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Add polyfills for File.ReadLinesAsync(...), TextReader.ReadLineAsync(CancellationToken), TextReader.ReadToEndAsync(CancellationToken) #68

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Merged
Tyrrrz merged 2 commits into from
Dec 3, 2025
Merged

Add polyfills for File.ReadLinesAsync(...), TextReader.ReadLineAsync(CancellationToken), TextReader.ReadToEndAsync(CancellationToken) #68

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Add polyfills for `File.ReadLinesAsync(...)`, `TextReader.ReadLineAsy…
Tyrrrz Dec 3, 2025
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asd
Tyrrrz Dec 3, 2025
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41 changes: 41 additions & 0 deletions PolyShim.Tests/Net70/FileTests.cs
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using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using FluentAssertions;
using Xunit;

namespace PolyShim.Tests.Net70;

public class FileTests
{
[Fact]
public async Task ReadLinesAsync_Test()
{
// Arrange
var linesToWrite = new[] { "Line 1", "Line 2", "Line 3" };
var tempFilePath = Path.GetTempFileName();
await File.WriteAllLinesAsync(tempFilePath, linesToWrite);

try
{
// Act
var readLines = new List<string>();
await foreach (var line in File.ReadLinesAsync(tempFilePath))
readLines.Add(line);

// Assert
readLines.Should().Equal(linesToWrite);
}
finally
{
try
{
File.Delete(tempFilePath);
}
catch
{
// Ignore
}
}
}
}
77 changes: 77 additions & 0 deletions PolyShim.Tests/Net70/TextReaderTests.cs
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using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using FluentAssertions;
using Xunit;

namespace PolyShim.Tests.Net70;

public class TextReaderTests
{
[Fact]
public async Task ReadLineAsync_Test()
{
// Arrange
using var stream = new MemoryStream("Line 1\nLine 2\nLine 3\n"u8.ToArray());
using var reader = new StreamReader(stream);

// Act
var line1 = await reader.ReadLineAsync(CancellationToken.None);
var line2 = await reader.ReadLineAsync(CancellationToken.None);
var line3 = await reader.ReadLineAsync(CancellationToken.None);
var line4 = await reader.ReadLineAsync(CancellationToken.None);

// Assert
line1.Should().Be("Line 1");
line2.Should().Be("Line 2");
line3.Should().Be("Line 3");
line4.Should().BeNull();
}

[Fact]
public async Task ReadLineAsync_Cancellation_Test()
{
// Arrange
using var stream = new MemoryStream("Line 1\nLine 2\nLine 3\n"u8.ToArray());
using var reader = new StreamReader(stream);
using var cts = new CancellationTokenSource();
await cts.CancelAsync();

// Act & Assert
await Assert.ThrowsAnyAsync<OperationCanceledException>(async () =>
{
await reader.ReadLineAsync(cts.Token);
});
}

[Fact]
public async Task ReadToEndAsync_Test()
{
// Arrange
using var stream = new MemoryStream("Hello, World!"u8.ToArray());
using var reader = new StreamReader(stream);

// Act
var content = await reader.ReadToEndAsync(CancellationToken.None);

// Assert
content.Should().Be("Hello, World!");
}

[Fact]
public async Task ReadToEndAsync_Cancellation_Test()
{
// Arrange
using var stream = new MemoryStream("Hello, World!"u8.ToArray());
using var reader = new StreamReader(stream);
using var cts = new CancellationTokenSource();
await cts.CancelAsync();

// Act & Assert
await Assert.ThrowsAnyAsync<OperationCanceledException>(async () =>
{
await reader.ReadToEndAsync(cts.Token);
});
}
}
79 changes: 79 additions & 0 deletions PolyShim/Net70/File.cs
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#if (NETCOREAPP && !NET7_0_OR_GREATER) || (NETFRAMEWORK) || (NETSTANDARD)
#nullable enable
// ReSharper disable RedundantUsingDirective
// ReSharper disable CheckNamespace
// ReSharper disable InconsistentNaming
// ReSharper disable PartialTypeWithSinglePart

using System.Collections.Generic;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;

internal static partial class PolyfillExtensions
{
// No file I/O on .NET Standard prior to 1.3
#if !NETSTANDARD || NETSTANDARD1_3_OR_GREATER
extension(File)
{
#if FEATURE_TASK && FEATURE_ASYNCINTERFACES
// https://learn.microsoft.com/dotnet/api/system.io.file.readlinesasync#system-io-file-readlinesasync(system-string-system-text-encoding-system-threading-cancellationtoken)
public static async IAsyncEnumerable<string> ReadLinesAsync(
string path,
Encoding encoding,
[EnumeratorCancellation] CancellationToken cancellationToken = default
)
{
using var stream = new FileStream(
path,
FileMode.Open,
FileAccess.Read,
FileShare.Read,
4096,
FileOptions.Asynchronous | FileOptions.SequentialScan
);

using var reader = new StreamReader(stream, encoding);

while (!reader.EndOfStream)
{
cancellationToken.ThrowIfCancellationRequested();

var line = await reader.ReadLineAsync(cancellationToken).ConfigureAwait(false);
if (line is not null)
yield return line;
}
}

