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ArgParser: add [<ArgumentDefaultValue foo>] for constant defaults
Shorthand for the common case where an [<ArgumentDefaultFunction>]'s function would just return a constant. The attribute argument is a SynExpr spliced verbatim into the generated code, exactly as [<ArgumentFlag>]'s value already is; the generated file inherits the source file's `open`s, so an identifier resolves there as it does at the use site. Because `foo` is an ordinary .NET custom-attribute argument, F# itself restricts it to compile-time constants (literals, [<Literal>] bindings, enum cases) on the user's own source line, so the generator's untyped pass need not validate it. A discriminated union case, including a flag DU's, is not such a constant and still needs [<ArgumentDefaultFunction>]. The new attribute joins the existing "at most one default source" check, which until now had no test coverage at all; it is now exercised over every pair drawn from the three default-supplying attributes. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Lines changed: 479 additions & 12 deletions

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‎CHANGELOG.md‎

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@@ -1,5 +1,10 @@
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Notable changes are recorded here.
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# WoofWare.Myriad.Plugins 10.4.1
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The `ArgParserGenerator` gains `[<ArgumentDefaultValue foo>]`: shorthand for an `[<ArgumentDefaultFunction>]` whose function just returns a constant.
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`foo` is an ordinary .NET attribute argument, so F# restricts it to compile-time constants (literals, `[<Literal>]` bindings, and enum cases); anything else, including a discriminated union case, still needs `[<ArgumentDefaultFunction>]`.
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# WoofWare.Myriad.Plugins 10.3.1
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The `ArgParserGenerator` now supports positional args together with arbitrary discriminated-union args.

‎ConsumePlugin/Args.fs‎

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@@ -196,6 +196,22 @@ type ContainsFlagDefaultValue =
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static member DefaultDryRun () = DryRunMode.Wet
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/// `[<ArgumentDefaultValue>]` is shorthand for an `[<ArgumentDefaultFunction>]` whose function
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/// returns a constant. The value is any valid .NET attribute argument: a literal, a `[<Literal>]`
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/// binding, or an enum case.
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[<ArgParser true>]
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type ContainsLiteralDefault =
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{
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[<ArgumentDefaultValue 3>]
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IntVar : Choice<int, int>
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[<ArgumentDefaultValue "hello world">]
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StringVar : Choice<string, string>
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// A non-literal argument requires parens: F#'s attribute syntax otherwise reads the
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// identifier as the start of a named argument.
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[<ArgumentDefaultValue(Consts.TRUE)>]
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BoolVar : Choice<bool, bool>
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}
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[<ArgParser true>]
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type ManyLongForms =
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{

