Add generic projection hooks with AsLeftJoin and AsProjectable support by Copilot · Pull Request #311 · arika0093/Linqraft

Copilot · 2026-03-18T10:23:37Z

This change adds a reusable projection-hook mechanism for *Expr generation so user-authored anonymous projections can opt into custom rewrites. It introduces built-in support for AsLeftJoin() and AsProjectable(), while enforcing that these hooks are only used inside generated projection contexts.

Projection hook infrastructure
- Added configurable projection hook definitions to the generator options.
- Support declarations now emit generated no-op extension methods for registered hooks.
- The mechanism is generic so future hooks can be added without introducing another one-off path.
AsLeftJoin() rewrite
- Added a built-in AsLeftJoin() hook for nullable navigation access inside generated projections.
- The emitter rewrites x.Child.AsLeftJoin().Foo into an explicit null-guarded form so the generated projection preserves outer rows instead of collapsing into inner-join-like behavior.
AsProjectable() rewrite
- Added a built-in AsProjectable() hook for inlining source-defined computed members into generated projections.
- Supports expansion of instance properties and methods by substituting the receiver and arguments into the declared body, so the generated *Expr behaves like the query body was written inline.
Analyzer enforcement
- Added a new analyzer error for projection hooks used outside SelectExpr / SelectManyExpr / GroupByExpr / Generate.
- This keeps the generated hook API intentionally inert unless it is consumed by the projection pipeline.
Coverage
- Added focused source-generator coverage for default and custom hook declaration generation.
- Added analyzer coverage for valid vs invalid hook usage.
- Added EF Core coverage for nullable-navigation left-join behavior and projectable member inlining.

Example usage:

query.SelectExpr(x => new
{
    ChildName = x.Child.AsLeftJoin().Name,
    Computed = x.SomeComputedMember.AsProjectable(),
});

This enables the intended flow:

user anonymous projection -> explicit hook -> generated *Expr rewrite

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…ting Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com>

Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com>

Copilot

Pull request overview

Adds a generic “projection hook” mechanism to Linqraft’s projection pipeline, enabling explicit, user-authored markers in anonymous projections that the generator rewrites (built-in: AsLeftJoin() and AsProjectable()), plus analyzer enforcement and test coverage.

Changes:

Introduces configurable projection hook definitions (defaulting to AsLeftJoin + AsProjectable) and emits corresponding no-op hook extension declarations.
Extends the projection expression emitter to rewrite AsLeftJoin into null-guarded access and to inline computed members via AsProjectable.
Adds analyzer rule LQRE003 to block projection hook usage outside generated projection contexts, with generator/analyzer/EFCore tests.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/Linqraft.Tests.SG/Program.cs	Adds SG coverage for default/custom hook declaration emission.
tests/Linqraft.Tests.EFCore/EfCoreModels.cs	Adds a computed query-shaped property for `AsProjectable` coverage.
tests/Linqraft.Tests.EFCore/EfCoreBasicProjectionTests.cs	Adds SQLite EFCore tests for `AsLeftJoin` and `AsProjectable` behavior.
tests/Linqraft.Tests.Analyzer/AnalyzerSmokeTests.cs	Adds `LQRE003` smoke tests for hook usage inside/outside projections.
src/Linqraft.Core/SourceGenerator/ProjectionSupportExtensionClassGenerator.cs	Emits generated no-op hook extension methods based on `ProjectionHooks`.
src/Linqraft.Core/SourceGenerator/ProjectionExpressionEmitter.cs	Implements hook rewriting: left-join null-guards + projectable inlining.
src/Linqraft.Core/Configuration/LinqraftGeneratorOptionsCore.cs	Adds hook definitions (`LinqraftProjectionHookDefinition`, `Kind`) and defaults.
src/Linqraft.Analyzer/LinqraftCompositeAnalyzer.cs	Adds projection-hook usage enforcement diagnostic reporting.
src/Linqraft.Analyzer/DiagnosticDescriptors.cs	Registers new analyzer error descriptor `LQRE003`.
src/Linqraft.Analyzer/AnalyzerHelpers.cs	Adds helper detection for hook invocations and hook-context detection.

