Merge pull request #2011 from lightpanda-io/mcp-fixes

MCP fixes

src/mcp/resources.zig

@@ -22,12 +22,14 @@ pub const resource_list = [_]protocol.Resource{
 };
 
 pub fn handleList(server: *Server, req: protocol.Request) !void {
-    try server.sendResult(req.id.?, .{ .resources = &resource_list });
+    const id = req.id orelse return;
+    try server.sendResult(id, .{ .resources = &resource_list });
 }
 
 const ReadParams = struct {
     uri: []const u8,
 };
+const Format = enum { html, markdown };
 
 const ResourceStreamingResult = struct {
     contents: []const struct {
@@ -38,7 +40,7 @@ const ResourceStreamingResult = struct {
 
     const StreamingText = struct {
         page: *lp.Page,
-        format: enum { html, markdown },
+        format: Format,
 
         pub fn jsonStringify(self: @This(), jw: *std.json.Stringify) !void {
             try jw.beginWriteRaw();
@@ -47,9 +49,11 @@ const ResourceStreamingResult = struct {
             switch (self.format) {
                 .html => lp.dump.root(self.page.document, .{}, &escaped.writer, self.page) catch |err| {
                     log.err(.mcp, "html dump failed", .{ .err = err });
+                    return error.WriteFailed;
                 },
                 .markdown => lp.markdown.dump(self.page.document.asNode(), .{}, &escaped.writer, self.page) catch |err| {
                     log.err(.mcp, "markdown dump failed", .{ .err = err });
+                    return error.WriteFailed;
                 },
             }
             try jw.writer.writeByte('"');
@@ -86,28 +90,25 @@ pub fn handleRead(server: *Server, arena: std.mem.Allocator, req: protocol.Reque
         return server.sendError(req_id, .PageNotLoaded, "Page not loaded");
     };
 
-    switch (uri) {
+    const format: Format = switch (uri) {
-        .@"mcp://page/html" => {
+        .@"mcp://page/html" => .html,
-            const result: ResourceStreamingResult = .{
+        .@"mcp://page/markdown" => .markdown,
-                .contents = &.{.{
+    };
-                    .uri = params.uri,
+    const mime_type: []const u8 = switch (uri) {
-                    .mimeType = "text/html",
+        .@"mcp://page/html" => "text/html",
-                    .text = .{ .page = page, .format = .html },
+        .@"mcp://page/markdown" => "text/markdown",
-                }},
+    };
-            };
+
-            try server.sendResult(req_id, result);
+    const result: ResourceStreamingResult = .{
-        },
+        .contents = &.{.{
-        .@"mcp://page/markdown" => {
+            .uri = params.uri,
-            const result: ResourceStreamingResult = .{
+            .mimeType = mime_type,
-                .contents = &.{.{
+            .text = .{ .page = page, .format = format },
-                    .uri = params.uri,
+        }},
-                    .mimeType = "text/markdown",
+    };
-                    .text = .{ .page = page, .format = .markdown },
+    server.sendResult(req_id, result) catch {
-                }},
+        return server.sendError(req_id, .InternalError, "Failed to serialize resource content");
-            };
+    };
-            try server.sendResult(req_id, result);
-        },
-    }
 }
 
 const testing = @import("../testing.zig");

src/mcp/router.zig

@@ -16,6 +16,7 @@ pub fn processRequests(server: *Server, reader: *std.io.Reader) !void {
         const buffered_line = reader.takeDelimiter('\n') catch |err| switch (err) {
             error.StreamTooLong => {
                 log.err(.mcp, "Message too long", .{});
+                try server.sendError(.null, .InvalidRequest, "Message too long");
                 continue;
             },
             else => return err,
@@ -80,6 +81,7 @@ pub fn handleMessage(server: *Server, arena: std.mem.Allocator, msg: []const u8)
 }
 
 fn handleInitialize(server: *Server, req: protocol.Request) !void {
+    const id = req.id orelse return;
     const result = protocol.InitializeResult{
         .protocolVersion = "2025-11-25",
         .capabilities = .{
@@ -92,7 +94,7 @@ fn handleInitialize(server: *Server, req: protocol.Request) !void {
         },
     };
 
-    try server.sendResult(req.id.?, result);
+    try server.sendResult(id, result);
 }
 
 fn handlePing(server: *Server, req: protocol.Request) !void {

src/mcp/tools.zig

@@ -172,7 +172,8 @@ pub const tool_list = [_]protocol.Tool{
 
 pub fn handleList(server: *Server, arena: std.mem.Allocator, req: protocol.Request) !void {
     _ = arena;
-    try server.sendResult(req.id.?, .{ .tools = &tool_list });
+    const id = req.id orelse return;
+    try server.sendResult(id, .{ .tools = &tool_list });
 }
 
 const GotoParams = struct {
@@ -205,17 +206,18 @@ const ToolStreamingText = struct {
         switch (self.action) {
             .markdown => lp.markdown.dump(self.page.document.asNode(), .{}, w, self.page) catch |err| {
                 log.err(.mcp, "markdown dump failed", .{ .err = err });
+                return error.WriteFailed;
             },
             .links => {
-                if (lp.links.collectLinks(self.page.call_arena, self.page.document.asNode(), self.page)) |links| {
+                const links = lp.links.collectLinks(self.page.call_arena, self.page.document.asNode(), self.page) catch |err| {
-                    var first = true;
-                    for (links) |href| {
-                        if (!first) try w.writeByte('\n');
-                        try w.writeAll(href);
-                        first = false;
-                    }
-                } else |err| {
                     log.err(.mcp, "query links failed", .{ .err = err });
+                    return error.WriteFailed;
+                };
+                var first = true;
+                for (links) |href| {
+                    if (!first) try w.writeByte('\n');
+                    try w.writeAll(href);
+                    first = false;
                 }
             },
             .semantic_tree => {
@@ -241,6 +243,7 @@ const ToolStreamingText = struct {
 
                 st.textStringify(w) catch |err| {
                     log.err(.mcp, "semantic tree dump failed", .{ .err = err });
+                    return error.WriteFailed;
                 };
             },
         }
@@ -331,7 +334,9 @@ fn handleMarkdown(server: *Server, arena: std.mem.Allocator, id: std.json.Value,
     const content = [_]protocol.TextContent(ToolStreamingText){.{
         .text = .{ .page = page, .action = .markdown },
     }};
-    try server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content });
+    server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content }) catch {
+        return server.sendError(id, .InternalError, "Failed to serialize markdown content");
+    };
 }
 
 fn handleLinks(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
@@ -341,7 +346,9 @@ fn handleLinks(server: *Server, arena: std.mem.Allocator, id: std.json.Value, ar
     const content = [_]protocol.TextContent(ToolStreamingText){.{
         .text = .{ .page = page, .action = .links },
     }};
-    try server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content });
+    server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content }) catch {
+        return server.sendError(id, .InternalError, "Failed to serialize links content");
+    };
 }
 
 fn handleSemanticTree(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {
@@ -363,7 +370,9 @@ fn handleSemanticTree(server: *Server, arena: std.mem.Allocator, id: std.json.Va
             .maxDepth = args.maxDepth,
         },
     }};
-    try server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content });
+    server.sendResult(id, protocol.CallToolResult(ToolStreamingText){ .content = &content }) catch {
+        return server.sendError(id, .InternalError, "Failed to serialize semantic tree content");
+    };
 }
 
 fn handleInteractiveElements(server: *Server, arena: std.mem.Allocator, id: std.json.Value, arguments: ?std.json.Value) !void {