Angular ngx-filesaver compilation error: "Property '"method"' is incompatible with index signature."

Question

I just installed the ngx-filesaver using:

npm install file-saver ngx-filesaver

Then in app.module.ts added:

import { FileSaverModule } from 'ngx-filesaver';
...
@NgModule({
  imports: [
    ...
    FileSaverModule
  ],
  ...
})

Then I have this compilation error:

Error: node_modules/ngx-filesaver/src/filesaver.directive.d.ts:30:94 - error TS2344: Type '{ method: { alias: "method"; required: false; }; http: { alias: "http"; required: false; }; query: { alias: "query"; required: false; }; header: { alias: "header"; required: false; }; url: { alias: "url"; required: true; }; fileName: { ...; }; fsOptions: { ...; }; }' does not satisfy the constraint '{ [key: string]: string; }'. Property '"method"' is incompatible with index signature. Type '{ alias: "method"; required: false; }' is not assignable to type 'string'.

30 static ɵdir: i0.ɵɵDirectiveDeclaration<FileSaverDirective, "[fileSaver]", ["fileSaver"], { "method": { "alias": "method"; "required": false; }; "http": { "alias": "http"; "required": false; }; "query": { "alias": "query"; "required": false; }; "header": { "alias": "header"; "required": false; }; "url": { "alias": "url"; "required": true; }; "fileName": { "alias": "fileName"; "required": false; }; "fsOptions": { "alias": "fsOptions"; "required": false; }; }, { "success": "success"; "error": "error"; }, never, never, true, never>;

What am I missing here, and what is the remedy?

Answer 1

It appears that npm, which I was using, is not able to resolve the dependency of this module. While using yarn, this issue does not show up.

Answer 2

The error message is pointing out that the method property of this object is incompatible with the index signature that expects all keys to be of type string.

To resolve this error, you should review the declaration file (filesaver.directive.d.ts) for ngx-filesaver and make sure that the properties defined within the object match the expected types according to the index signature. In this case, it seems like the method property is expected to be a string, but the object definition has { alias: "method"; required: false; }, which doesn't match the expected type.

You need to correct the file located at '/node_modules/ngx-filesaver/src/filesaver.directive.d.ts'

import { ElementRef, EventEmitter, NgZone, OnDestroy, OnInit } from '@angular/core';
import { HttpClient, HttpResponse } from '@angular/common/http';
import { Observable } from 'rxjs';
import { FileSaverOptions } from 'file-saver';
import { FileSaverService } from './filesaver.service';
import * as i0 from "@angular/core";

export declare class FileSaverDirective implements OnInit, OnDestroy {
    private ngZone;
    private el;
    private fss;
    private httpClient;
    method: string; // Initialize method as a string
    http?: Observable<HttpResponse<Blob>>; // Adjust the type if needed
    query: any ; // Initialize query as a string or the appropriate type
    header: any ; // Initialize header as a string or the appropriate type
    url: string ; // Initialize url as a string
    fileName?: string; // Keep fileName as optional
    fsOptions?: FileSaverOptions; // Keep fsOptions as optional
    readonly success: EventEmitter<HttpResponse<Blob>>;
    readonly error: EventEmitter<any>;
    private readonly destroy$;
    
    constructor(ngZone: NgZone, el: ElementRef<HTMLButtonElement>, fss: FileSaverService, httpClient: HttpClient);
    
    ngOnInit(): void;
    ngOnDestroy(): void;
    private getName;
    setDisabled(status: boolean): void;
    private setupClickListener;
    private emitIfHasObservers;

    static ɵfac: i0.ɵɵFactoryDeclaration<FileSaverDirective, never>;
    static ɵdir: i0.ɵɵDirectiveDeclaration<FileSaverDirective, "[fileSaver]", ["fileSaver"], {
        "method": "method";
        "http": "http";
        "query": "query";
        "header": "header";
        "url": "url";
        "fileName": "fileName";
        "fsOptions": "fsOptions";
    }, {
        "success": "success";
        "error": "error";
    }, never, never, true, never>;
}