Generating F# code using its AST

AstRcd.fs

module Fantomas.AstRcd

open System
open Microsoft.FSharp.Compiler.Ast
open Microsoft.FSharp.Compiler.Range

type ParsedImplFileInputRcd = { 
    File: string
    IsScript: bool
    QualName: QualifiedNameOfFile
    Pragmas: ScopedPragma list
    HashDirectives: ParsedHashDirective list
    Modules: SynModuleOrNamespace list
    IsLastCompiland: bool 
    IsExe: bool}

type ParsedImplFileInput with
    member x.ToRcd
        with get() =
            let (ParsedImplFileInput(file, isScript, qualName, pragmas, hashDirectives, modules, (isLastCompiland, isExe))) = x
            { File = file; IsScript = isScript; QualName = qualName; Pragmas = pragmas; HashDirectives = hashDirectives; Modules = modules; IsLastCompiland = isLastCompiland; IsExe = isExe }

type ParsedImplFileInputRcd with
    member x.FromRcd
        with get() = ParsedImplFileInput(x.File, x.IsScript, x.QualName, x.Pragmas, x.HashDirectives, x.Modules, (x.IsLastCompiland, x.IsExe))

type SynModuleOrNamespaceRcd = {
    Id: LongIdent 
    IsModule: bool
    IsRecursive: bool
    Decls: SynModuleDecls
    XmlDoc: PreXmlDoc
    Attribs: SynAttributes
    Access: SynAccess option
    Range: range }

type SynModuleOrNamespace with
    member x.ToRcd
        with get() =
            let (SynModuleOrNamespace(id, isRecursive, isModule, decls, xmlDoc, attribs, access, range)) = x
            { Id = id; IsRecursive = isRecursive; IsModule = isModule; Decls = decls; XmlDoc = xmlDoc; Attribs = attribs; Access = access; Range = range }

type SynModuleOrNamespaceRcd with
    member x.FromRcd
        with get() = SynModuleOrNamespace(x.Id, x.IsRecursive, x.IsModule, x.Decls, x.XmlDoc, x.Attribs, x.Access, x.Range)

type SynTypeDefnRcd = {
    Info: SynComponentInfo
    Repr: SynTypeDefnRepr
    Members: SynMemberDefns
    Range: range }

type SynTypeDefn with
    member x.ToRcd
        with get() =
            let (TypeDefn(info, repr, members, range)) = x
            { Info = info; Repr = repr; Members = members; Range = range }

type SynTypeDefnRcd with
    member x.FromRcd
        with get() = TypeDefn(x.Info, x.Repr, x.Members, x.Range)

type SynComponentInfoRcd = {
    Attribs: SynAttributes
    TyParams: SynTyparDecl list
    Constraints: SynTypeConstraint list
    Id: LongIdent
    XmlDoc: PreXmlDoc
    PreferPostfix: bool
    Access: SynAccess option
    Range: range }

type SynComponentInfo with
    member x.ToRcd
        with get() =
            let (ComponentInfo(attribs, typarams, constraints, id, xmldoc, preferPostfix, access, range)) = x
            { Attribs = attribs; TyParams = typarams; Constraints = constraints; Id = id; XmlDoc = xmldoc; PreferPostfix = preferPostfix; Access = access; Range = range }

type SynComponentInfoRcd with
    member x.FromRcd
        with get() = ComponentInfo(x.Attribs, x.TyParams, x.Constraints, x.Id, x.XmlDoc, x.PreferPostfix, x.Access, x.Range)

type SynTypeDefnReprObjectModelRcd = {
    Kind: SynTypeDefnKind
    Members: SynMemberDefns
    Range: range }

type SynTypeDefnReprSimpleRcd = {
    Repr: SynTypeDefnSimpleRepr
    Range: range }

let internal failcase (x:Object) = failwithf "not expecting the disciminated union case of type %s" (x.GetType().FullName)

type SynTypeDefnRepr with
    member x.ToObjectModelRcd
        with get() = 
            match x with 
            | SynTypeDefnRepr.ObjectModel(kind, members, range) -> { Kind = kind; Members = members; Range = range }
            | _ -> failcase x
    member x.ToSimpleRcd
        with get() = 
            match x with 
            | SynTypeDefnRepr.Simple(repr, range) -> { Repr = repr; Range = range }
            | _ -> failcase x

type SynTypeDefnReprObjectModelRcd with
    member x.FromRcd
        with get() = SynTypeDefnRepr.ObjectModel(x.Kind, x.Members, x.Range)

type SynTypeDefnReprSimpleRcd with
    member x.FromRcd
        with get() = SynTypeDefnRepr.Simple(x.Repr, x.Range)

type SynBindingRcd = {
    Access: SynAccess option
    Kind: SynBindingKind
    IsInline: bool
    IsMutable: bool
    Attribs: SynAttributes
    XmlDoc: PreXmlDoc
    ValData: SynValData
    Pat: SynPat
    ReturnInfo: SynBindingReturnInfo option
    Expr: SynExpr
    Range: range
    Bind: SequencePointInfoForBinding }

type SynBinding with
    member x.ToRcd
        with get() =
            let (Binding(access, kind, isInline, isMutable, attrs, xmlDoc, info, headPat, retTyOpt, rhsExpr, mBind, spBind)) = x
            { Access = access; Kind = kind; IsInline = isInline; IsMutable = isMutable; Attribs = attrs; XmlDoc = xmlDoc; ValData = info; Pat = headPat; ReturnInfo = retTyOpt; Expr = rhsExpr; Range = mBind; Bind = spBind }

type SynBindingRcd  with
    member x.FromRcd
        with get() = Binding(x.Access, x.Kind, x.IsInline, x.IsMutable, x.Attribs, x.XmlDoc, x.ValData, x.Pat, x.ReturnInfo, x.Expr, x.Range, x.Bind)

let mkId name = Ident(name, range.Zero)
let mkQualifiedNameOfFile name = QualifiedNameOfFile(mkId name)

