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Reduce allocations in FeatureFlags.IsEnabled (#11076)
* Optimize FeatureFlags.IsEnabled with span based contains check. * PR feedback udpates. - Added a span based overload.s - Made an extension method.s - Test coverage improvements. * Minor improvements to method summary. * Fix linting issue. * Removing separator default value.
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‎release_notes.md

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- Fix Instance Manager for CV1 Migration (#11072)
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- Avoid setting up OTel and AzMon exporter in the placeholder mode. (#11090)
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- Update Java Worker Version to [2.19.1](https://github.com/Azure/azure-functions-java-worker/releases/tag/2.19.1)
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- Memory allocation optimizations in `FeatureFlags.IsEnabled` by adopting zero-allocation `ContainsToken` for efficient delimited token search (#11075)

‎src/WebJobs.Script/Config/FeatureFlags.cs

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// Licensed under the MIT License. See License.txt in the project root for license information.
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using System;
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using System.Linq;
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using Microsoft.Azure.WebJobs.Script.Extensions;
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namespace Microsoft.Azure.WebJobs.Script.Config
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{
@@ -16,14 +16,14 @@ public static class FeatureFlags
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public static bool IsEnabled(string name, IEnvironment environment)
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{
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string featureFlags = environment.GetEnvironmentVariable(EnvironmentSettingNames.AzureWebJobsFeatureFlags);
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if (!string.IsNullOrEmpty(featureFlags))
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var featureFlags = environment.GetEnvironmentVariable(EnvironmentSettingNames.AzureWebJobsFeatureFlags);
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if (string.IsNullOrEmpty(featureFlags))
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{
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string[] flags = featureFlags.Split(',');
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return flags.Contains(name, StringComparer.OrdinalIgnoreCase);
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return false;
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}
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return false;
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return featureFlags.ContainsToken(name, separator: ',', StringComparison.OrdinalIgnoreCase);
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}
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}
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}
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}

‎src/WebJobs.Script/Extensions/TokenExtensions.cs

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// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the MIT License. See License.txt in the project root for license information.
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using System;
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using System.Linq;
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namespace Microsoft.Azure.WebJobs.Script.Extensions
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{
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public static class TokenExtensions
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{
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/// <summary>
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/// Determines whether a delimited string contains a specific token, using the specified separator and string comparison.
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/// This method is a zero-allocation, faster alternative to splitting the string and using Contains, as it avoids unnecessary allocations.
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/// </summary>
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/// <param name="source">The string containing one or more tokens separated by a delimiter (e.g., "FeatureA,FeatureB").</param>
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/// <param name="token">The token to search for. Must not contain the separator character. A match is determined using the specified comparison type.</param>
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/// <param name="separator">The character used to separate tokens in the string. Example ','.</param>
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/// <param name="comparisonType">The string comparison type to use. Defaults to OrdinalIgnoreCase.</param>
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/// <returns>
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/// <c>true</c> if the token is found as an exact match in the delimited string; otherwise, <c>false</c>.
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/// </returns>
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/// <exception cref="ArgumentException">
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/// Thrown if <paramref name="token"/> contains the separator character.
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/// </exception>
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/// <remarks>
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/// If <paramref name="source"/> is empty or <paramref name="token"/> is empty, the method returns <c>false</c>.
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/// </remarks>
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public static bool ContainsToken(this string source, string token, char separator, StringComparison comparisonType = StringComparison.OrdinalIgnoreCase)
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{
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if (string.IsNullOrEmpty(source) || string.IsNullOrEmpty(token))
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{
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return false;
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}
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return source.AsSpan().ContainsToken(token.AsSpan(), separator, comparisonType);
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}
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/// <summary>
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/// Determines whether a delimited <see cref="ReadOnlySpan{Char}"/> contains a specific token,
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/// using the specified separator and string comparison. This method is a high-performance,
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/// zero-allocation alternative that avoids splitting or heap allocations.
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/// </summary>
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/// <param name="source">The span containing one or more tokens separated by a delimiter (e.g., "FeatureA,FeatureB").</param>
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/// <param name="token">The token to search for. Must not contain the separator character. A match is determined using the specified comparison type.</param>
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/// <param name="separator">The character used to separate tokens in the span. Example ','.</param>
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/// <param name="comparisonType">The string comparison type to use. Defaults to OrdinalIgnoreCase.</param>
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/// <returns>
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/// <c>true</c> if the token is found as an exact match in the delimited span; otherwise, <c>false</c>.
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/// </returns>
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/// <exception cref="ArgumentException">
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/// Thrown if <paramref name="token"/> contains the separator character.
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/// </exception>
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/// <remarks>
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/// If <paramref name="source"/> is empty or <paramref name="token"/> is empty, the method returns <c>false</c>.
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/// </remarks>
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public static bool ContainsToken(this ReadOnlySpan<char> source, ReadOnlySpan<char> token, char separator, StringComparison comparisonType = StringComparison.OrdinalIgnoreCase)
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{
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if (token.IsEmpty)
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{
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return false;
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}
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if (token.Contains(separator))
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{
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throw new ArgumentException($"The search token must not contain the separator character '{separator}'.", nameof(token));
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}
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var remaining = source;
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while (!remaining.IsEmpty)
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{
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var separatorIndex = remaining.IndexOf(separator);
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ReadOnlySpan<char> currentToken;
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if (separatorIndex >= 0)
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{
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currentToken = remaining.Slice(0, separatorIndex);
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remaining = remaining.Slice(separatorIndex + 1);
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}
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else
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{
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currentToken = remaining;
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remaining = default;
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}
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if (currentToken.Equals(token, comparisonType))
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{
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return true;
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}
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}
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return false;
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}
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}
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}

