用 F# 手寫 TypeScript 轉 C# 類型綁定生成器

使用 F# 手寫一個 Typedoc 轉 C# 代碼生成器，友善一切 C# 項目對 TypeScript 項目的封裝。

前言

我們經常會遇到這樣的事情：有時候我們找到了一個庫，但是這個庫是用 TypeScript 寫的，但是我們想在 C# 調用，于是我們需要設法将原來的 TypeScript 類型聲明翻譯成 C# 的代碼，然後如果是 UI 元件的話，我們需要将其封裝到一個 WebView 裡面，然後通過 JavaScript 和 C# 的互操作功能來調用該元件的各種方法，支援該元件的各種事件等等。

但是這是一個苦力活，尤其是類型翻譯這一步。

這個是我最近在幫助維護一個開源 UWP 項目 monaco-editor-uwp 所需要的，該項目将微軟的 monaco 編輯器封裝成了 UWP 元件。

然而它的 monaco.d.ts 足足有 1.5 mb，并且 API 經常會變化，如果人工翻譯，不僅工作量十分大，還可能會漏掉新的變化，但是如果有一個自動生成器的話，那麼人工的工作就會少很多。

目前 GitHub 上面有一個叫做 QuickType 的項目，但是這個項目對 TypeScript 的支援極其有限，仍然停留在 TypeScript 3.2，而且遇到不認識的類型就會報錯，比如 DOM 類型等等。

是以我決定手寫一個代碼生成器 TypedocConverter：https://github.com/hez2010/TypedocConverter

構思

本來是打算從 TypeScript 詞法和語義分析開始做的，但是發現有一個叫做 Typedoc 的項目已經幫我們完成了這一步，而且支援輸出 JSON schema，那麼剩下的事情就簡單了：我們隻需要将 TypeScript 的 AST 轉換成 C# 的 AST，然後再将 AST 還原成代碼即可。

那麼話不多說，這就開寫。

建構 Typescipt AST 類型綁定

借助于 F# 更加強大的類型系統，類型的聲明和使用非常簡單，并且具有完善的recursive pattern。pattern matching、option types 等支援，這也是該項目選用 F# 而不是 C# 的原因，雖然 C# 也支援這些，也有一定的 FP 能力，但是它還是偏 OOP，寫起來會有很多的樣闆代碼，非常的繁瑣。

我們将 Typescipt 的類型綁定定義到 Definition.fs 中，這一步直接将 Typedoc 的定義翻譯到 F# 即可：

首先是 ReflectionKind 枚舉，該枚舉表示了 JSON Schema 中各節點的類型：

type ReflectionKind = 
| Global = 0
| ExternalModule = 1
| Module = 2
| Enum = 4
| EnumMember = 16
| Variable = 32
| Function = 64
| Class = 128
| Interface = 256
| Constructor = 512
| Property = 1024
| Method = 2048
| CallSignature = 4096
| IndexSignature = 8192
| ConstructorSignature = 16384
| Parameter = 32768
| TypeLiteral = 65536
| TypeParameter = 131072
| Accessor = 262144
| GetSignature = 524288
| SetSignature = 1048576
| ObjectLiteral = 2097152
| TypeAlias = 4194304
| Event = 8388608
| Reference = 16777216

然後是類型修飾标志 ReflectionFlags，注意該 record 所有的成員都是 option 的

type ReflectionFlags = {
    IsPrivate: bool option
    IsProtected: bool option
    IsPublic: bool option
    IsStatic: bool option
    IsExported: bool option
    IsExternal: bool option
    IsOptional: bool option
    IsReset: bool option
    HasExportAssignment: bool option
    IsConstructorProperty: bool option
    IsAbstract: bool option
    IsConst: bool option
    IsLet: bool option
}

然後到了我們的 Reflection，由于每一種類型的 Reflection 都可以由 ReflectionKind 來區分，是以我選擇将所有類型的 Reflection 合并成為一個 record，而不是采用 Union Types，因為後者雖然看上去清晰，但是在實際 parse AST 的時候會需要大量 pattern matching 的代碼。

