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Migrating and configuring Eslint with Angular 11

Giovanni Sarciotto on November 30, 2020

In this post we will walk through migrating and configuring an Angular 11 project to utilize ESLint and as a bonus add the Prettier formatter. [21...

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Ben • Mar 17 '21

Hello Giovanni ! Thank you for this complete, up-to-date and beginner-friendly tutorial !

I followed the whole tutorial, but here :

"Test the configuration
Check to see if everything is working. For example, in your configuration above, the no unused variables is enabled, so open a Typescript file and create a new variable and check if the linting works."

I installed ESLint VSCode extension wrote an unused var in order to test my config (same as yours), and it didn't get red, so I couldn't check if the linting works . Maybe you could know why it didn't work for me ?

Thanks a lot,

Ben

Giovanni Sarciotto • Mar 17 '21

Hi Ben, thanks for the compliments!

Hmm, thats odd, try running the ng lint command. If it works then there is some setting in the extension that you need to see (probably the lint on save one). If it doesn't then reply and I will be glad to help

Ben • Mar 18 '21

Hi Giovanni, thank you for your quick reply !
When I run ng lint, I do have errors and warnings, and unused vars belong to the warning category - that might be the reason why it doesn't get red when I write an unused var. That's weird anyway, because I just followed your tuto.

Giovanni Sarciotto • Mar 18 '21

Yeah, in the config above unused vars is a warning. You can make it an error in the rules section, see this. I don't think you will need to disable the core ESLint rule since @typescript-eslint/recommended already does this, so just add the "@typescript-eslint/no-unused-vars": ["error"] line

fabio984 • Jan 12 '21

Hi, after eslint setup should we delete the lint
@angular-eslint/schematics": "1.0.0",
from package.json? Otherwise when npm install it warns that TSLINT is deprecated.

Finding which package depends on it:

npm ls tslint
-- @angular-eslint/schematics@1.0.0-- tslint-to-eslint-config@2.0.1
`-- tslint@6.1.3

tkx

Giovanni Sarciotto • Jan 14 '21

I don't think it would cause any problems to uninstall the schematics after the transition.

pmo1948 • Jan 18 '21

Hi,
Once everything has been configured, is there a way to run it, or add it to a github hook?
Before, I could run npm lint, where that would run ng lint and I could use that as needed. I tried running eslint from the terminal, but it did not give me any errors. (I know I have errors though, bc Webstorm is letting me know)

pmo1948 • Jan 21 '21

solution - in angular.json, change "builder" : "@angular-devkit/build-angular:tslint" to "builder": "@angular-eslint/builder:lint"

Dener Rocha • Feb 21 '21

Show! but SLint couldn't find the config "prettier/@typescript-eslint" to extend from. Please check that the name of the config is correct. How solve this issue ?

Giovanni Sarciotto • Feb 22 '21

Did you install the dependencies npm install -D prettier eslint-config-prettier eslint-plugin-prettier?

Dener Rocha • Feb 22 '21

Hi, yes, i did...

eslintrc.json

"extends": [
"plugin:@angular-eslint/recommended",
"plugin:@angular-eslint/template/process-inline-templates",
"eslint:recommended",
"plugin:@typescript-eslint/recommended",
"plugin:@typescript-eslint/recommended-requiring-type-checking",
"prettier",
"prettier/@typescript-eslint",
"plugin:prettier/recommended"
],

command

$ eslint --color -c .eslintrc.json --ext .ts ./src/

result

Oops! Something went wrong! :(
ESLint: 7.20.0
ESLint couldn't find the config "prettier/@typescript-eslint" to extend from. Please check that the name of the config is correct.
The config "prettier/@typescript-eslint" was referenced from the config file in ".eslintrc.json".
If you still have problems, please stop by eslint.org/chat/help to chat with the team.

