From fb15e89426b95a5559a08affeb722bec1c320953 Mon Sep 17 00:00:00 2001
From: Paul Gschwendtner <paulgschwendtner@gmail.com>
Date: Fri, 10 May 2019 23:29:12 +0200
Subject: [PATCH] build: add rule to warn for undecorated base classes (#15976)

With Ivy, directives or components no longer properly inherit
a constructor from a parent base class which is undecorated.

See more details here: FW-1238

In order to avoid dependency injection issues with Ivy, a new
custom TSLint rule reports a failure when a directive/component
uses dependency injection in a way that breaks with Ivy.

Related to #15975
---
 .../noUndecoratedBaseClassDiRule.ts           | 96 +++++++++++++++++++
 tslint.json                                   |  1 +
 2 files changed, 97 insertions(+)
 create mode 100644 tools/tslint-rules/noUndecoratedBaseClassDiRule.ts

diff --git a/tools/tslint-rules/noUndecoratedBaseClassDiRule.ts b/tools/tslint-rules/noUndecoratedBaseClassDiRule.ts
new file mode 100644
index 00000000000..1fc7bfd23ae
--- /dev/null
+++ b/tools/tslint-rules/noUndecoratedBaseClassDiRule.ts
@@ -0,0 +1,96 @@
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+
+const RULE_FAILURE = `Class inherits constructor using dependency injection from ` +
+    `undecorated base class. This breaks dependency injection with Ivy and can be fixed ` +
+    `by creating an explicit pass-through constructor.`;
+
+/**
+ * Rule that doesn't allow inheriting a constructor using dependency injection from an
+ * undecorated base class. With Ivy, undecorated base classes cannot use dependency
+ * injection. Classes that inherit the constructor from the base class can specify
+ * an explicit pass-through constructor to make DI work.
+ */
+export class Rule extends Lint.Rules.TypedRule {
+  applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
+    return this.applyWithWalker(
+        new Walker(sourceFile, this.getOptions(), program.getTypeChecker()));
+  }
+}
+
+class Walker extends Lint.RuleWalker {
+  constructor(
+      sourceFile: ts.SourceFile, options: Lint.IOptions, private typeChecker: ts.TypeChecker) {
+    super(sourceFile, options);
+  }
+
+  visitClassDeclaration(node: ts.ClassDeclaration) {
+    if (!this.hasDirectiveDecorator(node)) {
+      return;
+    }
+
+    // If the class already has an explicit constructor, it's not required
+    // for base classes to be decorated.
+    if (this.hasExplicitConstructor(node)) {
+      return;
+    }
+
+    const baseClass = this.getConstructorBaseClass(node);
+    if (baseClass && !this.hasDirectiveDecorator(baseClass)) {
+      this.addFailureAtNode(node, RULE_FAILURE);
+    }
+  }
+
+  /** Checks whether the given class declaration has an explicit constructor. */
+  hasExplicitConstructor(node: ts.ClassDeclaration): boolean {
+    return node.members.some(ts.isConstructorDeclaration);
+  }
+
+  /** Checks if the specified node has a "@Directive" or "@Component" decorator. */
+  hasDirectiveDecorator(node: ts.ClassDeclaration): boolean {
+    return !!node.decorators && node.decorators.some(d => {
+      if (!ts.isCallExpression(d.expression)) {
+        return false;
+      }
+
+      const decoratorText = d.expression.expression.getText();
+      return decoratorText === 'Directive' || decoratorText === 'Component';
+    });
+  }
+
+  /**
+   * Gets the first inherited class of the specified class that has an
+   * explicit constructor.
+   */
+  getConstructorBaseClass(node: ts.ClassDeclaration): ts.ClassDeclaration|null {
+    let currentClass = node;
+    while (currentClass) {
+      const baseTypes = this.getBaseTypeIdentifiers(currentClass);
+      if (!baseTypes || baseTypes.length !== 1) {
+        return null;
+      }
+      const symbol = this.typeChecker.getTypeAtLocation(baseTypes[0]).getSymbol();
+      if (!symbol || !ts.isClassDeclaration(symbol.valueDeclaration)) {
+        return null;
+      }
+      if (this.hasExplicitConstructor(symbol.valueDeclaration)) {
+        return symbol.valueDeclaration;
+      }
+      currentClass = symbol.valueDeclaration;
+    }
+    return null;
+  }
+
+  /** Determines the base type identifiers of a specified class declaration. */
+  getBaseTypeIdentifiers(node: ts.ClassDeclaration): ts.Identifier[]|null {
+    if (!node.heritageClauses) {
+      return null;
+    }
+
+    return node.heritageClauses.filter(clause => clause.token === ts.SyntaxKind.ExtendsKeyword)
+        .reduce(
+            (types, clause) => types.concat(clause.types), [] as ts.ExpressionWithTypeArguments[])
+        .map(typeExpression => typeExpression.expression)
+        .filter(ts.isIdentifier);
+  }
+}
diff --git a/tslint.json b/tslint.json
index 20343782cf7..05761ee1fc1 100644
--- a/tslint.json
+++ b/tslint.json
@@ -98,6 +98,7 @@
     "no-exposed-todo": true,
     "no-import-spacing": true,
     "no-private-getters": true,
+    "no-undecorated-base-class-di": true,
     "setters-after-getters": true,
     "ng-on-changes-property-access": true,
     "rxjs-imports": true,