由于部分 records 互相引用，是以我們使用

and

來定義 recursive records。

type Reflection = {
    Id: int
    Name: string
    OriginalName: string
    Kind: ReflectionKind
    KindString: string option
    Flags: ReflectionFlags
    Parent: Reflection option
    Comment: Comment option
    Sources: SourceReference list option
    Decorators: Decorator option
    Decorates: Type list option
    Url: string option
    Anchor: string option
    HasOwnDocument: bool option
    CssClasses: string option
    DefaultValue: string option
    Type: Type option
    TypeParameter: Reflection list option
    Signatures: Reflection list option
    IndexSignature: Reflection list option
    GetSignature: Reflection list option
    SetSignature: Reflection list option
    Overwrites: Type option
    InheritedFrom: Type option
    ImplementationOf: Type option
    ExtendedTypes: Type list option
    ExtendedBy: Type list option
    ImplementedTypes: Type list option
    ImplementedBy: Type list option
    TypeHierarchy: DeclarationHierarchy option
    Children: Reflection list option
    Groups: ReflectionGroup list option
    Categories: ReflectionCategory list option
    Reflections: Map<int, Reflection> option
    Directory: SourceDirectory option
    Files: SourceFile list option
    Readme: string option
    PackageInfo: obj option
    Parameters: Reflection list option
}
and DeclarationHierarchy = {
    Type: Type list
    Next: DeclarationHierarchy option
    IsTarget: bool option
}
and Type = {
    Type: string
    Id: int option
    Name: string option
    ElementType: Type option
    Value: string option
    Types: Type list option
    TypeArguments: Type list option
    Constraint: Type option
    Declaration: Reflection option
}
and Decorator = {
    Name: string
    Type: Type option
    Arguments: obj option
}
and ReflectionGroup = {
    Title: string
    Kind: ReflectionKind
    Children: int list
    CssClasses: string option
    AllChildrenHaveOwnDocument: bool option
    AllChildrenAreInherited: bool option
    AllChildrenArePrivate: bool option
    AllChildrenAreProtectedOrPrivate: bool option
    AllChildrenAreExternal: bool option
    SomeChildrenAreExported: bool option
    Categories: ReflectionCategory list option
}
and ReflectionCategory = {
    Title: string
    Children: int list
    AllChildrenHaveOwnDocument: bool option
}
and SourceDirectory = {
    Parent: SourceDirectory option
    Directories: Map<string, SourceDirectory>
    Groups: ReflectionGroup list option
    Files: SourceFile list
    Name: string option
    DirName: string option
    Url: string option
}
and SourceFile = {
    FullFileName: string
    FileName: string
    Name: string
    Url: string option
    Parent: SourceDirectory option
    Reflections: Reflection list option
    Groups: ReflectionGroup list option
}
and SourceReference = {
    File: SourceFile option
    FileName: string
    Line: int
    Character: int
    Url: string option
}
and Comment = {
    ShortText: string
    Text: string option
    Returns: string option
    Tags: CommentTag list option
}
and CommentTag = {
    TagName: string
    ParentName: string
    Text: string
}

這樣，我們就簡單的完成了類型綁定的翻譯，接下來要做的就是将 Typedoc 生成的 JSON 反序列化成我們所需要的東西即可。

反序列化

雖然想着好像一切都很順利，但是實際上 System.Text.Json、Newtonsoft.JSON 等均不支援 F# 的 option types，所需我們還需要一個 JsonConverter 處理 option types。

本項目采用 Newtonsoft.Json，因為 System.Text.Json 目前尚不成熟。得益于 F# 對 OOP 的相容，我們可以很容易的實作一個

OptionConverter

。

type OptionConverter() =
    inherit JsonConverter()
    override __.CanConvert(objectType: Type) : bool = 
        match objectType.IsGenericType with
        | false -> false
        | true -> typedefof<_ option> = objectType.GetGenericTypeDefinition()
    override __.WriteJson(writer: JsonWriter, value: obj, serializer: JsonSerializer) : unit = 
        serializer.Serialize(writer, 
            if isNull value then null
            else let _, fields = FSharpValue.GetUnionFields(value, value.GetType())
                 fields.[0]
        )
    override __.ReadJson(reader: JsonReader, objectType: Type, _existingValue: obj, serializer: JsonSerializer) : obj = 
        let innerType = objectType.GetGenericArguments().[0]
        let value = 
            serializer.Deserialize(
                reader, 
                if innerType.IsValueType 
                then (typedefof<_ Nullable>).MakeGenericType([|innerType|])
                else innerType
        )
        let cases = FSharpType.GetUnionCases objectType
        if isNull value then FSharpValue.MakeUnion(cases.[0], [||])
        else FSharpValue.MakeUnion(cases.[1], [|value|])

這樣所有的工作就完成了。

我們可以去 monaco-editor 倉庫下載下傳 monaco.d.ts 測試一下我們的 JSON Schema deserializer，可以發現 JSON Sechma 都被正确地反序列化了。

反序列化結果

建構 C# AST 類型

當然，此 "AST" 非彼 AST，我們沒有必要其細化到語句層面，因為我們隻是要寫一個簡單的代碼生成器，我們隻需要建構實體結構即可。

我們将實體結構定義到 Entity.fs 中，在此我們隻需支援 interface、class、enum 即可，對于 class 和 interface，我們隻需要支援 method、property 和 event 就足夠了。