log

0 info it worked if it ends with ok
1 verbose cli [
1 verbose cli 'C:\Program Files\nodejs\node.exe',
1 verbose cli 'C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js',
1 verbose cli 'run',
1 verbose cli 'eslint'
1 verbose cli ]
2 info using npm@6.14.11
3 info using node@v14.15.5
4 verbose run-script [ 'preeslint', 'eslint', 'posteslint' ]
5 info lifecycle app@1.0.0~preeslint: app@1.0.0
6 info lifecycle app@1.0.0~eslint: app@1.0.0
7 verbose lifecycle app@1.0.0~eslint: unsafe-perm in lifecycle true
8 verbose lifecycle app@1.0.0~eslint: PATH: C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\node-gyp-bin;D:\SISTEMAS\CLOUDCLASS\cloudclass-app\node_modules.bin;C:\Program Files\PowerShell\7;C:\Program Files (x86)\Common Files\Intel\Shared Libraries\redist\intel64\compiler;C:\Program Files\Python27\;C:\Program Files\Python27\Scripts;C:\Windows;C:\Windows\system32;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\ProgramData\chocolatey\bin;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\170\Tools\Binn\;C:\Program Files (x86)\Firebird\Firebird_2_5\bin;D:\SSL\BIN;D:\SSH;D:\SSH\tools;D:\SVN;D:\UTIL;D:\DLL;C:\Program Files\dotnet\;C:\Program Files\Git LFS;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files\NVIDIA Corporation\NVIDIA NvDLISR;C:\Program Files\Common Files\Tom Sawyer Software\10.0.0;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\System32\OpenSSH\;C:\Program Files\PowerShell\7-preview\preview;C:\Program Files\Java\bin;C:\Program Files\Docker\Docker\resources\bin;C:\ProgramData\DockerDesktop\version-bin;C:/Program Files (x86)/CS DEVICES/SatCare/Biblioteca de funções;C:\Program Files\PowerShell\7\;C:\Program Files\nodejs\;C:\Program Files\Git\cmd;C:\Users\dener\AppData\Local\Microsoft\WindowsApps;C:\Users\dener\AppData\Local\Programs\Microsoft VS Code Insiders\bin;C:\Program Files\kdiff3;C:\Users\dener.dotnet\tools;C:\Users\dener\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\dener\AppData\Local\Microsoft\WindowsApps;C:\Users\dener\AppData\Roaming\DBeaverData\drivers\clients\postgresql\win\12;C:\Users\dener.dotnet\tools;d:\harbour\bin;d:\bcc\bin;;C:\Program Files (x86)\CS DEVICES\SatCare\Biblioteca de funções;C:\Users\dener\AppData\Roaming\npm
9 verbose lifecycle app@1.0.0~eslint: CWD: D:\SISTEMAS\CLOUDCLASS\cloudclass-app
10 silly lifecycle app@1.0.0~eslint: Args: [ '/d /s /c', 'eslint --color -c .eslintrc.json --ext .ts ./src/' ]
11 silly lifecycle app@1.0.0~eslint: Returned: code: 2 signal: null
12 info lifecycle app@1.0.0~eslint: Failed to exec eslint script
13 verbose stack Error: app@1.0.0 eslint: eslint --color -c .eslintrc.json --ext .ts ./src/
13 verbose stack Exit status 2
13 verbose stack at EventEmitter. (C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\index.js:332:16)
13 verbose stack at EventEmitter.emit (events.js:315:20)
13 verbose stack at ChildProcess. (C:\Program Files\nodejs\node_modules\npm\node_modules\npm-lifecycle\lib\spawn.js:55:14)
13 verbose stack at ChildProcess.emit (events.js:315:20)
13 verbose stack at maybeClose (internal/child_process.js:1048:16)
13 verbose stack at Process.ChildProcess._handle.onexit (internal/child_process.js:288:5)
14 verbose pkgid app@1.0.0
15 verbose cwd D:\SISTEMAS\CLOUDCLASS\cloudclass-app
16 verbose Windows_NT 10.0.21318
17 verbose argv "C:\Program Files\nodejs\node.exe" "C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js" "run" "eslint"
18 verbose node v14.15.5
19 verbose npm v6.14.11
20 error code ELIFECYCLE
21 error errno 2
22 error app@1.0.0 eslint: eslint --color -c .eslintrc.json --ext .ts ./src/
22 error Exit status 2
23 error Failed at the app@1.0.0 eslint script.
23 error This is probably not a problem with npm. There is likely additional logging output above.
24 verbose exit [ 2, true ]

if comment "prettier/@typescript-eslint", works fine

Eugene Stativka • Feb 22 '21

I have the same problem and I install these dependendencies

Giovanni Sarciotto • Feb 22 '21

@stativka @denernun

I discovered the problem, eslint-config-prettier was updated yesterday and they changed somethings. Now you only need to extend plugin:prettier/recommended. So just remove both entries of prettier/@typescript-eslint from the config file and it should work.

