Add record constructor generator to auto-populate optional fields

ConsumePlugin/ConsumePlugin.fsproj

@@ -17,6 +17,10 @@
     <Compile Include="GeneratedRecord.fs">
       <MyriadFile>RecordFile.fs</MyriadFile>
     </Compile>
+    <Compile Include="RecordConstructor.fs"/>
+    <Compile Include="GeneratedRecordConstructor.fs">
+      <MyriadFile>RecordConstructor.fs</MyriadFile>
+    </Compile>
     <Compile Include="JsonRecord.fs"/>
     <Compile Include="GeneratedJson.fs">
       <MyriadFile>JsonRecord.fs</MyriadFile>

ConsumePlugin/GeneratedRecordConstructor.fs

@@ -0,0 +1,162 @@
+//------------------------------------------------------------------------------
+//        This code was generated by myriad.
+//        Changes to this file will be lost when the code is regenerated.
+//------------------------------------------------------------------------------
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the MixedConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module MixedConstructorRecord =
+    /// Create a value of type MixedConstructorRecord with every optional field set to None.
+    let create (arg_0: string) (arg_1: string) (arg_2: string) : MixedConstructorRecord =
+        { FirstRequired = arg_0
+          FirstOptional = None
+          SecondRequired = arg_1
+          SecondOptional = None
+          ThirdRequired = arg_2 }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the AllRequiredConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module AllRequiredConstructorRecord =
+    /// Create a value of type AllRequiredConstructorRecord with every optional field set to None.
+    let create (arg_0: string) (arg_1: string) (arg_2: string) : AllRequiredConstructorRecord =
+        { First = arg_0
+          Second = arg_1
+          Third = arg_2 }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the AllOptionalConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module AllOptionalConstructorRecord =
+    /// Create a value of type AllOptionalConstructorRecord with every optional field set to None.
+    let create () : AllOptionalConstructorRecord = { Number = None; Text = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the NestedOptionConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module NestedOptionConstructorRecord =
+    /// Create a value of type NestedOptionConstructorRecord with every optional field set to None.
+    let create (arg_0: Guid) : NestedOptionConstructorRecord =
+        { Id = arg_0
+          PostfixNested = None
+          PrefixOption = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the GenericConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module GenericConstructorRecord =
+    /// Create a value of type GenericConstructorRecord with every optional field set to None.
+    let create (arg_0: 'required) (arg_1: 'required list) : GenericConstructorRecord<'required, 'optional> =
+        { Required = arg_0
+          Optional = None
+          RequiredList = arg_1 }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the GenericAllOptionalConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module GenericAllOptionalConstructorRecord =
+    /// Create a value of type GenericAllOptionalConstructorRecord with every optional field set to None.
+    let create () : GenericAllOptionalConstructorRecord<'value> = { Value = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the InternalConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module internal InternalConstructorRecord =
+    /// Create a value of type InternalConstructorRecord with every optional field set to None.
+    let create (arg_0: string) : InternalConstructorRecord = { Required = arg_0; Optional = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the TupleAndFunctionConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module TupleAndFunctionConstructorRecord =
+    /// Create a value of type TupleAndFunctionConstructorRecord with every optional field set to None.
+    let create (arg_0: int * string) (arg_1: int -> string) : TupleAndFunctionConstructorRecord =
+        { Pair = arg_0
+          Transform = arg_1
+          OptionalTransform = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the NonSyntacticOptionConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module NonSyntacticOptionConstructorRecord =
+    /// Create a value of type NonSyntacticOptionConstructorRecord with every optional field set to None.
+    let create
+        (arg_0: ConstructorOptionAlias<int>)
+        (arg_1: string voption)
+        (arg_2: Nullable<int>)
+        : NonSyntacticOptionConstructorRecord =
+        { Alias = arg_0
+          ValueOption = arg_1
+          Nullable = arg_2
+          Optional = None }
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+/// Functions for constructing the NameHazardConstructorRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module NameHazardConstructorRecord =
+    /// Create a value of type NameHazardConstructorRecord with every optional field set to None.
+    let create (arg_0: string) (arg_1: string) (arg_2: string) (arg_3: string) : NameHazardConstructorRecord =
+        { ``type`` = arg_0
+          arg_0 = arg_1
+          Arg_0 = arg_2
+          ``two words`` = arg_3
+          ``two-words`` = None }
+namespace ConsumePlugin.FirstScopedOpen
+
+open RecordConstructorFirstInput
+
+/// Functions for constructing the ScopedOpenRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module ScopedOpenRecord =
+    /// Create a value of type ScopedOpenRecord with every optional field set to None.
+    let create (arg_0: Token) : ScopedOpenRecord = { Token = arg_0; Optional = None }
+namespace ConsumePlugin.SecondScopedOpen
+
+open RecordConstructorSecondInput
+
+/// Functions for constructing the ScopedOpenRecord record.
+[<RequireQualifiedAccess; CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module ScopedOpenRecord =
+    /// Create a value of type ScopedOpenRecord with every optional field set to None.
+    let create (arg_0: Token) : ScopedOpenRecord = { Token = arg_0; Optional = None }
+
+
+
+
+
+
+
+
+
+