當然，代碼中存在泛型的可能，這一點我們也需要考慮。

type EntityBodyType = {
    Type: string
    Name: string option
    InnerTypes: EntityBodyType list
}

type EntityMethod = {
    Comment: string
    Modifier: string list
    Type: EntityBodyType
    Name: string
    TypeParameter: string list
    Parameter: EntityBodyType list
}

type EntityProperty = {
    Comment: string
    Modifier: string list
    Name: string
    Type: EntityBodyType
    WithGet: bool
    WithSet: bool
    IsOptional: bool
    InitialValue: string option
}

type EntityEvent = {
    Comment: string
    Modifier: string list
    DelegateType: EntityBodyType
    Name: string
    IsOptional: bool
}

type EntityEnum = {
    Comment: string
    Name: string
    Value: int64 option
}

type EntityType = 
| Interface
| Class
| Enum
| StringEnum

type Entity = {
    Namespace: string
    Name: string
    Comment: string
    Methods: EntityMethod list
    Properties: EntityProperty list
    Events: EntityEvent list
    Enums: EntityEnum list
    InheritedFrom: EntityBodyType list
    Type: EntityType
    TypeParameter: string list
    Modifier: string list
}

文檔化注釋生成器

文檔化注釋也是少不了的東西，能極大友善開發者後續使用生成的類型綁定，而無需參照原 typescript 類型聲明上的注釋。

代碼很簡單，隻需要将文本處理成 xml 即可。

let escapeSymbols (text: string) = 
    if isNull text then ""
    else text
            .Replace("&", "&amp;")
            .Replace("<", "&lt;")
            .Replace(">", "&gt;")

let toCommentText (text: string) = 
    if isNull text then ""
    else text.Split "\n" |> Array.map (fun t -> "/// " + escapeSymbols t) |> Array.reduce(fun accu next -> accu + "\n" + next)

let getXmlDocComment (comment: Comment) =
    let prefix = "/// <summary>\n"
    let suffix = "\n/// </summary>"
    let summary = 
        match comment.Text with
        | Some text -> prefix + toCommentText comment.ShortText + toCommentText text + suffix
        | _ -> 
            match comment.ShortText with
            | "" -> ""
            | _ -> prefix + toCommentText comment.ShortText + suffix
    let returns = 
        match comment.Returns with
        | Some text -> "\n/// <returns>\n" + toCommentText text + "\n/// </returns>"
        | _ -> ""
    summary + returns

類型生成器

Typescript 的類型系統較為靈活，包括 union types、intersect types 等等，這些即使是目前的 C# 8 都不能直接表達，需要等到 C# 9 才行。當然我們可以生成一個 struct 并為其編寫隐式轉換操作符重載，支援 union types，但是目前尚未實作，我們就先用 union types 中的第一個類型代替，而對于 intersect types，我們姑且先使用 object。

然而 union types 有一個特殊情況：string literals types alias。就是這樣的東西：

type Size = "XS" | "S" | "M" | "L" | "XL";

即純 string 值組合的 type alias，這個我們還是有必要支援的，因為在 typescript 中用的非常廣泛。

C# 在沒有對應文法的時候要怎麼支援呢？很簡單，我們建立一個 enum，該 enum 包含該類型中的所有元素，然後我們為其編寫 JsonConverter，這樣就能確定序列化後，typescript 方能正确識别類型，而在 C# 又有 type sound 的編碼體驗。

另外，我們需要提供一些常用的類型轉換：

Array<T> -> T[]
Set<T> System.Collections.Generic.ISet<T>
Map<T> System.Collections.Generic.IDictionary<T>
Promise<T> System.Threading.Tasks.Task<T>
callbacks -> System.Func<T...> , System.Action<T...>
Tuple 類型
其他的數組類型如 Uint32Array
對于 <void> ，我們需要解除泛型，即 T<void> T