Eugene Stativka • Feb 22 '21

Thank you for your prompt reply and for this article!

d4lj1t • Dec 22 '23

this did it for me , i must have missed the other dependencies

David Bronfen • Aug 3 '21 • Edited

Hi, thanks for the informative and very helpful post :)
when I run the ng lint command I get errors that relate to type any of the angular form's value
Thrown error: Unsafe member access [curr] on an any value - @typescript-eslint/no-unsafe-member-access
Do I need to change any eslint - typescript configuration in order to avoid this type of errors?

error log

  155:6 error Unsafe member access [curr] on an any value  @typescript-eslint/no-unsafe-member-access
  160:6 error Unsafe member access [curr] on an any value @typescript-eslint/no-unsafe-member-access
  162:6 error Unsafe assignment of an any value @typescript-eslint/no-unsafe-assignment
  162:18 error Unsafe member access [curr] on an any value @typescript-eslint/no-unsafe-member-access

code snippet

getDataToUpdate(): Partial<IUserModelForAdmin> {
        return Object.keys(this.userForm.value).reduce(
            (acc: Partial<IUserModelForAdmin>, curr: string) => {
                if (
                    curr === "company" &&
                    this.user[curr] &&
                    // Line 155
                    this.userForm.value[curr] !== this.user[curr]["_id"]
                )
                    acc[curr]["_id"] = this.user[curr]["_id"];
                if (
                    curr !== "company" &&
                    // Line 160
                    this.userForm.value[curr] !== this.user[curr]
                )
                // line 162 
                    acc[curr] = this.userForm.value[curr]; 
                return acc;
            },
            { _id: this.user._id }
        );
    }

eslintrc.json

{
  "root": true,
  "ignorePatterns": [
    "projects/**/*",
    "src/app/verify/**/*"
  ],
  "overrides": [
    {
      "files": [
        "*.ts"
      ],
      "parserOptions": {
        "project": [
          "tsconfig.json",
          "tsconfig.spec.json",
          "e2e/tsconfig.json"
        ],
        "createDefaultProgram": true
      },
      "extends": [
        "plugin:@angular-eslint/recommended",
        "plugin:@angular-eslint/template/process-inline-templates",
        "eslint:recommended",
        "plugin:@typescript-eslint/recommended",
        "plugin:@typescript-eslint/recommended-requiring-type-checking",
        "plugin:prettier/recommended"
      ],
      "rules": {
        "@angular-eslint/component-selector": [
          "error",
          {
            "prefix": "app",
            "style": "kebab-case",
            "type": "element"
          }
        ],
        "@angular-eslint/directive-selector": [
          "error",
          {
            "prefix": "app",
            "style": "camelCase",
            "type": "attribute"
          }
        ]
      }
    },
    {
      "files": [
        "*.html"
      ],
      "extends": [
        "plugin:@angular-eslint/template/recommended",
        "plugin:prettier/recommended"
      ],
      "rules": {}
    }
  ]
}

Pranav Sarda • Jul 4 '21

great article. I did something similar to my angular12 projetct. But i don't think plugin:@typescript-eslint is required anymore. angular-eslint alone works nicely for me since there is no tslint in angular 12 anyways

nelisbijl • Jan 18 '21

Great article. However...

"plugin:@angular-eslint/template/process-inline-templates"
seems to extract an inline template and feed it to the html linter
The prettier extension for *.html ("plugin:prettier/recommended") produces errors regarding the code formatting. The indicated error position is wrong and you won't be able to resolve this anyhow inside your inline template.

Either use external templates or stop using the process-inline-templates extension. It does not seem to kill all linting as I still noticed a warning for a missing closing tag. What exactly you do loose, I don't know.

