代码编辑器：代码补全、悬停提示、参数提示、边写边检查

- 运行器新增 language-server 模式：常驻语言服务，和编译服务分开；用 Roslyn 的
  CompletionService、QuickInfoService（和 VS 的 IntelliSense 同一套引擎），参数提示用语义模型实现；
  每个浏览器标签页一份工程，只更新有变化的文件；去掉仿真类库的可空注解（string? → string）
- 编译和语言服务共用同一套编译选项和引用；检查结果带上禁止 API 的报错和中文提示
- 服务端 POST /api/language 转发请求（按用户区分会话，10 秒超时）
- 编辑器：补全（"." 触发，选中时取说明）、悬停、参数提示（"(" "," 触发）；停止输入 1 秒后检查整个工程，
  和"运行"时的编译结果以较新的为准
- 实测（2 核）：50 个标签页同时检查 1.2 秒内完成，同时补全 0.7 秒；内存约 260 MB

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

README.md

@@ -39,11 +39,12 @@ bun test/load.ts 100  # 压力测试：同时运行 100 个学生程序
 
 Docker Compose，HTTPS 由服务器上的 Nginx Proxy Manager 负责。推送到 GitHub 的 main 后，GitHub Actions 跑完测试，SSH 到服务器执行 `deploy/update.sh`：服务器从 git.xuyue.cc 拉代码、构建镜像、重启。详见 [deploy/README.md](deploy/README.md)。
 
-## 运行器的两种模式
+## 运行器的三种模式
 
 `Sim.Runner` 通过标准输入输出与 Bun 服务器交换 JSON 消息（每行一条）：
 
 - `compile-server`：常驻编译服务，全服务器共用一个。Roslyn 只加载一次，编译结果写回工程目录。
+- `language-server`：常驻语言服务，全服务器共用一个：代码补全、悬停提示、参数提示、边写边检查。
 - `run <工程目录>`：运行已编译的学生程序，每次运行一个进程，不加载编译器。
 
 ## 当前进度：第 0 阶段（技术验证）已跑通

docs/设计方案.md

@@ -170,7 +170,7 @@ IOT/
 | C# 运行时 | 仿真类库 | 自研：`System.Windows.Forms` 子集 + 教材设备类库 + `Font` 等少量 System.Drawing 类型 |
 | C# 运行时 | 数据库仿真 | 计划：仿冒 `System.Data.SqlClient`，底层 Microsoft.Data.Sqlite；T-SQL 用 ScriptDom 解析后转写 |
 | C# 运行时 | 图片编解码（如需） | 计划：SkiaSharp |
-| C# 运行时 | 代码补全 | 计划：Roslyn `CompletionService` |
+| C# 运行时 | 语言服务 | Roslyn `CompletionService`、`QuickInfoService`（和 VS 的 IntelliSense 同一套引擎），参数提示用语义模型自己实现；常驻进程 `language-server`，和编译服务分开 |
 | 工程 | 仓库 | Bun workspaces 单仓库 |
 | 工程 | 测试 | `bun test`（端到端、单元、压力测试）；计划：用教材参考工程做回归测试、Playwright |
 | 部署 | 服务器 | 一台 Linux 云服务器，2 核 8 GB |
@@ -275,6 +275,10 @@ flowchart TB
 - 2026-10-22：布置与提交作业：老师选实验、起点（界面已做好 / 空白工程，起点工程由设计器引擎从参考答案生成）、截止时间和每项分值（自动评分项 + 老师评分项）；布置时保存起点和评分规则的快照。学生在"我的作业"里打开作业，提交后排队评分（全站同时最多评 3 份、跑 6 个检查项），结果立即可见；截止后不能再交。老师看全班的提交情况和自动得分。
 - 2026-10-22：评阅与成绩：评阅页左边是全班学生（提交状态、得分、是否已评阅），右边是选中学生的代码（只读）、自动评分结果、规范提示（代码里用到却还是默认名字的控件、注释行数）和老师评分项打分、评语，可以"保存并看下一个"；"运行他的程序"在新标签页的实验页里打开学生的提交（可以操作实训台，改动不保存）。学生能看到老师的各项得分和评语。班级管理页加"成绩"标签页：学生 × 作业的总分（自动评分 + 老师评分），点分数进入评阅；单个作业和全班成绩都能导出 CSV（Excel 打开不乱码）。
 
+**其他改进**：
+
+- 2026-10-22：代码编辑器的语言功能：代码补全（输入 `btn_Open.` 列出按钮的属性、方法、事件，只列出平台仿真了的成员）、悬停提示、参数提示（`MessageBox.Show(` 列出重载，标出正在填的参数）、停止输入 1 秒后自动检查编译错误（提示和点"运行"时一样）。语言服务是一个常驻进程，每个浏览器标签页一份工程，只更新有变化的文件。实测（限制 2 核）：50 个标签页同时检查 1.2 秒内全部完成，同时补全 0.7 秒；内存约 260 MB。
+
 ## 技术风险与待确认事项
 