那麼實作如下：

let rec getType (typeInfo: Type): EntityBodyType = 
    let genericType =
        match typeInfo.Type with
        | "intrinsic" -> 
            match typeInfo.Name with
            | Some name -> 
                match name with
                | "number" -> { Type = "double"; InnerTypes = []; Name = None }
                | "boolean" -> { Type = "bool"; InnerTypes = []; Name = None }
                | "string" -> { Type = "string"; InnerTypes = []; Name = None }
                | "void" -> { Type = "void"; InnerTypes = []; Name = None }
                | _ -> { Type = "object"; InnerTypes = []; Name = None }
            | _ -> { Type = "object"; InnerTypes = []; Name = None }
        | "reference" | "typeParameter" -> 
            match typeInfo.Name with
            | Some name -> 
                match name with
                | "Promise" -> { Type = "System.Threading.Tasks.Task"; InnerTypes = []; Name = None }
                | "Set" -> { Type = "System.Collections.Generic.ISet"; InnerTypes = []; Name = None }
                | "Map" -> { Type = "System.Collections.Generic.IDictionary"; InnerTypes = []; Name = None }
                | "Array" -> { Type = "System.Array"; InnerTypes = []; Name = None }
                | "BigUint64Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "ulong"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Uint32Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "uint"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Uint16Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "ushort"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Uint8Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "byte"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "BigInt64Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "long"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Int32Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "int"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Int16Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "short"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "Int8Array" -> { Type = "System.Array"; InnerTypes = [{ Type = "char"; InnerTypes = [ ]; Name = None };]; Name = None };
                | "RegExp" -> { Type = "string"; InnerTypes = []; Name = None };
                | x -> { Type = x; InnerTypes = []; Name = None };
            | _ -> { Type = "object"; InnerTypes = []; Name = None }
        | "array" -> 
            match typeInfo.ElementType with
            | Some elementType -> { Type = "System.Array"; InnerTypes = [getType elementType]; Name = None }
            | _ -> { Type = "System.Array"; InnerTypes = [{ Type = "object"; InnerTypes = []; Name = None }]; Name = None }
        | "stringLiteral" -> { Type = "string"; InnerTypes = []; Name = None }
        | "tuple" ->
            match typeInfo.Types with
            | Some innerTypes -> 
                match innerTypes with
                | [] -> { Type = "object"; InnerTypes = []; Name = None }
                | _ -> { Type = "System.ValueTuple"; InnerTypes = innerTypes |> List.map getType; Name = None }
            | _ -> { Type = "object"; InnerTypes = []; Name = None }
        | "union" -> 
            match typeInfo.Types with
            | Some innerTypes -> 
                match innerTypes with
                | [] -> { Type = "object"; InnerTypes = []; Name = None }
                | _ -> 
                    printWarning ("Taking only the first type " + innerTypes.[0].Type + " for the entire union type.")
                    getType innerTypes.[0] // TODO: generate unions
| _ ->{ Type = "object"; InnerTypes = []; Name = None }
        | "intersection" -> { Type = "object"; InnerTypes = []; Name = None } // TODO: generate intersections
| "reflection" -> 
            match typeInfo.Declaration with
            | Some dec -> 
                match dec.Signatures with
                | Some [signature] -> 
                    let paras = 
                        match signature.Parameters with
                        | Some p -> 
                            p 
                            |> List.map
                                (fun pi -> 
                                    match pi.Type with 
                                    | Some pt -> Some (getType pt)
                                    | _ -> None
                                )
                            |> List.collect
                                (fun x -> 
                                    match x with
                                    | Some s -> [s]
                                    | _ -> []
                                )
                        | _ -> []
                    let rec getDelegateParas (paras: EntityBodyType list): EntityBodyType list =
                        match paras with
                        | [x] -> [{ Type = x.Type; InnerTypes = x.InnerTypes; Name = None }]
                        | (front::tails) -> [front] @ getDelegateParas tails
                        | _ -> []
                    let returnsType = 
                        match signature.Type with
                        | Some t -> getType t
                        | _ -> { Type = "void"; InnerTypes = []; Name = None }
                    let typeParas = getDelegateParas paras
                    match typeParas with
                    | [] -> { Type = "System.Action"; InnerTypes = []; Name = None }
                    | _ -> 
                        if returnsType.Type = "void" 
                        then { Type = "System.Action"; InnerTypes = typeParas; Name = None } 
                        else { Type = "System.Func"; InnerTypes = typeParas @ [returnsType]; Name = None }
                | _ -> { Type = "object"; InnerTypes = []; Name = None }
            | _ -> { Type = "object"; InnerTypes = []; Name = None }
        | _ -> { Type = "object"; InnerTypes = []; Name = None }
    let mutable innerTypes = 
        match typeInfo.TypeArguments with
        | Some args -> getGenericTypeArguments args
        | _ -> []
    if genericType.Type = "System.Threading.Tasks.Task"
    then 
        match innerTypes with
        | (front::_) -> if front.Type = "void" then innerTypes <- [] else ()
        | _ -> ()
    else ()
    { 
        Type = genericType.Type; 
        Name = None; 
        InnerTypes = if innerTypes = [] then genericType.InnerTypes else innerTypes; 
    }
and getGenericTypeArguments (typeInfos: Type list): EntityBodyType list = 
    typeInfos |> List.map getType
and getGenericTypeParameters (nodes: Reflection list) = // TODO: generate constaints
let types = 
        nodes 
        |> List.where(fun x -> x.Kind = ReflectionKind.TypeParameter)
        |> List.map (fun x -> x.Name)
    types |> List.map (fun x -> {| Type = x; Constraint = "" |})