CreateAst.fs

[<AutoOpen>]
module ConsoleApp.CreateAst

open Fantomas
open Microsoft.FSharp.Compiler.Ast
open Microsoft.FSharp.Compiler.Range

let createAst() =

    // create member
    let memberFlags : MemberFlags = {IsInstance = true; IsDispatchSlot = false; IsOverrideOrExplicitImpl = false; IsFinal = false; MemberKind = MemberKind.Member}
    let b : SynBindingRcd = 
        {   Access = None
            Kind = SynBindingKind.NormalBinding
            IsInline = false
            IsMutable = false
            Attribs = SynAttributes.Empty
            XmlDoc = PreXmlDoc.Empty
            ValData = SynValData(Some memberFlags, SynValInfo([], SynArgInfo(SynAttributes.Empty, false, None)), None)
            Pat = SynPat.LongIdent(LongIdentWithDots([mkId "x"; mkId "Points"], [range.Zero]), None, None, SynConstructorArgs.Pats[], None, range.Zero)
            ReturnInfo = None
            Expr = SynExpr.Const(SynConst.Int32 3, range.Zero)
            Range = range.Zero
            Bind = SequencePointInfoForBinding.NoSequencePointAtInvisibleBinding
        }

    // create Type
    let ti : SynComponentInfoRcd = 
        {   Attribs = SynAttributes.Empty
            TyParams = []
            Constraints = []
            Id = [mkId "Triangle"]
            XmlDoc = PreXmlDoc.Empty
            PreferPostfix = false
            Access = None
            Range = range.Zero
        }

    let ms : SynMemberDefns = 
        [
            SynMemberDefn.ImplicitCtor(None, SynAttributes.Empty, [], None, range.Zero)
            SynMemberDefn.Member(b.FromRcd, range.Zero)
        ]

    let r : SynTypeDefnReprObjectModelRcd = 
        {   //Kind = SynTypeDefnKind.TyconClass
            Kind = SynTypeDefnKind.TyconUnspecified
            Members = ms
            Range = range.Zero
        }

    let t : SynTypeDefnRcd = 
        {   Info = ti.FromRcd
            Repr = r.FromRcd
            Members = []
            Range = range.Zero
        }

    // create module
    let m : SynModuleOrNamespaceRcd = 
        {   Id = [mkId "Hello"]
            IsModule = true
            Decls = [SynModuleDecl.Types([t.FromRcd], range.Zero)]
            XmlDoc = PreXmlDoc.Empty
            Attribs = SynAttributes.Empty
            Access = None
            Range = range.Zero
        }

    // create file
    let pi : ParsedImplFileInputRcd = 
        {   File = "Hello.fs"
            IsScript = false
            QualName = QualifiedNameOfFile(mkId "Hello")
            Pragmas = []
            HashDirectives = []
            Modules = [m.FromRcd]
            IsLastCompiland = true
        }

    let txt = formatAst (ParsedInput.ImplFile pi.FromRcd)
    printfn "%s" txt

FormatFs.fs

[<AutoOpen>]
module ConsoleApp.FormatFs

open System.IO
open Fantomas

let formatAst ast =
    let cfg = { FormatConfig.FormatConfig.Default with StrictMode = true } // no comments
    let noOriginalSourceCode = "//"
    CodeFormatter.formatAST ast noOriginalSourceCode cfg

let formatFs() =
    let s = File.ReadAllText @"C:\Projects\fantomas\src\ConsoleApplication1\Hello.fs"
    let isFsi = false
    let ast = CodeFormatter.parse isFsi s
    let txt = formatAst ast
    printfn "%s" txt

Hello.fs

module Hello

type Triangle   () =
    member x.Points =    3

Hello.Reformatted.fs

module Hello

type Triangle() = 
    member x.Points = 3

PrintAstInfo.fs

[<AutoOpen>]
module ConsoleApp.PrintAstInfo

open System.IO
open Fantomas
open Microsoft.FSharp.Compiler.Ast

let printAstInfo() =
    let s = File.ReadAllText @"C:\Projects\fantomas\src\ConsoleApplication1\Hello.fs"
    let isFsi = false
    let ast = CodeFormatter.parse isFsi s
    match ast with
    | ParsedInput.ImplFile f ->
        let fr = f.ToRcd
        let m = fr.Modules.Head.ToRcd
        printfn "module: %s" m.Id.Head.idText
        match m.Decls.Head with
        | SynModuleDecl.Types(types, _) ->
            let t = types.Head.ToRcd
            printfn "type: %s" t.Info.ToRcd.Id.Head.idText
            let om = t.Repr.ToObjectModelRcd
            let m1 = om.Members.[1] // [[0] is ImplicitCtor
            match om.Members.[1] with
            | SynMemberDefn.Member(b, _) ->
                let br = b.ToRcd
                match br.Pat with
                | SynPat.LongIdent(id,_,_,_,_,_) ->
                    printfn "member: %s %s" id.Lid.[0].idText id.Lid.[1].idText
                match br.Expr with
                | SynExpr.Const(c,_) ->
                    match c with
                    | SynConst.Int32 i -> printfn "member value: %d" i

printAstInfo.txt

module: Hello
type: Triangle
member: x Points
member value: 3