‎test/WebJobs.Script.Tests/Utils/TokenExtensionTests.cs

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// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the MIT License. See License.txt in the project root for license information.
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using System;
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using Microsoft.Azure.WebJobs.Script.Extensions;
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using Xunit;
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namespace Microsoft.Azure.WebJobs.Script.Tests.Utils
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{
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public sealed class TokenExtensionTests
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{
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[Theory]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureB", ',', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureD", ',', false)]
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[InlineData("FeatureA,FeatureB,FeatureC", "featureb", ',', true)]
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[InlineData("FeatureA|FeatureB|FeatureC", "FeatureC", '|', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureA", ',', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureC", ',', true)]
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[InlineData(null, "FeatureA", ',', false)]
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[InlineData("", "FeatureA", ',', false)]
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[InlineData("", "", ',', false)]
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[InlineData("FeatureA,,FeatureB", "FeatureA", ',', true)]
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[InlineData("FeatureA,,FeatureB", "FeatureB", ',', true)]
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[InlineData(",FeatureA", "FeatureA", ',', true)]
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[InlineData("FeatureA,", "FeatureA", ',', true)]
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[InlineData("FeatureA,FeatureB,", "FeatureB", ',', true)]
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public void ContainsToken_WorksAsExpected(string delimited, string token, char separator, bool expected)
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{
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var result = delimited.ContainsToken(token, separator);
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Assert.Equal(expected, result);
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}
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[Theory]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureB", ',', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureD", ',', false)]
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[InlineData("FeatureA,FeatureB,FeatureC", "featureb", ',', true)]
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[InlineData("FeatureA|FeatureB|FeatureC", "FeatureC", '|', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureA", ',', true)]
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[InlineData("FeatureA,FeatureB,FeatureC", "FeatureC", ',', true)]
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[InlineData("FeatureA,,FeatureB", "FeatureA", ',', true)]
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[InlineData("FeatureA,,FeatureB", "FeatureB", ',', true)]
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[InlineData(",FeatureA", "FeatureA", ',', true)]
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[InlineData("FeatureA,", "FeatureA", ',', true)]
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[InlineData("FeatureA,FeatureB,", "FeatureB", ',', true)]
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public void ContainsToken_SpanOverload_WorksAsExpected(string delimited, string token, char separator, bool expected)
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{
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var result = delimited.AsSpan().ContainsToken(token.AsSpan(), separator);
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Assert.Equal(expected, result);
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}
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[Fact]
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public void ContainsToken_ThrowsArgumentException_WhenTokenContainsSeparator_StringOverload()
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{
57+
var ex = Assert.Throws<ArgumentException>(() =>
58+
{
59+
string source = "FeatureA,FeatureB";
60+
string invalidToken = "FeatureA,FeatureB";
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char separator = ',';
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63+
source.ContainsToken(invalidToken, separator);
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});
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Assert.Contains("must not contain the separator", ex.Message);
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}
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[Fact]
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public void ContainsToken_ThrowsArgumentException_WhenTokenContainsSeparator_SpanOverload()
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{
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var ex = Assert.Throws<ArgumentException>(() =>
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{
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ReadOnlySpan<char> source = "FeatureA|FeatureB".AsSpan();
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ReadOnlySpan<char> invalidToken = "FeatureA|FeatureB".AsSpan();
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source.ContainsToken(invalidToken, '|');
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});
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Assert.Contains("must not contain the separator", ex.Message);
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}
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}
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}

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