feat(prefer-async-pipe): Add rule.

package.json

@@ -59,7 +59,7 @@
     "test": "yarn run lint && yarn run test:build && yarn run test:mocha && yarn run test:tslint-v5 && yarn run test:tslint-v6 && yarn run test:tslint-v6-compat",
     "test:build": "yarn run test:clean && tsc -p tsconfig.json",
     "test:clean": "rimraf build",
-    "test:debug": "tslint --test ./test/v6/fixtures/prefer-observer/**/tslint.json",
+    "test:debug": "tslint --test ./test/v6/fixtures/prefer-async-pipe/**/tslint.json",
     "test:issues": "yarn run test:clean && tsc -p tsconfig.json && tslint --test ./test/v6/fixtures/issues/**/tslint.json",
     "test:mocha": "mocha build/**/*-spec.js",
     "test:tslint-v5": "yarn --cwd ./test/v5 install && yarn --cwd ./test/v5 upgrade && tslint --test ./test/v5/fixtures/**/tslint.json",

source/rules/rxjsPreferAsyncPipeRule.ts

@@ -0,0 +1,59 @@
+/**
+ * @license Use of this source code is governed by an MIT-style license that
+ * can be found in the LICENSE file at https://github.com/cartant/rxjs-tslint-rules
+ */
+
+import * as Lint from "tslint";
+import * as ts from "typescript";
+import * as tsutils from "tsutils";
+import { tsquery } from "@phenomnomnominal/tsquery";
+import { couldBeType } from "../support/util";
+
+export class Rule extends Lint.Rules.TypedRule {
+
+    public static metadata: Lint.IRuleMetadata = {
+        description: "Disallows the calling of `subscribe` within an Angular component.",
+        options: null,
+        optionsDescription: "Not configurable.",
+        requiresTypeInfo: true,
+        ruleName: "rxjs-prefer-async-pipe",
+        type: "style",
+        typescriptOnly: true
+    };
+
+    public static FAILURE_STRING = "Prefer async pipe over subscribe";
+
+    public applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
+
+        const failures: Lint.RuleFailure[] = [];
+        const typeChecker = program.getTypeChecker();
+
+        const componentIdentifiers = tsquery(
+            sourceFile,
+            `ClassDeclaration Identifier[name=/Component$/]`
+        );
+        componentIdentifiers.forEach(componentIdentifier => {
+            const { parent: classDeclaration } = componentIdentifier;
+            const propertyAccessExpressions = tsquery(
+                classDeclaration,
+                `CallExpression PropertyAccessExpression[name.name="subscribe"]`
+            );
+            propertyAccessExpressions.forEach(propertyAccessExpression => {
+                if (tsutils.isPropertyAccessExpression(propertyAccessExpression)) {
+                    const type = typeChecker.getTypeAtLocation(propertyAccessExpression.expression);
+                    if (couldBeType(type, "Observable")) {
+                        const { name } = propertyAccessExpression;
+                        failures.push(new Lint.RuleFailure(
+                            sourceFile,
+                            name.getStart(),
+                            name.getStart() + name.getWidth(),
+                            Rule.FAILURE_STRING,
+                            this.ruleName
+                        ));
+                    }
+                }
+            });
+        });
+        return failures;
+    }
+}

test/v6/fixtures/prefer-async-pipe/default/fixture.ts.lint

@@ -0,0 +1,15 @@
+import { Component OnInit } from "@angular/core";
+import { of } from "rxjs";
+
+@Component({
+    selector: "some-component",
+    template: "<span>something</span>"
+})
+export class SomeComponent implements OnInit {
+    ngOnInit() {
+        of("foo").subscribe();
+                  ~~~~~~~~~                     [prefer-async-pipe]
+    }
+}
+
+[prefer-async-pipe]: Prefer async pipe over subscribe

test/v6/fixtures/prefer-async-pipe/default/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "baseUrl": ".",
+    "lib": ["es2015"],
+    "noEmit": true,
+    "paths": {
+      "rxjs": ["../../node_modules/rxjs"]
+    },
+    "skipLibCheck": true,
+    "target": "es5"
+  },
+  "include": ["fixture.ts"]
+}

test/v6/fixtures/prefer-async-pipe/default/tslint.json

@@ -0,0 +1,8 @@
+{
+  "defaultSeverity": "error",
+  "jsRules": {},
+  "rules": {
+    "rxjs-prefer-async-pipe": { "severity": "error" }
+  },
+  "rulesDirectory": "../../../../../build/rules"
+}