當然，目前尚不支援生成泛型限制，如果以後有時間的話會考慮添加。

修飾生成器

例如

public

、

private

protected

static

等等。這一步很簡單，直接将 ReflectionFlags 轉換一下即可，個人覺得使用 mutable 代碼會讓代碼變得非常不優雅，但是有的時候還是需要用一下的，不然會極大地提高代碼的複雜度。

let getModifier (flags: ReflectionFlags) = 
    let mutable modifier = []
    match flags.IsPublic with
    | Some flag -> if flag then modifier <- modifier |> List.append [ "public" ] else ()
    | _ -> ()
    match flags.IsAbstract with
    | Some flag -> if flag then modifier <- modifier |> List.append [ "abstract" ] else ()
    | _ -> ()
    match flags.IsPrivate with
    | Some flag -> if flag then modifier <- modifier |> List.append [ "private" ] else ()
    | _ -> ()
    match flags.IsProtected with
    | Some flag -> if flag then modifier <- modifier |> List.append [ "protected" ] else ()
    | _ -> ()
    match flags.IsStatic with
    | Some flag -> if flag then modifier <- modifier |> List.append [ "static" ] else ()
    | _ -> ()
    modifier

Enum 生成器

終于到 parse 實體的部分了，我們先從最簡單的做起：枚舉。代碼很簡單，直接将原 AST 中的枚舉部分轉換一下即可。

let parseEnum (section: string) (node: Reflection): Entity =
    let values = match node.Children with
                 | Some children ->
                     children
                     |> List.where (fun x -> x.Kind = ReflectionKind.EnumMember)
                 | None -> []
    { 
        Type = EntityType.Enum;
        Namespace = if section = "" then "TypeDocGenerator" else section;
        Modifier = getModifier node.Flags;
        Name = node.Name
        Comment = 
            match node.Comment with
            | Some comment -> getXmlDocComment comment
            | _ -> ""
        Methods = []; Properties = []; Events = []; InheritedFrom = [];
        Enums = values |> List.map (fun x ->
            let comment = 
                match x.Comment with
                | Some comment -> getXmlDocComment comment
                | _ -> ""
            let mutable intValue = 0L
            match x.DefaultValue with
            // ?????
            | Some value -> if Int64.TryParse(value, &intValue) then { Comment = comment; Name = toPascalCase x.Name; Value = Some intValue; }
                            else match getEnumReferencedValue values value x.Name with
                                 | Some t -> { Comment = comment; Name = x.Name; Value = Some (int64 t); }
                                 | _ -> { Comment = comment; Name = x.Name; Value = None; }
            | _ -> { Comment = comment; Name = x.Name; Value = None; }
        );
        TypeParameter = []
    }

你會注意到一個上面我有一處标了個

?????

，這是在幹什麼呢？

其實，TypeScript 的 enum 是 recursive 的，也就意味着定義的時候，一個元素可以引用另一個元素，比如這樣:

enum MyEnum {
    A = 1,
    B = 2,
    C = A
}

這個時候，我們需要查找它引用的枚舉值，比如在上面的例子裡面，處理 C 的時候，需要将它的值 A 用真實值 1 代替。是以我們還需要一個查找函數：

let rec getEnumReferencedValue (nodes: Reflection list) value name = 
    match nodes 
          |> List.where(fun x -> 
              match x.DefaultValue with
              | Some v -> v <> value && not (name = x.Name)
              | _ -> true
          ) 
          |> List.where(fun x -> x.Name = value)
          |> List.tryFind(fun x -> 
                            let mutable intValue = 0
                            match x.DefaultValue with
                            | Some y -> Int32.TryParse(y, &intValue)
                            | _ -> true
           ) with
    | Some t -> t.DefaultValue
    | _ -> None

這樣我們的 Enum parser 就完成了。

Interface 和 Class 生成器

下面到了重頭戲，interface 和 class 才是類型綁定的關鍵。

我們的函數簽名是這樣的：

let parseInterfaceAndClass (section: string) (node: Reflection) (isInterface: bool): Entity = ...

首先我們從 Reflection 節點中查找并生成注釋、修飾、名稱、泛型參數、繼承關系、方法、屬性和事件：

let comment = 
    match node.Comment with
    | Some comment -> getXmlDocComment comment
    | _ -> ""
let exts = 
    (match node.ExtendedTypes with
    | Some types -> types |> List.map(fun x -> getType x)
    | _ -> []) @
    (match node.ImplementedTypes with
    | Some types -> types |> List.map(fun x -> getType x)
    | _ -> [])
let genericType =
    let types = 
          match node.TypeParameter with
          | Some tp -> Some (getGenericTypeParameters tp)
          | _ -> None
    match types with
    | Some result -> result
    | _ -> []
let properties = 
    match node.Children with
    | Some children -> 
        if isInterface then
            children 
            |> List.where(fun x -> x.Kind = ReflectionKind.Property)
            |> List.where(fun x -> x.InheritedFrom = None) // exclude inhreited properties
            |> List.where(fun x -> x.Overwrites = None) // exclude overrites properties
        else children |> List.where(fun x -> x.Kind = ReflectionKind.Property)
    | _ -> []
let events = 
    match node.Children with
    | Some children -> 
        if isInterface then
            children 
            |> List.where(fun x -> x.Kind = ReflectionKind.Event)
            |> List.where(fun x -> x.InheritedFrom = None) // exclude inhreited events
            |> List.where(fun x -> x.Overwrites = None) // exclude overrites events
        else children |> List.where(fun x -> x.Kind = ReflectionKind.Event)
    | _ -> []
let methods = 
    match node.Children with
    | Some children -> 
        if isInterface then
            children 
            |> List.where(fun x -> x.Kind = ReflectionKind.Method)
            |> List.where(fun x -> x.InheritedFrom = None) // exclude inhreited methods
            |> List.where(fun x -> x.Overwrites = None) // exclude overrites methods
        else children |> List.where(fun x -> x.Kind = ReflectionKind.Method)
    | _ -> []