‎ConsumePlugin/GeneratedArgs.fs‎

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@@ -4772,6 +4772,229 @@ open System
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open System.IO
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open WoofWare.Myriad.Plugins
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/// Methods to parse arguments for the type ContainsLiteralDefault
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[<AutoOpen>]
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module ContainsLiteralDefaultArgParse =
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/// Extension methods for argument parsing
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type ContainsLiteralDefault with
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static member parse'
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(getEnvironmentVariable : string -> string option)
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(args : string list)
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: ContainsLiteralDefault
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=
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let helpText () =
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[
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(sprintf
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"%s %s%s%s"
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(sprintf "--%s" "int-var")
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"int32"
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((3).ToString () |> sprintf " (default value: %s)")
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"")
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(sprintf
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"%s %s%s%s"
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(sprintf "--%s" "string-var")
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"string"
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(("hello world").ToString () |> sprintf " (default value: %s)")
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"")
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(sprintf
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"%s %s%s%s"
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(sprintf "--%s" "bool-var")
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"bool"
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(((Consts.TRUE)).ToString () |> sprintf " (default value: %s)")
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"")
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]
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|> String.concat "\n"
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let parser_LeftoverArgs : string ResizeArray = ResizeArray ()
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let mutable arg_0 : Choice<int, int> option = None
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let mutable arg_1 : Choice<string, string> option = None
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let mutable arg_2 : Choice<bool, bool> option = None
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let parser_schema : ArgParserRuntime_BasicNoPositionals.ErasedSchema =
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{
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Leaves =
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[
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{
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Id = 0
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Forms = [ "int-var" ]
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AcceptsNegation = false
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Arity = ArgParserRuntime_BasicNoPositionals.ErasedArity.One
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Repeatable = false
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Requirement = ArgParserRuntime_BasicNoPositionals.ErasedRequirement.HasDefault
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TypeDescription = ""
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Help = None
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}
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{
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Id = 1
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Forms = [ "string-var" ]
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AcceptsNegation = false
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Arity = ArgParserRuntime_BasicNoPositionals.ErasedArity.One
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Repeatable = false
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Requirement = ArgParserRuntime_BasicNoPositionals.ErasedRequirement.HasDefault
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TypeDescription = ""
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Help = None
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}
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{
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Id = 2
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Forms = [ "bool-var" ]
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AcceptsNegation = false
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Arity = ArgParserRuntime_BasicNoPositionals.ErasedArity.BoolLike
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Repeatable = false
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Requirement = ArgParserRuntime_BasicNoPositionals.ErasedRequirement.HasDefault
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TypeDescription = ""
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Help = None
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}
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]
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Tree =
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(ArgParserRuntime_BasicNoPositionals.ErasedTree.Product (
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[
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ArgParserRuntime_BasicNoPositionals.ErasedTree.Leaf 0
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ArgParserRuntime_BasicNoPositionals.ErasedTree.Leaf 1
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ArgParserRuntime_BasicNoPositionals.ErasedTree.Leaf 2
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]
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))
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Positionals = List.empty
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}
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let parser_storeOccurrence
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(occurrence : ArgParserRuntime_BasicNoPositionals.ErasedOccurrence)
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: string option
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=
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match occurrence.LeafId with
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| 0 ->
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match arg_0 with
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| Some _ -> None
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| None ->
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match occurrence.Value with
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| Some value ->
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try
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arg_0 <- Some (Choice1Of2 (value |> (fun x -> System.Int32.Parse x)))
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None
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with _ as exc ->
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(sprintf "%s (at arg %s)" exc.Message occurrence.Source) |> Some
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| None ->
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failwith
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"WoofWare.Myriad internal error in generated parser: arity-one occurrence with no value"
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| 1 ->
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match arg_1 with
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| Some _ -> None
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| None ->
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match occurrence.Value with
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| Some value ->
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try
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arg_1 <- Some (Choice1Of2 (value |> (fun x -> x)))
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None
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with _ as exc ->
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(sprintf "%s (at arg %s)" exc.Message occurrence.Source) |> Some
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| None ->
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failwith
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"WoofWare.Myriad internal error in generated parser: arity-one occurrence with no value"
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| 2 ->
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match arg_2 with
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| Some _ -> None
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| None ->
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match occurrence.Value with
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| Some value ->
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try
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let parsedBool = System.Boolean.Parse value
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let parsedBool = if occurrence.Negated then not parsedBool else parsedBool
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arg_2 <- Some (Choice1Of2 (parsedBool))
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None
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with _ as exc ->
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(sprintf "%s (at arg %s)" exc.Message occurrence.Source) |> Some
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| None ->
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arg_2 <- Some (Choice1Of2 ((if occurrence.Negated then false else true)))
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None
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| _ -> failwith "WoofWare.Myriad internal error in generated parser: unknown argument id"
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let parser_storePositional (positionalId : int) (value : string) (afterSeparator : bool) : string option =
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failwith "WoofWare.Myriad internal error in generated parser: no positional sink exists"
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let parser_renderStored (leafId : int) : string =
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match leafId with
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| 0 ->
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match arg_0 with
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| Some (Choice1Of2 x) -> x.ToString ()
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| Some (Choice2Of2 x) -> x.ToString ()
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| None -> "<no value>"
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| 1 ->
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match arg_1 with
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| Some (Choice1Of2 x) -> x.ToString ()
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| Some (Choice2Of2 x) -> x.ToString ()
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| None -> "<no value>"
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| 2 ->
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match arg_2 with
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| Some (Choice1Of2 x) -> x.ToString ()
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| Some (Choice2Of2 x) -> x.ToString ()
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| None -> "<no value>"
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| _ -> "<no value>"
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let parser_applyDefault (leafId : int) : string option =
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match leafId with
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| 0 ->
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arg_0 <- Some (Choice2Of2 ((3)))
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None
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| 1 ->
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arg_1 <- Some (Choice2Of2 (("hello world")))
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None
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| 2 ->
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arg_2 <- Some (Choice2Of2 (((Consts.TRUE))))
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None
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| _ -> failwith "WoofWare.Myriad internal error in generated parser: unknown defaulted argument id"
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let parser_callbacks : ArgParserRuntime_BasicNoPositionals.TypedCallbacks =
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{
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StoreOccurrence = parser_storeOccurrence
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StorePositional = parser_storePositional
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HelpText = helpText
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RenderStored = parser_renderStored
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ApplyDefault = parser_applyDefault
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}
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match
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ArgParserRuntime_BasicNoPositionals.runParse
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(ArgParserRuntime_BasicNoPositionals.WellFormedSchema.checkOrFail parser_schema)
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parser_callbacks
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args
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with
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| ArgParserRuntime_BasicNoPositionals.ParseOutcome.Success parser_selection ->
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{
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BoolVar =
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(match arg_2 with
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| Some x -> x
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| None ->
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failwith
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"WoofWare.Myriad internal error in generated parser: required argument missing after successful parse")
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IntVar =
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(match arg_0 with
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| Some x -> x
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| None ->
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failwith
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"WoofWare.Myriad internal error in generated parser: required argument missing after successful parse")
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StringVar =
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(match arg_1 with
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| Some x -> x
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| None ->
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failwith
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"WoofWare.Myriad internal error in generated parser: required argument missing after successful parse")
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}
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| ArgParserRuntime_BasicNoPositionals.ParseOutcome.HelpRequested ->
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helpText () |> failwithf "Help text requested.\n%s"
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| ArgParserRuntime_BasicNoPositionals.ParseOutcome.Fatal message -> failwith message
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| ArgParserRuntime_BasicNoPositionals.ParseOutcome.Errors errors ->
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errors |> String.concat "\n" |> failwithf "Errors during parse!\n%s"
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static member parse (args : string list) : ContainsLiteralDefault =
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ContainsLiteralDefault.parse' (System.Environment.GetEnvironmentVariable >> Option.ofObj) args
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namespace ConsumePlugin
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open System
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open System.IO
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open WoofWare.Myriad.Plugins
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47754998
/// Methods to parse arguments for the type ManyLongForms
47764999
[<AutoOpen>]
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module ManyLongFormsArgParse =