 最大的风险是仿真 WinForms 的覆盖面和交互流畅度；交互流畅度已在第 0 阶段验证。

runtime/Sim.Runner/LanguageServer.cs

@@ -0,0 +1,339 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.Encodings.Web;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.QuickInfo;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Sim.Runner;
+
+/// <summary>
+/// 常驻语言服务：给浏览器里的代码编辑器提供代码补全、悬停提示、参数提示和边写边检查的编译错误。
+/// 和 VS 的 IntelliSense 用同一套 Roslyn 引擎。从标准输入读取 {"id":…,"type":…,"session":…,"files":[…],"file":…,"line":…,"column":…}，
+/// 回复 {"id":…,…}。请求并行处理（同一个会话内按顺序），学生在不同标签页里互不等待。
+/// 每个浏览器标签页一个会话，保存一份工程；请求带上全部文件，只更新有变化的文件，Roslyn 能复用没变的部分。
+/// 和编译服务分开成两个进程：编译不会被补全请求拖慢，反之亦然。
+/// </summary>
+internal static class LanguageServer
+{
+    private static readonly JsonSerializerOptions JsonOptions = new() { Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping };
+    private static readonly object OutputLock = new();
+    private static readonly ConcurrentDictionary<string, Session> Sessions = new();
+    private const int MaxSessions = 300;
+    private const int MaxCompletionItems = 2000;
+
+    public static int Run()
+    {
+        using var input = new StreamReader(Console.OpenStandardInput(), new UTF8Encoding(false));
+        var output = new StreamWriter(Console.OpenStandardOutput(), new UTF8Encoding(false)) { AutoFlush = true };
+
+        WarmUp();
+        Write(output, new JsonObject { ["type"] = "ready" });
+
+        while (input.ReadLine() is { } line)
+        {
+            _ = Task.Run(() => HandleAsync(line, output));
+        }
+        return 0;
+    }
+
+    private static void Write(StreamWriter output, JsonObject message)
+    {
+        var text = message.ToJsonString(JsonOptions);
+        lock (OutputLock) output.WriteLine(text);
+    }
+
+    private static async Task HandleAsync(string line, StreamWriter output)
+    {
+        JsonNode? id = null;
+        JsonObject reply;
+        try
+        {
+            var request = JsonNode.Parse(line)!.AsObject();
+            id = request["id"]?.DeepClone();
+            reply = await DispatchAsync(request);
+        }
+        catch (Exception ex)
+        {
+            reply = new JsonObject { ["type"] = "error", ["message"] = ex.Message };
+        }
+        reply["id"] = id;
+        Write(output, reply);
+    }
+
+    private static async Task<JsonObject> DispatchAsync(JsonObject request)
+    {
+        var session = GetSession((string?)request["session"] ?? "default");
+        await session.Lock.WaitAsync();
+        try
+        {
+            session.LastUsed = DateTime.UtcNow;
+            if (request["files"] is JsonArray files) session.Update(files);
+            var type = (string?)request["type"];
+            if (type == "diagnostics") return await DiagnosticsAsync(session);
+            if (type == "completionDetail") return await CompletionDetailAsync(session, (int?)request["index"] ?? -1);
+
+            var document = session.Document((string?)request["file"] ?? "");
+            if (document == null) return new JsonObject { ["type"] = "empty" };
+            var text = await document.GetTextAsync();
+            var line = Math.Clamp(((int?)request["line"] ?? 1) - 1, 0, text.Lines.Count - 1);
+            var column = Math.Clamp(((int?)request["column"] ?? 1) - 1, 0, text.Lines[line].End - text.Lines[line].Start);
+            var position = text.Lines.GetPosition(new LinePosition(line, column));
+            return type switch
+            {
+                "complete" => await CompleteAsync(session, document, text, position),
+                "hover" => await HoverAsync(document, text, position),
+                "signature" => await SignatureAsync(document, position),
+                _ => new JsonObject { ["type"] = "error", ["message"] = $"不认识的请求 {type}" },
+            };
+        }
+        finally
+        {
+            session.Lock.Release();
+        }
+    }
+
+    private static Session GetSession(string id)
+    {
+        if (Sessions.TryGetValue(id, out var existing)) return existing;
+        // 会话太多时丢掉最久没用的（浏览器关了也不会通知这里）
+        if (Sessions.Count >= MaxSessions)
+        {
+            foreach (var old in Sessions.OrderBy(s => s.Value.LastUsed).Take(Sessions.Count - MaxSessions + 1)) Sessions.TryRemove(old.Key, out _);
+        }
+        return Sessions.GetOrAdd(id, _ => new Session());
+    }
+
+    // ---------- 代码补全 ----------
+
+    private static async Task<JsonObject> CompleteAsync(Session session, Document document, SourceText text, int position)
+    {
+        var service = CompletionService.GetService(document)!;
+        var list = await service.GetCompletionsAsync(document, position);
+        session.LastCompletion = (document, list);
+        var items = new JsonArray();
+        foreach (var item in list.ItemsList.Take(MaxCompletionItems))
+        {
+            items.Add(new JsonObject
+            {
+                ["label"] = item.DisplayTextPrefix + item.DisplayText + item.DisplayTextSuffix,
+                ["insert"] = item.DisplayText,
+                ["filter"] = item.FilterText,
+                ["sort"] = item.SortText,