ConsumePlugin/RecordConstructor.fs

@@ -0,0 +1,117 @@
+namespace ConsumePlugin
+
+open System
+open WoofWare.Myriad.Plugins
+
+type ConstructorOptionAlias<'value> = 'value option
+
+[<GenerateRecordConstructor>]
+type MixedConstructorRecord =
+    {
+        FirstRequired : string
+        FirstOptional : int option
+        SecondRequired : string
+        SecondOptional : bool option
+        ThirdRequired : string
+    }
+
+[<GenerateRecordConstructor>]
+type AllRequiredConstructorRecord =
+    {
+        First : string
+        Second : string
+        Third : string
+    }
+
+[<GenerateRecordConstructor>]
+type AllOptionalConstructorRecord =
+    {
+        Number : int option
+        Text : string option
+    }
+
+[<GenerateRecordConstructor>]
+type NestedOptionConstructorRecord =
+    {
+        Id : Guid
+        PostfixNested : int option option
+        PrefixOption : Option<string>
+    }
+
+[<GenerateRecordConstructor>]
+type GenericConstructorRecord<'required, 'optional> =
+    {
+        Required : 'required
+        Optional : 'optional option
+        RequiredList : 'required list
+    }
+
+[<GenerateRecordConstructor>]
+type GenericAllOptionalConstructorRecord<'value> =
+    {
+        Value : 'value option
+    }
+
+[<GenerateRecordConstructor>]
+type internal InternalConstructorRecord =
+    {
+        Required : string
+        Optional : int option
+    }
+
+[<GenerateRecordConstructor>]
+type TupleAndFunctionConstructorRecord =
+    {
+        Pair : int * string
+        Transform : int -> string
+        OptionalTransform : (int -> string) option
+    }
+
+[<GenerateRecordConstructor>]
+type NonSyntacticOptionConstructorRecord =
+    {
+        Alias : ConstructorOptionAlias<int>
+        ValueOption : string voption
+        Nullable : Nullable<int>
+        Optional : decimal option
+    }
+
+[<GenerateRecordConstructor>]
+type NameHazardConstructorRecord =
+    {
+        ``type`` : string
+        arg_0 : string
+        Arg_0 : string
+        ``two words`` : string
+        ``two-words`` : string option
+    }
+
+namespace RecordConstructorFirstInput
+
+type Token = | FirstToken of int
+
+namespace RecordConstructorSecondInput
+
+type Token = | SecondToken of string
+
+namespace ConsumePlugin.FirstScopedOpen
+
+open RecordConstructorFirstInput
+
+[<WoofWare.Myriad.Plugins.GenerateRecordConstructor>]
+type ScopedOpenRecord =
+    {
+        Token : Token
+        Optional : int option
+    }
+
+namespace ConsumePlugin.SecondScopedOpen
+
+open RecordConstructorSecondInput
+
+[<WoofWare.Myriad.Plugins.GenerateRecordConstructor>]
+type ScopedOpenRecord =
+    {
+        Token : Token
+        Optional : int option
+    }

