gstack/browse/test/server-sanitize-surrogates....

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import { describe, test, expect } from 'bun:test';
import * as fs from 'fs';
import * as path from 'path';
// The sanitizer is module-private in server.ts. Rather than refactor it to a
// separate module just for testing, we extract its source via a regex slice and
// eval it in a fresh function scope. Keeps the production layout untouched.
const SERVER_PATH = path.resolve(import.meta.dir, '..', 'src', 'server.ts');
const SERVER_SRC = fs.readFileSync(SERVER_PATH, 'utf-8');
const fnMatch = SERVER_SRC.match(
/function sanitizeLoneSurrogates\(str: string\): string \{[\s\S]*?\n\}/
);
if (!fnMatch) throw new Error('Could not locate sanitizeLoneSurrogates in server.ts');
// Strip TS annotations so eval works under plain JS.
const jsSrc = fnMatch[0].replace('(str: string): string', '(str)');
const sanitizeLoneSurrogates = new Function(`${jsSrc}\nreturn sanitizeLoneSurrogates;`)() as (
s: string,
) => string;
describe('sanitizeLoneSurrogates — unit cases', () => {
test('passthrough ASCII', () => {
expect(sanitizeLoneSurrogates('hello')).toBe('hello');
});
test('passthrough empty string', () => {
expect(sanitizeLoneSurrogates('')).toBe('');
});
test('preserves valid surrogate pair (U+1F389 🎉)', () => {
expect(sanitizeLoneSurrogates('hi 🎉')).toBe('hi 🎉');
});
test('replaces lone high surrogate mid-string', () => {
expect(sanitizeLoneSurrogates('a\uD800b')).toBe('a<>b');
});
test('replaces lone low surrogate mid-string', () => {
expect(sanitizeLoneSurrogates('a\uDC00b')).toBe('a<>b');
});
test('replaces trailing lone high at end of string', () => {
expect(sanitizeLoneSurrogates('a\uD800')).toBe('a<>');
});
test('replaces leading lone low at start of string', () => {
expect(sanitizeLoneSurrogates('\uDC00b')).toBe('<27>b');
});
test('replaces two adjacent lone highs', () => {
expect(sanitizeLoneSurrogates('\uD800\uD800')).toBe('<27><>');
});
test('replaces two adjacent lone lows', () => {
expect(sanitizeLoneSurrogates('\uDC00\uDC00')).toBe('<27><>');
});
test('preserves valid pair followed by lone low', () => {
// 𐀀 = U+10000 = 𐀀, then a separate lone low.
const input = '𐀀\uDC00';
const output = sanitizeLoneSurrogates(input);
// Valid pair intact, trailing lone low replaced.
expect(output).toBe('𐀀<>');
});
test('preserves valid pair preceded by lone low', () => {
const input = '\uDC00𐀀';
const output = sanitizeLoneSurrogates(input);
expect(output).toBe('<27>𐀀');
});
});
describe('sanitizeLoneSurrogates — bug-repro (D5)', () => {
// Pin the regression intent: a future refactor that drops sanitization
// must fail this test even if happy-path tests still pass.
test('unsanitized lone surrogate causes UTF-8 encode to substitute, sanitized version is stable', () => {
const badPayload = 'page content\uD800more content';
// Buffer.from(str, 'utf-8') silently substitutes invalid sequences with
// EF BF BD (U+FFFD). Round-trip is therefore lossy for lone surrogates.
const roundTrippedRaw = Buffer.from(badPayload, 'utf-8').toString('utf-8');
expect(roundTrippedRaw).not.toBe(badPayload); // proves the bug exists pre-sanitize
// After sanitization the round-trip is stable.
const sanitized = sanitizeLoneSurrogates(badPayload);
const roundTrippedSanitized = Buffer.from(sanitized, 'utf-8').toString('utf-8');
expect(roundTrippedSanitized).toBe(sanitized);
});
test('JSON.parse(JSON.stringify(...)) round-trip is stable after sanitization', () => {
// Anthropic's API path wraps the response body in a tool_result JSON
// object. JSON.stringify CAN encode a lone surrogate (escapes it), but
// some downstream consumers reject the resulting body.
const badPayload = 'before\uD800after';
const sanitized = sanitizeLoneSurrogates(badPayload);
const wrapped = JSON.stringify({ content: sanitized });
const reparsed = JSON.parse(wrapped) as { content: string };
// .toBe(sanitized) already proves the surrogate was replaced; the
// additional explicit check below documents the specific code points.
expect(reparsed.content).toBe(sanitized);
expect(reparsed.content.charCodeAt(6)).toBe(0xfffd); // <20> not \uD800
});
});
describe('sanitizeLoneSurrogates — wiring invariants', () => {
test('server.ts wraps every command result through handleCommandInternal', () => {
// The architectural choice is to wrap once at handleCommandInternal so
// both single-command HTTP and the batch loop inherit. If a future
// refactor moves sanitization back to handleCommand only, this test
// fails by detecting the missing wrapper.
expect(SERVER_SRC).toContain('async function handleCommandInternalImpl(');
expect(SERVER_SRC).toContain('result: sanitizeLoneSurrogates(cr.result)');
});
test('SSE activity feed sanitizes outbound frames via sanitizeReplacer', () => {
// Replacer must run DURING stringify; post-stringify regex is ineffective
// because JSON.stringify converts \uD800 → "\\ud800" before our regex sees it.
expect(SERVER_SRC).toContain('JSON.stringify(entry, sanitizeReplacer)');
});
test('SSE inspector stream sanitizes outbound frames via sanitizeReplacer', () => {
expect(SERVER_SRC).toContain('JSON.stringify(event, sanitizeReplacer)');
});
test('sanitizeReplacer is a function defined in server.ts', () => {
expect(SERVER_SRC).toContain('function sanitizeReplacer(');
});
});