Errors related to missing RxJS operators are occurring in the browser, but are not showing up in Visual Studio

Question

Errors related to missing RxJS operators are occurring in the browser, but are not showing up in Visual Studio

Recently, I encountered a peculiar problem with my Angular4 project, which is managed under Angular-CLI and utilizes the RxJS library. Upon updating the RxJS library to version 5.5.2, the project started experiencing issues with Observable operators. The specific error messages displayed in Google Chrome were as follows:

ERROR TypeError: this.apiService.request(...).switchMap is not a function

To address this issue, I am aware that it can be resolved by including the following import statement:

import 'rxjs/add/operator/switchMap';

However, the challenge lies with my IDE, namely Visual Studio Code, as it fails to indicate which operator imports are missing. Currently, the only method I have found to detect these missing operators is by running the application and monitoring for errors in the browser using the Developer Console. Consequently, I have two questions:

Is there a more efficient way to identify missing operators within an updated project? Why does the build process not recognize the absence of certain operators?
Can Visual Studio Code be configured to highlight such errors prior to code deployment, rather than discovering them post-push during browser testing? It appears that syntax completion in this IDE functions even with unimported operators, which seems incorrect.

For reference, here is the output from ng -v:

    _                      _                 ____ _     ___
   / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
  / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
 / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
/_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
               |___/

Angular CLI: 1.5.3
Node: 6.11.2
OS: darwin x64
Angular: 4.4.6
... animations, common, compiler, compiler-cli, core, forms
... http, platform-browser, platform-browser-dynamic
... platform-server, router, tsc-wrapped

@angular/cdk: 2.0.0-beta.12
@angular/cli: 1.5.3
@angular/flex-layout: 2.0.0-beta.8
@angular/material: 2.0.0-beta.12
@angular-devkit/build-optimizer: 0.0.33
@angular-devkit/core: 0.0.21
@angular-devkit/schematics: 0.0.37
@ngtools/json-schema: 1.1.0
@ngtools/webpack: 1.8.3
@schematics/angular: 0.1.7
typescript: 2.3.4
webpack: 3.8.1

Additionally, the output from npm list --depth=0 is provided below:

...

javascript angular typescript visual-studio-code rxjs

Answer 1

Answer №1

If anyone is experiencing a similar issue to mine, here's what I found:

The problem stemmed from how I was importing certain *.ts files. For instance, if you're importing an object like this:

import { Observable } from 'rxjs';

This is incorrect because Visual Studio Code won't catch missing operators. The same goes for ng serve.

However, if you import like this instead:

import { Observable } from 'rxjs/Observable';

Then both Visual Studio Code and ng serve will flag missing operators. So, it's important to avoid importing directly from 'rxjs'. It's recommended to refactor any code with imports from 'rxjs' to something like 'rxjs/Observable', etc...

Answer 2

If anyone is experiencing a similar issue to mine, here's what I found:

The problem stemmed from how I was importing certain *.ts files. For instance, if you're importing an object like this:

import { Observable } from 'rxjs';

This is incorrect because Visual Studio Code won't catch missing operators. The same goes for ng serve.

However, if you import like this instead:

import { Observable } from 'rxjs/Observable';

Then both Visual Studio Code and ng serve will flag missing operators. So, it's important to avoid importing directly from 'rxjs'. It's recommended to refactor any code with imports from 'rxjs' to something like 'rxjs/Observable', etc...

Answer 3

Answer №2

By incorporating rxjs added operators, I am able to ensure TypeScript reference checking.

To enable typescript reference checking with rxjs added operators, try setting

"typescript.referencesCodeLens.enabled": true

in the File/Preferences/Settings section.

There are a few other settings that may also be relevant:

"typescript.validate.enable": true (to display rxjs reference errors)
"javascript.validate.enable": true

For more information on extensions using CodeLens, you can refer to this link.

To view all errors, navigate to the Problems tab (Ctrl+Shift+M).

An additional tip is to gather all rxjs imports in a single top-level file and then import it into app.module.

import './rxjs-extensions';

rxjs-extensions.js

import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Subscription } from 'rxjs/Subscription';

import 'rxjs/add/operator/defaultIfEmpty';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/concat';
...

import 'rxjs/add/observable/interval';
import 'rxjs/add/observable/empty';
import 'rxjs/add/observable/from';
import 'rxjs/add/observable/of';
import 'rxjs/add/observable/throw';

Answer 4

By incorporating rxjs added operators, I am able to ensure TypeScript reference checking.

To enable typescript reference checking with rxjs added operators, try setting

"typescript.referencesCodeLens.enabled": true

in the File/Preferences/Settings section.

There are a few other settings that may also be relevant:

"typescript.validate.enable": true (to display rxjs reference errors)
"javascript.validate.enable": true

For more information on extensions using CodeLens, you can refer to this link.

To view all errors, navigate to the Problems tab (Ctrl+Shift+M).

An additional tip is to gather all rxjs imports in a single top-level file and then import it into app.module.

import './rxjs-extensions';

rxjs-extensions.js

import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Subscription } from 'rxjs/Subscription';

import 'rxjs/add/operator/defaultIfEmpty';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/concat';
...

import 'rxjs/add/observable/interval';
import 'rxjs/add/observable/empty';
import 'rxjs/add/observable/from';
import 'rxjs/add/observable/of';
import 'rxjs/add/observable/throw';

Errors related to missing RxJS operators are occurring in the browser, but are not showing up in Visual Studio

Answer №1

Answer №2

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