+                ["kind"] = item.Tags.FirstOrDefault() ?? "",
+                ["detail"] = item.InlineDescription,
+            });
+        }
+        return new JsonObject { ["type"] = "completions", ["range"] = Range(text, list.Span), ["items"] = items };
+    }
+
+    /// <summary>补全列表里选中某一项时，取它的说明（签名和文档）</summary>
+    private static async Task<JsonObject> CompletionDetailAsync(Session session, int index)
+    {
+        if (session.LastCompletion is not var (document, list) || index < 0 || index >= list.ItemsList.Count)
+        {
+            return new JsonObject { ["type"] = "detail", ["text"] = null };
+        }
+        var description = await CompletionService.GetService(document)!.GetDescriptionAsync(document, list.ItemsList[index]);
+        return new JsonObject { ["type"] = "detail", ["text"] = WithoutNullable(description?.Text) };
+    }
+
+    // ---------- 悬停提示 ----------
+
+    private static async Task<JsonObject> HoverAsync(Document document, SourceText text, int position)
+    {
+        var info = await QuickInfoService.GetService(document)!.GetQuickInfoAsync(document, position);
+        if (info == null) return new JsonObject { ["type"] = "hover", ["text"] = null };
+        var sections = info.Sections.Select(s => s.Text).Where(t => !string.IsNullOrWhiteSpace(t));
+        return new JsonObject { ["type"] = "hover", ["text"] = WithoutNullable(string.Join("\n\n", sections)), ["range"] = Range(text, info.Span) };
+    }
+
+    // ---------- 参数提示 ----------
+
+    /// <summary>不显示可空注解：仿真类库开启了可空检查，学生代码没有开，VS 里看到的也是 string 而不是 string?</summary>
+    private static readonly SymbolDisplayFormat TypeFormat = SymbolDisplayFormat.MinimallyQualifiedFormat
+        .RemoveMiscellaneousOptions(SymbolDisplayMiscellaneousOptions.IncludeNullableReferenceTypeModifier);
+
+    /// <summary>Roslyn 生成的说明文字里去掉可空注解（如 string? → string）</summary>
+    private static string? WithoutNullable(string? text) =>
+        text == null ? null : Regex.Replace(text, @"(?<=[\w>\]])\?(?=[\s,)\]>]|$)", "");
+
+    /// <summary>光标在方法调用或 new 的括号里时，列出各个重载，标出正在填的是第几个参数</summary>
+    private static async Task<JsonObject> SignatureAsync(Document document, int position)
+    {
+        var empty = new JsonObject { ["type"] = "signature", ["signatures"] = new JsonArray() };
+        var root = await document.GetSyntaxRootAsync();
+        var model = await document.GetSemanticModelAsync();
+        if (root == null || model == null) return empty;
+
+        var argumentList = root.FindToken(Math.Max(position - 1, 0)).Parent?
+            .AncestorsAndSelf()
+            .OfType<ArgumentListSyntax>()
+            .FirstOrDefault(a => position > a.OpenParenToken.SpanStart && (a.CloseParenToken.IsMissing || position <= a.CloseParenToken.SpanStart));
+        if (argumentList == null) return empty;
+
+        IEnumerable<IMethodSymbol> methods;
+        ISymbol? chosen;
+        switch (argumentList.Parent)
+        {
+            case InvocationExpressionSyntax invocation:
+                methods = model.GetMemberGroup(invocation.Expression).OfType<IMethodSymbol>();
+                chosen = model.GetSymbolInfo(invocation).Symbol;
+                break;
+            case BaseObjectCreationExpressionSyntax creation when model.GetTypeInfo(creation).Type is INamedTypeSymbol type:
+                methods = type.InstanceConstructors.Where(c => c.DeclaredAccessibility == Accessibility.Public);
+                chosen = model.GetSymbolInfo(creation).Symbol;
+                break;
+            default:
+                return empty;
+        }
+
+        var activeParameter = argumentList.Arguments.GetSeparators().Count(comma => comma.SpanStart < position);
+        var signatures = new JsonArray();
+        var list = methods.ToList();
+        foreach (var method in list)
+        {
+            var label = new StringBuilder(method.MethodKind == MethodKind.Constructor ? method.ContainingType.Name : method.Name).Append('(');
+            var parameters = new JsonArray();
+            foreach (var p in method.Parameters)
+            {
+                if (p.Ordinal > 0) label.Append(", ");
+                var start = label.Length;
+                label.Append(p.Type.ToDisplayString(TypeFormat)).Append(' ').Append(p.Name);
+                parameters.Add(new JsonArray(start, label.Length));
+            }
+            label.Append(')');
+            if (method.MethodKind != MethodKind.Constructor) label.Insert(0, method.ReturnType.ToDisplayString(TypeFormat) + " ");
+            // 返回类型插在前面，参数位置要跟着后移
+            var offset = method.MethodKind != MethodKind.Constructor ? method.ReturnType.ToDisplayString(TypeFormat).Length + 1 : 0;
+            foreach (var range in parameters.OfType<JsonArray>())
+            {
+                range[0] = (int)range[0]! + offset;
+                range[1] = (int)range[1]! + offset;
+            }
+            signatures.Add(new JsonObject { ["label"] = label.ToString(), ["parameters"] = parameters });
+        }
+        // 已经能确定是哪个重载时选它，否则选参数够多的第一个
+        var active = list.FindIndex(m => SymbolEqualityComparer.Default.Equals(m, chosen));