有一點要注意，就是對于 interface 來說，子 interface 無需重複父 interface 的成員，是以需要排除。

然後我們直接傳回一個 record，代表該節點的實體即可。

{
    Type = if isInterface then EntityType.Interface else EntityType.Class;
    Namespace = if section = "" then "TypedocConverter" else section;
    Name = node.Name;
    Comment = comment;
    Modifier = getModifier node.Flags;
    InheritedFrom = exts;
    Methods = 
        methods 
        |> List.map (
            fun x -> 
                let retType = 
                    match (
                            match x.Signatures with
                            | Some signatures -> 
                                signatures |> List.where(fun x -> x.Kind = ReflectionKind.CallSignature)
                            | _ -> []) 
                        with
                        | [] -> { Type = "object"; InnerTypes = []; Name = None }
                        | (front::_) ->
                            match front.Type with
                            | Some typeInfo -> getType typeInfo
                            | _ -> { Type = "object"; InnerTypes = []; Name = None }
                let typeParameter = 
                    match x.Signatures with
                    | Some (sigs::_) -> 
                        let types = 
                              match sigs.TypeParameter with
                              | Some tp -> Some (getGenericTypeParameters tp)
                              | _ -> None
                        match types with
                        | Some result -> result
                        | _ -> []
                    | _ -> []
                    |> List.map (fun x -> x.Type)
                let parameters = 
                    getMethodParameters 
                        (match x.Signatures with
                        | Some signatures -> 
                            signatures 
                            |> List.where(fun x -> x.Kind = ReflectionKind.CallSignature) 
                            |> List.map(
                                fun x -> 
                                    match x.Parameters with
                                    | Some parameters -> parameters |> List.where(fun p -> p.Kind = ReflectionKind.Parameter)
                                    | _ -> []
                                )
                            |> List.reduce(fun accu next -> accu @ next)
                        | _ -> [])
                {
                    Comment = 
                        match x.Comment with
                        | Some comment -> getXmlDocComment comment
                        | _ -> ""
                    Modifier = if isInterface then [] else getModifier x.Flags;
                    Type = retType
                    Name = x.Name
                    TypeParameter = typeParameter
                    Parameter = parameters
                }
        );
    Events = 
        events
        |> List.map (
            fun x -> 
                let paras = 
                    match x.Signatures with
                    | Some sigs -> 
                        sigs 
                        |> List.where (fun x -> x.Kind = ReflectionKind.Event)
                        |> List.map(fun x -> x.Parameters)
                        |> List.collect (fun x ->
                            match x with
                            | Some paras -> paras
                            | _ -> [])
                    | _ -> []
                { 
                    Name = x.Name; 
                    IsOptional = 
                        match x.Flags.IsOptional with
                        | Some optional -> optional
                        | _ -> false
                        ;
                    DelegateType = 
                        match paras with
                        | (front::_) -> 
                            match front.Type with
                            | Some typeInfo -> getType typeInfo
                            | _ -> { Type = "System.Delegate"; Name = None; InnerTypes = [] }
                        | _ -> 
                            match x.Type with
                            | Some typeInfo -> getType typeInfo
                            | _ -> { Type = "System.Delegate"; Name = None; InnerTypes = [] }
                        ;
                    Comment = 
                        match x.Comment with
                        | Some comment -> getXmlDocComment comment
                        | _ -> ""
                        ;
                    Modifier = if isInterface then [] else getModifier x.Flags;
                }
        );
    Properties = 
        properties 
        |> List.map (
            fun x -> 
                {
                    Comment = 
                        match x.Comment with
                        | Some comment -> getXmlDocComment comment
                        | _ -> ""
                    Modifier = if isInterface then [] else getModifier x.Flags;
                    Name = x.Name
                    Type = 
                        match x.Type with
                        | Some typeInfo -> getType typeInfo
                        | _ -> { Type = "object"; Name = None; InnerTypes = [] }
                    WithGet = true;
                    WithSet = true;
                    IsOptional =
                        match x.Flags.IsOptional with
                        | Some optional -> optional
                        | _ -> false
                        ;
                    InitialValue = 
                        match x.DefaultValue with
                        | Some value -> Some value
                        | _ -> None
                }
        );
    Enums = [];
    TypeParameter = genericType |> List.map(fun x -> x.Type);
}