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src/Linqraft.Core/SourceGenerator/ProjectionExpressionEmitter.cs

+    private bool TryEmitProjectableHook(
+        InvocationExpressionSyntax invocation,
+        string? overrideReceiver,
+        out string rewritten
+    )
+    {
+        rewritten = string.Empty;
+        if (!IsProjectionHookInvocation(invocation, LinqraftProjectionHookKind.Projectable))
+        {
+            return false;
+        }
+
+        if (!TryExpandProjectableInvocation(invocation, overrideReceiver, out var expanded))
+        {
+            return false;
+        }
+
+        rewritten = Emit(expanded);
+        return true;
+    }


src/Linqraft.Analyzer/AnalyzerHelpers.cs

+    public static bool IsProjectionExprInvocation(InvocationExpressionSyntax invocation)
+    {
+        return GetInvocationName(invocation.Expression) is "SelectExpr" or "SelectManyExpr" or "GroupByExpr";
+    }
+
+    public static bool IsProjectionHookInvocation(InvocationExpressionSyntax invocation)
+    {
+        return ProjectionHookNames.Contains(GetInvocationName(invocation.Expression));
+    }
+
+    public static bool IsInsideProjectionHookContext(SyntaxNode node)
+    {
+        return node.AncestorsAndSelf()
+            .OfType<InvocationExpressionSyntax>()
+            .Any(invocation =>
+                IsProjectionExprInvocation(invocation)
+                || string.Equals(
+                    GetInvocationName(invocation.Expression),
+                    "Generate",
+                    StringComparison.Ordinal
+                )
+            );
+    }


src/Linqraft.Analyzer/LinqraftCompositeAnalyzer.cs

+    private static void AnalyzeProjectionHookUsage(
+        SyntaxNodeAnalysisContext context,
+        InvocationExpressionSyntax invocation
+    )
+    {
+        if (
+            !AnalyzerHelpers.IsProjectionHookInvocation(invocation)
+            || AnalyzerHelpers.IsInsideProjectionHookContext(invocation)
+        )
+        {
+            return;
+        }
+
+        context.ReportDiagnostic(
+            Diagnostic.Create(
+                DiagnosticDescriptors.ProjectionHookUsage,
+                invocation.GetLocation(),
+                AnalyzerHelpers.GetInvocationName(invocation.Expression)
+            )
+        );


src/Linqraft.Core/SourceGenerator/ProjectionSupportExtensionClassGenerator.cs

+        foreach (
+            var hook in generatorOptions
+                .ProjectionHooks.GroupBy(
+                    hook => hook.MethodName,
+                    global::System.StringComparer.Ordinal
+                )
+                .Select(group => group.First())
+        )
+        {


Initial plan

95312c4

Copilot AI assigned Copilot and arika0093 Mar 18, 2026

Copilot started work on behalf of arika0093 March 18, 2026 10:23 View session

Copilot AI and others added 2 commits March 18, 2026 10:40

feat: add projection hook support for left join and projectable rewri…

9e9870d

…ting Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com>

test: align projection hook test naming

4392f2d

Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add AsLeftJoin and AsProjectable methods for EFCore~~ Add generic projection hooks with AsLeftJoin and AsProjectable support Mar 18, 2026

Copilot AI requested a review from arika0093 March 18, 2026 10:44

Copilot finished work on behalf of arika0093 March 18, 2026 10:45

arika0093 requested a review from Copilot March 18, 2026 10:56

Copilot started reviewing on behalf of arika0093 March 18, 2026 10:56 View session

Copilot AI reviewed Mar 18, 2026

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Add generic projection hooks with AsLeftJoin and AsProjectable support#311

Add generic projection hooks with AsLeftJoin and AsProjectable support#311
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copilot/add-asleftjoin-and-asprojectable

Copilot AI commented Mar 18, 2026 •

edited

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Copilot AI commented Mar 18, 2026 •

edited

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