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fix(a2a-client): fake MCP server on the ASP.NET framework, question-first results, safer file names

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This commit is contained in:
EugeneTes
2026-10-08 12:46:32 +00:00
parent ef906b34dd
commit 24747858eb
8 changed files with 95 additions and 25 deletions
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46
extensions/Volcanic.AgenticCore.Extensions.A2A/A2AResults.cs
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@@ -4,6 +4,12 @@ using A2AMessage = global::A2A.Message;
namespace Volcanic.AgenticCore.Extensions.A2A;
/// <summary>Parts not saved because they were over the size limit.</summary>
internal sealed record SkippedFiles(IReadOnlyList<string> Names, long MaxBytes);
/// <summary>What <see cref="A2AResults.SaveFiles"/> did: workspace-relative paths saved, and parts skipped for size.</summary>
internal sealed record SaveResult(IReadOnlyList<string> Saved, SkippedFiles Skipped);
/// <summary>How remote tasks read for the model: state names, the answer text, saved files, result and delivery texts.</summary>
internal static class A2AResults
{
@@ -44,17 +50,19 @@ internal static class A2AResults
}
/// <summary>Saves file parts (inline bytes) under <c>inbox/a2a/&lt;agent&gt;/</c>; returns workspace-relative paths.</summary>
public static IReadOnlyList<string> SaveFiles(string workspace, string agent, AgentTask task, long maxBytes)
public static SaveResult SaveFiles(string workspace, string agent, AgentTask task, long maxBytes)
{
var saved = new List<string>();
var skipped = new List<string>();
foreach (var artifact in task.Artifacts ?? [])
foreach (var part in artifact.Parts ?? [])
{
if (part.ContentCase != PartContentCase.Raw || part.Raw is not { } bytes || bytes.Length > maxBytes) continue;
if (part.ContentCase != PartContentCase.Raw || part.Raw is not { } bytes) continue;
var name = Sanitize(part.Filename ?? artifact.Name ?? artifact.ArtifactId);
if (bytes.Length > maxBytes) { skipped.Add(name); continue; }
var relative = $"inbox/a2a/{agent}/{name}";
var full = Path.Combine(workspace, relative);
for (var n = 2; File.Exists(full); n++)
for (var n = 2; File.Exists(full) || Directory.Exists(full); n++)
{
relative = $"inbox/a2a/{agent}/{Path.GetFileNameWithoutExtension(name)}-{n}{Path.GetExtension(name)}";
full = Path.Combine(workspace, relative);
@@ -63,7 +71,7 @@ internal static class A2AResults
File.WriteAllBytes(full, bytes);
saved.Add(relative);
}
return saved;
return new SaveResult(saved, new SkippedFiles(skipped, maxBytes));
}
/// <summary>Links the remote agent returned instead of bytes (not downloaded).</summary>
@@ -72,40 +80,54 @@ internal static class A2AResults
.Select(p => p.Url!).ToList();
/// <summary>The tool result for a task.</summary>
public static string Describe(string agent, AgentTask task, IReadOnlyList<string> files)
public static string Describe(string agent, AgentTask task, IReadOnlyList<string> files, SkippedFiles? skipped = null)
{
var sb = new StringBuilder();
sb.Append($"Agent \"{agent}\": task {task.Id} (context {task.ContextId}) is {StateName(task.Status.State)}.");
AppendBody(sb, task, files);
AppendBody(sb, task, files, skipped);
return sb.ToString();
}
/// <summary>The follow-up prompt a watch delivers.</summary>
public static string DeliveryText(string agent, AgentTask task, IReadOnlyList<string> files)
public static string DeliveryText(string agent, AgentTask task, IReadOnlyList<string> files, SkippedFiles? skipped = null)
{
var kind = task.Status.State is TaskState.InputRequired or TaskState.AuthRequired ? "question" : "result";
var sb = new StringBuilder($"[A2A {kind} from \"{agent}\", task {task.Id} ({StateName(task.Status.State)})]");
sb.Append($"\nContext: {task.ContextId}");
AppendBody(sb, task, files);
AppendBody(sb, task, files, skipped);
return sb.ToString();
}
private static void AppendBody(StringBuilder sb, AgentTask task, IReadOnlyList<string> files)
private static void AppendBody(StringBuilder sb, AgentTask task, IReadOnlyList<string> files, SkippedFiles? skipped)
{
if (FinalText(task) is { } text) sb.Append('\n').Append(text);
var waiting = task.Status.State is TaskState.InputRequired or TaskState.AuthRequired;
// Waiting for us: the question (status message) leads; artifacts may be stale output of earlier turns.
var text = waiting ? WaitingText(task) : FinalText(task);
if (text is not null) sb.Append('\n').Append(text);
if (files.Count > 0) sb.Append("\nFiles: ").Append(string.Join(", ", files));
if (skipped is { Names.Count: > 0 })
sb.Append($"\nFiles skipped (over {skipped.MaxBytes} bytes): ").Append(string.Join(", ", skipped.Names));
var links = Links(task);
if (links.Count > 0) sb.Append("\nLinks: ").Append(string.Join(", ", links));
if (task.Status.State is TaskState.InputRequired or TaskState.AuthRequired)
sb.Append($"\nThe agent is waiting for an answer: reply with action=send, agent, taskId={task.Id} and your answer.");
}
private static string? WaitingText(AgentTask task)
{
var question = TextOf(task.Status.Message);
var rest = string.Join("\n", (task.Artifacts ?? []).Select(a => TextOf(a.Parts)).Where(t => t.Length > 0));
var all = string.Join("\n", new[] { question, rest }.Where(t => t.Length > 0));
return all.Length > 0 ? all : null;
}
private static string Sanitize(string? name)
{
var file = Path.GetFileName(name ?? "");
if (string.IsNullOrWhiteSpace(file)) return "file";
if (string.IsNullOrWhiteSpace(file) || file is "." or "..") return "file";
var invalid = Path.GetInvalidFileNameChars();
var clean = new string(file.Select(c => invalid.Contains(c) || char.IsWhiteSpace(c) ? '_' : c).ToArray());
var clean = new string(file.Select(c => invalid.Contains(c) || char.IsWhiteSpace(c) ? '_' : c).Where(c => !char.IsControl(c)).ToArray());
if (clean.Length == 0 || clean is "." or "..") return "file";
return clean.Length > 80 ? clean[^80..] : clean;
}
}

