feat(FN-4948): complete Step 4 — classify and drop misrouted foreign commits

Fusion-Task-Id: FN-4948
Fusion-Task-Lineage: dc622643-4c3e-4217-9219-a6a6e5424427

packages/engine/src/__tests__/branch-conflicts-misrouted-foreign.test.ts

@@ -0,0 +1,126 @@
+import { describe, expect, it } from "vitest";
+import { execSync } from "node:child_process";
+import { mkdtempSync, rmSync, writeFileSync, mkdirSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { classifyMisroutedForeignCommit } from "../branch-conflicts.js";
+
+function git(dir: string, cmd: string): string {
+  return execSync(cmd, { cwd: dir, stdio: "pipe" }).toString().trim();
+}
+
+describe("classifyMisroutedForeignCommit", () => {
+  it("classifies trailer-attributed .changeset-only commit as misrouted", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "fn-4948-misrouted-"));
+    try {
+      git(dir, "git init -b main");
+      git(dir, 'git config user.email "test@example.com"');
+      git(dir, 'git config user.name "Test"');
+      writeFileSync(join(dir, "README.md"), "init\n");
+      git(dir, "git add README.md && git commit -m 'init'");
+      mkdirSync(join(dir, ".changeset"), { recursive: true });
+      writeFileSync(join(dir, ".changeset", "fn-1234-fix.md"), "patch\n");
+      git(dir, "git add .changeset/fn-1234-fix.md");
+      git(dir, "git commit -m 'chore: changeset only' -m 'Fusion-Task-Id: FN-1234'");
+      const sha = git(dir, "git rev-parse HEAD");
+
+      const result = await classifyMisroutedForeignCommit({
+        repoDir: dir,
+        sha,
+        commitSubject: "chore: changeset only",
+        commitBody: "Fusion-Task-Id: FN-1234",
+        currentTaskId: "FN-8888",
+      });
+
+      expect(result.misrouted).toBe(true);
+      expect(result.foreignTaskId).toBe("FN-1234");
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
+  it("classifies subject-only task attribution and normalizes case", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "fn-4948-misrouted-subject-"));
+    try {
+      git(dir, "git init -b main");
+      git(dir, 'git config user.email "test@example.com"');
+      git(dir, 'git config user.name "Test"');
+      git(dir, "git commit --allow-empty -m init");
+      mkdirSync(join(dir, ".changeset"), { recursive: true });
+      writeFileSync(join(dir, ".changeset", "fn-7777-feature.md"), "minor\n");
+      git(dir, "git add .changeset/fn-7777-feature.md && git commit -m 'feat(fn-7777): add feature' ");
+      const sha = git(dir, "git rev-parse HEAD");
+
+      const result = await classifyMisroutedForeignCommit({
+        repoDir: dir,
+        sha,
+        commitSubject: "feat(fn-7777): add feature",
+        commitBody: "",
+        currentTaskId: "FN-0001",
+      });
+
+      expect(result.misrouted).toBe(true);
+      expect(result.foreignTaskId).toBe("FN-7777");
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
+  it("does not classify misrouted when shared paths are present", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "fn-4948-misrouted-shared-"));
+    try {
+      git(dir, "git init -b main");
+      git(dir, 'git config user.email "test@example.com"');
+      git(dir, 'git config user.name "Test"');
+      writeFileSync(join(dir, "README.md"), "init\n");
+      git(dir, "git add README.md && git commit -m 'init'");
+      mkdirSync(join(dir, ".changeset"), { recursive: true });
+      mkdirSync(join(dir, "packages", "engine", "src"), { recursive: true });
+      writeFileSync(join(dir, ".changeset", "fn-4321-fix.md"), "patch\n");
+      writeFileSync(join(dir, "packages", "engine", "src", "executor.ts"), "x\n");
+      git(dir, "git add .changeset/fn-4321-fix.md packages/engine/src/executor.ts");
+      git(dir, "git commit -m 'fix(FN-4321): mixed paths' -m 'Fusion-Task-Id: FN-4321'");
+      const sha = git(dir, "git rev-parse HEAD");
+
+      const result = await classifyMisroutedForeignCommit({
+        repoDir: dir,
+        sha,
+        commitSubject: "fix(FN-4321): mixed paths",
+        commitBody: "Fusion-Task-Id: FN-4321",
+        currentTaskId: "FN-1111",
+      });
+
+      expect(result.misrouted).toBe(false);
+      expect(result.foreignTaskId).toBe("FN-4321");
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
+  it("does not classify when attribution matches current task", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "fn-4948-misrouted-same-"));
+    try {
+      git(dir, "git init -b main");
+      git(dir, 'git config user.email "test@example.com"');
+      git(dir, 'git config user.name "Test"');
+      git(dir, "git commit --allow-empty -m init");
+      mkdirSync(join(dir, ".changeset"), { recursive: true });
+      writeFileSync(join(dir, ".changeset", "fn-9000-fix.md"), "patch\n");
+      git(dir, "git add .changeset/fn-9000-fix.md && git commit -m 'test(FN-9000): same task' ");
+      const sha = git(dir, "git rev-parse HEAD");
+
+      const result = await classifyMisroutedForeignCommit({
+        repoDir: dir,
+        sha,
+        commitSubject: "test(FN-9000): same task",
+        commitBody: "",
+        currentTaskId: "fn-9000",
+      });
+
+      expect(result.misrouted).toBe(false);
+      expect(result.foreignTaskId).toBeUndefined();
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+});