A new version of Mappa (v10.1.0) has been released.

Mappa 10.1.0 builds on the 10.0.0 foundation with expanded enum mapping, richer parse and format MappaSettings, identity deep-copy and collection buffer options, stronger diagnostics, safer generated code, and a migrated test stack. Documentation now includes a full feature catalog. Full changelog: v10.0.0…v10.1.0

Breaking changes

When upgrading from 10.0.0, see the upgrade guide.

MappaSettings rename

  • ForceCaseInsensitivePropertyMap renamed to CaseInsensitivePropertyMap (#257, #260)
    • Update attribute usage: [MappaSettings(CaseInsensitivePropertyMap = BooleanSetting.Enable)]
    • Update .editorconfig: mappa.caseinsensitivepropertymap = enable
    • The legacy .editorconfig key mappa.forcecaseinsensitivepropertymap is no longer supported

Stricter diagnostics

Projects that previously compiled may now fail with new or tightened generator errors:

  • MP00042 — ambiguous invoke-method resolution (#233, #266) — When multiple methods match [MappaInvokeMethod] or a polymorphism InvokeMethod default, the generator reports an error instead of silently selecting the first match.
  • MP00038 — invalid parse style values (#231, #241) — Arbitrary integer DateTimeStyles / NumberStyles values in [MappaSettings] now produce a generator diagnostic instead of being silently decomposed into known flag bits.

What’s new

Test infrastructure

  • Migrate to xUnit v3 (#119, #222) — Test projects now use xUnit v3 and Microsoft Testing Platform.
  • Replace FluentAssertions with AwesomeAssertions (#208, #223) — Assertion library updated across all test projects.

New features

  • IdentityMapDeepCopy setting (#14, #267) — Control shallow, deep, and nested same-type copying in identity mappings via [MappaSettings].
  • EnumerableConcreteType setting (#29, #268) — Prefer T[] over List<T> when mapping to sequence-like interface targets (e.g. IEnumerable<T>).
  • DateTimeStyle for parse (#214, #224) — Per-type DateTimeStyles for Parse / ParseExact on DateTime, DateOnly, and TimeOnly.
  • NumberStyles for parse (#215, #226) — Per-type NumberStyles for string-to-numeric Parse conversions.
  • GlobalDateTimeStyle and GlobalNumberStyle (#225, #228) — Shared parse-style defaults applied across date/time and numeric types.

Enum mapping

  • Description attribute support (#15, #16, #265) — Map enums using [Description] for enum-to-string, string-to-enum, and enum-to-enum conversions.
  • Case-insensitive string-to-enum (#17, #258) — Optional case-insensitive matching when parsing strings to enums.
  • Numeric enum-to-enum mapping (#18, #264) — Map enums by numeric value instead of member name via EnumToEnumMapSetting.
  • Partial enum-to-enum warning (MP00039) (#19, #244) — Warn when not all source enum members can be mapped to the target enum.
  • CaseInsensitiveEnumMap (#15, #265) — Optional case-insensitive enum member matching.
  • Rename ForceCaseInsensitivePropertyMap (#257, #260) — Setting renamed to CaseInsensitivePropertyMap; legacy .editorconfig key removed.

[MappaInvokeMethod] attribute

  • Optional SourcePropertyName parameter (#67, #243) — Invoke a method with an explicit source property value instead of the full source object.
  • Ambiguous invoke-method diagnostic (MP00042) (#233, #266) — Report a diagnostic when [MappaInvokeMethod] or polymorphism invoke-method resolution is ambiguous.

Diagnostics and quality

  • Invalid style values (MP00038) (#231, #241) — Diagnose arbitrary integer DateTimeStyles / NumberStyles values in [MappaSettings].
  • Test coverage improvements (#220, #239) — Additional generator, builder, and settings-stack tests for previously uncovered paths.
  • Fix .editorconfig CurrentCulture mapping (#229, #235) — Correct global culture resolution in MappaGlobalOptions.
  • Rename misleading local in CanMapStringToNumber (#234, #242) — Internal readability fix in string strategy detection.

Generated code safety

  • Escape format and culture strings (#230, #236) — User-controlled format and culture strings are safely escaped in generated mapping code.
  • Escape attribute string literals (#232, #237) — User-controlled literals from mapping attributes are escaped in generated code.

Documentation and samples

  • Feature catalog (Documentation/features.md) (#262, #263) — New page listing all Mappa features with links to tutorial, attributes, algorithm, and samples.
  • Generator algorithm documentation alignment (#227, #240) — Algorithm docs and generator README brought in line with the current implementation.
  • Suppress MP00039 in EnumToEnumMapper sample (#259, #261) — Intentional partial enum mapping demonstrated with #pragma warning disable.

What’s next

This is a tentative and non exhaustive list of issues that I would like to cover in the upcoming version of Mappa:

Mapping / generator features

  • #255 — Richer enum mapping configuration
  • #250 — Before / after map hooks
  • #249 — Circular reference / reference handling
  • #248 — Generic mapping methods
  • #246 — Reverse / bidirectional mapping
  • #245 — IQueryable projection (ProjectTo)
  • #184 — More relaxed nullability when matching methods
  • #120 — Flattening and unflattening
  • #108 — Allow preventing Enumerable.Count when targeting arrays, Span, and Memory
  • #73 — Support fields, not only properties
  • #34 — Allow choosing .Add vs. the indexer for dictionary-to-dictionary mapping

Language / platform

  • #174 — Support C# 14 extension blocks in static classes (partial classes assumed)

Diagnostics and maintainability

  • #141 — Improved debug feature
  • #238 — Reduce ReportGenerator CRAP score and cyclomatic complexity in Mappa.Generator