DESIGN.md

@@ -0,0 +1,74 @@
+# Generated record constructors
+
+## Problem
+
+Constructing an F# record with many `option` fields is needlessly repetitive when the usual initial state for every optional field is `None`. The generator should make the required part of construction explicit while retaining ordinary record-update syntax for later optional values.
+
+## Public API
+
+Annotating a record with `GenerateRecordConstructorAttribute`:
+
+```fsharp
+[<WoofWare.Myriad.Plugins.GenerateRecordConstructor>]
+type Request =
+    {
+        Name : string
+        RetryCount : int option
+        Enabled : bool
+    }
+```
+
+generates a companion module and a curried `create` function:
+
+```fsharp
+[<RequireQualifiedAccess>]
+[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+module Request =
+    /// Create a Request with every optional field set to None.
+    let create (arg_0 : string) (arg_1 : bool) : Request =
+        {
+            Name = arg_0
+            RetryCount = None
+            Enabled = arg_1
+        }
+```
+
+Required arguments appear in record declaration order. If every field is optional, `create` takes `unit`, so the generated API remains a function and generic records do not encounter the value restriction. The generated module has the source type's accessibility.
+
+Parameters are named `arg_0`, `arg_1`, and so on in required-field order. These names are deterministic, legal for every record-label spelling, and cannot collide when labels differ only by casing or identifier sanitisation.
+
+The Myriad generator is exposed as `RecordConstructorGenerator` with the identifier `record-constructor`.
+
+## Meaning of optional
+
+A field is optional exactly when its outermost syntactic type constructor is F# `option`, including the ordinary postfix and prefix spellings understood by the parsed syntax. Such a field is initialized with `None`, even when its element type is itself optional.
+
+Type aliases cannot be resolved from the untyped syntax tree. An alias of `option`, `voption`, `System.Nullable<_>`, and all other types are therefore required arguments. This boundary keeps generation deterministic and reflection-free.
+
+## Functional core and generator shell
+
+The implementation is split into three parts:
+
+1. A syntax-independent constructor planner accepts an ordered list of fields classified as required or optional. It returns inert data describing ordered parameters and every record-field initializer (`FromParameter` or `UseNone`).
+2. A thin Fantomas/FCS adapter classifies parsed record fields and renders that plan as an AST. It also constructs the applied return type for generic records.
+3. The Myriad shell parses the input file, finds annotated types, rejects a use on a non-record, and emits the rendered modules.
+
+The planner is the semantic core. It has no IO, compiler service, formatting, or Myriad dependencies, and its output can be interpreted directly in property tests. The syntax adapter is checked by parsing generated record shapes and observing their plans, while a checked-in consumer project supplies the renderer and compilation boundary.
+
+## Guarantees
+
+- Every source field appears exactly once in the generated record expression and remains in declaration order.
+- Every direct `option` field is initialized with `None` and creates no parameter.
+- Every other field has exactly one typed parameter, and its initializer references that parameter.
+- Parameter order is the declaration order of required fields.
+- Parameter names are unique and are the consecutive sequence `arg_0` through `arg_(n-1)`.
+- Generic parameters used only by optional fields remain represented in the result type.
+- Generated source is deterministic for a given input syntax tree.
+
+## Deliberate limits
+
+- The attribute applies only to records; placing it on another type is an error.
+- The record must be declared directly in a namespace. F# modules cannot be reopened from another file, so an annotation nested inside a module is rejected explicitly.
+- There is no attribute-free `MyriadParams` spelling or extension-member mode in this first version.
+- A record with private type or representation accessibility cannot be constructed from a separate generated file and is rejected with an explicit error.
+- A pre-existing companion module can collide with the generated module, as it can for the non-extension JsonParse generator.