Let task agents create and manage subtasks

web/src/task.ts

@@ -155,16 +155,21 @@ function taskHead(rerender: () => void): Head {
       const target = state.projects.find((p) => p.id === task.project_id)?.default_branch ?? "the default branch";
       const busy = sess?.state === "running";
       const held = task.merge_queued_at !== undefined;
+      const intoParent = task.merging_into_parent;
       const merge = h(
         "button",
         {
           class: "merge-button",
-          disabled: busy || held || unmerged?.taskId !== task.id || !unmerged.has,
-          title: held
-            ? "Waiting for the merge in progress in this project to finish"
-            : `The agent merges ${target} in, then byre squashes into one commit on ${target} and pushes it to origin; held while another task in the project is merging (⌘S)`,
+          disabled: busy || held || intoParent || unmerged?.taskId !== task.id || !unmerged.has,
+          title: intoParent
+            ? "Waiting for the parent task's agent to merge this subtask"
+            : held
+              ? "Waiting for the merge in progress in this project to finish"
+              : task.parent_task_id !== undefined
+                ? `Merge this subtask into its parent task's branch, or into ${target} (⌘S)`
+                : `The agent merges ${target} in, then byre squashes into one commit on ${target} and pushes it to origin; held while another task in the project is merging (⌘S)`,
         },
-        held ? "Merge held" : "Merge",
+        intoParent ? "Merging into parent" : held ? "Merge held" : "Merge",
       );
       merge.onclick = () => confirmMerge(task.id);
       const mergeIn = h("button", { disabled: busy, title: `Ask the agent to bring ${target} into this branch and resolve any conflicts` }, `Sync from ${target}`);
@@ -1068,30 +1073,28 @@ function renderEvent(ev: ByreEvent, ctx: Ctx): HTMLElement | null {
     }
 
     case "task.created": {
-      if (typeof p["forked_from"] !== "string") {
-        return null;
+      if (typeof p["forked_from"] === "string") {
+        return h(
+          "div",
+          { class: "note" },
+          `${ev.actor} forked this task from `,
+          taskLink(p["forked_from"]),
+          ` at snapshot #${String(p["forked_at"])}; its agent continues that task's conversation as it stood there `,
+          when,
+        );
       }
-      const src = findTask(p["forked_from"]);
-      const title = src?.title ?? p["forked_from"];
-      const link =
-        src?.status === "active"
-          ? h(
-              "a",
-              {
-                href: `#/task/${src.id}`,
-                class: "task-link",
-                style: taskStyle(src.id),
-                onclick: (e: MouseEvent) => {
-                  e.preventDefault();
-                  focusTask(src.id);
-                },
-              },
-              title,
-            )
-          : title;
-      return h("div", { class: "note" }, `${ev.actor} forked this task from `, link, ` at snapshot #${String(p["forked_at"])}; its agent continues that task's conversation as it stood there `, when);
+      if (typeof p["parent_task_id"] === "string") {
+        return h("div", { class: "note" }, "subtask of ", taskLink(p["parent_task_id"]), ", created by its agent ", when);
+      }
+      return null;
     }
 
+    case "task.parent_merge_started":
+      return h("div", { class: "note" }, `${ev.actor} asked `, taskLink(String(p["parent_task_id"])), "'s agent to merge this subtask into its branch ", when);
+
+    case "task.parent_merge_stopped":
+      return h("div", { class: "note error" }, "the merge into the parent task didn't start ", when);
+
     case "task.merge_title":
       return h("div", { class: "note" }, `${ev.actor} set the merge commit title to "${String(p["merge_title"])}" `, when);
 