+        if (active < 0) active = Math.Max(list.FindIndex(m => m.Parameters.Length > activeParameter), 0);
+        return new JsonObject { ["type"] = "signature", ["signatures"] = signatures, ["activeSignature"] = active, ["activeParameter"] = activeParameter };
+    }
+
+    // ---------- 边写边检查 ----------
+
+    /// <summary>整个工程的编译错误和警告（不生成程序集），提示和真正编译时一样</summary>
+    private static async Task<JsonObject> DiagnosticsAsync(Session session)
+    {
+        var project = session.Workspace.CurrentSolution.GetProject(session.ProjectId)!;
+        var compilation = (CSharpCompilation)(await project.GetCompilationAsync())!;
+        var diagnostics = new JsonArray();
+        foreach (var diagnostic in compilation.GetDiagnostics()
+                     .Concat(ApiPolicy.Check(compilation))
+                     .Where(d => d.Severity is DiagnosticSeverity.Error or DiagnosticSeverity.Warning && d.Location.IsInSource)
+                     .OrderBy(d => d.Severity == DiagnosticSeverity.Error ? 0 : 1))
+        {
+            diagnostics.Add(StudentCompiler.ToJson(diagnostic));
+        }
+        return new JsonObject { ["type"] = "diagnostics", ["diagnostics"] = diagnostics };
+    }
+
+    private static JsonObject Range(SourceText text, TextSpan span)
+    {
+        var lines = text.Lines.GetLinePositionSpan(span);
+        return new JsonObject
+        {
+            ["startLine"] = lines.Start.Line + 1,
+            ["startColumn"] = lines.Start.Character + 1,
+            ["endLine"] = lines.End.Line + 1,
+            ["endColumn"] = lines.End.Character + 1,
+        };
+    }
+
+    /// <summary>启动时做一遍补全和检查，让 MEF 组合和 JIT 提前完成，学生第一次按"."时不用等几秒</summary>
+    private static void WarmUp()
+    {
+        var session = new Session();
+        session.Update(new JsonArray(new JsonObject
+        {
+            ["path"] = "Program.cs",
+            ["content"] = "using System.Windows.Forms; static class P { static void Main() { var f = new Form(); f.Text = \"预热\"; MessageBox.Show(\"\"); } }",
+        }));
+        var document = session.Document("Program.cs")!;
+        var text = document.GetTextAsync().Result;
+        var position = text.ToString().IndexOf("f.Text", StringComparison.Ordinal) + 2;
+        CompleteAsync(session, document, text, position).Wait();
+        HoverAsync(document, text, position).Wait();
+        SignatureAsync(document, text.ToString().IndexOf("Show(", StringComparison.Ordinal) + 5).Wait();
+        DiagnosticsAsync(session).Wait();
+    }
+
+    /// <summary>一个浏览器标签页的工程</summary>
+    private sealed class Session
+    {
+        public readonly AdhocWorkspace Workspace = new(MefHostServices.DefaultHost);
+        public readonly ProjectId ProjectId = ProjectId.CreateNewId();
+        public readonly SemaphoreSlim Lock = new(1, 1);
+        public DateTime LastUsed = DateTime.UtcNow;
+        /// <summary>最近一次补全的结果，选中某项时据此取说明</summary>
+        public (Document, CompletionList)? LastCompletion;
+        private readonly Dictionary<string, (DocumentId Id, string Content)> documents = new();
+
+        public Session()
+        {
+            Workspace.AddProject(ProjectInfo.Create(
+                ProjectId, VersionStamp.Create(), "StudentApp", "StudentApp", LanguageNames.CSharp,
+                compilationOptions: StudentCompiler.CompilationOptions,
+                parseOptions: StudentCompiler.ParseOptions,
+                metadataReferences: StudentCompiler.References.Value));
+        }
+
+        /// <summary>同步浏览器里的文件：只更新有变化的，删掉已经没有的</summary>
+        public void Update(JsonArray files)
+        {
+            var solution = Workspace.CurrentSolution;
+            var seen = new HashSet<string>();
+            foreach (var file in files.OfType<JsonObject>())
+            {
+                var path = (string?)file["path"];
+                var content = (string?)file["content"] ?? "";
+                if (path == null || !path.EndsWith(".cs", StringComparison.Ordinal)) continue;
+                seen.Add(path);
+                if (documents.TryGetValue(path, out var doc))
+                {
+                    if (doc.Content == content) continue;
+                    solution = solution.WithDocumentText(doc.Id, SourceText.From(content));
+                    documents[path] = (doc.Id, content);
+                }
+                else
+                {
+                    var id = DocumentId.CreateNewId(ProjectId);
+                    solution = solution.AddDocument(id, path, SourceText.From(content), filePath: path);
+                    documents[path] = (id, content);
+                }
+            }
+            foreach (var path in documents.Keys.Where(p => !seen.Contains(p)).ToList())
+            {
+                solution = solution.RemoveDocument(documents[path].Id);
+                documents.Remove(path);
+            }
+            Workspace.TryApplyChanges(solution);
+        }
+
+        public Document? Document(string path) =>
+            documents.TryGetValue(path, out var doc) ? Workspace.CurrentSolution.GetDocument(doc.Id) : null;
+    }
+}

