Error encountered in metadata generated for exported symbol when constructing an angular 6 library

Question

I'm getting the following error while performing 'ng build' from my library.

I'm using Angular 6 at the moment, but I believe this error is not version related.

/home/rafaelvicio/desenv/my-lib/arquitetura-web/projects/pf-siseg/src/lib/keycloak-service/keycloak.service.ts:13:1: Error encountered in metadata generated for exported symbol 'KeycloakService':
/home/rafaelvicio/desenv/my-lib/arquitetura-web/projects/pf-siseg/src/lib/keycloak-service/keycloak.service.ts:18:12: Metadata collected contains an error that will be reported at runtime: Only initialized variables and constants can be referenced because the value of this variable is needed by the template compiler.
{"__symbolic":"error","message":"Variable not initialized","line":17,"character":11} Error: /home/rafaelvicio/desenv/my-lib/arquitetura-web/projects/pf-siseg/src/lib/keycloak-service/keycloak.service.ts:13:1: Error encountered in metadata generated for exported symbol 'KeycloakService':
/home/rafaelvicio/desenv/my-lib/arquitetura-web/projects/pf-siseg/src/lib/keycloak-service/keycloak.service.ts:18:12: Metadata collected contains an error that will be reported at runtime: Only initialized variables and constants can be referenced because the value of this variable is needed by the template compiler.
{"__symbolic":"error","message":"Variable not initialized","line":17,"character":11} at /home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/metadata/collector.js:707:31 at Array.forEach () at validateMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/metadata/collector.js:695:46) at MetadataCollector.getMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/metadata/collector.js:550:21) at MetadataCache.getMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/transformers/metadata_cache.js:86:41) at Object.getSourceFileMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/transformers/compiler_host.js:112:56) at Object.readMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/transformers/metadata_reader.js:46:37) at TsCompilerAotCompilerTypeCheckHostAdapter.getMetadataFor (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler-cli/src/transformers/compiler_host.js:464:38) at StaticSymbolResolver.getModuleMetadata (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler/src/aot/static_symbol_resolver.js:480:49) at StaticSymbolResolver._createSymbolsOf (/home/rafaelvicio/desenv/my-lib/arquitetura-web/node_modules/@angular/compiler/src/aot/static_symbol_resolver.js:268:33)

keycloak.service.ts:

import { Injectable } from '@angular/core';
import { KeycloakLoginOptions } from './keycloak.d';

import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';

import * as Keycloak from './keycloak';

export type KeycloakClient = Keycloak.KeycloakInstance;
type InitOptions = Keycloak.KeycloakInitOptions;

@Injectable()
export class KeycloakService {

    constructor(private http: HttpClient) { }

    static keycloakAuth: KeycloakClient;

.... More code here

Answer 1

add // @dynamic before the class that declares static methods

Answer 2

I encountered this issue today in an util class providing static methods as helpers.

I solved it by replacing this with ObjectUtils (the class name itself), and it works.

Also as @NicolasThierion mentioned in his reply commented by @stack247, you could also try the following hack

// @dynamic
export class SomeClass {
    public static get() { return 'someValue'; } 
}

Answer 3

I'm using Angular V8 and had the same problem. Angular does not allow a static variable to not be initialized. The solution was to initialize with null to avoid errors.

@Injectable()
export class ExampleService {

    static URL: string = null;
...