Add prefer-no-dependencies rule

Closes #134

docs/rules.md

@@ -138,4 +138,5 @@ Rules allow npm-package-json-lint to be fully customizable. npm-package-json-lin
 > Generates an error if the node is present
 
 * [prefer-no-engineStrict](rules/disallowed-nodes/prefer-no-engineStrict)
+* [prefer-no-dependencies](rules/disallowed-nodes/prefer-no-dependencies)
 * [prefer-no-devDependencies](rules/disallowed-nodes/prefer-no-devDependencies)

docs/rules/disallowed-nodes/prefer-no-dependencies.md

@@ -0,0 +1,51 @@
+---
+id: prefer-no-dependencies
+title: prefer-no-dependencies
+---
+
+Enabling this rule will result in an error being generated if `dependencies` is present.
+
+## Example .npmpackagejsonlintrc configuration
+
+```json
+{
+  "rules": {
+    "prefer-no-dependencies": "error"
+  }
+}
+```
+
+With exceptions
+
+```json
+{
+  "rules": {
+    "prefer-no-dependencies": ["error", {
+      "exceptions": ["myModule"]
+    }]
+  }
+}
+```
+
+
+## Rule Details
+
+### *Incorrect* example(s)
+
+```json
+{
+  "dependencies": "dummy-value"
+}
+```
+
+### *Correct* example(s)
+
+```json
+{
+  "prefer-no-dependencies": "error"
+}
+```
+
+## History
+
+* Introduced in version 4.1.0

src/rules/prefer-no-dependencies.js

@@ -0,0 +1,20 @@
+const {exists} = require('../validators/property');
+const LintIssue = require('../LintIssue');
+
+const lintId = 'prefer-no-dependencies';
+const nodeName = 'dependencies';
+const message = 'dependencies should not be defined';
+const ruleType = 'optionalObject';
+
+const lint = (packageJsonData, severity) => {
+  if (exists(packageJsonData, nodeName)) {
+    return new LintIssue(lintId, severity, nodeName, message);
+  }
+
+  return true;
+};
+
+module.exports = {
+  lint,
+  ruleType
+};

test/unit/rules/prefer-no-dependencies.test.js

@@ -0,0 +1,49 @@
+const ruleModule = require('../../../src/rules/prefer-no-dependencies');
+const property = require('../../../src/validators/property');
+
+const {lint, ruleType} = ruleModule;
+
+jest.mock('../../../src/validators/property');
+
+const nodeName = 'dependencies';
+
+describe('prefer-no-dependencies Unit Tests', () => {
+  describe('a rule type value should be exported', () => {
+    test('it should equal "optionalObject"', () => {
+      expect(ruleType).toStrictEqual('optionalObject');
+    });
+  });
+
+  describe('when package.json has dependencies node', () => {
+    test('LintIssue object should be returned', () => {
+      property.exists.mockReturnValue(true);
+
+      const packageJsonData = {
+        dependencies: 'dummy-value'
+      };
+      const response = lint(packageJsonData, 'error');
+
+      expect(response.lintId).toStrictEqual('prefer-no-dependencies');
+      expect(response.severity).toStrictEqual('error');
+      expect(response.node).toStrictEqual(nodeName);
+      expect(response.lintMessage).toStrictEqual('dependencies should not be defined');
+
+      expect(property.exists).toHaveBeenCalledTimes(1);
+      expect(property.exists).toHaveBeenCalledWith(packageJsonData, nodeName);
+    });
+  });
+
+  describe('when package.json does not have node', () => {
+    test('true should be returned', () => {
+      property.exists.mockReturnValue(false);
+
+      const packageJsonData = {};
+      const response = lint(packageJsonData, 'error');
+
+      expect(response).toBe(true);
+
+      expect(property.exists).toHaveBeenCalledTimes(1);
+      expect(property.exists).toHaveBeenCalledWith(packageJsonData, nodeName);
+    });
+  });
+});