This issue seems related:
github.com/angular-eslint/angular-...

Giovanni Sarciotto • Jan 21 '21

Yeah, I don't use inline templates so I didn't notice anything related to that, I will link this issue in the article. Thanks for the head up

John Tsombakos • Mar 17 '21

Unless I miss something, it looks like this change removes the TSlint requirement of semi-colons on the end of lines? And mis-aligned statements (whitespace)? Is there a way to get this back?

Giovanni Sarciotto • Mar 17 '21

This config enforces semi-colons at the end of lines and should fix alignment with Prettier. Did you run the eslint command or are trying to see in your editor? In the latter case, install the eslint extension to allow for the editor to lint when you save etc

John Tsombakos • Mar 18 '21

I didn’t install the prettier part (I don’t like it’s default settings and some I can’t configure). I have the eslint extension in VSCode but it does not show an error if I don’t have a semi. Before I made the changes you suggest for the “recommended” settings, it does show a message for missing semi’s. Once I made the changes, that setting is not there. I had to copy the rule from the “all” rules into my eslint config to get it to work. I also could not get it to mark mis-aligned lines (though formatting the document fixes that)

Giovanni Sarciotto • Mar 18 '21

Fair enough, maybe eslint-angular is disabling these rules since I know that at least the semi one is enabled by @typescript-eslint/recommended, will check it out later. Glad you could figure it out tho!

John Tsombakos • Mar 18 '21 • Edited

As far as I can see, looking through the rules, semi is not enabled by @typescript-eslint/recommended

rules: {
        '@typescript-eslint/adjacent-overload-signatures': 'error',
        '@typescript-eslint/ban-ts-comment': 'error',
        '@typescript-eslint/ban-types': 'error',
        '@typescript-eslint/explicit-module-boundary-types': 'warn',
        'no-array-constructor': 'off',
        '@typescript-eslint/no-array-constructor': 'error',
        'no-empty-function': 'off',
        '@typescript-eslint/no-empty-function': 'error',
        '@typescript-eslint/no-empty-interface': 'error',
        '@typescript-eslint/no-explicit-any': 'warn',
        '@typescript-eslint/no-extra-non-null-assertion': 'error',
        'no-extra-semi': 'off',
        '@typescript-eslint/no-extra-semi': 'error',
        '@typescript-eslint/no-inferrable-types': 'error',
        '@typescript-eslint/no-misused-new': 'error',
        '@typescript-eslint/no-namespace': 'error',
        '@typescript-eslint/no-non-null-asserted-optional-chain': 'error',
        '@typescript-eslint/no-non-null-assertion': 'warn',
        '@typescript-eslint/no-this-alias': 'error',
        'no-unused-vars': 'off',
        '@typescript-eslint/no-unused-vars': 'warn',
        '@typescript-eslint/no-var-requires': 'error',
        '@typescript-eslint/prefer-as-const': 'error',
        '@typescript-eslint/prefer-namespace-keyword': 'error',
        '@typescript-eslint/triple-slash-reference': 'error',
    },

which extends:

           rules: {
                'constructor-super': 'off',
                'getter-return': 'off',
                'no-const-assign': 'off',
                'no-dupe-args': 'off',
                'no-dupe-class-members': 'off',
                'no-dupe-keys': 'off',
                'no-func-assign': 'off',
                'no-import-assign': 'off',
                'no-new-symbol': 'off',
                'no-obj-calls': 'off',
                'no-redeclare': 'off',
                'no-setter-return': 'off',
                'no-this-before-super': 'off',
                'no-undef': 'off',
                'no-unreachable': 'off',
                'no-unsafe-negation': 'off',
                'no-var': 'error',
                'prefer-const': 'error',
                'prefer-rest-params': 'error',
                'prefer-spread': 'error',
                'valid-typeof': 'off', // ts(2367)
            },

the no-extra-semi rule just warns if there is more than one semi-colon (;;)

John Tsombakos • Mar 18 '21

This is what I had to add to my eslintrc.json to get the behavior I wanted:

"@typescript-eslint/member-delimiter-style": [
"error",
{
"multiline": {
"delimiter": "semi",
"requireLast": true
},
"singleline": {
"delimiter": "semi",
"requireLast": false
}
}
],
"quotes": "off",
"@typescript-eslint/quotes": [
"error",
"single",
{
"allowTemplateLiterals": true
}
],
"@typescript-eslint/semi": [
"error",
"always"
],

(copied from ./node_modules/@angular-eslint/eslint-plugin/dist/configs/ng-cli-compat--formatting-add-on.json)

Shiran Pasternak • Feb 5 '21

Is it possible to run this migration without ng? I have an existing Angular project without ng. Retrofitting an ng workspace seems like a science project.

