Improve source generator and analyzer responsiveness

[PhenX]

While limiting useless executions on unrelated code as much as possible

Here are the results of the source generator benchmark.

GeneratorBenchmarks — Overview

The benchmark measures the performance of ProjectionExpressionGenerator (the Roslyn incremental source generator) under a synthetic but realistic workload. In Setup, it builds a CSharpCompilation containing a configurable number of [Projectable] members (ProjectableCount = 1 / 100 / 1 000), spread across multiple files of 1–9 members each, covering all 9 transformer paths in the generator (simple properties, null-conditionals, switch expressions, block-bodied methods, etc.). An equal number of noise files — plain classes with no [Projectable] members — are added to simulate a realistic project where only a fraction of files are relevant to the generator. Two additional compilations are pre-built in Setup, each identical to the baseline but with a single trailing comment appended to either a noise file or a projectable file.

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Methods

Cold benchmarks (new driver every iteration)

Method	What it measures
RunGenerator (baseline)	Full cold run on the unmodified compilation. Establishes the cost of running the generator from scratch with no prior state.
RunGenerator_NoiseChange	Full cold run on the compilation where a noise file was edited. Shows whether the cold path is sensitive to which files changed.
RunGenerator_ProjectableChange	Full cold run on the compilation where a projectable file was edited (comment only, no member body change).

Incremental benchmarks (pre-warmed driver)

Method	What it measures
RunGenerator_Incremental_NoiseChange	Warm incremental run after a trivial edit in a noise file. The generator finds no [Projectable] nodes in the changed tree and should return all cached outputs immediately — this is the minimum incremental overhead.
RunGenerator_Incremental_ProjectableChange	Warm incremental run after a trivial edit in a projectable file (comment only). The generator must re-examine every [Projectable] node it previously found in that tree, compare them to cached values, and only then confirm the cache is still valid — isolating the incremental re-examination overhead vs. the noise case.

BEFORE:

AFTER:

We can see that the incremental generator is significatively slower on files containing projectables. It remains acceptable though (under 10ms). It is faster though on files not containing projectables.

[Copilot]

Pull request overview

This PR refactors the incremental generator pipeline to reduce unnecessary work by snapshotting [Projectable] attribute arguments into stable plain data and introducing custom equality comparers intended to improve caching behavior across edits.

Changes:

• Snapshot [Projectable] attribute named arguments into a new ProjectableAttributeData record struct and pass it through the pipeline.
• Rework generator initialization to avoid flowing “live” Roslyn objects from the syntax transform, and build semantic information only in the final source output step.
• Replace the previous member/compilation comparers with new comparer logic based on syntax tree identity, member text, attribute snapshot, and external references.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/EntityFrameworkCore.Projectables.Generator/ProjectionExpressionGenerator.cs	Updates incremental pipeline to carry stable attribute snapshots and compute semantic info in the output step.
src/EntityFrameworkCore.Projectables.Generator/ProjectableInterpreter.cs	Updates descriptor creation to consume precomputed symbol + attribute snapshot, optionally requiring Compilation for constructors.
src/EntityFrameworkCore.Projectables.Generator/ProjectableAttributeData.cs	Adds a plain-data snapshot type for [Projectable] named arguments.
src/EntityFrameworkCore.Projectables.Generator/MemberDeclarationSyntaxEqualityComparer.cs	Replaces name-based equality with syntax-tree identity + full text equality/hash.
src/EntityFrameworkCore.Projectables.Generator/MemberDeclarationSyntaxAndCompilationEqualityComparer.cs	Introduces a custom comparer for (member+attribute, compilation) intended to skip work on unrelated edits.

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[Copilot]

@PhenX I've opened a new pull request, #172, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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