任务说明：实验页"任务"面板、布置作业时可改写；先写项目 3 任务 2、项目 6 任务 2 两份

- 每个实验一份 task.md（任务目标、控件名表格、实现步骤、和书上不一样的地方、在平台上怎么试）
- 工具栏"评价项"改成"任务"：上面是任务说明，下面是评价项和自己检查；不遮挡页面，第一次打开实验时自动打开
- 自己写的 Markdown 子集渲染，先转义全部 HTML（老师可以改写说明）
- 作业保存任务说明（新列 task），以前布置的作业用实验现在的说明
- 测试：任务说明表格里的控件名都在示例的 Designer.cs 里
- 修改作业时实验下拉框显示标题而不是编号

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/app.ts

@@ -25,7 +25,7 @@ import { getReview, gradebook, manualScore, saveReview, studentDetail, submissio
 import type { GradingQueue } from './grading/queue'
 import { config } from './config'
 import { deleteUserDatabases, restoreExperimentDatabases, userDatabaseDir } from './databases'
-import { listSamples, loadChecks, loadSample } from './samples'
+import { listSamples, loadChecks, loadSample, loadTask } from './samples'
 import { SqlError, sqlService } from './sql-service'
 import { serveStatic } from './static'
 import { deleteWork, getWork, saveWork, validFiles, validScreenshots } from './works'
@@ -112,6 +112,9 @@ export function createApp(db: Database, gradingQueue: GradingQueue, aiQueue: AiQ
     return c.json(parseChecks(checks).map((check) => check.title))
   })
 
+  /** 实验的任务说明（Markdown）；没有时 task 为 null */
+  app.get('/api/samples/:id/task', async (c) => c.json({ task: await loadTask(c.req.param('id')) }))
+
   app.post('/api/samples/:id/selfcheck', async (c) => {
     const sampleId = c.req.param('id')
     const yaml = (await listSamples()).some((s) => s.id === sampleId) ? await loadChecks(sampleId) : null
@@ -202,11 +205,18 @@ export function createApp(db: Database, gradingQueue: GradingQueue, aiQueue: AiQ
     )
   })
 
-  app.get('/api/assignments/:id', (c) => {
+  app.get('/api/assignments/:id', async (c) => {
     const assignment = visibleAssignment(c)
     if (!assignment) return c.json({ message: '作业不存在' }, 404)
     const userId = c.get('user').id
-    return c.json({ assignment, template: assignmentTemplate(db, assignment.id), latest: latestSubmission(db, assignment.id, userId), review: getReview(db, assignment.id, userId) })
+    // 以前布置的作业没有保存任务说明，用实验现在的说明
+    const task = assignment.task ?? (await loadTask(assignment.sampleId))
+    return c.json({
+      assignment: { ...assignment, task },
+      template: assignmentTemplate(db, assignment.id),
+      latest: latestSubmission(db, assignment.id, userId),
+      review: getReview(db, assignment.id, userId),
+    })
   })
 
   app.post('/api/assignments/:id/submit', async (c) => {
@@ -298,7 +308,7 @@ export function createApp(db: Database, gradingQueue: GradingQueue, aiQueue: AiQ
   )
 
   app.post('/api/teacher/assignments', async (c) => {
-    const a = await body<{ classId: number; sampleId: string; title: string; startMode: StartMode; template: unknown; scoring: Scoring; deadline: number | null }>(c)
+    const a = await body<{ classId: number; sampleId: string; title: string; startMode: StartMode; template: unknown; scoring: Scoring; deadline: number | null; task: string | null }>(c)
     if (!listClasses(db).some((cls) => cls.id === a.classId)) return c.json({ message: '班级不存在' }, 404)
     const checks = typeof a.sampleId === 'string' ? await loadChecks(a.sampleId) : null
     if (!checks) return c.json({ message: '这个实验还没有评分规则' }, 400)
@@ -313,13 +323,22 @@ export function createApp(db: Database, gradingQueue: GradingQueue, aiQueue: AiQ
       checks,
       scoring: a.scoring as Scoring,
       deadline: typeof a.deadline === 'number' ? a.deadline : null,
+      task: typeof a.task === 'string' ? a.task : null,
     })
     return 'error' in result ? c.json({ message: result.error }, 400) : c.json(result)
   })
 
   app.patch('/api/teacher/assignments/:id', async (c) => {
-    const a = await body<{ title: string; deadline: number | null; scoring: Scoring }>(c)
-    return reply(c, updateAssignment(db, id(c), { title: String(a.title ?? ''), deadline: typeof a.deadline === 'number' ? a.deadline : null, scoring: a.scoring as Scoring }))
+    const a = await body<{ title: string; deadline: number | null; scoring: Scoring; task: string | null }>(c)
+    return reply(
+      c,
+      updateAssignment(db, id(c), {
+        title: String(a.title ?? ''),
+        deadline: typeof a.deadline === 'number' ? a.deadline : null,
+        scoring: a.scoring as Scoring,
+        task: typeof a.task === 'string' ? a.task : null,
+      }),
+    )
   })
 
   app.delete('/api/teacher/assignments/:id', (c) => {

server/src/assignments.ts

@@ -15,10 +15,11 @@ interface AssignmentRow {
   scoring: string
   deadline: number | null
   created_at: number
+  task: string | null
 }
 