runtime/Sim.Runner/Program.cs

@@ -2,20 +2,22 @@ using System;
 using System.IO;
 using Sim.Runner;
 
-// 两种模式，都通过标准输入输出与 Bun 服务器交换 JSON 消息（每行一条）：
+// 三种模式，都通过标准输入输出与 Bun 服务器交换 JSON 消息（每行一条）：
 //   dotnet Sim.Runner.dll compile-server   常驻编译服务，全服务器共用一个，编译学生工程并把程序集写回工程目录
+//   dotnet Sim.Runner.dll language-server  常驻语言服务，全服务器共用一个：代码补全、悬停提示、参数提示、边写边检查
 //   dotnet Sim.Runner.dll run <工程目录>    运行已编译的学生程序，每次运行一个进程
 // 运行模式不加载 Roslyn，单个学生程序的内存占用因此小得多。
 
 return args switch
 {
     ["compile-server"] => CompileServer.Run(),
+    ["language-server"] => LanguageServer.Run(),
     ["run", var dir] when Directory.Exists(dir) => StudentProgramHost.Run(dir),
     _ => Usage(),
 };
 
 static int Usage()
 {
-    Console.Error.WriteLine("用法：Sim.Runner compile-server | Sim.Runner run <工程目录>");
+    Console.Error.WriteLine("用法：Sim.Runner compile-server | Sim.Runner language-server | Sim.Runner run <工程目录>");
     return 2;
 }

runtime/Sim.Runner/Sim.Runner.csproj

@@ -11,6 +11,8 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.14.0" />
+    <!-- 语言服务（代码补全、悬停提示）：和 VS 的 IntelliSense 用同一套引擎；只有 language-server 模式会加载 -->
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Features" Version="4.14.0" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="../Sim.WinForms/Sim.WinForms.csproj" />

runtime/Sim.Runner/StudentCompiler.cs

@@ -31,9 +31,18 @@ internal static class StudentCompiler
 
     public sealed record Result(bool Success, byte[] Assembly, byte[] Pdb, JsonArray Diagnostics);
 
+    /// <summary>编译和语言服务（代码补全等）共用同一套选项</summary>
+    internal static readonly CSharpParseOptions ParseOptions = new(LanguageVersion.Latest);
+
+    internal static readonly CSharpCompilationOptions CompilationOptions = new CSharpCompilationOptions(OutputKind.WindowsApplication)
+        .WithOptimizationLevel(OptimizationLevel.Debug)
+        .WithNullableContextOptions(NullableContextOptions.Disable)
+        .WithAllowUnsafe(false)
+        .WithConcurrentBuild(true);
+
     public static Result Compile(string projectDir)
     {
-        var parseOptions = new CSharpParseOptions(LanguageVersion.Latest);
+        var parseOptions = ParseOptions;
         var trees = Directory.EnumerateFiles(projectDir, "*.cs", SearchOption.AllDirectories)
             .Where(path => !IsBuildOutput(projectDir, path))
             .OrderBy(path => path, StringComparer.Ordinal)
@@ -43,13 +52,7 @@ internal static class StudentCompiler
                 path: Path.GetRelativePath(projectDir, path)))
             .ToList();
 
-        var options = new CSharpCompilationOptions(OutputKind.WindowsApplication)
+        var compilation = CSharpCompilation.Create("StudentApp", trees, References.Value, CompilationOptions);
-            .WithOptimizationLevel(OptimizationLevel.Debug)
-            .WithNullableContextOptions(NullableContextOptions.Disable)
-            .WithAllowUnsafe(false)
-            .WithConcurrentBuild(true);
-
-        var compilation = CSharpCompilation.Create("StudentApp", trees, References.Value, options);
 
         using var peStream = new MemoryStream();
         using var pdbStream = new MemoryStream();
@@ -67,7 +70,7 @@ internal static class StudentCompiler
         return new Result(emit.Success && denied.Count == 0, peStream.ToArray(), pdbStream.ToArray(), diagnostics);
     }
 
-    private static JsonObject ToJson(Diagnostic diagnostic)
+    internal static JsonObject ToJson(Diagnostic diagnostic)
     {
         var span = diagnostic.Location.GetMappedLineSpan();
         var message = diagnostic.GetMessage(Chinese);
@@ -92,7 +95,7 @@ internal static class StudentCompiler
     }
 
     /// <summary>学生代码可引用的程序集：.NET 框架（去掉冲突的门面）+ 仿真库</summary>
-    private static readonly Lazy<IReadOnlyList<MetadataReference>> References = new(() =>
+    internal static readonly Lazy<IReadOnlyList<MetadataReference>> References = new(() =>
     {
         var frameworkDir = Path.GetDirectoryName(typeof(object).Assembly.Location)!;
         var framework = Directory.EnumerateFiles(frameworkDir, "*.dll")

server/src/app.ts

@@ -16,6 +16,7 @@ import {
   updateAssignment,
 } from './assignments'
 import { parseChecks } from './grading/checks'
+import { languageService } from './language-service'
 import { getReview, gradebook, manualScore, saveReview, studentDetail, submissionFiles } from './reviews'
 import type { GradingQueue } from './grading/queue'
 import { listSamples, loadChecks, loadSample } from './samples'
@@ -83,6 +84,17 @@ export function createApp(db: Database, gradingQueue: GradingQueue) {
     return files ? c.json(files) : c.notFound()
   })
 
