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Fix reserved expansion (e.g. "{+var}") when matching resources (#1142)

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Stephen Halter 2026-01-27 14:23:31 -08:00 • committed by GitHub
commit 81664c3fce
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1 changed files with 967 additions and 50 deletions
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89
src/ModelContextProtocol.Core/UriTemplate.cs
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@ -67,7 +67,7 @@ internal static partial class UriTemplate
public static Regex CreateParser(string uriTemplate)
{
DefaultInterpolatedStringHandler pattern = new(0, 0, CultureInfo.InvariantCulture, stackalloc char[256]);
pattern.AppendFormatted('^');
pattern.AppendLiteral("^");
int lastIndex = 0;
for (Match m = UriTemplateExpression().Match(uriTemplate); m.Success; m = m.NextMatch())
@ -84,17 +84,20 @@ internal static partial class UriTemplate
switch (m.Groups["operator"].Value)
{
case "#": AppendExpression(ref pattern, paramNames, '#', "[^,]+"); break;
case "/": AppendExpression(ref pattern, paramNames, '/', "[^/?]+"); break;
default: AppendExpression(ref pattern, paramNames, null, "[^/?&]+"); break;
case "+": AppendExpression(ref pattern, paramNames, null, "[^?&#]*"); break;
case "#": AppendExpression(ref pattern, paramNames, '#', ".*"); break;
case ".": AppendExpression(ref pattern, paramNames, '.', "[^/?#]*"); break;
case "/": AppendExpression(ref pattern, paramNames, '/', "[^/?#]*"); break;
default: AppendExpression(ref pattern, paramNames, null, "[^/?&#]*"); break;
case "?": AppendQueryExpression(ref pattern, paramNames, '?'); break;
case "&": AppendQueryExpression(ref pattern, paramNames, '&'); break;
case ";": AppendPathParameterExpression(ref pattern, paramNames); break;
}
}
pattern.AppendFormatted(Regex.Escape(uriTemplate.Substring(lastIndex)));
pattern.AppendFormatted('$');
pattern.AppendLiteral("$");
return new Regex(
pattern.ToStringAndClear(),
@ -113,7 +116,7 @@ internal static partial class UriTemplate
{
Debug.Assert(prefix is '?' or '&');
pattern.AppendFormatted("(?:\\");
pattern.AppendLiteral("(?:\\");
pattern.AppendFormatted(prefix);
if (paramNames.Count > 0)
@ -121,55 +124,93 @@ internal static partial class UriTemplate
AppendParameter(ref pattern, paramNames[0]);
for (int i = 1; i < paramNames.Count; i++)
{
pattern.AppendFormatted("\\&?");
pattern.AppendLiteral("\\&?");
AppendParameter(ref pattern, paramNames[i]);
}
static void AppendParameter(ref DefaultInterpolatedStringHandler pattern, string paramName)
{
paramName = Regex.Escape(paramName);
pattern.AppendFormatted("(?:");
pattern.AppendLiteral("(?:");
pattern.AppendFormatted(paramName);
pattern.AppendFormatted("=(?<");
pattern.AppendLiteral("=(?<");
pattern.AppendFormatted(paramName);
pattern.AppendFormatted(">[^/?&]+))?");
pattern.AppendLiteral(">[^/?&]*))?");
}
}
pattern.AppendFormatted(")?");
pattern.AppendLiteral(")?");
}
// Chooses a regex character‐class (`valueChars`) based on the initial `prefix` to define which
// characters make up a parameter value. Then, for each name in `paramNames`, it optionally
// appends the escaped `prefix` (only on the first parameter, then switches to ','), and
// adds an optional named capture group `(?<paramName>valueChars)` to match and capture that value.
// Note: For "+" (reserved expansion) operator, prefix is null but valueChars allows "/" characters.
