[Bug]: Commit silently skips a resolved merge when its tree matches HEAD #35749

import { mkdtempSync, mkdirSync, writeFileSync, rmSync, existsSync } from "node:fs";
import { join, resolve } from "node:path";
import { tmpdir, release } from "node:os";
import { createRequire } from "node:module";
import { pathToFileURL } from "node:url";
import { execFileSync } from "node:child_process";

const checkout = resolve(process.argv[2] ?? ".");
const scratch = mkdtempSync(join(tmpdir(), "t3-merge-repro-"));
for (const name of Object.keys(process.env)) {
  if (name.startsWith("GIT_")) delete process.env[name];
}
for (const [name, folder] of [["HOME", "home"], ["TMPDIR", "tmp"], ["T3CODE_HOME", "state"]]) {
  process.env[name] = join(scratch, folder);
  mkdirSync(process.env[name]!, { recursive: true });
}
process.env.GIT_CONFIG_NOSYSTEM = "1";
process.env.GIT_CONFIG_GLOBAL = "/dev/null";
const req = createRequire(join(checkout, "apps/server/package.json"));
const load = (name: string) => import(pathToFileURL(req.resolve(name)).href);
const source = (name: string) => import(pathToFileURL(join(checkout, name)).href);
const git = (cwd: string, ...args: string[]) => execFileSync("git", args, {
  cwd, encoding: "utf8", stdio: ["ignore", "pipe", "pipe"],
}).trim();
let status = 2;
try {
  console.log(git(checkout, "--version"));
  console.log(`node ${process.versions.node}; ${process.platform} ${release()} ${process.arch}`);
  console.log(`checkout ${git(checkout, "rev-parse", "HEAD")}`);
  const [Effect, Layer, NodeServices, NodeCrypto, Config, Core, Manager, Driver, Providers, Text, Registry, Setup, Settings, Projection, Projects] = await Promise.all([
    load("effect/Effect"), load("effect/Layer"), load("@effect/platform-node/NodeServices"), load("@effect/platform-node/NodeCrypto"),
    source("apps/server/src/config.ts"), source("apps/server/src/vcs/GitVcsDriverCore.ts"), source("apps/server/src/git/GitManager.ts"), source("apps/server/src/vcs/GitVcsDriver.ts"),
    source("apps/server/src/sourceControl/SourceControlProviderRegistry.ts"), source("apps/server/src/textGeneration/TextGeneration.ts"), source("apps/server/src/provider/ProviderRegistry.ts"),
    source("apps/server/src/project/ProjectSetupScriptRunner.ts"), source("apps/server/src/serverSettings.ts"), source("apps/server/src/orchestration-v2/ProjectionStore.ts"), source("apps/server/src/orchestration-v2/ProjectStore.ts"),
  ]);
  function fixture(name: string, resolution: string) {
    const cwd = join(scratch, name);
    mkdirSync(cwd);
    git(cwd, "init", "-q", "-b", "main");
    git(cwd, "config", "user.name", "Test");
    git(cwd, "config", "user.email", "test@example.invalid");
    writeFileSync(join(cwd, "note.txt"), "base\n");
    git(cwd, "add", "."); git(cwd, "commit", "-qm", "Base");
    git(cwd, "switch", "-qc", "topic");
    writeFileSync(join(cwd, "note.txt"), "topic\n"); git(cwd, "commit", "-qam", "Topic");
    git(cwd, "switch", "-q", "main");
    writeFileSync(join(cwd, "note.txt"), "main\n"); git(cwd, "commit", "-qam", "Main");
    try { git(cwd, "merge", "topic"); } catch { /* Expected conflict. */ }
    if (!existsSync(join(cwd, ".git/MERGE_HEAD"))) throw new Error("Fixture has no merge");
    writeFileSync(join(cwd, "note.txt"), resolution);
    return cwd;
  }
  async function commit(cwd: string) {
    return Effect.runPromise(Effect.scoped(Effect.gen(function* () {
      const driver = yield* Core.makeGitVcsDriverCore();
      const dependencies = Layer.mergeAll(
        Layer.succeed(Driver.GitVcsDriver, driver),
        Layer.mock(Providers.SourceControlProviderRegistry)({ resolve: () => Effect.fail(new Error("No host in fixture")) }),
        Layer.mock(Text.TextGeneration)({}), Layer.mock(Registry.ProviderRegistry)({ getProviders: Effect.succeed([]) }),
        Layer.mock(Setup.ProjectSetupScriptRunner)({}), Settings.layerTest(),
        Layer.mock(Projection.ProjectionStoreV2)({}), Layer.mock(Projects.ProjectStoreV2)({}),
      );
      const manager = yield* Manager.make.pipe(Effect.provide(dependencies));
      return yield* manager.runStackedAction({ cwd, action: "commit", commitMessage: "Complete merge" });
    })).pipe(Effect.provide(Config.layerTest(cwd, join(scratch, "server"))), Effect.provide(Layer.mergeAll(NodeServices.layer, NodeCrypto.layer))));
  }
  const parents = (cwd: string) => git(cwd, "show", "-s", "--format=%P", "HEAD").split(" ").length;
  const control = fixture("changed-resolution", "main\ntopic\n");
  const controlResult = await commit(control);
  if (controlResult.commit.status !== "created" || parents(control) !== 2 || existsSync(join(control, ".git/MERGE_HEAD"))) throw new Error("Changed-resolution control failed");
  console.log("control: created merge with two parents");
  const cwd = fixture("unchanged-resolution", "main\n");
  console.log(`before: ${git(cwd, "status", "--porcelain")}`);
  const result = await commit(cwd);
  console.log(`action: ${result.commit.status}; toast: ${result.toast.title}`);
  const pending = existsSync(join(cwd, ".git/MERGE_HEAD"));
  console.log(`merge still pending: ${pending}`);
  if (result.commit.status === "created" && parents(cwd) === 2 && !pending) {
    status = 0;
  } else if (result.commit.status === "skipped_no_changes" && pending) {
    git(cwd, "add", "-A"); git(cwd, "commit", "-qm", "Complete merge");
    if (parents(cwd) !== 2) throw new Error("Git control failed");
    console.log("Git control: created merge with two parents");
    status = 1;
  }
} catch (error) {
  const message = String(error).replaceAll(scratch, "<scratch>").replaceAll(checkout, "<checkout>");
  console.log(`setup or control failed: ${message}`);
} finally {
  rmSync(scratch, { recursive: true, force: true });
}
console.log(status === 0 ? "RESULT: expected behavior" : status === 1 ? "RESULT: defect reproduced" : "RESULT: inconclusive");
process.exit(status);