[Improvement/Web] Define undefined in PowerSyncCredentials

[guillempuche]

Proposition

Modify expiresAt type in PowerSyncCredentials https://github.com/powersync-ja/powersync-js/blob/66412323c27a54d8623bba17c5e54832f5b60063/packages/common/src/client/connection/PowerSyncCredentials.ts#L1-L6 to

export interface PowerSyncCredentials {
  endpoint: string;
  token: string;
  expiresAt?: Date | undefined;
}

Problem

In fetchCredentials of PowerSyncBackendConnector like here

powersync-js/demos/react-supabase-todolist/src/library/powersync/SupabaseConnector.ts

Lines 99 to 103 in 6641232

	return {
	endpoint: this.config.powersyncUrl,
	token: session.access_token ?? '',
	expiresAt: session.expires_at ? new Date(session.expires_at * 1000) : undefined
	};

I'm using a restrictive Tsconfig, exactOptionalPropertyTypes. And I'm also using satisfies to be safer:

    return {
      endpoint: this.config.powersyncUrl,
      token: session.access_token ?? '',
      expiresAt: session.expires_at ? new Date(session.expires_at * 1000) : undefined
    } satisfies PowerSyncCredentials; // <-- Compile error, more belo

I get this compile error.

Type '{ endpoint: string; token: string; expiresAt: Date | undefined; }' does not satisfy the expected type 'PowerSyncCredentials'.
  Types of property 'expiresAt' are incompatible.
    Type 'Date | undefined' is not assignable to type 'Date'.
      Type 'undefined' is not assignable to type 'Date'.ts(1360)

Provisional Solution

const credentials: PowerSyncCredentials = {
	endpoint: config.powerSyncUrl,
	token: session.value.access_token ?? '',
}

if (session.value.expires_at !== undefined) {
	credentials.expiresAt = new Date(
		session.value.expires_at * 1000,
	)
}

return credentials satisfies PowerSyncCredentials

Suggestion

In all your tsconfig files, start using exactOptionalPropertyTypes for safer code.