} = ruleModule;
+
+describe('exports-valid Unit Tests', () => {
+  describe('a rule type value should be exported', () => {
+    test('it should equal "standard"', () => {
+      expect(ruleType).toStrictEqual('standard');
+    });
+  });
+
+  describe('when package.json has invalid node', () => {
+    const failures = [
+      {
+        title: 'root is `true`',
+        input: true,
+        message: 'Value of `exports` field should be string or object',
+      },
+      {
+        title: 'root is a number',
+        input: 4,
+        message: 'Value of `exports` field should be string or object',
+      },
+      {
+        title: 'key is `/`',
+        input: {'/': 'foo.js'},
+        message: 'Unsupported condition key `/`. Supported conditions are `[]`',
+      },
+      {
+        title: 'key starts with `/`',
+        input: {'/foo': 'foo.js'},
+        message: 'Unsupported condition key `/foo`. Supported conditions are `[]`',
+      },
+      {
+        title: 'key is short relative path',
+        input: {foo: 'foo.js'},
+        message: 'Unsupported condition key `foo`. Supported conditions are `[]`',
+      },
+      {
+        title: 'main-only sugar path starts with `/`',
+        input: '/main.js',
+        message: 'Invalid path `/main.js`. Paths must start with `./`',
+      },
+      {
+        title: 'main-only sugar path short form relative',
+        input: 'main.js',
+        message: 'Invalid path `main.js`. Paths must start with `./`',
+      },
+      {
+        title: 'short form relative path',
+        input: {'./a': 'a.js'},
+        message: 'Invalid path `a.js`. Paths must start with `./`',
+      },
+      {
+        title: 'unsupported condition',
+        config: {conditions: ['foo']},
+        input: {bar: './main.js'},
+        message: "Unsupported condition `bar`. Supported conditions are `['foo']`",
+      },
+      {
+        title: 'folder mapped to file',
+        input: {'./': './a.js'},
+        message: 'The value of the folder mapping key `./` must end with `/`',
+      },
+
+      // conditional import key `node` must be after `import` and `require` if any of them exists
+
+      // conditional import key `default` must be last
+
+      // support fallbacks. at least one of the values must be valid
+    ];
+    failures.forEach(({title, input, fails}) => {
+      // eslint-disable-next-line jest/valid-title
+      test(title, () => {
+        const packageJsonData = {exports: input};
+        const response = lint(packageJsonData, 'error');
+
+        expect(response.lintId).toStrictEqual('exports-valid');
+        expect(response.severity).toStrictEqual('error');
+        expect(response.node).toStrictEqual('exports');
+        const failsListString = fails.map(([path, message]) => `\`${path}\`: ${message}`);
+        expect(response.lintMessage).toStrictEqual(`Invalid paths: ${failsListString}`);
+      });
+    });
+  });
+
+  describe('when package.json has valid node', () => {
+    const valids = [
+      {
+        title: 'main-only sugar',
+        input: './main.js',
+      },
+      {
+        title: 'supported condition',
+        config: {conditions: ['foo']},
+        input: {foo: './main.js'},
+      },
+    ];
+  });
+
+  describe('when package.json does not have node', () => {
+    test('true should be returned', () => {
+      const packageJsonData = {};
+      const response = lint(packageJsonData, 'error');
+
+      expect(response).toBe(true);
+    });
+  });
+});