[BUG]: addSource with an empty samples array succeeds and renders boilerplate for a nonexistent type

[schani]

Issue Type

quicktype-core API (input validation).

Context (Environment, Version, Language)

Input Format: JSON
Output Language: any (tested with TypeScript)

CLI, npm, or app.quicktype.io: npm (quicktype-core)
Version: 25.0.0-pre1 (also reproduces on 24.0.2)

Description

Calling addSource with samples: [] neither throws nor produces an error later — quicktype() happily renders output (168 lines of TypeScript converter boilerplate in my test) for a type that has no evidence at all:

const { quicktype, InputData, jsonInputForTargetLanguage } = require("quicktype-core");

const jsonInput = jsonInputForTargetLanguage("typescript");
await jsonInput.addSource({ name: "X", samples: [] });   // no samples!
const inputData = new InputData();
inputData.addInput(jsonInput);
const result = await quicktype({ inputData, lang: "typescript" });
console.log(result.lines.length); // 168 — full converter scaffolding, no meaningful type

An empty samples array is almost certainly a caller bug (e.g. a glob that matched nothing, or a filtered list that came up empty), and the current behavior masks it.

Expected Behavior

addSource({ name, samples: [] }) should throw a clear error, the same way malformed JSON in a sample already does (Syntax error in input JSON X: ...).

🤖 Filed with Claude Code