+  // 代码编辑器的语言服务：补全、悬停提示、参数提示、边写边检查
+  const LANGUAGE_REQUESTS = new Set(['complete', 'completionDetail', 'hover', 'signature', 'diagnostics'])
+  app.post('/api/language', async (c) => {
+    const r = await body<{ type: string; session: string; files: unknown; file: string; line: number; column: number; index: number }>(c)
+    if (!LANGUAGE_REQUESTS.has(String(r.type)) || typeof r.session !== 'string') return c.json({ message: '请求格式不对' }, 400)
+    if (r.files !== undefined && !validFiles(r.files)) return c.json({ message: '作品格式不对或太大' }, 400)
+    // 会话按用户区分，不同学生的工程不会混在一起
+    const reply = await languageService.request({ ...r, session: `${c.get('user').id}:${r.session.slice(0, 64)}` })
+    return c.json(reply ?? { type: 'empty' })
+  })
+
   // 自己的作品：key 如 "sample:p2-t1-LED显示屏"
   app.get('/api/works/:key', (c) => c.json(getWork(db, c.get('user').id, c.req.param('key'))))
 

server/src/index.ts

@@ -2,6 +2,7 @@ import type { ClientMessage, ServerMessage } from '@iot/shared'
 import { createApp } from './app'
 import { ensureTeacher, tokenUser } from './auth'
 import { compileService } from './compile-service'
+import { languageService } from './language-service'
 import { config } from './config'
 import { openDatabase } from './db'
 import { createGradingQueue } from './grading/queue'
@@ -69,5 +70,5 @@ const server = Bun.serve({
 })
 
 console.log(`服务器已启动：http://localhost:${server.port}`)
-await compileService.start()
+await Promise.all([compileService.start(), languageService.start()])
 console.log('C# 编译服务已就绪')

server/src/language-service.ts

@@ -0,0 +1,75 @@
+import type { Subprocess } from 'bun'
+import { config } from './config'
+import { readLines } from './runner-process'
+
+/** 一个请求最多等多久；语言服务忙或卡住时，编辑器不弹补全也不影响写代码 */
+const TIMEOUT_MS = 10_000
+
+/**
+ * 常驻语言服务：代码补全、悬停提示、参数提示、边写边检查。全服务器共用一个进程（和编译服务分开），
+ * 请求按编号对应回复。进程意外退出时，挂起的请求失败，下一次请求自动重启。
+ */
+class LanguageService {
+  private proc?: Subprocess<'pipe', 'pipe', 'inherit'>
+  private ready?: Promise<void>
+  private nextId = 1
+  private readonly pending = new Map<number, (reply: Record<string, unknown> | null) => void>()
+
+  /** 发一个请求（type、session、files、file、line、column 等原样转给语言服务）；超时或出错返回 null */
+  async request(body: Record<string, unknown>): Promise<Record<string, unknown> | null> {
+    await this.start()
+    const id = this.nextId++
+    const reply = new Promise<Record<string, unknown> | null>((resolve) => {
+      const timer = setTimeout(() => {
+        this.pending.delete(id)
+        resolve(null)
+      }, TIMEOUT_MS)
+      this.pending.set(id, (r) => {
+        clearTimeout(timer)
+        resolve(r)
+      })
+    })
+    this.proc!.stdin.write(`${JSON.stringify({ ...body, id })}\n`)
+    this.proc!.stdin.flush()
+    return reply
+  }
+
+  stop() {
+    this.proc?.kill()
+  }
+
+  /** 服务器启动时调用，提前完成加载和预热 */
+  start() {
+    if (this.ready) return this.ready
+    const proc = Bun.spawn(['dotnet', config.runnerDll, 'language-server'], {
+      stdin: 'pipe',
+      stdout: 'pipe',
+      stderr: 'inherit',
+      env: { PATH: process.env.PATH ?? '/usr/bin:/bin', HOME: process.env.HOME ?? '/tmp', DOTNET_CLI_TELEMETRY_OPTOUT: '1', DOTNET_NOLOGO: '1' },
+    })
+    this.proc = proc
+    this.ready = new Promise<void>((resolveReady) => {
+      void readLines(proc.stdout, (line) => {
+        const message = JSON.parse(line) as { type: string; id?: number }
+        if (message.type === 'ready') {
+          resolveReady()
+          return
+        }
+        const resolve = this.pending.get(message.id!)
+        if (!resolve) return
+        this.pending.delete(message.id!)
+        resolve(message.type === 'error' ? null : message)
+      })
+    })
+    proc.exited.then(() => {
+      if (this.proc !== proc) return
+      this.proc = undefined
+      this.ready = undefined
+      for (const resolve of this.pending.values()) resolve(null)
+      this.pending.clear()
+    })
+    return this.ready
+  }
+}
+
+export const languageService = new LanguageService()

server/test/api.test.ts

@@ -1,10 +1,11 @@
 // HTTP 接口测试：内存数据库，直接调用 app.fetch。
-import { beforeEach, describe, expect, test } from 'bun:test'
+import { afterAll, beforeEach, describe, expect, test } from 'bun:test'
 import { createApp } from '../src/app'
 import { ensureTeacher } from '../src/auth'
 import { config } from '../src/config'
 import { openDatabase } from '../src/db'
 import { createGradingQueue, type GradingQueue } from '../src/grading/queue'
+import { languageService } from '../src/language-service'
 import { loadSample } from '../src/samples'
 
