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Improve source generation both for Roslyn-based and for BT-based SG #1732
Description
Summary
We should use IIncrementalSourceGenerator for CsWin32 not only because it's recommended but because NativeMethods.txt is expected to have relatively a large number of entries. Re-generating the whole source every time NativeMethods.txt or .json degrades the VS performance on large projects.
Plus, the BuildTask one has Inputs and Outputs @ GenerateCsWin32Code but once called, it generates the whole source.
Roslyn-based SG Design
[Generator]
public sealed class SourceGenerator : IIncrementalGenerator
{
public void Initialize(IncrementalGeneratorInitializationContext context)
{
var options = context.AdditionalTextsProvider
.Where(static file => Path.GetFileName(file.Path).EndsWith("NativeMethods.json", StringComparison.OrdinalIgnoreCase))
.Collect()
.Select(static (files, ct) => ParseOptions(files, ct));
var nativeMethods = context.AdditionalTextsProvider
.Where(static file => Path.GetFileName(file.Path).EndsWith("NativeMethods.txt", StringComparison.OrdinalIgnoreCase))
.Select(static (file, ct) => ReadNativeMethods(file, ct))
.Collect();
var buildProps = context.AnalyzerConfigOptionsProvider
.Select(static (provider, ct) => ReadBuildProperties(provider.GlobalOptions));
var inputs = context.CompilationProvider
.Combine(context.ParseOptionsProvider)
.Combine(options)
.Combine(nativeMethods)
.Combine(buildProps);
context.RegisterSourceOutput(inputs, static (spc, input) =>
{
// existing Execute body, but driven from immutable input models
Generate(spc, input);
});
}
}BuildTask-based SG Design
string sourceText = unit.Value.GetText(Encoding.UTF8).ToString();
bool changed = WriteFileIfChanged(filePath, sourceText);
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