// https://learn.microsoft.com/dotnet/api/system.io.file.readlinesasync#system-io-file-readlinesasync(system-string-system-threading-cancellationtoken)
public static async IAsyncEnumerable<string> ReadLinesAsync(
string path,
[EnumeratorCancellation] CancellationToken cancellationToken = default
)
{
using var stream = new FileStream(
path,
FileMode.Open,
FileAccess.Read,
FileShare.Read,
4096,
FileOptions.Asynchronous | FileOptions.SequentialScan
);

using var reader = new StreamReader(stream);

while (!reader.EndOfStream)
{
cancellationToken.ThrowIfCancellationRequested();

var line = await reader.ReadLineAsync(cancellationToken).ConfigureAwait(false);
if (line is not null)
yield return line;
}
}
#endif
}
#endif
}
#endif
50 changes: 50 additions & 0 deletions PolyShim/Net70/TextReader.cs
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#if (NETCOREAPP && !NET7_0_OR_GREATER) || (NETFRAMEWORK) || (NETSTANDARD)
#nullable enable
// ReSharper disable RedundantUsingDirective
// ReSharper disable CheckNamespace
// ReSharper disable InconsistentNaming
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

internal static partial class PolyfillExtensions
{
extension(TextReader reader)
{
#if FEATURE_TASK
// https://learn.microsoft.com/dotnet/api/system.io.textreader.readlineasync#system-io-textreader-readlineasync(system-threading-cancellationtoken)
public Task<string?> ReadLineAsync(CancellationToken cancellationToken)
{
// Impossible to polyfill this properly as it requires to track the buffer's state
cancellationToken.ThrowIfCancellationRequested();
return reader.ReadLineAsync();
}

// https://learn.microsoft.com/dotnet/api/system.io.textreader.readtoendasync#system-io-textreader-readtoendasync(system-threading-cancellationtoken)
public async Task<string> ReadToEndAsync(CancellationToken cancellationToken)
{
var result = new StringBuilder();
var buffer = new char[4096];

while (true)
{
var charsRead = await reader
.ReadAsync(buffer, cancellationToken)
.ConfigureAwait(false);

if (charsRead <= 0)
break;

result.Append(buffer, 0, charsRead);
}

return result.ToString();
}
#endif
}
}
#endif
8 changes: 6 additions & 2 deletions PolyShim/Signatures.md
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# Signatures

- **Total:** 335
- **Total:** 339
- **Types:** 74
- **Members:** 261
- **Members:** 265

___

Expand Down Expand Up @@ -89,6 +89,8 @@ ___
- `FeatureSwitchDefinitionAttribute`
- [**[class]**](https://learn.microsoft.com/dotnet/api/system.diagnostics.codeanalysis.featureswitchdefinitionattribute) <sup><sub>.NET 9.0</sub></sup>
- `File`
- [`IAsyncEnumerable<string> ReadLinesAsync(string, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.file.readlinesasync#system-io-file-readlinesasync(system-string-system-threading-cancellationtoken)) <sup><sub>.NET 7.0</sub></sup>
- [`IAsyncEnumerable<string> ReadLinesAsync(string, Encoding, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.file.readlinesasync#system-io-file-readlinesasync(system-string-system-text-encoding-system-threading-cancellationtoken)) <sup><sub>.NET 7.0</sub></sup>
- [`Task AppendAllBytesAsync(string, byte[], CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.file.appendallbytesasync#system-io-file-appendallbytesasync(system-string-system-byte()-system-threading-cancellationtoken)) <sup><sub>.NET 9.0</sub></sup>
- [`Task AppendAllLinesAsync(string, IEnumerable<string>, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.file.appendalllinesasync#system-io-file-appendalllinesasync(system-string-system-collections-generic-ienumerable((system-string))-system-threading-cancellationtoken)) <sup><sub>.NET Core 2.0</sub></sup>
- [`Task AppendAllLinesAsync(string, IEnumerable<string>, Encoding, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.file.appendalllinesasync#system-io-file-appendalllinesasync(system-string-system-collections-generic-ienumerable((system-string))-system-text-encoding-system-threading-cancellationtoken)) <sup><sub>.NET Core 2.0</sub></sup>
Expand Down Expand Up @@ -413,6 +415,8 @@ ___
- `TextReader`
- [`int Read(Span<char>)`](https://learn.microsoft.com/dotnet/api/system.io.textreader.read#system-io-textreader-read(system-span((system-char)))) <sup><sub>.NET Core 2.1</sub></sup>
- [`Task<int> ReadAsync(Memory<char>, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.textreader.readasync#system-io-textreader-readasync(system-memory((system-char))-system-threading-cancellationtoken)) <sup><sub>.NET Core 2.1</sub></sup>
- [`Task<string?> ReadLineAsync(CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.textreader.readlineasync#system-io-textreader-readlineasync(system-threading-cancellationtoken)) <sup><sub>.NET 7.0</sub></sup>
- [`Task<string> ReadToEndAsync(CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.textreader.readtoendasync#system-io-textreader-readtoendasync(system-threading-cancellationtoken)) <sup><sub>.NET 7.0</sub></sup>
- `TextWriter`
- [`Task DisposeAsync()`](https://learn.microsoft.com/dotnet/api/system.io.textwriter.disposeasync) <sup><sub>.NET Core 3.0</sub></sup>
- [`Task WriteAsync(ReadOnlyMemory<char>, CancellationToken)`](https://learn.microsoft.com/dotnet/api/system.io.textwriter.writeasync#system-io-textwriter-writeasync(system-readonlymemory((system-char))-system-threading-cancellationtoken)) <sup><sub>.NET Core 2.1</sub></sup>
Expand Down
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