@@ -1113,6 +1116,9 @@ function renderEvent(ev: ByreEvent, ctx: Ctx): HTMLElement | null {
     }
 
     case "task.merged":
+      if (typeof p["parent_task_id"] === "string") {
+        return h("div", { class: "note" }, `${ev.actor} merged the task into `, taskLink(p["parent_task_id"]), `, now at ${String(p["commit"]).slice(0, 7)} `, when);
+      }
       return h(
         "div",
         { class: "note" },
@@ -1133,6 +1139,26 @@ function renderEvent(ev: ByreEvent, ctx: Ctx): HTMLElement | null {
   return null;
 }
 
+function taskLink(id: string): Node {
+  const task = findTask(id);
+  if (task?.status !== "active") {
+    return document.createTextNode(task?.title ?? id);
+  }
+  return h(
+    "a",
+    {
+      href: `#/task/${task.id}`,
+      class: "task-link",
+      style: taskStyle(task.id),
+      onclick: (e: MouseEvent) => {
+        e.preventDefault();
+        focusTask(task.id);
+      },
+    },
+    task.title,
+  );
+}
+
 function messageImages(ids: unknown): HTMLElement | null {
   if (!Array.isArray(ids) || ids.length === 0) {
     return null;
@@ -1161,7 +1187,12 @@ export async function confirmMerge(taskId: string): Promise<void> {
     void showAlert("Merge already held behind another merge in this project");
     return;
   }
+  if (task.merging_into_parent) {
+    void showAlert("Already waiting for the parent task's agent to merge this subtask");
+    return;
+  }
   const target = state.projects.find((p) => p.id === task.project_id)?.default_branch ?? "the default branch";
+  const parent = task.parent_task_id !== undefined ? findTask(task.parent_task_id) : undefined;
   let coAuthors;
   try {
     const [unmerged, people] = await Promise.all([
@@ -1196,11 +1227,36 @@ export async function confirmMerge(taskId: string): Promise<void> {
     field.select();
   };
   const warnings = h("ul", { class: "merge-warnings" });
-  const question: Node[] = [h("p", { class: "merge-into" }, `Merge into ${target} as:`), row, warnings];
+  const into = h("p", { class: "merge-into" }, `Merge into ${target} as:`);
   const co = coAuthorsSummary(coAuthors);
-  if (co) {
-    question.push(co);
+  const toMain: Node[] = co ? [into, row, co] : [into, row];
+  let toParent = false;
+  const question: Node[] = [];
+  if (parent?.status === "active") {
+    toParent = true;
+    const option = (value: boolean, label: string, hint: string) => {
+      const radio = h("input", { type: "radio", name: "merge-target", checked: value === toParent });
+      radio.onchange = () => {
+        toParent = value;
+        for (const n of toMain) {
+          (n as HTMLElement).hidden = toParent;
+        }
+      };
+      return h("label", { class: "merge-target" }, radio, h("span", {}, label, h("span", { class: "merge-target-hint" }, hint)));
+    };
+    question.push(
+      h(
+        "div",
+        { class: "merge-targets" },
+        option(true, `Into ${parent.title}`, "Its agent merges this subtask's branch into the parent's branch; the subtask closes once it has."),
+        option(false, `Into ${target}`, "Squashed into one commit on the default branch and pushed, like any task."),
+      ),
+    );
+    for (const n of toMain) {
+      (n as HTMLElement).hidden = true;
+    }
   }
+  question.push(...toMain.slice(0, 2), warnings, ...toMain.slice(2));
   const leave = (go: () => void) => {
     mergeDrafts.set(taskId, input?.value ?? title);
     warnings.closest("dialog")?.close("cancel");
@@ -1210,7 +1266,8 @@ export async function confirmMerge(taskId: string): Promise<void> {
   await watch.ready;
   try {
     await confirmThen(question, "Merge", false, document.querySelector(".merge-button"), async () => {
-      await post("/api/tasks/{taskId}/merge", { path: { taskId }, body: { merge_title: input?.value ?? title } });
+      const body = toParent ? { target: "parent" as const } : { merge_title: input?.value ?? title };
+      await post("/api/tasks/{taskId}/merge", { path: { taskId }, body });
     });
   } finally {
     watch.dispose();