test(FN-5103): address review gaps in landed-files coverage

Fusion-Task-Id: FN-5103
Fusion-Task-Lineage: e4e4d9ba-4884-4feb-b18b-a30e799c3fb1

packages/engine/src/__tests__/merger-landed-files-capture.test.ts

@@ -103,6 +103,42 @@ describe("FN-4646 aiMergeTask landedFiles capture", () => {
     expect(detailsUpdate?.[1].modifiedFiles).toBeUndefined();
   });
 
+  it("sums shortstat across multiple own commits on rebase", async () => {
+    const store = makeStore({ directMergeCommitStrategy: "always-rebase" });
+    vi.spyOn(attributionModule, "filterFilesToOwnTaskCommits").mockResolvedValue({
+      files: ["a.ts", "b.ts", "c.ts"],
+      foreignCommits: [],
+      ownCommitCount: 3,
+      ownCommitShas: ["ownsha1", "ownsha2", "ownsha3"],
+      rawDiffFileCount: 3,
+    });
+    mockedExecSync.mockImplementation((cmd: any) => {
+      const s = String(cmd);
+      if (s.includes("rev-parse --verify")) return Buffer.from("abc123");
+      if (s === "git rev-parse HEAD" || s.startsWith("git rev-parse HEAD ")) return "rebasesha123";
+      if (s.includes("git log")) return "- feat: summary";
+      if (s.includes("merge-base")) return Buffer.from("abc123");
+      if (s.includes("rev-parse \"abc123\"")) return "rebasebase123";
+      if (s.includes("rev-list --reverse \"rebasebase123..fusion/FN-4646\"")) return "";
+      if (s.includes("status --porcelain")) return "";
+      if (s.includes("rev-parse --git-path CHERRY_PICK_HEAD")) return ".git/CHERRY_PICK_HEAD";
+      if (s.includes("rev-parse --git-path sequencer")) return ".git/sequencer";
+      if (s.includes("show --shortstat --format= \"ownsha1\"")) return "1 file changed, 3 insertions(+), 1 deletion(-)";
+      if (s.includes("show --shortstat --format= \"ownsha2\"")) return "2 files changed, 5 insertions(+), 2 deletions(-)";
+      if (s.includes("show --shortstat --format= \"ownsha3\"")) return "1 file changed, 2 insertions(+)";
+      if (s.includes("branch -d") || s.includes("branch -D") || s.includes("worktree remove")) return Buffer.from("");
+      return Buffer.from("");
+    });
+
+    await mergerModule.aiMergeTask(store, "/tmp/root", "FN-4646");
+    const detailsUpdate = (store.updateTask as any).mock.calls.find((call: any[]) => call[1]?.mergeDetails?.commitSha === "rebasesha123");
+    expect(detailsUpdate?.[1].mergeDetails.landedFiles).toEqual(["a.ts", "b.ts", "c.ts"]);
+    expect(detailsUpdate?.[1].mergeDetails.filesChanged).toBe(3);
+    expect(detailsUpdate?.[1].mergeDetails.insertions).toBe(10);
+    expect(detailsUpdate?.[1].mergeDetails.deletions).toBe(3);
+    expect(detailsUpdate?.[1].mergeDetails.landedFilesAttributionRestricted).toBe(true);
+  });
+
   it("falls back to legacy rebase capture when attribution fails", async () => {
     const store = makeStore({ directMergeCommitStrategy: "always-rebase" });
     vi.spyOn(attributionModule, "filterFilesToOwnTaskCommits").mockRejectedValue(new BranchAttributionError("boom"));

packages/engine/src/__tests__/reliability-interactions/landed-files-attribution.test.ts

@@ -3,7 +3,7 @@ import { mkdtemp, rm, writeFile } from "node:fs/promises";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
 import { execSync, spawnSync } from "node:child_process";
-import { BranchAttributionError, filterFilesToOwnTaskCommits } from "../../branch-attribution.js";
+import { filterFilesToOwnTaskCommits } from "../../branch-attribution.js";
 
 const hasGit = spawnSync("git", ["--version"], { stdio: "pipe" }).status === 0;
 const describeIfGit = hasGit ? describe : describe.skip;
@@ -82,8 +82,26 @@ describeIfGit("FN-5103 reliability interaction: landed-files attribution", () =>
     expect(attribution.foreignCommits.length).toBe(1);
   });
 
-  it("supports attribution failure fallback signal path", async () => {
-    const error = new BranchAttributionError("synthetic attribution failure");
-    expect(error.message).toContain("synthetic attribution failure");
+  it("surfaces attribution failure when git reads fail", async () => {
+    const { repoDir, baseSha } = await initRepo("fn-5103-ri-");
+    dirs.push(repoDir);
+    const taskId = "FN-5103";
+
+    git(repoDir, `git checkout -b fusion/${taskId.toLowerCase()}`);
+    await commitFile(repoDir, "task-owned.ts", "owned\n", "feat(FN-5103): own", taskId);
+
+    await expect(
+      filterFilesToOwnTaskCommits({
+        worktreePath: repoDir,
+        baseRef: baseSha,
+        taskId,
+        execAsyncImpl: async () => {
+          throw new Error("forced attribution failure");
+        },
+      }),
+    ).rejects.toMatchObject({
+      name: "BranchAttributionError",
+      message: expect.stringContaining("forced attribution failure"),
+    });
   });
 });