feat(rule): add use-injectable-provided-in

src/angular/metadata.ts

@@ -55,5 +55,5 @@ export class ModuleMetadata {
 }
 
 export class InjectableMetadata {
-  constructor(readonly controller: ts.ClassDeclaration, readonly decorator: ts.Decorator) {}
+  constructor(readonly controller: ts.ClassDeclaration, readonly decorator: ts.Decorator, readonly providedIn?: string | ts.Expression) {}
 }

src/angular/metadataReader.ts

@@ -107,7 +107,9 @@ export class MetadataReader {
   }
 
   protected readInjectableMetadata(d: ts.ClassDeclaration, dec: ts.Decorator): DirectiveMetadata {
-    return new InjectableMetadata(d, dec);
+    const providedInExpression = getDecoratorPropertyInitializer(dec, 'providedIn');
+
+    return new InjectableMetadata(d, dec, providedInExpression);
   }
 
   protected readComponentMetadata(d: ts.ClassDeclaration, dec: ts.Decorator): ComponentMetadata {

src/index.ts

@@ -47,6 +47,7 @@ export { Rule as TemplateNoNegatedAsyncRule } from './templateNoNegatedAsyncRule
 export { Rule as TemplateUseTrackByFunctionRule } from './templateUseTrackByFunctionRule';
 export { Rule as UseComponentSelectorRule } from './useComponentSelectorRule';
 export { Rule as UseComponentViewEncapsulationRule } from './useComponentViewEncapsulationRule';
+export { Rule as UseInjectableProvidedInRule } from './useInjectableProvidedInRule';
 export { Rule as UseLifecycleInterfaceRule } from './useLifecycleInterfaceRule';
 export { Rule as UsePipeDecoratorRule } from './usePipeDecoratorRule';
 export { Rule as UsePipeTransformInterfaceRule } from './usePipeTransformInterfaceRule';

src/useInjectableProvidedInRule.ts

@@ -0,0 +1,38 @@
+import { IRuleMetadata, RuleFailure } from 'tslint';
+import { AbstractRule } from 'tslint/lib/rules';
+import { SourceFile } from 'typescript';
+import { InjectableMetadata } from './angular';
+import { NgWalker } from './angular/ngWalker';
+
+export class Rule extends AbstractRule {
+  static readonly metadata: IRuleMetadata = {
+    description: "Enforces classes decorated with @Injectable to use the 'providedIn' property.",
+    options: null,
+    optionsDescription: 'Not configurable.',
+    rationale: "Using the 'providedIn' property makes classes decorated with @Injectable tree shakeable.",
+    ruleName: 'use-injectable-provided-in',
+    type: 'functionality',
+    typescriptOnly: true
+  };
+
+  static readonly FAILURE_STRING = "Classes decorated with @Injectable should use the 'providedIn' property";
+
+  apply(sourceFile: SourceFile): RuleFailure[] {
+    const walker = new Walker(sourceFile, this.getOptions());
+
+    return this.applyWithWalker(walker);
+  }
+}
+
+class Walker extends NgWalker {
+  protected visitNgInjectable(metadata: InjectableMetadata): void {
+    this.validateInjectable(metadata);
+    super.visitNgInjectable(metadata);
+  }
+
+  private validateInjectable(metadata: InjectableMetadata): void {
+    if (metadata.providedIn) return;
+
+    this.addFailureAtNode(metadata.decorator, Rule.FAILURE_STRING);
+  }
+}

test/useInjectableProvidedInRule.spec.ts

@@ -0,0 +1,46 @@
+import { Rule } from '../src/useInjectableProvidedInRule';
+import { assertAnnotated, assertSuccess } from './testHelper';
+
+const {
+  metadata: { ruleName },
+  FAILURE_STRING
+} = Rule;
+
+describe(ruleName, () => {
+  describe('failures', () => {
+    it('should fail if providedIn property is not set', () => {
+      const source = `
+        @Injectable()
+        ~~~~~~~~~~~~~
+        class Test {}
+      `;
+      assertAnnotated({
+        message: FAILURE_STRING,
+        ruleName,
+        source
+      });
+    });
+  });
+
+  describe('success', () => {
+    it('should succeed if providedIn property is set to a literal string', () => {
+      const source = `
+        @Injectable({
+          providedIn: 'root'
+        })
+        class Test {}
+      `;
+      assertSuccess(ruleName, source);
+    });
+
+    it('should succeed if providedIn property is set to a module', () => {
+      const source = `
+        @Injectable({
+          providedIn: SomeModule
+        })
+        class Test {}
+      `;
+      assertSuccess(ruleName, source);
+    });
+  });
+});