feat: Add no-redundant-notify rule.

package.json

@@ -78,7 +78,7 @@
     "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/issues/105/tslint.json\"",
+    "test:debug": "tslint --test \"./test/v6/fixtures/no-redundant-notify/default/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/rxjsNoRedundantNotifyRule.ts

@@ -0,0 +1,55 @@
+/**
+ * @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 { tsquery } from "@phenomnomnominal/tsquery";
+import * as Lint from "tslint";
+import * as tsutils from "tsutils";
+import * as ts from "typescript";
+import { couldBeType } from "../support/util";
+
+export class Rule extends Lint.Rules.TypedRule {
+  public static metadata: Lint.IRuleMetadata = {
+    description:
+      "Disallows redundant notifications from completed or errored observables.",
+    options: null,
+    optionsDescription: "Not configurable.",
+    requiresTypeInfo: true,
+    ruleName: "rxjs-no-redundant-notify",
+    type: "functionality",
+    typescriptOnly: true
+  };
+
+  public static FAILURE_STRING = "Redundant notifications are forbidden";
+
+  public applyWithProgram(
+    sourceFile: ts.SourceFile,
+    program: ts.Program
+  ): Lint.RuleFailure[] {
+    const failures: Lint.RuleFailure[] = [];
+    const typeChecker = program.getTypeChecker();
+
+    const query = `ExpressionStatement[expression.expression.name.text=/(complete|error)/] ~ ExpressionStatement[expression.expression.name.text=/(next|complete|error)/]`;
+    const expressionStatements = tsquery(sourceFile, query);
+    expressionStatements.forEach(node => {
+      const expressionStatement = node as ts.ExpressionStatement;
+      if (ts.isCallExpression(expressionStatement.expression)) {
+        const callExpression = expressionStatement.expression;
+        if (ts.isPropertyAccessExpression(callExpression.expression)) {
+          const { name } = callExpression.expression;
+          failures.push(
+            new Lint.RuleFailure(
+              sourceFile,
+              name.getStart(),
+              name.getStart() + name.getWidth(),
+              Rule.FAILURE_STRING,
+              this.ruleName
+            )
+          );
+        }
+      }
+    });
+    return failures;
+  }
+}

test/v6/fixtures/no-redundant-notify/default/fixture.ts.lint

@@ -0,0 +1,90 @@
+import { Observable, Subject } from "rxjs";
+
+const examples = [
+  new Observable<number>(observer => {
+    observer.next(42);
+    observer.complete();
+  }),
+  new Observable<number>(observer => {
+    observer.next(42);
+    observer.error(new Error("Kaboom!"));
+  }),
+  new Observable<number>(observer => {
+    observer.complete();
+    observer.next(42);
+             ~~~~                               [no-redundant-notify]
+  }),
+  new Observable<number>(observer => {
+    observer.complete();
+    observer.complete();
+             ~~~~~~~~                           [no-redundant-notify]
+  }),
+  new Observable<number>(observer => {
+    observer.complete();
+    observer.error(new Error("Kaboom!"));
+             ~~~~~                              [no-redundant-notify]
+  }),
+  new Observable<number>(observer => {
+    observer.error(new Error("Kaboom!"));
+    observer.next(42);
+             ~~~~                               [no-redundant-notify]
+  }),
+  new Observable<number>(observer => {
+    observer.error(new Error("Kaboom!"));
+    observer.complete();
+             ~~~~~~~~                           [no-redundant-notify]
+  }),
+  new Observable<number>(observer => {
+    observer.error(new Error("Kaboom!"));
+    observer.error(new Error("Kaboom!"));
+             ~~~~~                              [no-redundant-notify]
+  }
+  () => {
+    const subject = new Subject<number>();
+    subject.next(42);
+    subject.complete();
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.next(42);
+    subject.error(new Error("Kaboom!"));
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.complete();
+    subject.next(42);
+            ~~~~                                [no-redundant-notify]
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.complete();
+    subject.complete();
+            ~~~~~~~~                            [no-redundant-notify]
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.complete();
+    subject.error(new Error("Kaboom!"));
+            ~~~~~                               [no-redundant-notify]
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.error(new Error("Kaboom!"));
+    subject.next(42);
+            ~~~~                                [no-redundant-notify]
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.error(new Error("Kaboom!"));
+    subject.complete();
+            ~~~~~~~~                            [no-redundant-notify]
+  },
+  () => {
+    const subject = new Subject<number>();
+    subject.error(new Error("Kaboom!"));
+    subject.error(new Error("Kaboom!"));
+            ~~~~~                               [no-redundant-notify]
+  }
+];
+
+[no-redundant-notify]: Redundant notifications are forbidden

test/v6/fixtures/no-redundant-notify/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/no-redundant-notify/default/tslint.json

@@ -0,0 +1,8 @@
+{
+  "defaultSeverity": "error",
+  "jsRules": {},
+  "rules": {
+    "rxjs-no-redundant-notify": { "severity": "error" }
+  },
+  "rulesDirectory": "../../../../../build/rules"
+}