// Note: For "." (label expansion) operator, the separator is "." instead of ",".
static void AppendExpression(ref DefaultInterpolatedStringHandler pattern, List<string> paramNames, char? prefix, string valueChars)
{
Debug.Assert(prefix is '#' or '/' or null);
Debug.Assert(prefix is '#' or '/' or '.' or null);
if (paramNames.Count > 0)
{
if (prefix is not null)
{
pattern.AppendFormatted('\\');
pattern.AppendLiteral("\\");
pattern.AppendFormatted(prefix);
pattern.AppendFormatted('?');
pattern.AppendLiteral("?");
}
AppendParameter(ref pattern, paramNames[0], valueChars);
// For label expansion (.), the separator between values is also a dot
// For path segment expansion (/), the separator between values is also a slash
string separator = prefix switch
{
'.' => "\\.",
'/' => "\\/",
_ => "\\,"
};
for (int i = 1; i < paramNames.Count; i++)
{
pattern.AppendFormatted("\\,?");
pattern.AppendFormatted(separator);
pattern.AppendLiteral("?");
AppendParameter(ref pattern, paramNames[i], valueChars);
}
static void AppendParameter(ref DefaultInterpolatedStringHandler pattern, string paramName, string valueChars)
{
pattern.AppendFormatted("(?<");
pattern.AppendLiteral("(?<");
pattern.AppendFormatted(Regex.Escape(paramName));
pattern.AppendFormatted('>');
pattern.AppendLiteral(">");
pattern.AppendFormatted(valueChars);
pattern.AppendFormatted(")?");
pattern.AppendLiteral(")?");
}
}
}
// Appends a regex fragment for path-style parameter expansion (;).
// Format: ;name=value or ;name (if value is empty), separated by semicolons.
// Each parameter is made optional and captured by a named group.
static void AppendPathParameterExpression(ref DefaultInterpolatedStringHandler pattern, List<string> paramNames)
{
if (paramNames.Count > 0)
{
AppendParameter(ref pattern, paramNames[0]);
for (int i = 1; i < paramNames.Count; i++)
{
AppendParameter(ref pattern, paramNames[i]);
}
static void AppendParameter(ref DefaultInterpolatedStringHandler pattern, string paramName)
{
// Match ;name or ;name=value
paramName = Regex.Escape(paramName);
pattern.AppendLiteral("(?:;");
pattern.AppendFormatted(paramName);
pattern.AppendLiteral("(?:=(?<");
pattern.AppendFormatted(paramName);
pattern.AppendLiteral(">[^;/?&]*))?)?");
}
}
}
@ -363,7 +404,7 @@ internal static partial class UriTemplate
}
}
if (expansions.Count > 0 &&
if (expansions.Count > 0 &&
(modifierBehavior.PrefixEmptyExpansions || !expansions.All(string.IsNullOrEmpty)))
{
builder.AppendLiteral(modifierBehavior.Prefix);
@ -435,7 +476,7 @@ internal static partial class UriTemplate
if (c <= 0x7F)
{
builder.AppendFormatted('%');
builder.AppendLiteral("%");
builder.AppendFormatted(hexDigits[c >> 4]);
builder.AppendFormatted(hexDigits[c & 0xF]);
}
@ -448,7 +489,7 @@ internal static partial class UriTemplate
foreach (byte b in Encoding.UTF8.GetBytes([c]))
#endif
{
builder.AppendFormatted('%');
builder.AppendLiteral("%");
builder.AppendFormatted(hexDigits[b >> 4]);
builder.AppendFormatted(hexDigits[b & 0xF]);
}
@ -460,13 +501,13 @@ internal static partial class UriTemplate
/// Defines an equality comparer for Uri templates as follows:
/// 1. Non-templated Uris use regular System.Uri equality comparison (host name is case insensitive).
/// 2. Templated Uris use regular string equality.
///
///
/// We do this because non-templated resources are looked up directly from the resource dictionary
/// and we need to make sure equality is implemented correctly. Templated Uris are resolved in a
/// fallback step using linear traversal of the resource dictionary, so their equality is only
/// there to distinguish between different templates.
/// </summary>
public sealed class UriTemplateComparer : IEqualityComparer<string>
internal sealed class UriTemplateComparer : IEqualityComparer<string>
{
public static IEqualityComparer<string> Instance { get; } = new UriTemplateComparer();