 let app: ReturnType<typeof createApp>
@@ -405,3 +406,20 @@ describe('评阅与成绩', () => {
     expect((await student.get(`/api/teacher/submissions/${submission.id}`)).status).toBe(403)
   }, 60000)
 })
+
+describe('语言服务', () => {
+  afterAll(() => languageService.stop())
+
+  test('代码补全、边写边检查（中文提示）；请求格式不对拒绝；没登录不能用', async () => {
+    const t = await teacher()
+    const files = [{ path: 'Program.cs', content: 'using System.Windows.Forms;\nstatic class P\n{\n    static void Main()\n    {\n        var b = new Button();\n        b.\n    }\n}\n' }]
+    const completions = await t.post('/api/language', { type: 'complete', session: 'tab1', files, file: 'Program.cs', line: 7, column: 11 })
+    expect(completions.body.items.map((i: any) => i.label)).toEqual(expect.arrayContaining(['Text', 'Click', 'Enabled']))
+
+    const check = await t.post('/api/language', { type: 'diagnostics', session: 'tab1', files })
+    expect(check.body.diagnostics).toEqual(expect.arrayContaining([expect.objectContaining({ code: 'CS1002', hint: 'C# 每条语句末尾要有英文分号 ;' })]))
+
+    expect((await t.post('/api/language', { type: 'run', session: 'tab1' })).status).toBe(400)
+    expect((await new Browser().post('/api/language', { type: 'complete', session: 'tab1', files })).status).toBe(401)
+  }, 60000)
+})

web/src/editor/CodeEditor.vue

@@ -1,8 +1,10 @@
 <script setup lang="ts">
 // 代码编辑器：每个文件一个 Monaco 模型（各自保留撤销记录），切换标签页时换模型。
-// 编译错误以波浪线标在代码里。F5 / Shift+F5 由页面统一处理（见 App.vue），这里不再单独绑定。
+// 编译错误以波浪线标在代码里：点"运行"时的编译结果，以及停止输入一会儿后的自动检查结果，以较新的为准。
+// 代码补全、悬停提示、参数提示见 language.ts。F5 / Shift+F5 由页面统一处理，这里不再单独绑定。
 import { onBeforeUnmount, onMounted, ref, shallowRef, watch } from 'vue'
 import type { Diagnostic, SourceFile } from '@iot/shared'
+import { checkProject, registerLanguageFeatures, setLanguageFiles } from './language'
 import { monaco } from './monaco'
 
 const props = defineProps<{
@@ -25,7 +27,10 @@ function modelFor(file: SourceFile) {
   let model = models.get(file.path)
   if (!model) {
     model = monaco.editor.createModel(file.content, 'csharp', monaco.Uri.file(file.path))
-    model.onDidChangeContent(() => emit('change', file.path, model!.getValue()))
+    model.onDidChangeContent(() => {
+      emit('change', file.path, model!.getValue())
+      scheduleCheck()
+    })
     models.set(file.path, model)
   } else if (model.getValue() !== file.content) {
     // 外部换了内容（切换示例、恢复原始代码）
@@ -53,9 +58,12 @@ function showActive() {
   if (editor.value.getModel() !== model) editor.value.setModel(model)
 }
 
+/** 当前显示的错误：新的编译结果或自动检查结果到来时替换 */
+let shown: Diagnostic[] = props.diagnostics
+
 function applyMarkers() {
   for (const [path, model] of models) {
-    const markers = props.diagnostics
+    const markers = shown
       .filter((d) => d.file === path)
       .map((d) => ({
         severity: d.severity === 'error' ? monaco.MarkerSeverity.Error : monaco.MarkerSeverity.Warning,
@@ -83,7 +91,28 @@ function reveal(path: string, line: number, column: number) {
 
 defineExpose({ reveal })
 
+// ---------- 边写边检查：停止输入 1 秒后检查整个工程 ----------
+const CHECK_DELAY_MS = 1000
+let checkTimer: ReturnType<typeof setTimeout> | undefined
+
+function scheduleCheck() {
+  if (props.readOnly) return
+  clearTimeout(checkTimer)
+  checkTimer = setTimeout(() => void check(), CHECK_DELAY_MS)
+}
+
+async function check() {
+  const versions = new Map([...models].map(([path, model]) => [path, model.getVersionId()]))
+  const result = await checkProject()
+  // 检查期间又改了代码：这次的结果作废，等下一次
+  if (!result || [...models].some(([path, model]) => versions.get(path) !== model.getVersionId())) return
+  shown = result
+  applyMarkers()
+}
+
 onMounted(() => {
+  registerLanguageFeatures()
+  setLanguageFiles(() => props.files)
   editor.value = monaco.editor.create(container.value!, {
     language: 'csharp',
     theme: 'vs',
@@ -111,9 +140,16 @@ watch(() => props.files, () => {
   applyMarkers()
 })
 watch(() => props.activeFile, showActive)
-watch(() => props.diagnostics, applyMarkers)
+watch(
+  () => props.diagnostics,
+  (diagnostics) => {
+    shown = diagnostics
+    applyMarkers()
+  },
+)
 
 onBeforeUnmount(() => {
+  clearTimeout(checkTimer)
   editor.value?.dispose()
   for (const model of models.values()) model.dispose()
   models.clear()