2
extensions/Volcanic.AgenticCore.Extensions.A2A/AgentsFile.cs
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@@ -14,7 +14,7 @@ public sealed record AgentsFileResult(IReadOnlyList<RemoteAgentEntry> Agents, IR
/// </summary>
public static partial class AgentsFile
{
[GeneratedRegex("^[a-z0-9-]{1,40}$", RegexOptions.CultureInvariant)]
[GeneratedRegex("^[a-z0-9-]{1,40}\\z", RegexOptions.CultureInvariant)]
private static partial Regex NamePattern();
public static string PathFor(string workspace) => Path.Combine(workspace, ".volcanic", "a2a", "agents.json");

10
extensions/Volcanic.AgenticCore.Extensions.A2A/PendingFile.cs
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@@ -47,9 +47,17 @@ public static class PendingFile
var path = PathFor(workspace);
Directory.CreateDirectory(Path.GetDirectoryName(path)!);
var temp = path + "." + Guid.NewGuid().ToString("N") + ".tmp";
try
{
File.WriteAllText(temp, JsonSerializer.Serialize(list, Json));
File.Move(temp, path, overwrite: true);
}
catch
{
try { File.Delete(temp); } catch (IOException) { } catch (UnauthorizedAccessException) { }
throw;
}
}
}
private static List<WatchRecord> ReadUnlocked(string workspace)
@@ -57,7 +65,7 @@ public static class PendingFile
var path = PathFor(workspace);
try
{
return File.Exists(path) ? JsonSerializer.Deserialize<List<WatchRecord>>(File.ReadAllText(path), Json) ?? [] : [];
return File.Exists(path) ? JsonSerializer.Deserialize<List<WatchRecord?>>(File.ReadAllText(path), Json)?.OfType<WatchRecord>().ToList() ?? [] : [];
}
catch (Exception ex) when (ex is JsonException or IOException or UnauthorizedAccessException)
{

1
tests/Volcanic.AgenticCore.Extensions.Tests.FakeMcpServer/Volcanic.AgenticCore.Extensions.Tests.FakeMcpServer.csproj
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@@ -6,6 +6,7 @@
<Description>Test helper: a stdio MCP server whose behaviour FAKE_MCP_MODE selects.</Description>
</PropertyGroup>
<ItemGroup>
<FrameworkReference Include="Microsoft.AspNetCore.App" />
<PackageReference Include="ModelContextProtocol.Core" Version="2.2.0" />
</ItemGroup>
</Project>

