feat: forward additional mapping method parameters by Demivan · Pull Request #2193 · riok/mapperly

Demivan · 2026-03-19T17:57:46Z

Description

Additional parameters on mapping methods (beyond source/target/referenceHandler) are now forwarded to user-defined nested mapping methods, MapValue(Use=...), MapProperty(Use=...), and MapPropertyFromSource(Use=...) methods.
Works with queryable projections - additional parameters become captured variables in the generated expression.

Parameters are matched by name, but mappings to map them when types don't match are not generated. It is more complex to support that. Should I add type checks while that is not supported? Currently, parameter string ctx will match int ctx but will produce a non-compilable code.

Besides unit tests, I have tested it on real project and parameterized mapping methods and projections were generated correctly.

Note: I have used Claude, but I was steering is constantly - no vibecoding

Fixes #1472
Fixes #1765 (user needs to define mappings with parameters)

Supersedes #1946

Checklist

I did not use AI tools to generate this PR, or I have manually verified that the code is correct, optimal, and follows the project guidelines and architecture
I understand that low-quality, AI-generated PRs will be closed immediately without further explanation
The existing code style is followed
The commit message follows our guidelines
Performed a self-review of my code
Hard-to-understand areas of my code are commented
The documentation is updated (as applicable)
Unit tests are added/updated
Integration tests are added/updated (as applicable, especially if feature/bug depends on roslyn or framework version in use)

latonz

Thanks for the pull request, and for your patience. I was a bit out during the Easter holidays, but I’ve now added my feedback.

src/Riok.Mapperly/Descriptors/ParameterScope.cs

src/Riok.Mapperly/Descriptors/Mappings/UserMappings/UserImplementedInlinedExpressionMapping.cs

src/Riok.Mapperly/Descriptors/Mappings/TypeMappingBuildContext.cs

src/Riok.Mapperly/Descriptors/MappingCollection.cs

docs/docs/configuration/additional-mapping-parameters.mdx

src/Riok.Mapperly/Diagnostics/DiagnosticDescriptors.cs

src/Riok.Mapperly/Descriptors/ParameterScope.cs

src/Riok.Mapperly/Descriptors/MappingBuilders/InlineExpressionMappingBuilder.cs

test/Riok.Mapperly.Tests/Mapping/UserMethodAdditionalParameterForwardingTest.cs

…ters foundation

…lass invocations

…ilderContext Always allow additional parameters in BuildUserImplementedMapping (remove allowAdditionalParameters parameter — was true at all call sites)

…rameters

…t mappings

… parameter tracking

- MapPropertyFromSource(Use=...) unsatisfiable params → RMG097 - MapValue(Use=...) partially matching params → RMG096 + RMG082 - Nested mapping with multiple additional params - MappingTarget + MapProperty(Use=...) with params - Param consumed only by Use method → no false RMG082 - Param consumed only by nested mapping → no false RMG082 - Multiple unused params → multiple RMG082 - Init-only and constructor params from additional parameters - Nested projection inlining with additional params - Collection mapping test for additional parameter forwarding

fix: move diagnostics to AnalyzerReleases.Shipped.md and add diagnostic docs Per contributing guidelines: - Move RMG096/RMG097 from Unshipped to Shipped (Mapperly does not use Unshipped) - Add RMG096.mdx and RMG097.mdx diagnostic documentation pages

…nal parameters Projections with additional parameters now only pick up MapProperty/ MapPropertyFromSource configurations from element mappings whose additional parameters match. No fallback to default element mappings that ignore the parameters. Projections without additional parameters continue to use the default element mapping as before.

…meters feat: support additional parameters on external and MapPropertyFromSource Use methods - Remove IsExternal guard from BuildArguments in UserImplementedMethodMapping and UserImplementedExistingTargetMethodMapping — external mapper methods now forward additional parameters like internal ones - Always allow additional parameters in BuildUserImplementedMapping (remove allowAdditionalParameters parameter — was true at all call sites) - Enable MapPropertyFromSource(Use=...) with additional parameters by discovering user-implemented methods with extra params during initial extraction

…arameters

…nd TryUseParameters

… ParameterScope When a non-empty scope is passed, Find performs a parameterized-only lookup; otherwise it does the regular dictionary lookup. This removes the separate FindUserMappingWithParameters method from the entire chain.

…eterizedUserMapping Mark parameters as used directly in FindByParameters, eliminating the need for a separate FindParameterizedUserMapping wrapper. This simplifies FindOrBuildMapping and FindOrBuildLooseNullableMapping cascades.