‎README.md‎

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@@ -186,6 +186,8 @@ type Foo =
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B : Choice<int, int>
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[<ArgumentDefaultEnvironmentVariable "MY_ENV_VAR">]
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BWithEnv : Choice<int, int>
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[<ArgumentDefaultValue 4>]
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BWithConstant : Choice<int, int>
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[<ArgumentDefaultFunction>]
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DryRun : Choice<DryRunMode, DryRunMode>
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AnimalPart : AnimalArgs
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A = None
226228
B = Choice2Of2 4
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BWithEnv = Choice2Of2 100 // whatever the value of $MY_ENV_VAR was, or a failed parse
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BWithConstant = Choice2Of2 4
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DryRun = Choice2Of2 DryRunMode.Wet
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AnimalPart = AnimalArgs.Fowl { Species = "pheasant" }
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}
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A = None
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B = Choice2Of2 4
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BWithEnv = Choice1Of2 8
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BWithConstant = Choice2Of2 4
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DryRun = Choice1Of2 DryRunMode.Dry
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AnimalPart = AnimalArgs.Fish { Fins = 39 }
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}
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Default arguments are handled as `Choice<'a, 'a>`:
243247
you get a `Choice1Of2` if the user provided the input, or a `Choice2Of2` if the parser filled in your specified default value.
244248