32
tests/Volcanic.AgenticCore.Extensions.Tests/A2A/A2AResultsTests.cs
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@@ -45,7 +45,7 @@ public sealed class A2AResultsTests : IDisposable
ArtifactId = "f1", Name = "plan.pdf", Parts = [Part.FromRaw(Encoding.UTF8.GetBytes("pdf!"), "application/pdf", "../../plan.pdf")],
});
var files = A2AResults.SaveFiles(_ws, "travel-bot", task, 1024);
var file = Assert.Single(files);
var file = Assert.Single(files.Saved);
Assert.Equal("inbox/a2a/travel-bot/plan.pdf", file);
Assert.Equal("pdf!", File.ReadAllText(Path.Combine(_ws, file)));
}
@@ -71,5 +71,35 @@ public sealed class A2AResultsTests : IDisposable
Assert.Contains("Files: inbox/a2a/travel-bot/x.pdf", text);
}
[Fact]
public void Describe_InputRequired_QuestionComesBeforeStaleResponseArtifact()
{
var task = Task_(TaskState.InputRequired, "Which date?",
new Artifact { ArtifactId = "response", Parts = [Part.FromText("old answer")] });
var text = A2AResults.Describe("travel-bot", task, []);
Assert.True(text.IndexOf("Which date?", StringComparison.Ordinal) < text.IndexOf("old answer", StringComparison.Ordinal));
}
[Fact]
public void SaveFiles_DotDotName_BecomesFile_AndControlCharsStripped()
{
var task = Task_(TaskState.Completed, null,
new Artifact { ArtifactId = "a", Parts = [Part.FromRaw(Encoding.UTF8.GetBytes("x"), "text/plain", "..")] },
new Artifact { ArtifactId = "b", Parts = [Part.FromRaw(Encoding.UTF8.GetBytes("y"), "text/plain", "a\u0001b.txt")] });
var files = A2AResults.SaveFiles(_ws, "bot", task, 1024).Saved;
Assert.Equal(["inbox/a2a/bot/file", "inbox/a2a/bot/ab.txt"], files);
}
[Fact]
public void SaveFiles_ReportsOversizedParts_AndDescribeListsThem()
{
var task = Task_(TaskState.Completed, null,
new Artifact { ArtifactId = "a", Parts = [Part.FromRaw(new byte[100], "text/plain", "big.bin")] });
var result = A2AResults.SaveFiles(_ws, "bot", task, 10);
Assert.Empty(result.Saved);
Assert.Equal(["big.bin"], result.Skipped.Names);
Assert.Contains("Files skipped (over 10 bytes): big.bin", A2AResults.Describe("bot", task, result.Saved, result.Skipped));
}
public void Dispose() { try { Directory.Delete(_ws, true); } catch (IOException) { } }
}

7
tests/Volcanic.AgenticCore.Extensions.Tests/A2A/AgentsFileTests.cs
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@@ -46,6 +46,13 @@ public sealed class AgentsFileTests : IDisposable
Assert.DoesNotContain(r.Problems, p => p.Contains("secret"));
}
[Fact]
public void Read_NameWithTrailingNewline_Rejected()
{
Write("""[ { "name": "a\n", "url": "https://a.example/" } ]""");
Assert.Empty(AgentsFile.Read(_ws).Agents);
}
[Fact]
public void Agents_FileEdited_AppliesToNextCall()
{

10
tests/Volcanic.AgenticCore.Extensions.Tests/A2A/PendingFileTests.cs
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@@ -22,6 +22,16 @@ public sealed class PendingFileTests : IDisposable
Assert.Equal("b", Assert.Single(PendingFile.Read(_ws)).WatchId);
}
[Fact]
public void Read_NullElements_Filtered()
{
Directory.CreateDirectory(Path.GetDirectoryName(PendingFile.PathFor(_ws))!);
File.WriteAllText(PendingFile.PathFor(_ws), "[null]");
Assert.Empty(PendingFile.Read(_ws));
PendingFile.Upsert(_ws, Record("a"));
Assert.Single(PendingFile.Read(_ws));
}
[Fact]
public void Read_MissingOrMalformed_Empty()
{

8
tests/Volcanic.AgenticCore.Extensions.Tests/Volcanic.AgenticCore.Extensions.Tests.csproj
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@@ -29,12 +29,4 @@
<ProjectReference Include="../../extensions/Volcanic.AgenticCore.Extensions.Scheduler/Volcanic.AgenticCore.Extensions.Scheduler.csproj" />
<ProjectReference Include="../Volcanic.AgenticCore.Extensions.Tests.FakeMcpServer/Volcanic.AgenticCore.Extensions.Tests.FakeMcpServer.csproj" />
</ItemGroup>
<!-- The ASP.NET shared framework (FrameworkReference above) makes the SDK skip copying Microsoft.Extensions.* assemblies,
but the fake MCP server runs on Microsoft.NETCore.App only and needs its own copies next to its dll. -->
<Target Name="CopyFakeMcpServerFrameworkAssemblies" AfterTargets="Build">
<ItemGroup>
<FakeMcpExtraDll Include="$(MSBuildProjectDirectory)/../Volcanic.AgenticCore.Extensions.Tests.FakeMcpServer/bin/$(Configuration)/$(TargetFramework)/Microsoft.Extensions.*.dll" />
</ItemGroup>
<Copy SourceFiles="@(FakeMcpExtraDll)" DestinationFolder="$(OutDir)" SkipUnchangedFiles="true" />
</Target>
</Project>