Skip to content

Encode supplementary characters in reserved URI template expansion #1931

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
pournasserian wants to merge 1 commit into
base: main
Choose a base branch
from
+26 −6
Open

Encode supplementary characters in reserved URI template expansion #1931

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
16 changes: 10 additions & 6 deletions src/ModelContextProtocol.Core/UriTemplate.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -464,29 +464,33 @@ private static string Encode(string value, bool allowReserved)
}
else
{
AppendHex(ref builder, c);
// A supplementary character is a surrogate pair and must be UTF-8 encoded as a single scalar.
int charCount = char.IsHighSurrogate(c) && i + 1 < value.Length && char.IsLowSurrogate(value[i + 1]) ? 2 : 1;
AppendHex(ref builder, value.AsSpan(i, charCount));
i += charCount - 1;
}
}

return builder.ToStringAndClear();

static void AppendHex(ref DefaultInterpolatedStringHandler builder, char c)
static void AppendHex(ref DefaultInterpolatedStringHandler builder, ReadOnlySpan<char> chars)
{
ReadOnlySpan<char> hexDigits = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'];

if (c <= 0x7F)
if (chars.Length == 1 && chars[0] <= 0x7F)
{
char c = chars[0];
builder.AppendLiteral("%");
builder.AppendFormatted(hexDigits[c >> 4]);
builder.AppendFormatted(hexDigits[c & 0xF]);
}
else
{
#if NET
Span<byte> utf8 = stackalloc byte[Encoding.UTF8.GetMaxByteCount(1)];
foreach (byte b in utf8.Slice(0, new Rune(c).EncodeToUtf8(utf8)))
Span<byte> utf8 = stackalloc byte[Encoding.UTF8.GetMaxByteCount(2)];
foreach (byte b in utf8.Slice(0, Encoding.UTF8.GetBytes(chars, utf8)))
#else
foreach (byte b in Encoding.UTF8.GetBytes([c]))
foreach (byte b in Encoding.UTF8.GetBytes(chars.ToArray()))
#endif
{
builder.AppendLiteral("%");
Expand Down
16 changes: 16 additions & 0 deletions tests/ModelContextProtocol.Tests/Client/McpClientResourceTemplateTests.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,22 @@ public async Task UriTemplate_InputsProduceExpectedOutputs(
}
}

[Theory]
[InlineData("test://resource/{+name}", "hello\U0001F600", "test://resource/hello%F0%9F%98%80")]
[InlineData("test://resource/{#name}", "hello\U0001F600", "test://resource/#hello%F0%9F%98%80")]
[InlineData("test://resource/{+name}", "a\U0001F600b\U00010348/c", "test://resource/a%F0%9F%98%80b%F0%90%8D%88/c")]
[InlineData("test://resource/{+name}", "ü\U0001F600€", "test://resource/%C3%BC%F0%9F%98%80%E2%82%AC")]
public async Task ReservedExpansion_EncodesSupplementaryUnicodeScalar(string uriTemplate, string value, string expectedUri)
{
await using McpClient client = await CreateMcpClientForServer();

var result = await client.ReadResourceAsync(
uriTemplate, new Dictionary<string, object?> { ["name"] = value }, null, TestContext.Current.CancellationToken);

var actualUri = Assert.IsType<TextResourceContents>(Assert.Single(result.Contents)).Text;
Assert.Equal(expectedUri, actualUri);
}

public class TestGroup
{
[JsonPropertyName("level")]
Expand Down