249+
`[<ArgumentDefaultValue foo>]` is shorthand for an `[<ArgumentDefaultFunction>]` whose function just returns a constant.
250+
Since `foo` is an ordinary .NET attribute argument, F# restricts it to compile-time constants: literals, `[<Literal>]` bindings, and enum cases.
251+
(A discriminated union case, such as a flag DU's, is not one of those, so those still need `[<ArgumentDefaultFunction>]`.)
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Note that F# requires parentheses around an attribute argument which is not a bare literal: `[<ArgumentDefaultValue(Consts.Foo)>]`, but `[<ArgumentDefaultValue 4>]`.
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You can control `TimeSpan` and friends with the `[<InvariantCulture>]` and `[<ParseExact @"hh\:mm\:ss">]` attributes.
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247256
You can generate extension methods for the type, instead of a module with the type's name, using `[<ArgParser (* isExtensionMethod = *) true>]`.

‎WoofWare.Myriad.Plugins.Attributes/ArgParserAttributes.fs‎

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@@ -62,6 +62,28 @@ type ArgumentDefaultFunctionAttribute () =
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type ArgumentDefaultEnvironmentVariableAttribute (envVar : string) =
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inherit Attribute ()
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/// Attribute indicating that this field shall have the given constant default value.
66+
/// This is shorthand for `[<ArgumentDefaultFunction>]` in the common case where the default function
67+
/// would simply return a constant.
68+
///
69+
/// This attribute can only be placed on fields of type `Choice<_, _>` where both type parameters
70+
/// are the same.
71+
/// After a successful parse, the value is Choice1Of2 if the user supplied an input,
72+
/// or Choice2Of2 if the input was this constant.
73+
///
74+
/// The value you supply is spliced verbatim into the generated code, so it must have the field's
75+
/// element type: `[<ArgumentDefaultValue 3>]` on a `Choice<int, int>`, but
76+
/// `[<ArgumentDefaultValue 3L>]` on a `Choice<int64, int64>`. A mismatch is a compile error in
77+
/// the generated file rather than at the attribute itself.
78+
///
79+
/// Since this is an ordinary .NET attribute argument, F# restricts you to compile-time constants:
80+
/// literals, `[<Literal>]` values, and enum cases. (Anything else, and in particular a discriminated
81+
/// union case such as a flag DU's, needs `[<ArgumentDefaultFunction>]` instead.) Note that F#'s
82+
/// attribute syntax requires parentheses around an argument which is not a bare literal:
83+
/// `[<ArgumentDefaultValue(Consts.Foo)>]`, but `[<ArgumentDefaultValue 3>]`.
84+
type ArgumentDefaultValueAttribute (defaultValue : obj) =
85+
inherit Attribute ()
86+
6587
/// Attribute indicating that this field or type shall have the given help text, when `--help` is invoked
6688
/// or when a parse error causes us to print help text.
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/// When applied to a record type, the help text appears at the top of the help output, before the field descriptions.

‎WoofWare.Myriad.Plugins.Attributes/SurfaceBaseline.txt‎

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@@ -7,6 +7,8 @@ WoofWare.Myriad.Plugins.ArgumentDefaultEnvironmentVariableAttribute inherit Syst
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WoofWare.Myriad.Plugins.ArgumentDefaultEnvironmentVariableAttribute..ctor [constructor]: string
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WoofWare.Myriad.Plugins.ArgumentDefaultFunctionAttribute inherit System.Attribute
99
WoofWare.Myriad.Plugins.ArgumentDefaultFunctionAttribute..ctor [constructor]: unit
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WoofWare.Myriad.Plugins.ArgumentDefaultValueAttribute inherit System.Attribute
11+
WoofWare.Myriad.Plugins.ArgumentDefaultValueAttribute..ctor [constructor]: obj
1012
WoofWare.Myriad.Plugins.ArgumentFlagAttribute inherit System.Attribute
1113
WoofWare.Myriad.Plugins.ArgumentFlagAttribute..ctor [constructor]: bool
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WoofWare.Myriad.Plugins.ArgumentHelpTextAttribute inherit System.Attribute

‎WoofWare.Myriad.Plugins.Attributes/version.json‎

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@@ -1,5 +1,5 @@
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{
2-
"version": "3.8",
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"version": "3.9",
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"publicReleaseRefSpec": [
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"^refs/heads/main$"
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],

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