Domainprimitive Builder

domainprimitive-builder — Skill Specification

Language & Platform Scope

This skill applies only to C# projects using the AltaSoft DomainPrimitives framework and its source generator.

Agent must:

• Generate C# code only
• Use modern C# syntax compatible with the project target framework and if applicable use C# Copilot instructions
• Follow C# type system rules for structs, classes, attributes, and static methods
• Assume .NET and Roslyn source generator environment
• prefer var over explicit types when the type is obvious from the right-hand side

Agent must NOT:

• Generate implementations in other languages
• Suggest non-C# patterns (Java/Kotlin/TypeScript/etc.)
• Translate DomainPrimitive patterns into other ecosystems

All templates, rules, and examples in this skill are C#-specific.

Purpose

This skill guides the agent to correctly create and maintain DomainPrimitive types using the AltaSoft DomainPrimitives framework. It ensures primitives are generator-compatible, domain-safe, and follow strict structural and validation rules.

Use this skill when:

• Creating a new DomainPrimitive type
• Adding or modifying validation logic
• Adding normalization (Transform)
• Applying DomainPrimitive attributes
• Refactoring primitive invariants
• Creating chained primitives

Clarification-First Generation Policy

When the user asks to create a DomainPrimitive and the domain rules are not fully specified, the agent must ask clarification questions before generating code.

Agent must not generate a primitive implementation unless it is confident about the domain invariants and validation rules.

If uncertainty exists, the agent must pause generation and ask targeted questions.

When Clarification Is Required

Agent must ask questions when any of the following are unclear:

• allowed value range
• precision or scale (for decimal/amount types)
• rounding rules
• normalization expectations
• maximum or minimum limits
• whether normalization vs rejection is required
• format strictness
• overflow handling
• operator support expectations
• serialization format requirements

Example — TransactionAmount Primitive

If the user asks to create TransactionAmount, the agent should ask questions such as:

• What is the maximum allowed amount?
• Is zero allowed or forbidden?
• Are negative values allowed?
• What decimal precision is required?
• Should values be rounded or rejected if precision is exceeded?
• If rounding is allowed — what rounding mode should be used?
• Should currency minor-unit scale be enforced (e.g., 2 digits)?
• Is normalization allowed or must invalid precision fail validation?
• Should arithmetic operators be restricted?

Agent must wait for answers before generating the primitive.

Generation Confidence Rule

Agent may generate immediately only if:

• domain constraints are explicitly provided, OR
• primitive semantics are universally obvious (e.g., NonEmptyString, PositiveInt)

Otherwise → clarification required.

Safe Suggestion Mode

Before clarification, agent may suggest:

• possible validation rules
• recommended constraints
• attribute options
• transform options

But must label them as proposals, not final implementation.

Global Type Rules (Project-Specific — MUST FOLLOW)

These rules are project-specific and override any generic recommendations.

Shape Rule — Class vs Struct

• If the underlying type is string → primitive MUST be a sealed partial class
• If the underlying type is not string → primitive MUST be a readonly partial struct
• Agent must not choose class vs struct heuristically

Correct:

public sealed partial class Email : IDomainValue
public readonly partial struct OrderId : IDomainValue

Forbidden:

public readonly partial struct Email : IDomainValue
public sealed partial class OrderId : IDomainValue

Allowed Underlying Types Only

DomainPrimitives may wrap only these C# types:

• string
• Guid
• byte
• sbyte
• short
• ushort
• int
• uint
• long
• ulong
• decimal
• double
• float
• bool
• char
• TimeSpan
• DateTime
• DateTimeOffset
• DateOnly
• TimeOnly

Rules:

• No other underlying types are allowed
• Unsupported types → agent must refuse and suggest closest supported type
• Custom types are only allowed if they are already DomainPrimitives

Structural Generator Safety Rules

These rules are mandatory and must never be violated.

Required Interface

Every DomainPrimitive must implement:

IDomainValue (AltaSoft.DomainPrimitives)

Partial Declaration

All DomainPrimitive types must be declared partial.

Constructors Are Forbidden

Do not generate:

• parameterless constructors
• value constructors
• private constructors

Construction is generator-controlled.

No Public Fields or Properties

Do not declare:

• public fields
• public properties
• manual backing storage

Generator provides storage and access APIs.

Reserved Member Names (Forbidden)

Do not declare:

• _value
• _valueOrDefault
• _isInitialized

Validate Method Signature

Must be exactly:

public static PrimitiveValidationResult Validate(T value)

Rules:

• public
• static
• correct parameter type
• return PrimitiveValidationResult

No Side Effects in Validate or Transform

Forbidden:

• database access
• HTTP calls
• file I/O
• logging
• DI usage
• configuration reads

Validation must be pure.

Validation Logic Rules

Validation defines domain invariants and must be explicit and domain-focused. Validation method must not call Transform.

Preferred Error Return Style

Use implicit string → PrimitiveValidationResult conversion:

if (value < 0) return "number is negative";

Avoid PrimitiveValidationResult.Error(...) unless explicitly required.

Success Return Rule

Always return:

PrimitiveValidationResult.Ok

when validation passes.

Early Return Pattern

Use ordered early-return checks:

if (value.Length == 0) return "must not be empty";

if (value.Length > 50) return "too long";

return PrimitiveValidationResult.Ok;

Avoid nested validation trees.

Validation Logic Generation Rules

Agent must generate concrete domain validation — not placeholders.

Forbidden outputs:

• TODO validate
• add validation here
• always return Ok without reason

Validation must match primitive semantics inferred from the name.

Examples:

• PositiveAmount → value > 0
• Percentage → 0–100
• Id → not empty / not zero / not Guid.Empty
• Code → character set + length

Validation must stay local to the value and not depend on external systems.

Error Message Style

Validation error messages must be:

• short
• domain-focused
• human-readable
• action-oriented

Good:

• "must be positive"
• "length must be between 3 and 20"
• "contains non-ASCII characters"

Bad:

• "invalid input"
• "validation failed"
• "system error"

Primitive Creation Templates

Agent must select template strictly by underlying type.

String Template

sealed partial class + IDomainValue

Non-String Template

readonly partial struct + IDomainValue

Templates must follow Structural Generator Safety Rules.

Transform (Normalization) Rules

Optional normalization hook executed before Validate.

Signature:

static T Transform(T value)

Allowed:

• trim
• casing
• canonical formatting

Forbidden:

• hiding invalid data
• defaults substitution
• external lookups

Must be idempotent.

Attribute Usage Rules

Attributes express structural or mechanical constraints.
Validate expresses domain semantics.

StringLength

Use only for string primitives with fixed length limits.

SupportedOperations

Use for numeric primitives to restrict arithmetic operators: Addition, Subtraction, Multiplication, Division, Modulus.

SerializationFormat

Use for Date/Time/Duration types when canonical external format is required.

Do not use attributes for dynamic or contextual rules.

Custom Static ToString Formatting Hook

DomainPrimitives may define:

public static string ToString(T value)

This is a generator formatting hook — not an override.

Rules:

• static
• pure
• deterministic
• invariant culture only

Example:

public static string ToString(DateOnly value) => value.ToString("dd", CultureInfo.InvariantCulture);

Do not add when default formatting is sufficient or when SerializationFormat covers the need.

Agent Refusal Rules

Agent must refuse to generate primitives that:

• violate struct/class shape rule
• use unsupported underlying types
• declare constructors
• add public fields or properties
• perform external validation
• throw in Validate
• use non-C# implementations

Source: altasoft/DomainPrimitives — distributed by TomeVault.