File Server/Exception/MissingRequiredClientCapabilityException.php

1:	<?php
2:
3:	declare(strict_types=1);
4:
5:	/**
6:	* This file is part of the Nexus MCP SDK package.
7:	*
8:	* (c) 2026 John Paul E. Balandan, CPA <paulbalandan@gmail.com>
9:	*
10:	* For the full copyright and license information, please view
11:	* the LICENSE file that was distributed with this source code.
12:	*/
13:
14:	namespace Nexus\Mcp\Server\Exception;
15:
16:	use Nexus\Mcp\Core\Exception\AbstractJsonRpcProtocolException;
17:	use Nexus\Mcp\Core\Schema\ClientCapabilities;
18:	use Nexus\Mcp\Core\Schema\Enum\ProtocolErrorCode;
19:	use Nexus\Mcp\Core\Schema\RequestId;
20:
21:	/**
22:	* Thrown when serving a request would rely on a client capability absent from the request's
23:	* `io.modelcontextprotocol/clientCapabilities`.
24:	*/
25:	final class MissingRequiredClientCapabilityException extends AbstractJsonRpcProtocolException
26:	{
27:	public function __construct(
28:	public readonly ClientCapabilities $requiredCapabilities,
29:	?RequestId $requestId = null,
30:	?\Throwable $previous = null,
31:	) {
32:	parent::__construct(
33:	$requestId,
34:	\sprintf(
35:	'This request requires client capabilities the client did not declare: %s.',
36:	implode(', ', $this->describeCapabilities($requiredCapabilities->toArray())),
37:	),
38:	$previous,
39:	errorData: ['requiredCapabilities' => $requiredCapabilities->toArray()],
40:	);
41:	}
42:
43:	#[\Override]
44:	public static function getErrorCode(): ProtocolErrorCode
45:	{
46:	return ProtocolErrorCode::MissingRequiredClientCapability;
47:	}
48:
49:	/**
50:	* Renders each required slot, naming the nested members of a map-valued slot
51:	* (`extensions.com.example/feature`).
52:	*
53:	* @param array<string, mixed> $capabilities
54:	*
55:	* @return list<string>
56:	*/
57:	private function describeCapabilities(array $capabilities): array
58:	{
59:	$described = [];
60:
61:	foreach ($capabilities as $slot => $members) {
62:	if (\is_array($members) && [] !== $members && $this->hasOnlyStringKeys($members)) {
63:	foreach (array_keys($members) as $member) {
64:	$described[] = \sprintf('%s.%s', $slot, $member);
65:	}
66:
67:	continue;
68:	}
69:
70:	$described[] = $slot;
71:	}
72:
73:	return $described;
74:	}
75:
76:	/**
77:	* Whether every key names a member, which is what separates a map-valued slot from a list.
78:	*
79:	* @param non-empty-array<array-key, mixed> $members
80:	*/
81:	private function hasOnlyStringKeys(array $members): bool
82:	{
83:	foreach (array_keys($members) as $key) {
84:	if (! \is_string($key)) {
85:	return false;
86:	}
87:	}
88:
89:	return true;
90:	}
91:	}
92:

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Exceptions