chore: create tslint rule to allow @HostListener and @HostBinding in abstract classes (#8036)

Author: josephperrott

tools/tslint-rules/noHostDecoratorInConcreteRule.ts

@@ -0,0 +1,37 @@
+import * as ts from 'typescript';
+import * as Lint from 'tslint';
+
+export class Rule extends Lint.Rules.AbstractRule {
+  apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+    return this.applyWithWalker(new Walker(sourceFile, this.getOptions()));
+  }
+}
+
+class Walker extends Lint.RuleWalker {
+  visitClassDeclaration(node: ts.ClassDeclaration) {
+    if (!node.modifiers || !this.getOptions().length) { return; }
+
+    // Do not check the class if its abstract.
+    if (!!node.modifiers.find(modifier => modifier.kind === ts.SyntaxKind.AbstractKeyword)) {
+      return;
+    }
+
+    node.members
+        .filter(el => el.decorators)
+        .map(el => el.decorators!)
+        .forEach(decorators => {
+          decorators.forEach(decorator => {
+            const decoratorText: string = decorator.getChildAt(1).getText();
+            const matchedDecorator: string = this.getOptions().find(
+              (item: string) => decoratorText.startsWith(item));
+            if (!!matchedDecorator) {
+              this.addFailureFromStartToEnd(decorator.getChildAt(1).pos - 1, decorator.end,
+                  `The @${matchedDecorator} decorator may only be used in abstract classes. In ` +
+                  `concrete classes use \`host\` in the component definition instead.`);
+            }
+          });
+        });
+
+    super.visitClassDeclaration(node);
+  }
+}

tslint.json

@@ -75,9 +75,7 @@
       ["fit"],
       ["fdescribe"],
       ["xit"],
-      ["xdescribe"],
-      { "name": "HostBinding", "message": "Use `host` in the component definition instead." },
-      { "name": "HostListener", "message": "Use `host` in the component definition instead." }
+      ["xdescribe"]
     ],
     // Disallows importing the whole RxJS library. Submodules can be still imported.
     "import-blacklist": [true, "rxjs"],
@@ -87,6 +85,11 @@
     // Custom Rules
     "ts-loader": true,
     "no-exposed-todo": true,
+    "no-host-decorator-in-concrete": [
+      true,
+      "HostBinding",
+      "HostListener"
+    ],
     "validate-decorators": [true, {
       "Component": {
         "encapsulation": "\\.None$",