 const SELECT_ASSIGNMENT = `
-  SELECT a.id, a.class_id, c.name AS class_name, a.sample_id, a.title, a.start_mode, a.checks, a.scoring, a.deadline, a.created_at
+  SELECT a.id, a.class_id, c.name AS class_name, a.sample_id, a.title, a.start_mode, a.checks, a.scoring, a.deadline, a.created_at, a.task
   FROM assignments a JOIN classes c ON c.id = a.class_id`
 
 function toAssignment(row: AssignmentRow): Assignment {
@@ -33,6 +34,7 @@ function toAssignment(row: AssignmentRow): Assignment {
     createdAt: row.created_at,
     checkTitles: parseChecks(row.checks).map((c) => c.title),
     scoring: JSON.parse(row.scoring) as Scoring,
+    task: row.task,
   }
 }
 
@@ -76,32 +78,46 @@ export interface NewAssignment {
   checks: string
   scoring: Scoring
   deadline: number | null
+  /** 任务说明（Markdown），null 表示用实验的说明 */
+  task: string | null
 }
 
+/** 任务说明最长多少字 */
+export const MAX_TASK_LENGTH = 20_000
+
 export function createAssignment(db: Database, a: NewAssignment): { id: number } | { error: string } {
   if (!a.title.trim()) return { error: '作业名称不能为空' }
-  const error = scoringError(a.scoring, parseChecks(a.checks).length)
+  const error = scoringError(a.scoring, parseChecks(a.checks).length) ?? taskError(a.task)
   if (error) return { error }
   const result = db
     .query(
-      `INSERT INTO assignments (class_id, sample_id, title, start_mode, template, checks, scoring, deadline, created_at)
-       VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+      `INSERT INTO assignments (class_id, sample_id, title, start_mode, template, checks, scoring, deadline, created_at, task)
+       VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
     )
-    .run(a.classId, a.sampleId, a.title.trim(), a.startMode, JSON.stringify(a.template), a.checks, JSON.stringify(a.scoring), a.deadline, Date.now())
+    .run(a.classId, a.sampleId, a.title.trim(), a.startMode, JSON.stringify(a.template), a.checks, JSON.stringify(a.scoring), a.deadline, Date.now(), a.task)
   return { id: Number(result.lastInsertRowid) }
 }
 
-/** 修改名称、截止时间、分值（起点工程和评分规则布置后不能改） */
-export function updateAssignment(db: Database, id: number, changes: { title: string; deadline: number | null; scoring: Scoring }): { error?: string } {
+function taskError(task: string | null) {
+  return task !== null && task.length > MAX_TASK_LENGTH ? `任务说明不能超过 ${MAX_TASK_LENGTH} 字` : null
+}
+
+/** 修改名称、截止时间、分值、任务说明（起点工程和评分规则布置后不能改） */
+export function updateAssignment(
+  db: Database,
+  id: number,
+  changes: { title: string; deadline: number | null; scoring: Scoring; task: string | null },
+): { error?: string } {
   const checks = assignmentChecks(db, id)
   if (!checks) return { error: '作业不存在' }
   if (!changes.title.trim()) return { error: '作业名称不能为空' }
-  const error = scoringError(changes.scoring, checks.length)
+  const error = scoringError(changes.scoring, checks.length) ?? taskError(changes.task)
   if (error) return { error }
-  db.query('UPDATE assignments SET title = ?, deadline = ?, scoring = ? WHERE id = ?').run(
+  db.query('UPDATE assignments SET title = ?, deadline = ?, scoring = ?, task = ? WHERE id = ?').run(
     changes.title.trim(),
     changes.deadline,
     JSON.stringify(changes.scoring),
+    changes.task,
     id,
   )
   // 分值变了，已评分的提交重新算分

server/src/db.ts

@@ -101,6 +101,10 @@ const MIGRATIONS = [
   ALTER TABLE submissions ADD COLUMN screenshots TEXT;
   ALTER TABLE submissions ADD COLUMN ai_review TEXT;
   `,
+  // 作业的任务说明（Markdown）；以前布置的作业为 NULL，用实验现在的说明
+  `
+  ALTER TABLE assignments ADD COLUMN task TEXT;
+  `,
 ]
 
 /** 打开数据库并执行未执行过的迁移。path 为 ":memory:" 时用内存数据库（测试用） */

server/src/samples.ts

@@ -33,6 +33,14 @@ export async function loadSample(id: string): Promise<SourceFile[] | null> {
   return files.length > 0 ? files.sort((a, b) => a.path.localeCompare(b.path)) : null
 }
 
+/** 示例的任务说明（task.md 原文，Markdown）；没有说明返回 null */
+export async function loadTask(id: string): Promise<string | null> {
+  const path = resolve(SAMPLES_DIR, id, 'task.md')
+  if (!path.startsWith(`${SAMPLES_DIR}/`)) return null
+  const file = Bun.file(path)
+  return (await file.exists()) ? file.text() : null
+}
+
 /** 示例的评分规则（checks.yaml 原文）；没有规则返回 null */
 export async function loadChecks(id: string): Promise<string | null> {
   const path = resolve(SAMPLES_DIR, id, 'checks.yaml')