MSBuild properties

These properties change what the generator writes. Set them in the project file of the project that declares the validated types:

<PropertyGroup>
  <ValidationModules_FieldNaming>SnakeCase</ValidationModules_FieldNaming>
  <ValidationModules_CodeNamespace>shop</ValidationModules_CodeNamespace>
</PropertyGroup>

The ValidationModules.SourceGenerator package declares each property as a CompilerVisibleProperty, which is what makes it visible to the generator. A project that references the generator with a ProjectReference instead of the package must declare them itself.

Each ValidationModules_* property except ValidationModules_CodeNamespace takes one of a fixed set of values, and the values are not case-sensitive. A value that a property does not accept means the property's default, and the generator reports VM5004 with the values it accepts.

ValidationModules_FieldNaming

This property sets how member names become field names in errors.

Value	PostalCode becomes
not set, or CamelCase	postalCode
SnakeCase	postal_code
PascalCase or AsDeclared	PostalCode

[JsonPropertyName] on a property takes precedence. [Display(Name)] labels the property in messages and does not change the field. The registration method also registers the matching IValidationFieldNamer: CamelCaseFieldNamer, SnakeCaseFieldNamer or PascalCaseFieldNamer. A namer you register first takes precedence. Custom namers derive from FieldNamer.

ValidationModules_CodeNamespace

This property sets a prefix for the codes you set with Code on a built-in attribute, a CustomConstraintAttribute or an IConstraintFor<T> attribute, and for the codes of Ensure, set with code: or derived. With shop, the code stay_order becomes shop.stay_order. Codes passed to Report calls and helpers are not prefixed, and built-in codes are never prefixed. It is not set by default.

ValidationModules_PatternPolicy

This property sets what the generator does with an inline [Pattern("...")] and with a DataAnnotations [RegularExpression], which compiles to the same thing.

Value	Effect
not set, or Auto	VM1301 error when PublishAot or IsAotCompatible is true. Allowed otherwise.
Error	VM1301 error.
Warn	VM1301 warning, and the pattern is compiled.
Allow	Allowed.

See Patterns.

ValidationModules_DataAnnotations

Set to Ignore to stop the generator compiling System.ComponentModel.DataAnnotations attributes. It then reports VM2001 for each one. The default, Compile, compiles them. See DataAnnotations.

ValidationModules_FailFast

Set to false or Disabled to leave out the early return after each check. The validators get smaller. A StopOnFirstError pass still records only one error but runs every check. It is on by default, and true or Enabled turns it on explicitly.

ValidationModules_CaptureValues

Set to false or Disabled to stop recording the failed value in ValidationError.Value. It is on by default, and true or Enabled turns it on explicitly.

ValidationModules_Registration

This property selects the registration code the generator writes.

Value	Effect
not set, or Auto	DependencyModules when the project references DependencyModules, ServiceCollection otherwise.
ServiceCollection	The Add<Assembly>Validators() extension method only.
DependencyModules	The extension method, registration into each module entry point, and a ValidationModule class when there is no entry point.
None	No registration code.

See Registration.

Other properties

Property	Package	Effect
ValidationModulesLanguages	ValidationModules.Messages	Which built-in languages to compile: a list such as fr;de, all (the default), or none.
GeneratedCodeStyle	ValidationModules.SourceGenerator	KAndR or K&R, in any case, for K&R braces in the generated code. Allman braces otherwise. DependencyModules reads the same property.
PublishAot, IsAotCompatible	.NET SDK	When either is true, the default pattern policy rejects inline patterns.
EmitCompilerGeneratedFiles	.NET SDK	Writes the generated files under obj/ so that you can read them.
PackageValidationModulesIncludeSource	ValidationModules.SourceGenerator.Impl	See below.

Building your own generator

ValidationModules.SourceGenerator.Impl contains the generator's source code, for authors who want to drive the same front ends and emitters from a generator of their own. Setting PackageValidationModulesIncludeSource to true compiles that source into the project that references the package.

The package contains no [Generator] class, so it never runs by itself. Your generator provides the entry point, reads its own options, and reports its own errors. The main types are AttributeFrontEnd and RulesFrontEnd, which read declarations, and ValidatorEmitter, RegistrationEmitter and LanguagePackEmitter, which write code. Do not run ValidationModules.SourceGenerator over the same types as well, or each type gets two validators.

EmitterContract.Probe(compilation) checks that the referenced runtime is new enough and returns the diagnostic to report when it is not. The runtime package also publishes the version of its contract as the MSBuild property ValidationModulesRuntimeContract, for hosts that check compatibility without a compilation. A generator that builds its own table of registrations can pass it to services.AddValidationModules(registrations).