注意處理 event 的時候，委托的類型需要特殊處理一下。

Type alias 生誠器

還記得我們最上面說的一種特殊的 union types 嗎？這裡就是處理純 string 的 type alias 的。

let parseUnionTypeAlias (section: string) (node: Reflection) (nodes: Type list): Entity list =
    let notStringLiteral = nodes |> List.tryFind(fun x -> x.Type <> "stringLiteral")
    let enums = 
        match notStringLiteral with
        | Some _ -> 
            printWarning ("Type alias " + node.Name + " is not supported.")
            []
        | None ->
            nodes 
            |> List.collect
                (fun x ->
                    match x.Value with
                    | Some value -> 
                        [{
                            Name = toPascalCase value
                            Comment = "///<summary>\n" + toCommentText value + "\n///</summary>"
                            Value = None
                        }]
                    | _ -> []
                )
    if enums = [] then []
    else 
        [
            {
                Namespace = section
                Name = node.Name
                Comment = 
                    match node.Comment with
                    | Some comment -> getXmlDocComment comment
                    | _ -> ""
                Methods = []
                Events = []
                Properties = []
                Enums = enums
                InheritedFrom = []
                Type = EntityType.StringEnum
                TypeParameter = []
                Modifier = getModifier node.Flags
            }
        ]

let parseTypeAlias (section: string) (node: Reflection): Entity list =
    let typeInfo = node.Type
    match typeInfo with
    | Some aliasType ->
        match aliasType.Type with
        | "union" -> 
            match aliasType.Types with
            | Some types -> parseUnionTypeAlias section node types
            | _ -> 
                printWarning ("Type alias " + node.Name + " is not supported.")
                []
        | _ ->
            printWarning ("Type alias " + node.Name + " is not supported.")
            []
    | _ -> []

組合 Prasers

我們最後将以上 parsers 組合起來就 ojbk 了：

let rec parseNode (section: string) (node: Reflection): Entity list =
    match node.Kind with
    | ReflectionKind.Global ->
        match node.Children with
        | Some children -> parseNodes section children
        | _ -> []
    | ReflectionKind.Module ->
        match node.Children with
        | Some children ->
            parseNodes (if section = "" then node.Name else section + "." + node.Name) children
        | _ -> []
    | ReflectionKind.ExternalModule ->
        match node.Children with
        | Some children -> parseNodes section children
        | _ -> []
    | ReflectionKind.Enum -> [parseEnum section node]
    | ReflectionKind.Interface -> [parseInterfaceAndClass section node true]
    | ReflectionKind.Class -> [parseInterfaceAndClass section node false]
    | ReflectionKind.TypeAlias -> 
        match node.Type with
        | Some _ -> parseTypeAlias section node
        | _ -> []
    | _ -> []

and parseNodes section (nodes: Reflection list): Entity list =
    match nodes with
    | ([ front ]) -> parseNode section front
    | (front :: tails) ->
        parseNode section front @ parseNodes section tails
    | _ -> []

至此，我們的 parse 工作全部搞定，完結撒花~~~

代碼生成

有了 C# 的實體類型，代碼生成還困難嗎？

不過有一點要注意的是，我們需要将名稱轉換為 Pascal Case，還需要生成 string literals union types 的 JsonConverter。不過這些都是樣闆代碼，非常簡單。

這裡就不放代碼了，感興趣的同學可以自行去我的 GitHub 倉庫檢視。

測試效果

原 typescipt 代碼：

declare namespace test {
  /**
   * The declaration of an enum
   */
  export enum MyEnum {
    A = 0,
    B = 1,
    C = 2,
    D = C
  }

  /**
   * The declaration of an interface
   */
  export interface MyInterface1 {
    /**
     * A method
     */
    testMethod(arg: string, callback: () => void): string;
    /**
     * An event
     * @event
     */
    onTest(listener: (e: MyInterface1) => void): void;
    /**
     * An property
     */
    readonly testProp: string;
  }

  /**
   * Another declaration of an interface
   */
  export interface MyInterface2<T> {
    /**
     * A method
     */
    testMethod(arg: T, callback: () => void): T;
    /**
     * An event
     * @event
     */
    onTest(listener: (e: MyInterface2<T>) => void): void;
    /**
     * An property
     */
    readonly testProp: T;
  }

  /**
   * The declaration of a class
   */
  export class MyClass1<T> implements MyInterface1 {
    /**
     * A method
     */
    testMethod(arg: string, callback: () => void): string;
    /**
     * An event
     * @event
     */
    onTest(listener: (e: MyInterface1) => void): void;
    /**
     * An property
     */
    readonly testProp: string;
    static staticMethod(value: string, isOption?: boolean): UnionStr;
  }

