Primary Parameter

Description

Using a Field, RefField, Property or DoNotUse attribute on parameters.

Automatically generate private readonly fields or private readonly ref readonly fields or public properties.

Forbid the use of primary constructor's parameters.

Usage

partial class C([Field(Name = "_a", AssignFormat = "{0}.ToString()", Type = typeof(string)), Field(Name = nameof(C._b)), Field, Property(Setter = "init", Summary = "Documentation")]int i) // type must be partial, but can be class / struct
{
# region Generated members
    // private readonly string _a = i.ToString();   // generated field (with type and formated assignment)
    // private readonly int _b = i;                 // generated field (with computed name)
    // private readonly int _i = i;                 // generated field
    /// <summary>
    /// Documentation
    /// </summary>
    // private int I { get; init; } = i;            // generated Property
# endregion

    public void M0()
    {
        i++;                    // error on usage of i
        Console.WriteLine(i);   // error on usage of i
    }

    public void M1()
    {
        var i = 0;
        i++;                    // don't error on usage of locals
        Console.WriteLine(_i);  // automaticaly created readonly field
        Console.WriteLine(_a);  // automaticaly created readonly field based on Name property
        Console.WriteLine(I);   // automaticaly created readonly property
    }
}

ref partial struct Ref([RefField(IsReadonlyRef = false, IsRefReadonly = false), RefField(Name = nameof(Ref.I), Scope = "public")]int i)
{
# region Generated members
    private ref int _i = ref i;
    public readonly ref readonly int I = ref i;
# endregion
}

To enable the feature, type [Field], [RefField], [Property], or [DoNotUse] before the primary parameter you want.

You can type as many attributes as you want on a single parameter (Except for DoNotUse).

Attribute Properties

Attribute	Property	Comments	Default value
Field	Name	Property to modify the generated field name	_i (for a parameter named i)
	IsReadnoly	To generate the readonly modifier	true
	Scope	To change the scope of the generated property	private
	AssignFormat	To change the assignment for that field	{0}
	Type	To change the type for that field	same type as parameter
	Summary	The <summary> documentation tag	null
RefField	Name	Property to modify the generated field name	_i (for a parameter named i)
	IsReadnolyRef	To generate the readonly ref modifier	true
	IsRefReadnoly	To generate the ref readonly modifier	true
	Scope	To change the scope of the generated property	private
	Summary	The <summary> documentation tag	null
Property	Name	Property to modify the generated field name	I (for a parameter named i)
	Setter	To generate the set, init or neither accessor along the get	init
	Scope	To change the scope of the generated property	public
	AssignFormat	To change the assignment for that property	{0}
	Type	To change the type for that property	same type as parameter
	Summary	The <summary> documentation tag	null
	WithoutBackingStorage	Generate the body of the accessors, without a backing storage	false
DoNotUse	AllowInMemberInit	Change to allow the use of parameter in member initializer	true

Reported Diagnostics

Code	Title	Message	Severity
PC01	Accessing a Primary Parameter	Can't access a primary parameter ('{0}') with a [Field], [RefField], [Property] or [DoNotUse] attribute, use {1}	Error
PC02	Attribute generate nothing	Use this attribute only on primary parameter	Warning
PC03	Attribute generate nothing	This member's name ('{0}') is already used	Warning Error when a member's name is already used in the type
PC04	RefField in non ref struct	Can't apply [RefField] in non ref struct '{0}'	Error
PC05	RefField on non ref parameter	Can't apply [RefField] on non ref parameter '{0}'	Error

.csproj properties

Property	Description	Default value
Fields
PrimaryParameter_Field_DefaultScope	The default scope for fields generation	private
PrimaryParameter_Field_DefaultReadonly	Should fields generates with readonly modifier	true
Ref Fields
PrimaryParameter_RefField_DefaultScope	The default scope for ref field generation	private
PrimaryParameter_RefField_DefaultReadonlyRef	Should ref fields generates with readonly ref modifier	true
PrimaryParameter_RefField_DefaultRefReadonly	Should ref fields generates with ref readonly modifier	true
Properties
PrimaryParameter_Property_DefaultScope	The default scope for properties generation	public
PrimaryParameter_Property_DefaultSetter	Should properties generates with set, init or neither accessor	init

Versions

Version	Date	Comments
v1.7.0	23/06/2024	Added WithoutBackingStorage for Property
v1.6.0	22/06/2024	Fix a bug: accept arrays
v1.5.1	19/05/2024	Modified some errors message
v1.5.0	18/05/2024	Don't generate PC01 on a primary contructor base call
v1.4.0	18/05/2024	Added Conditional on generated attributes
v1.3.4	18/05/2024	Added <summary> generation
v1.3.3	01/12/2023	Renamed DontUse to DoNotUse
v1.3.2	19/11/2023	Don't generate the partial generated type if not needed
v1.3.1	19/11/2023	Fix a bug with member initialization
v1.3.0	19/11/2023	Added DontUseAttribute Add a code-fix for CS0282 Changed PropertyAttribute.WithInit to PropertyAttribute.Setter
v1.2.0	25/08/2023	Support for default values customization
v1.1.0	15/08/2023	dotnet/roslyn#67371 fixed (related to v0.4.6)
v1.0.0	01/08/2023	Added code-fixes
v0.4.7	16/07/2023	Don't error on nameof access or inside the same argument list usage
v0.4.6.1	16/07/2023	Fix typos in Readme.md
v0.4.6	16/07/2023	Added RefField attribute Currently uses Unsafe.AsRef() due to a compiler bug dotnet/roslyn#67371
v0.4.5	18/05/2023	Added Scope and IsReadonly properties on Field Scope property on Property defaulted to public
v0.4.4	28/04/2023	Added AssignFormat and Type properties
v0.4.3	27/04/2023	Field and Property now have using global::System
v0.4.2	26/04/2023	Bug-fix with previous update
v0.4.1	25/04/2023	More precise warnings/errors location
v0.4.0	22/04/2023	Added PC02 and PC03 warnings/errors
v0.3.1	21/04/2023	Added Scope property on Property attribute Attributes are internal
v0.3.0	20/04/2023	Added Property attribute
v0.2.0	20/04/2023	Support for Name fields and multiple Field
v0.1.0	19/04/2023	Initial release