From 46e6116d80de0a45cc30162d972095a39dc13781 Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@users.noreply.github.com>
Date: Thu, 7 Jun 2018 07:55:16 +0200
Subject: [PATCH] build: add tslint rule to enforce consistent rxjs imports
 (#11629)

Adds a small tslint rule that will help us catch cases like [this one](https://github.com/angular/material2/blob/master/src/demo-app/virtual-scroll/virtual-scroll-demo.ts#L10), which can come up when the IDE auto-imports something from rjxs.
---
 .../virtual-scroll/virtual-scroll-demo.ts     |  2 +-
 tools/tslint-rules/rxjsImportsRule.ts         | 23 +++++++++++++++++++
 tslint.json                                   |  1 +
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tools/tslint-rules/rxjsImportsRule.ts

diff --git a/src/demo-app/virtual-scroll/virtual-scroll-demo.ts b/src/demo-app/virtual-scroll/virtual-scroll-demo.ts
index 8b797703b3b..8aff47670d9 100644
--- a/src/demo-app/virtual-scroll/virtual-scroll-demo.ts
+++ b/src/demo-app/virtual-scroll/virtual-scroll-demo.ts
@@ -7,7 +7,7 @@
  */
 
 import {Component, ViewEncapsulation} from '@angular/core';
-import {BehaviorSubject} from 'rxjs/index';
+import {BehaviorSubject} from 'rxjs';
 
 
 type State = {
diff --git a/tools/tslint-rules/rxjsImportsRule.ts b/tools/tslint-rules/rxjsImportsRule.ts
new file mode 100644
index 00000000000..c942e6c1970
--- /dev/null
+++ b/tools/tslint-rules/rxjsImportsRule.ts
@@ -0,0 +1,23 @@
+import * as ts from 'typescript';
+import * as Lint from 'tslint';
+
+/**
+ * Rule that ensures that all rxjs imports come only from `rxjs` and `rxjs/operators`.
+ */
+export class Rule extends Lint.Rules.AbstractRule {
+  apply(sourceFile: ts.SourceFile) {
+    return this.applyWithWalker(new Walker(sourceFile, this.getOptions()));
+  }
+}
+
+class Walker extends Lint.RuleWalker {
+  visitImportDeclaration(node: ts.ImportDeclaration) {
+    const specifier = node.moduleSpecifier.getText().slice(1, -1);
+
+    if (specifier.startsWith('rxjs') && specifier !== 'rxjs' && specifier !== 'rxjs/operators') {
+      this.addFailureAtNode(node, 'RxJS imports are only allowed from `rxjs` or `rxjs/operators`.');
+    }
+
+    super.visitImportDeclaration(node);
+  }
+}
diff --git a/tslint.json b/tslint.json
index 6c91e04fa59..ff30b9385e5 100644
--- a/tslint.json
+++ b/tslint.json
@@ -98,6 +98,7 @@
     "ts-loader": true,
     "no-exposed-todo": true,
     "setters-after-getters": true,
+    "rxjs-imports": true,
     "no-host-decorator-in-concrete": [
       true,
       "HostBinding",