Error "Object is of type unknown" when using graphql-codegen in the Angular application

Question

I have this Angular application which enjoys graphql-codegen to generate model for the application through graphql end point.

the component includes an image tag inside a container:

<ng-container *ngFor="let blog of (blogPosts | async)?.blogPost  | paginate: config">
    <img class="image" *ngIf="blog.image.urls" src="http://localhost:5002{{blog.image.urls}}"
                        alt="Placeholder image">
</ng-container>

The compiler complains on both (blogPosts | async)?.blogPost and image part of the blog the former says:

Argument of type '({ __typename?: "BlogPost" | undefined; path: string; subtitle?: string | null | undefined; displayText?: string | null | undefined; owner: string; publishedUtc?: any; markdownBody?: { ...; } | ... 1 more ... | undefined; image?: { ...; } | ... 1 more ... | undefined; } | null)[] | null | undefined' is not assignable to parameter of type 'Collection<unknown>'

And the latter says:

Object is of type 'unknown'

The typescript part of the component includes a graphql query which is in the generated code by the graphql-codegen library:

import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';
import { Observable } from 'rxjs';
import { map, take} from 'rxjs/operators';
import { BlogPostsQuery, BlogPostsGQL } from '../graphql/graphql';


@Component({
  selector: 'app-blog',
  templateUrl: './blog.component.html',
  styleUrls: ['./blog.component.scss']
})
export class BlogComponent implements OnInit {
  public responsive: boolean = true;
  blogPosts!: Observable<BlogPostsQuery>;
  modalIsActive!: boolean;
  values!: string;
  
  
  public config = {
    itemsPerPage: 1,
    // tslint:disable-next-line: radix
    currentPage: parseInt(sessionStorage.getItem('blogPage') || '') || 0
  };

  constructor(
    private router: Router,
    private allBlogPostGQL: BlogPostsGQL
  ) {

  }

  ngOnInit() {

    this.blogPosts =  this.allBlogPostGQL
    .watch()
    .valueChanges
    .pipe(
      map(blogs =>  blogs.data
      ));

  }


  onPageChange(number: number) {
    sessionStorage.setItem('blogPage', JSON.stringify(number));
    this.config.currentPage = number;
    console.log('eeeee', number);

  }

  showMore(name: string) {
    this.router.navigate(['/blog', name]);
    console.log('aaaaaaaa', this.config.currentPage)
  }


}

As shown in the code above BlogPostsGQL is the source of data in the blog component and its code is as below:

import { gql } from 'apollo-angular';
import { Injectable } from '@angular/core';
import * as Apollo from 'apollo-angular';
export type Maybe<T> = T | null;
export type InputMaybe<T> = Maybe<T>;
export type Exact<T extends { [key: string]: unknown }> = { [K in keyof T]: T[K] };
export type MakeOptional<T, K extends keyof T> = Omit<T, K> & { [SubKey in K]?: Maybe<T[SubKey]> };
export type MakeMaybe<T, K extends keyof T> = Omit<T, K> & { [SubKey in K]: Maybe<T[SubKey]> };

export type BlogPostsQuery = { __typename?: 'Query', blogPost?: Array<{ __typename?: 'BlogPost', path: string, subtitle?: string | null, displayText?: string | null, owner: string, publishedUtc?: any | null, markdownBody?: { __typename?: 'MarkdownBodyPart', markdown?: string | null } | null, image?: { __typename?: 'MediaField', urls?: Array<string | null> | null } | null } | null> | null };

export type BlogPostsQueryVariables = Exact<{ [key: string]: never; }>;

    @Injectable({
        providedIn: 'root'
      })
      export class BlogPostsGQL extends Apollo.Query<BlogPostsQuery, BlogPostsQueryVariables> {
        document = BlogPostsDocument;
        
        constructor(apollo: Apollo.Apollo) {
          super(apollo);
        }
      }
    export const CurrentBlogDocument = gql`
        query currentBlog($urlPath: String) {
      blogPost(where: {path: $urlPath}) {
        path
        subtitle
        displayText
        owner
        publishedUtc
        image {
          urls
        }
        markdownBody {
          markdown
        }
      }
    }
        `;

The packages I use in this application are as below:

    "@apollo/client": "^3.0.0",
    "@graphql-codegen/cli": "^2.7.0",
    "@graphql-codegen/introspection": "^2.1.1",
    "@graphql-codegen/typescript": "^2.6.0",
    "@graphql-codegen/typescript-apollo-angular": "^3.4.13",
    "@graphql-codegen/typescript-operations": "^2.4.3",
    "apollo-angular": "^3.0.1",
    "graphql": "^16.5.0",

How can I get rid of these errors?

Thanks!

Yes, it works. But is it any way that Angular recognize them as a known type? — amin mohammadi
– amin mohammadi, Commented Jul 6, 2022 at 6:36

Vega · Accepted Answer · 2022-07-06 07:14:37Z

1

There is obvious type checking incoherence between the Blogposts type and re-affectation later in the code.

use

$any((blogPosts | async)...

to avoid type-checking error without correcting the type incoherence.

As for the legibility of $any, here is what is in the doc:

Use the $any() type-cast function in certain contexts to opt out of type-checking for a part of the expression

answered Jul 6, 2022 at 7:14

Vega

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