ersatztv/web/vite-plugins/trackedSourceFiles.test.ts

import { describe, expect, it } from 'vitest';
import {
  TRACKED_SOURCE_FILES_ID,
  type FileExists,
  type GitRunner,
  resolveTrackedSourceFiles,
  trackedSourceFilesPlugin
} from './trackedSourceFiles';

/**
 * The population this plugin supplies is what `web/src/api/pageSizeCallSites.guard.test.ts` asserts
 * completeness over (#819), so the plugin is verification code and carries its own proof rather
 * than inheriting the guard's — `testing.verification-code-needs-its-own-proof`.
 */

const RESOLVED_ID = `\0${TRACKED_SOURCE_FILES_ID}`;
const allPresent: FileExists = () => true;

/** `ls-files` answers the tracked query; `--others` answers the untracked one. */
function runnerReturning(tracked: string, others = ''): { run: GitRunner; calls: (readonly string[])[] } {
  const calls: (readonly string[])[] = [];
  return {
    calls,
    run: (args) => {
      calls.push(args);
      return args.includes('--others') ? others : tracked;
    }
  };
}

/** Drives `load()` through the plugin's own `configResolved`, as Vite does. */
function loadedBy(plugin: ReturnType<typeof trackedSourceFilesPlugin>, root = '/repo/web'): string | undefined {
  const configResolved = plugin.configResolved as (config: { root: string }) => void;
  configResolved.call(plugin, { root });
  return (plugin.load as (id: string) => string | undefined).call(plugin, RESOLVED_ID);
}

describe('resolveTrackedSourceFiles (#819)', () => {
  it("splits git's NUL-separated output into paths, dropping the trailing empty field", () => {
    const { run } = runnerReturning('src/a.ts\0src/b.tsx\0');
    expect(resolveTrackedSourceFiles('/repo/web', run, allPresent).tracked).toEqual(['src/a.ts', 'src/b.tsx']);
  });

  it('reports UNTRACKED paths from a SEPARATE query, so a narrowed index cannot hide behind them', () => {
    // #819 round 6: every other comparison in the guard is between two things derived from
    // `tracked`, so a filter applied to `tracked` cancels out of all of them. `others` comes from a
    // different git query and is what makes that filter visible — narrowing `tracked` adds nothing
    // here, so the walk finds a file in neither list.
    const { run } = runnerReturning('src/a.ts\0', 'src/scratch.ts\0src/notes.ts\0');
    const result = resolveTrackedSourceFiles('/repo/web', run, allPresent);

    expect(result.tracked).toEqual(['src/a.ts']);
    expect(result.others).toEqual(['src/scratch.ts', 'src/notes.ts']);
  });

  it('THROWS when the untracked query fails, rather than degrading to an empty set', () => {
    // An empty `others` would make a narrowed index look like a real hole AND, worse, is the
    // direction that could be used to silence the cross-check.
    const run: GitRunner = (args) => {
      if (args.includes('--others')) throw new Error('git exploded');
      return 'src/a.ts\0';
    };
    expect(() => resolveTrackedSourceFiles('/repo/web', run, allPresent)).toThrow(
      /could not enumerate untracked files/
    );
  });

  it('asks git for NUL-separated output, scoped to src/, in the given root', () => {
    // Pins `-z` specifically. Without it git applies `core.quotePath` to a non-ASCII name and
    // returns a C-quoted string that no longer equals the path Vite reports, which would drop that
    // file from the population silently — the guard would then under-enumerate while looking green.
    const { run, calls } = runnerReturning('src/a.ts\0');
    resolveTrackedSourceFiles('/repo/web', run, allPresent);
    expect(calls).toEqual([
      ['-C', '/repo/web', 'ls-files', '-z', '--', 'src'],
      ['-C', '/repo/web', 'ls-files', '-z', '--others', '--', 'src']
    ]);
  });

  it('keeps a path containing spaces intact rather than splitting on whitespace', () => {
    const { run } = runnerReturning('src/screens/My Screen.tsx\0src/b.ts\0');
    expect(resolveTrackedSourceFiles('/repo/web', run, allPresent).tracked).toEqual([
      'src/screens/My Screen.tsx',
      'src/b.ts'
    ]);
  });

