Data Sources

A data source provides definitions to the resolver. Every call to showwhat() or resolve() needs one — passed via options.data.

At its simplest, a data source implements the DefinitionReader interface:

interface DefinitionReader {
  get(key: string): Promise<Definition | null>;
  getAll(): Promise<Definitions>;
  load?(): Promise<void>;
  close?(): Promise<void>;
  ping?(): Promise<void>;
}

Built-in

Source	Description
MemoryData	In-memory — parse YAML or JSON, no I/O after setup

Custom

Need to load definitions from a database, API, or filesystem? Implement DefinitionReader — see the Extending Data Sources guide.

For read-write sources, implement both DefinitionReader and DefinitionWriter to get a DefinitionData. Use isWritable() to narrow at runtime:

import { isWritable } from "showwhat";

if (isWritable(data)) {
  await data.put("my_flag", definition);
}