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fix(FN-2855): scope task diff base to baseCommitSha when branch is null

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When a dependency task merges and its branch is deleted, self-healing nulls
the dependent task's baseBranch. Both resolveDiffBase (dashboard) and
resolveTaskDiffBaseRef (merger) defaulted to "main" in that case, widening
the diff range to merge-base(HEAD, main) and surfacing unrelated history —
e.g. FN-2855 reported 108 changed files instead of 16. Skip the merge-base
step when baseBranch is unset and a baseCommitSha is recorded; fall back to
"main" only for legacy tasks lacking both hints.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
gsxdsm
2026-04-28 07:44:04 -07:00
parent 0f40d96e50
commit 49e8da1961
3 changed files with 59 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
packages/dashboard/src/__tests__/routes-file-diffs.test.ts
View File

@@ -232,6 +232,31 @@ describe("resolveDiffBase", () => {
expect(diffBase).toBe("origin-merge-base");
});
it("uses baseCommitSha directly when baseBranch is null (upstream branch deleted)", async () => {
// Regression: FN-2855 showed 108 changed files because the dashboard fell
// back to merge-base(HEAD, main) after self-healing nulled the original
// baseBranch. With a valid baseCommitSha recorded, we must skip the
// "main" default and use the SHA so the diff range stays task-scoped.
const runGit = vi.fn(async (args: string[]) => {
if (args.join(" ") === "merge-base --is-ancestor task-base-789 HEAD") return "";
throw new Error(`Unexpected command: ${args.join(" ")}`);
});
const diffBase = await resolveDiffBase(
{ baseCommitSha: "task-base-789" },
"/tmp/worktree",
"HEAD",
runGit,
);
expect(diffBase).toBe("task-base-789");
expect(runGit).not.toHaveBeenCalledWith(
["merge-base", "HEAD", "main"],
"/tmp/worktree",
5000,
);
});
it("falls back to HEAD~1 when merge-base is unavailable and baseCommitSha is stale", async () => {
const runGit = vi.fn(async (args: string[]) => {
if (args.join(" ") === "merge-base HEAD main") {

19
packages/dashboard/src/routes/resolve-diff-base.ts
View File

@@ -60,17 +60,24 @@ export async function resolveDiffBase(
headRef = "HEAD",
runGit: (args: string[], cwd?: string, timeout?: number) => Promise<string> = runGitCommand,
): Promise<string | undefined> {
const baseBranch = task.baseBranch ?? "main";
// When baseBranch was nulled (e.g., upstream dep merged and its branch was
// deleted) but a task-scoped baseCommitSha is still recorded, skip the
// merge-base step so we don't widen the diff range to merge-base(HEAD, main)
// and surface unrelated history. Only fall back to "main" when neither hint
// is available (legacy tasks).
const baseBranch = task.baseBranch?.trim() || (task.baseCommitSha ? undefined : "main");
let mergeBase: string | undefined;
try {
if (baseBranch) {
try {
mergeBase = (await runGit(["merge-base", headRef, baseBranch], cwd, 5000)).trim() || undefined;
try {
mergeBase = (await runGit(["merge-base", headRef, baseBranch], cwd, 5000)).trim() || undefined;
} catch {
mergeBase = (await runGit(["merge-base", headRef, `origin/${baseBranch}`], cwd, 5000)).trim() || undefined;
}
} catch {
mergeBase = (await runGit(["merge-base", headRef, `origin/${baseBranch}`], cwd, 5000)).trim() || undefined;
// base branch may no longer exist locally/remotely
}
} catch {
// base branch may no longer exist locally/remotely
}
// If merge-base equals headRef, the live merge-base would produce an empty

35
packages/engine/src/merger.ts
View File

@@ -1287,26 +1287,33 @@ export async function resolveTaskDiffBaseRef({
baseBranch,
baseCommitSha,
}: DiffBaseResolutionInput): Promise<string | undefined> {
const resolvedBaseBranch = baseBranch?.trim() || "main";
// When baseBranch was nulled (e.g., upstream dep merged and its branch was
// deleted) but a task-scoped baseCommitSha is still recorded, skip the
// merge-base step so we don't widen the diff range to merge-base(HEAD, main)
// and surface unrelated history. Only fall back to "main" when neither hint
// is available (legacy tasks).
const resolvedBaseBranch = baseBranch?.trim() || (baseCommitSha ? undefined : "main");
const quotedHeadRef = quoteArg(headRef);
let mergeBase: string | undefined;
try {
if (resolvedBaseBranch) {
try {
const { stdout } = await execAsync(`git merge-base ${quotedHeadRef} ${quoteArg(resolvedBaseBranch)}`, {
cwd,
encoding: "utf-8",
});
mergeBase = stdout.trim() || undefined;
try {
const { stdout } = await execAsync(`git merge-base ${quotedHeadRef} ${quoteArg(resolvedBaseBranch)}`, {
cwd,
encoding: "utf-8",
});
mergeBase = stdout.trim() || undefined;
} catch {
const { stdout } = await execAsync(`git merge-base ${quotedHeadRef} ${quoteArg(`origin/${resolvedBaseBranch}`)}`, {
cwd,
encoding: "utf-8",
});
mergeBase = stdout.trim() || undefined;
}
} catch {
const { stdout } = await execAsync(`git merge-base ${quotedHeadRef} ${quoteArg(`origin/${resolvedBaseBranch}`)}`, {
cwd,
encoding: "utf-8",
});
mergeBase = stdout.trim() || undefined;
// Base branch may not exist locally/remotely.
}
} catch {
// Base branch may not exist locally/remotely.
}
// Same guard as dashboard routes: when merge-base === headRef, the range