  it('REPORTS tracked paths with no file on disk rather than dropping them', () => {
    // The consumer needs a mid-edit deletion (transient, tolerated) told apart from a tracked file
    // the walk cannot see (a real hole). Collapsing them is how a population silently shrinks.
    const { run } = runnerReturning('src/present.ts\0src/deleted.ts\0');
    const seen: string[] = [];
    const exists: FileExists = (path) => {
      seen.push(path);
      return !path.endsWith('deleted.ts');
    };

    const result = resolveTrackedSourceFiles('/repo/web', run, exists);

    expect(result.tracked).toEqual(['src/present.ts', 'src/deleted.ts']);
    expect(result.absentFromDisk).toEqual(['src/deleted.ts']);
    // Existence is checked against the ROOT-joined path, not the repo-relative one.
    expect(seen).toEqual(['/repo/web/src/present.ts', '/repo/web/src/deleted.ts']);
  });

  it('deduplicates a path git emits once per merge-conflict stage', () => {
    // `git ls-files` lists an unmerged path once per stage. Nothing downstream needs the repetition.
    const { run } = runnerReturning('src/a.ts\0src/a.ts\0src/b.ts\0');
    expect(resolveTrackedSourceFiles('/repo/web', run, allPresent).tracked).toEqual([
      'src/a.ts',
      'src/b.ts'
    ]);
  });

  it('THROWS when git fails, instead of degrading to an unfiltered walk', () => {
    // The failure this rejects is the fail-open one: answering "could not tell" with the very
    // population the index was brought in to replace is a permanent no-op that reports green.
    const boom: GitRunner = () => {
      throw new Error('not a git repository');
    };
    expect(() => resolveTrackedSourceFiles('/repo/web', boom, allPresent)).toThrow(/could not read the git index/);
  });

  it('THROWS when git reports zero tracked files (anti-vacuity at the source)', () => {
    const { run } = runnerReturning('');
    expect(() => resolveTrackedSourceFiles('/repo/web', run, allPresent)).toThrow(/ZERO tracked files/);
  });
});

describe('trackedSourceFilesPlugin (#819)', () => {
  it('resolves only its own virtual id', () => {
    const plugin = trackedSourceFilesPlugin(runnerReturning('src/a.ts\0').run, allPresent);
    const resolveId = plugin.resolveId as (id: string) => string | undefined;

    expect(resolveId.call(plugin, TRACKED_SOURCE_FILES_ID)).toBe(RESOLVED_ID);
    expect(resolveId.call(plugin, 'react')).toBeUndefined();
    expect(resolveId.call(plugin, './pageSizeScan')).toBeUndefined();
  });

  it('emits the tracked list and the absent set as a default-exported module', () => {
    const plugin = trackedSourceFilesPlugin(runnerReturning('src/a.ts\0src/b.tsx\0').run, allPresent);

    expect(loadedBy(plugin)).toBe(
      'export default {"tracked":["src/a.ts","src/b.tsx"],"absentFromDisk":[],"others":[]};\n'
    );
  });

  it('REFUSES rather than guessing when configResolved never ran', () => {
    // A wrong root is a silent wrong answer. Seeding it with `process.cwd()` would happen to work
    // in this repo's layout and quietly derive the population from the wrong tree elsewhere.
    const { run, calls } = runnerReturning('src/a.ts\0');
    const plugin = trackedSourceFilesPlugin(run, allPresent);
    const load = plugin.load as (id: string) => string | undefined;

    expect(() => load.call(plugin, RESOLVED_ID)).toThrow(/configResolved` hook never ran/);
    expect(calls).toHaveLength(0);
  });

  it('does NOT shell out to git unless the virtual module is actually loaded', () => {
    // Constructing the plugin, or loading anything else, must not run git — otherwise registering
    // it in vite.config.ts would break every build in a context without a repository.
    const { run, calls } = runnerReturning('src/a.ts\0');
    const plugin = trackedSourceFilesPlugin(run, allPresent);
    const configResolved = plugin.configResolved as (config: { root: string }) => void;
    const load = plugin.load as (id: string) => string | undefined;

    configResolved.call(plugin, { root: '/repo/web' });
    expect(calls).toHaveLength(0);
    expect(load.call(plugin, '\0some-other-virtual-module')).toBeUndefined();
    expect(calls).toHaveLength(0);

    load.call(plugin, RESOLVED_ID);
    // Two: the tracked query and the separate untracked one.
    expect(calls).toHaveLength(2);
  });
});