…ficient parameterized lookup

…n SourceValueBuilder

…ntion

…eration

…e static helper

…y fast path

… parameter names

…ctions

Demivan · 2026-04-09T15:50:18Z

@latonz, I have fixed the review comments and rebased on the latest main

latonz

Thank you for the updates! One nitpick left, then it looks good to merge 😊

src/Riok.Mapperly/Descriptors/UserMappingMethodParameterExtractor.cs

latonz · 2026-04-10T07:38:11Z

Thank you for this contribution to Mapperly 🥳

Demivan force-pushed the parameter-mapping branch 8 times, most recently from 09facb6 to 4d0ce3d Compare March 22, 2026 18:00

latonz self-requested a review March 27, 2026 09:28

latonz added the enhancement New feature or request label Apr 9, 2026

latonz requested changes Apr 9, 2026

View reviewed changes

Demivan force-pushed the parameter-mapping branch from 0d6cac2 to 3f503f6 Compare April 9, 2026 15:13

Demivan requested a review from latonz April 9, 2026 15:15

Demivan added 17 commits April 9, 2026 18:24

feat: add ParameterScope and TypeMappingBuildContext.AdditionalParame…

a886999

…ters foundation

feat: forward additional parameters in MethodMapping.Build() and subc…

34ce1bd

…lass invocations

feat: integrate ParameterScope into MembersMappingState and MappingBu…

a8b638c

…ilderContext Always allow additional parameters in BuildUserImplementedMapping (remove allowAdditionalParameters parameter — was true at all call sites)

feat: support additional parameters in MapValue Use methods

8642f58

feat: prefer user-defined nested mappings with matching additional pa…

0e08bdf

…rameters

feat: forward additional parameters through UseNamedMappingBuilder

9970a90

feat: support additional parameters in queryable projection inlining

6564a95

feat: support additional parameters with MappingTarget existing targe…

ca57b9a

…t mappings

test: add edge case tests for additional parameter forwarding

5d1f751

refactor: use ParameterScope as single source of truth for additional…

3773229

… parameter tracking

refactor: remove dead allowAdditionalParameters parameter from BuildP…

d096032

…arameters

refactor: consolidate ParameterScope.MarkUsed into batch overloads

34a6262

refactor: make ParameterScope non-nullable with Empty singleton default

358b9a9

Demivan added 14 commits April 9, 2026 18:35

refactor: unify ParameterScope matching API with CanMatchParameters a…

f5618be

…nd TryUseParameters

refactor: index user mappings by type pair with ListDictionary for ef…

5bbcba7

…ficient parameterized lookup

refactor: eliminate duplicate GetAllDirectlyAccessibleMethods query i…

c829a0a

…n SourceValueBuilder

refactor: rename EmptyParameters to _emptyParameters per naming conve…

f9fa755

…ntion

refactor: use Skip(1).Any() instead of Count() > 1 to avoid full enum…

d0b1a73

…eration

refactor: rename test to describe expected state without implying change

c5006a4

refactor: make CanMatchParameters(IReadOnlyCollection) private

91b20cf

refactor: centralize TrimStart('@') into MethodParameter.NormalizeNam…

ddbfc6f

…e static helper

docs: split queryable projections example into tabs and fix formatting

274e463

refactor: optimize inline expression parameter lookup with ContainsKe…

5f8de3d

…y fast path

feat: add RMG098 diagnostic for case-insensitive duplicate additional…

445b165

… parameter names

test: add integration test for additional parameter inlining in proje…

fd3abff

…ctions

Demivan force-pushed the parameter-mapping branch from 3f503f6 to fd3abff Compare April 9, 2026 15:46

latonz requested changes Apr 10, 2026

View reviewed changes

src/Riok.Mapperly/Descriptors/UserMappingMethodParameterExtractor.cs Outdated Show resolved Hide resolved

refactor: optimize Linq Count call

69dbdde

latonz enabled auto-merge (squash) April 10, 2026 07:38

latonz approved these changes Apr 10, 2026

View reviewed changes

latonz merged commit c61a57a into riok:main Apr 10, 2026
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feat: forward additional mapping method parameters#2193

feat: forward additional mapping method parameters#2193
latonz merged 32 commits intoriok:mainfrom
Demivan:parameter-mapping

Demivan commented Mar 19, 2026 •

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Demivan commented Mar 19, 2026 •

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