web/src/editor/language.ts

@@ -0,0 +1,154 @@
+// C# 语言功能：代码补全、悬停提示、参数提示、边写边检查。由服务器上的 Roslyn 语言服务计算（和 VS 的 IntelliSense 同一套引擎）。
+// 请求带上整个工程的文件；服务器按浏览器标签页（session）保存工程，只更新有变化的文件。
+import type { Diagnostic, SourceFile } from '@iot/shared'
+import { api } from '../api'
+import { monaco } from './monaco'
+
+/** 每个浏览器标签页一个会话 */
+const session = crypto.randomUUID()
+
+/** 当前工程的文件，由代码编辑器设置 */
+let currentFiles: () => SourceFile[] = () => []
+
+export function setLanguageFiles(files: () => SourceFile[]) {
+  currentFiles = files
+}
+
+/** 模型对应的文件路径（模型用 Uri.file(path) 创建） */
+const pathOf = (model: monaco.editor.ITextModel) => model.uri.path.replace(/^\//, '')
+
+interface Range {
+  startLine: number
+  startColumn: number
+  endLine: number
+  endColumn: number
+}
+
+function request<T>(body: Record<string, unknown>): Promise<T | null> {
+  return api<T & { type: string }>('POST', '/api/language', { ...body, session })
+    .then((r) => (r.type === 'empty' ? null : r))
+    .catch(() => null)
+}
+
+const toRange = (r: Range) => new monaco.Range(r.startLine, r.startColumn, r.endLine, r.endColumn)
+
+const Kind = monaco.languages.CompletionItemKind
+/** Roslyn 补全项的标签（第一个标签是种类）对应 Monaco 的图标 */
+const KINDS: Record<string, monaco.languages.CompletionItemKind> = {
+  Class: Kind.Class,
+  Structure: Kind.Struct,
+  Interface: Kind.Interface,
+  Enum: Kind.Enum,
+  EnumMember: Kind.EnumMember,
+  Delegate: Kind.Function,
+  Event: Kind.Event,
+  Field: Kind.Field,
+  Constant: Kind.Constant,
+  Property: Kind.Property,
+  Method: Kind.Method,
+  ExtensionMethod: Kind.Method,
+  Local: Kind.Variable,
+  Parameter: Kind.Variable,
+  RangeVariable: Kind.Variable,
+  Namespace: Kind.Module,
+  Keyword: Kind.Keyword,
+  Snippet: Kind.Snippet,
+  TypeParameter: Kind.TypeParameter,
+  Label: Kind.Reference,
+}
+
+interface Completions {
+  range: Range
+  items: { label: string; insert: string; filter: string; sort: string; kind: string; detail: string }[]
+}
+
+type Item = monaco.languages.CompletionItem & { index: number }
+
+let registered = false
+
+/** 注册到 Monaco（全局只需一次） */
+export function registerLanguageFeatures() {
+  if (registered) return
+  registered = true
+
+  monaco.languages.registerCompletionItemProvider('csharp', {
+    triggerCharacters: ['.'],
+    async provideCompletionItems(model, position) {
+      const result = await request<Completions>({
+        type: 'complete',
+        files: currentFiles(),
+        file: pathOf(model),
+        line: position.lineNumber,
+        column: position.column,
+      })
+      if (!result) return { suggestions: [] }
+      const range = toRange(result.range)
+      return {
+        suggestions: result.items.map(
+          (item, index): Item => ({
+            index,
+            label: item.label,
+            insertText: item.insert,
+            filterText: item.filter,
+            sortText: item.sort,
+            kind: KINDS[item.kind] ?? Kind.Text,
+            detail: item.detail || undefined,
+            range,
+          }),
+        ),
+      }
+    },
+    // 选中某一项时再取它的签名和说明
+    async resolveCompletionItem(item) {
+      const result = await request<{ text: string | null }>({ type: 'completionDetail', index: (item as Item).index })
+      if (result?.text) item.documentation = { value: '```csharp\n' + result.text + '\n```' }
+      return item
+    },
+  })
+
+  monaco.languages.registerHoverProvider('csharp', {
+    async provideHover(model, position) {
+      const result = await request<{ text: string | null; range: Range }>({
+        type: 'hover',
+        files: currentFiles(),
+        file: pathOf(model),
+        line: position.lineNumber,
+        column: position.column,
+      })
+      if (!result?.text) return null
+      // 第一段是签名，用代码格式显示；后面是说明文字
+      const [signature, ...rest] = result.text.split('\n\n')
+      return {
+        range: toRange(result.range),
+        contents: [{ value: '```csharp\n' + signature + '\n```' }, ...rest.map((value) => ({ value }))],
+      }
+    },
+  })
+
+  monaco.languages.registerSignatureHelpProvider('csharp', {
+    signatureHelpTriggerCharacters: ['(', ','],
+    signatureHelpRetriggerCharacters: [','],
+    async provideSignatureHelp(model, position) {
+      const result = await request<{
+        signatures: { label: string; parameters: [number, number][] }[]
+        activeSignature: number
+        activeParameter: number
+      }>({ type: 'signature', files: currentFiles(), file: pathOf(model), line: position.lineNumber, column: position.column })
+      if (!result || result.signatures.length === 0) return null
+      return {
+        value: {
+          signatures: result.signatures.map((s) => ({ label: s.label, parameters: s.parameters.map((label) => ({ label })) })),
+          activeSignature: result.activeSignature,
+          activeParameter: result.activeParameter,
+        },
+        dispose() {},
+      }
+    },
+  })
+}
+
+/** 整个工程的编译错误和警告（不生成程序集）；出错时返回 null */
+export async function checkProject(): Promise<Diagnostic[] | null> {
+  const result = await request<{ diagnostics: Diagnostic[] }>({ type: 'diagnostics', files: currentFiles() })
+  return result?.diagnostics ?? null
+}