fix(review): resolve jj default target from trunk

packages/server/jj.test.ts

@@ -41,23 +41,24 @@ describe("jj diff args", () => {
 });
 
 describe("jj compare targets", () => {
-  test("prefers available default bookmarks before falling back to trunk", () => {
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: ["main@origin"],
-    })).toBe("main@origin");
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: ["main@git"],
-    })).toBe("main@git");
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: [],
-    })).toBe("main");
-    expect(selectDefaultJjCompareTarget({
-      local: ["release"],
-      remote: ["production@git"],
-    })).toBe("trunk()");
+  test("resolves default target from jj trunk bookmarks", async () => {
+    await expect(selectDefaultJjCompareTarget({
+      async runJj() {
+        return { stdout: '[{"name":"main"},{"name":"main","remote":"origin"}]\n', stderr: "", exitCode: 0 };
+      },
+    })).resolves.toBe("main@origin");
+
+    await expect(selectDefaultJjCompareTarget({
+      async runJj() {
+        return { stdout: '[{"name":"main"}]\n', stderr: "", exitCode: 0 };
+      },
+    })).resolves.toBe("main");
+
+    await expect(selectDefaultJjCompareTarget({
+      async runJj() {
+        return { stdout: "[]\n", stderr: "", exitCode: 0 };
+      },
+    })).resolves.toBe("trunk()");
   });
 
   test("treats bookmarks and revsets correctly in line-of-work revsets", () => {

packages/shared/jj-core.test.ts

@@ -84,23 +84,38 @@ describe("jj diff args", () => {
 });
 
 describe("jj compare targets", () => {
-  test("prefers available default bookmarks before falling back to trunk", () => {
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: ["main@origin"],
-    })).toBe("main@origin");
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: ["main@git"],
-    })).toBe("main@git");
-    expect(selectDefaultJjCompareTarget({
-      local: ["main"],
-      remote: [],
-    })).toBe("main");
-    expect(selectDefaultJjCompareTarget({
-      local: ["release"],
-      remote: ["production@git"],
-    })).toBe("trunk()");
+  test("resolves default target from jj trunk remote bookmarks", async () => {
+    const calls: string[][] = [];
+    const runtime: ReviewJjRuntime = {
+      async runJj(args) {
+        calls.push(args);
+        return { stdout: '[{"name":"main"},{"name":"main","remote":"origin"}]\n', stderr: "", exitCode: 0 };
+      },
+    };
+
+    await expect(selectDefaultJjCompareTarget(runtime, "/repo"))
+      .resolves.toBe("main@origin");
+    expect(calls).toEqual([[
+      "log",
+      "--no-graph",
+      "-r",
+      "trunk()",
+      "-T",
+      "json(bookmarks)",
+    ]]);
+  });
+
+  test("falls back to local bookmark then trunk revset", async () => {
+    const runtimeFor = (stdout: string): ReviewJjRuntime => ({
+      async runJj() {
+        return { stdout, stderr: "", exitCode: 0 };
+      },
+    });
+
+    await expect(selectDefaultJjCompareTarget(runtimeFor('[{"name":"develop"}]\n')))
+      .resolves.toBe("develop");
+    await expect(selectDefaultJjCompareTarget(runtimeFor('[]\n')))
+      .resolves.toBe("trunk()");
   });
 
   test("treats bookmarks and revsets correctly in line-of-work revsets", () => {

packages/shared/jj-core.ts

@@ -38,7 +38,7 @@ export async function getJjContext(
 ): Promise<GitContext> {
   const root = await detectJjWorkspace(runtime, cwd);
   const targets = await listJjCompareTargets(runtime, root ?? cwd);
-  const defaultTarget = selectDefaultJjCompareTarget(targets);
+  const defaultTarget = await selectDefaultJjCompareTarget(runtime, root ?? cwd);
   const contextCwd = root ?? cwd;
 
   return {
@@ -178,23 +178,55 @@ export function getJjDiffArgs(
   }
 }
 
-export function selectDefaultJjCompareTarget(targets: { local: string[]; remote: string[] }): string {
-  const preferredNames = ["main", "develop", "master", "trunk"];
-  for (const name of preferredNames) {
-    const preferredRemote = [
-      `${name}@origin`,
-      `${name}@upstream`,
-      `${name}@git`,
-      ...targets.remote.filter((target) => target.startsWith(`${name}@`)).sort(),
-    ].find((target) => targets.remote.includes(target));
-    if (preferredRemote) return preferredRemote;
-
-    if (targets.local.includes(name)) return name;
-  }
+export async function selectDefaultJjCompareTarget(
+  runtime: ReviewJjRuntime,
+  cwd?: string,
+): Promise<string> {
+  const result = await runtime.runJj([
+    "log",
+    "--no-graph",
+    "-r",
+    JJ_TRUNK_REVSET,
+    "-T",
+    "json(bookmarks)",
+  ], { cwd });
+  if (result.exitCode !== 0) return JJ_TRUNK_REVSET;
+
+  return parseJjResolvedBookmarks(result.stdout)[0] ?? JJ_TRUNK_REVSET;
+}
+
+function parseJjResolvedBookmarks(value: string): string[] {
+  try {
+    const parsed = JSON.parse(value);
+    if (!Array.isArray(parsed)) return [];
+
+    const local: string[] = [];
+    const remote: string[] = [];
 
-  // `trunk()` honors JJ's repository default bookmark/remote and user aliases
-  // when the repository has no obvious default bookmark to compare against.
-  return JJ_TRUNK_REVSET;
+    for (const bookmark of parsed) {
+      if (typeof bookmark === "string") {
+        local.push(bookmark);
+        continue;
+      }
+
+      if (!bookmark || typeof bookmark !== "object") continue;
+
+      const name = typeof bookmark.name === "string" ? bookmark.name : null;
+      if (!name) continue;
+
+      const remoteName = typeof bookmark.remote === "string" ? bookmark.remote : null;
+      if (remoteName) {
+        remote.push(`${name}@${remoteName}`);
+        continue;
+      }
+
+      local.push(name);
+    }
+
+    return [...remote, ...local];
+  } catch {
+    return [];
+  }
 }
 
 async function listJjCompareTargets(