Giovanni Sarciotto • Feb 6 '21

Automatically I dont think so because of the schematics. You can however do the migration full manual, see the repo

George Pagotelis • Nov 11 '21

Agree with the other person about .scss requires a link!

SCSS is difficult to find ESLINT that works in Angular. For example:
a {
@include flexbox(row)
height: 100%;
padding: 20px;
border-radius: 3px;
}

The above should be picked up in linting (missing semicolon on flexbox) but ESLINT doesn't.

If I open the file vscode-prettier or eslint IS picking it up.

I have tried (npmjs.com/package/eslint-plugin-cs...) but doesn't appear to trigger:
"overrides": [
{
// TODO: this isn't triggering on flexbox semicolon errors
"files": "*.scss",
"plugins": ["css-modules"],
"extends": ["plugin:css-modules/recommended"],
"rules": {
"css-modules/no-unused-class": [2, { "camelCase": true }],
"css-modules/no-undef-class": [2, { "camelCase": true }]
}
},

Ryan • Feb 18 '21

Very beginner friendly explanation ! Got me started. Thanks.

Bogac Guven • Feb 14 '21 • Edited

Thanks for putting this together.

Remi Kristelijn • Mar 11 '21

Very good article also that you keep improving it. It may be worth noting that the status of having it integrated with Angular is available here: github.com/angular/angular-cli/iss...

pkhand0 • Jan 28 '22 • Edited

Hi Giovanni!

Thanks for the wonderful article. Actually i tried all the above steps but not getting error in VSS code . But when running ng lint seeing bunch of error.

Can you suggest what may be issue

This is the error i am seeing in ESLint COnsole
doesn't export a CLIEngine. You need at least eslint@1.0.0

Julien BONNET • Feb 4 '21

Thanks for this, it was interesting. But but i don't understand a thing : what is the advantage using Prettier when every options are present in ESlint ??

Giovanni Sarciotto • Feb 4 '21

Yes, ESLint has a lot of styling options, however I prefer to use Prettier for 2 reasons:

ESLint is a linter, therefore its main job is to analyze code to find errors, potential bugs and code structure (not style, i.e big functions/classes) not conforming to some standard. Prettier is a formatter, therefore its only job is to format the code. I prefer this logic separation. If you have extremely customized linting rules, it can be hard to find the styles rules if they are in the same logic unit (in the .eslintrc), you can workaround this by using a separate .eslintrc file just for your style rules but I don't like it.
The main reason though is because Prettier is opinionated and have some pretty strong defaults, you don't actually need to configure Prettier if you don't want to and it will work just fine.

Julien BONNET • Feb 5 '21

hmm ... i understand. Thank you

singhshubham97 • Feb 3 '21

I have two questions:
1)The Html plugins mentioned here (those prettier ones) are giving parse errors.
2)Do we have other plugins for using ESLINT for HTML templates in angular

Giovanni Sarciotto • Feb 3 '21

1) What does the error says?

2) There are pure HTML plugins for eslint, however I dont think they would play nice with the features of angular (template binding, etc)

singhshubham97 • Feb 3 '21 • Edited

The parse error in index.html
dev-to-uploads.s3.amazonaws.com/i/...

Giovanni Sarciotto • Feb 4 '21

Alright, I managed to solve the problem in my machine. It seems like prettier isn't able to decide which parser to use for some reason. Add the following in your .prettierrc:

"overrides": [
        {
            "files": "*.component.html",
            "options": {
                "parser": "angular"
            }
        },
        {
            "files": "*.html",
            "options": {
                "parser": "html"
            }
        }
    ]