Feat/enforce custom provider type

.node-version

@@ -1 +1 @@
-v20
+v20.11.1

.nvmrc

@@ -0,0 +1 @@
+./.node-version

README.md

@@ -46,11 +46,12 @@ The "recommended" preset contains the rules listed below. If you need custom con
 
 ## Rules
 
-| Rule                                                                                 | Description                                                    | Recommended |
+| Rule                                                                                 | Description                                                    | Type |
 | ------------------------------------------------------------------------------------ | -------------------------------------------------------------- | ----------- |
-| [`@trilon/enforce-close-testing-module`](docs/rules/enforce-close-testing-module.md) | Ensures NestJS testing modules are closed properly after tests | ✅          |
-| [`@trilon/check-inject-decorator`](docs/rules/check-inject-decorator.md)             | Detects incorrect usage of `@Inject(TOKEN)` decorator          | ✅          |
-| [`@trilon/detect-circular-reference`](docs/rules/detect-circular-reference.md)       | Detects usage of `forwardRef()` method                         | ✅          |
+| [`@trilon/enforce-close-testing-module`](docs/rules/enforce-close-testing-module.md) | Ensures NestJS testing modules are closed properly after tests | Recommended ✅          |
+| [`@trilon/check-inject-decorator`](docs/rules/check-inject-decorator.md)             | Detects incorrect usage of `@Inject(TOKEN)` decorator          | Recommended ✅          |
+| [`@trilon/detect-circular-reference`](docs/rules/detect-circular-reference.md)       | Detects usage of `forwardRef()` method                         | Recommended ✅          |
+| [`@trilon/enforce-custom-provider-type`](docs/rules/enforce-custom-provider-type.md) | Enforces a styleguide for provider types                       | Strict ⚠️          |
 ---
 
 # Trilon Consulting 

docs/rules/enforce-custom-provider-type.md

@@ -0,0 +1,55 @@
+---
+description: 'Enforces a styleguide for provider types'
+---
+
+Large teams can have the desire to limit or enforce a particular style of creating [custom providers](https://docs.nestjs.com/fundamentals/custom-providers); e.g. banning request-scoped providers to avoid potential circular dependencies, or [preferring factory providers over value providers to significantly increase performance](https://github.com/nestjs/nest/pull/12753). This rule enforces a particular type of provider to be used.
+
+## Options
+
+This rule accepts an object with the "prefer" property, which is an array containing one or more of the following values:
+
+- `value`: Enforces the use of value providers.
+- `factory`: Enforces the use of factory providers.
+- `class`: Enforces the use of class providers.
+- `existing`: Enforces the use of existing providers.
+
+
+### Example of Options
+
+```json
+"rules": {
+  "@trilon/enforce-custom-provider-type": [ 
+   "warn", {  
+     "prefer": ["factory", "value"]
+   }
+  ]
+}
+```
+
+## Examples
+Considering the options above, the following examples will show how the rule behaves when the `prefer` option is set to `factory`.
+
+### ❌ Incorrect
+
+```ts
+const customValueProvider: Provider = {
+  provide: 'TOKEN',
+  useExisting: 'some-value' // ⚠️ provider is not of type ["factory", "value"]
+}
+
+const customClassProvider: Provider = {
+  provide: AbstractClass,
+  useClass: SomeClass  // ⚠️ provider is not of type ["factory", "value"]
+}
+```
+
+### ✅ Correct
+
+const factoryProvider: Provider = {
+  provide: 'TOKEN',
+  useFactory: () => 'some-value'
+}
+
+## When Not To Use It
+
+If you don't want to enforce a particular style of provider, you can disable this rule.

package.json

@@ -12,7 +12,7 @@
     "LICENSE"
   ],
   "engines": {
-    "node": ">=20.9.0",
+    "node": ">=18.*.*",
     "yarn": ">=4.0.2"
   },
   "scripts": {

src/index.ts

@@ -1,6 +1,7 @@
 import enforceCloseTestingModuleRule from './rules/enforce-close-testing-module.rule';
 import checkInjectDecoratorRule from './rules/check-inject-decorator.rule';
 import detectCircularReferenceRule from './rules/detect-circular-reference.rule';
+import enforceCustomProviderTypeRule from './rules/enforce-custom-provider-type.rule';
 // TODO: we should type this as ESLint.Plugin but there's a type incompatibilities with the utils package
 const plugin = {
   configs: {
@@ -11,11 +12,20 @@ const plugin = {
         '@trilon/detect-circular-reference': 'warn',
       },
     },
+    strict: {
+      rules: {
+        '@trilon/enforce-close-testing-module': 'error',
+        '@trilon/check-inject-decorator': 'error',
+        '@trilon/detect-circular-reference': 'error',
+        '@trilon/enforce-custom-provider-type': 'error',
+      },
+    },
   },
   rules: {
     'enforce-close-testing-module': enforceCloseTestingModuleRule,
     'check-inject-decorator': checkInjectDecoratorRule,
     'detect-circular-reference': detectCircularReferenceRule,
+    '@trilon/enforce-custom-provider-type': enforceCustomProviderTypeRule,
   },
 };
 

src/rules/enforce-custom-provider-type.rule.ts

@@ -0,0 +1,172 @@
+import {
+  ASTUtils,
+  AST_NODE_TYPES,
+  ESLintUtils,
+  type TSESTree,
+} from '@typescript-eslint/utils';
+
+const createRule = ESLintUtils.RuleCreator(
+  (name) => `https://eslint.org/docs/latest/rules/${name}`
+);
+
+type ProviderType = 'class' | 'factory' | 'value' | 'existing' | 'unknown';
+
+export type Options = [
+  {
+    prefer: ProviderType[];
+  },
+];
+
+const defaultOptions: Options = [
+  {
+    prefer: [],
+  },
+];
+
+export type MessageIds = 'providerTypeMismatch';
+
+export default createRule<Options, MessageIds>({
+  name: 'enforce-custom-provider-type',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'Ensure that custom providers are of the preferred type',
+    },
+    fixable: undefined,
+    schema: [
+      {
+        type: 'object',
+        properties: {
+          prefer: {
+            type: 'array',
+            items: {
+              type: 'string',
+              enum: ['class', 'factory', 'value', 'existing'],
+            },
+          },
+        },
+      },
+    ],
+    messages: {
+      providerTypeMismatch: 'Provider is not of type {{ preferred }}',
+    },
+  },
+  defaultOptions,
+  create(context) {
+    const options = context.options[0] || defaultOptions[0];
+    const preferredTypes = options.prefer;
+    const providerTypesImported: string[] = [];
+    return {
+      'ImportDeclaration[source.value="@nestjs/common"]': (
+        node: TSESTree.ImportDeclaration
+      ) => {
+        const specifiers = node.specifiers;
+
+        const isImportSpecifier = (
+          node: TSESTree.ImportClause
+        ): node is TSESTree.ImportSpecifier =>
+          node.type === AST_NODE_TYPES.ImportSpecifier;
+
+        const isProviderImport = (spec: TSESTree.ImportSpecifier) =>
+          [
+            'Provider',
+            'ClassProvider',
+            'FactoryProvider',
+            'ValueProvider',
+          ].includes(spec.imported.name);
+
+        specifiers
+          .filter(isImportSpecifier)
+          .filter(isProviderImport)
+          .forEach((spec) =>
+            providerTypesImported.push(spec.local.name ?? spec.imported.name)
+          );
+      },
+
+      'Property[key.name="providers"] > ArrayExpression > ObjectExpression': (
+        node: TSESTree.ObjectExpression
+      ) => {
+        for (const property of node.properties) {
+          if (property.type === AST_NODE_TYPES.Property) {
+            const providerType = providerTypeOfProperty(property);
+
+            if (
+              providerType &&
+              !preferredTypes.includes(providerType) &&
+              preferredTypes.length > 0
+            ) {
+              context.report({
+                node: property,
+                messageId: 'providerTypeMismatch',
+                data: {
+                  preferred: preferredTypes,
+                },
+              });
+            }
+          }
+        }
+      },
+
+      'Identifier[typeAnnotation.typeAnnotation.type="TSTypeReference"]': (
+        node: TSESTree.Identifier
+      ) => {
+        const typeName = (
+          node.typeAnnotation?.typeAnnotation as TSESTree.TSTypeReference
+        ).typeName;
+
+        if (
+          ASTUtils.isIdentifier(typeName) &&
+          providerTypesImported.includes(typeName.name) &&
+          preferredTypes.length > 0
+        ) {
+          const providerType = providerTypeOfIdentifier(node);
+          if (providerType && !preferredTypes.includes(providerType)) {
+            context.report({
+              node,
+              messageId: 'providerTypeMismatch',
+              data: {
+                preferred: preferredTypes,
+              },
+            });
+          }
+        }
+      },
+    };
+  },
+});
+
+function providerTypeOfIdentifier(
+  node: TSESTree.Identifier
+): ProviderType | undefined {
+  const parent = node.parent;
+
+  if (ASTUtils.isVariableDeclarator(parent)) {
+    const init = parent.init;
+    let type: ProviderType | undefined;
+    if (init?.type === AST_NODE_TYPES.ObjectExpression) {
+      const properties = init.properties;
+      for (const property of properties) {
+        if (property.type === AST_NODE_TYPES.Property) {
+          type = providerTypeOfProperty(property);
+        }
+      }
+    }
+
+    return type;
+  }
+}
+
+function providerTypeOfProperty(
+  node: TSESTree.Property
+): ProviderType | undefined {
+  const propertyKey = (node.key as TSESTree.Identifier)?.name;
+  return propertyKey === 'useClass'
+    ? 'class'
+    : propertyKey === 'useFactory'
+      ? 'factory'
+      : propertyKey === 'useValue'
+        ? 'value'
+        : propertyKey === 'useExisting'
+          ? 'existing'
+          : undefined;
+};