  /**
   * Another declaration of a class
   */
  export class MyClass2<T> implements MyInterface2<T> {
    /**
     * A method
     */
    testMethod(arg: T, callback: () => void): T;
    /**
     * An event
     * @event
     */
    onTest(listener: (e: MyInterface2<T>) => void): void;
    /**
     * An property
     */
    readonly testProp: T;
    static staticMethod(value: string, isOption?: boolean): UnionStr;
  }

  /**
   * The declaration of a type alias
   */
  export type UnionStr = "A" | "B" | "C" | "other";
}

Typedoc 生成的 JSON 後，将其作為輸入，生成 C# 代碼：

namespace TypedocConverter.Test
{

    /// <summary>
    /// The declaration of an enum
    /// </summary>
    enum MyEnum
    {
        [Newtonsoft.Json.JsonProperty("A", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        A = 0,
        [Newtonsoft.Json.JsonProperty("B", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        B = 1,
        [Newtonsoft.Json.JsonProperty("C", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        C = 2,
        [Newtonsoft.Json.JsonProperty("D", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        D = 2
    }
}

namespace TypedocConverter.Test
{

    /// <summary>
    /// The declaration of a class
    /// </summary>
    class MyClass1<T> : MyInterface1
    {
        /// <summary>
        /// An property
        /// </summary>
        [Newtonsoft.Json.JsonProperty("testProp", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        string TestProp { get => throw new System.NotImplementedException(); set => throw new System.NotImplementedException(); }
        event System.Action<MyInterface1> OnTest;
        string TestMethod(string arg, System.Action callback) => throw new System.NotImplementedException();
        static UnionStr StaticMethod(string value, bool isOption) => throw new System.NotImplementedException();
    }
}

namespace TypedocConverter.Test
{

    /// <summary>
    /// Another declaration of a class
    /// </summary>
    class MyClass2<T> : MyInterface2<T>
    {
        /// <summary>
        /// An property
        /// </summary>
        [Newtonsoft.Json.JsonProperty("testProp", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        T TestProp { get => throw new System.NotImplementedException(); set => throw new System.NotImplementedException(); }
        event System.Action<MyInterface2<T>> OnTest;
        T TestMethod(T arg, System.Action callback) => throw new System.NotImplementedException();
        static UnionStr StaticMethod(string value, bool isOption) => throw new System.NotImplementedException();
    }
}

namespace TypedocConverter.Test
{

    /// <summary>
    /// The declaration of an interface
    /// </summary>
    interface MyInterface1
    {
        /// <summary>
        /// An property
        /// </summary>
        [Newtonsoft.Json.JsonProperty("testProp", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        string TestProp { get; set; }
        event System.Action<MyInterface1> OnTest;
        string TestMethod(string arg, System.Action callback);
    }
}

namespace TypedocConverter.Test
{

    /// <summary>
    /// Another declaration of an interface
    /// </summary>
    interface MyInterface2<T>
    {
        /// <summary>
        /// An property
        /// </summary>
        [Newtonsoft.Json.JsonProperty("testProp", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        T TestProp { get; set; }
        event System.Action<MyInterface2<T>> OnTest;
        T TestMethod(T arg, System.Action callback);
    }
}

namespace TypedocConverter.Test
{

    /// <summary>
    /// The declaration of a type alias
    /// </summary>
    [Newtonsoft.Json.JsonConverter(typeof(UnionStrConverter))]
    enum UnionStr
    {
        ///<summary>
        /// A
        ///</summary>
        [Newtonsoft.Json.JsonProperty("A", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        A,
        ///<summary>
        /// B
        ///</summary>
        [Newtonsoft.Json.JsonProperty("B", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        B,
        ///<summary>
        /// C
        ///</summary>
        [Newtonsoft.Json.JsonProperty("C", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        C,
        ///<summary>
        /// other
        ///</summary>
        [Newtonsoft.Json.JsonProperty("Other", NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        Other
    }
    class UnionStrConverter : Newtonsoft.Json.JsonConverter
    {
        public override bool CanConvert(System.Type t) => t == typeof(UnionStr) || t == typeof(UnionStr?);
        public override object ReadJson(Newtonsoft.Json.JsonReader reader, System.Type t, object? existingValue, Newtonsoft.Json.JsonSerializer serializer)
            => reader.TokenType switch
            {
                Newtonsoft.Json.JsonToken.String =>
                    serializer.Deserialize<string>(reader) switch
                    {
                        "A" => UnionStr.A,
                        "B" => UnionStr.B,
                        "C" => UnionStr.C,
                        "Other" => UnionStr.Other,
                        _ => throw new System.Exception("Cannot unmarshal type UnionStr")
                    },
                _ => throw new System.Exception("Cannot unmarshal type UnionStr")
            };
        public override void WriteJson(Newtonsoft.Json.JsonWriter writer, object? untypedValue, Newtonsoft.Json.JsonSerializer serializer)
        {
            if (untypedValue is null) { serializer.Serialize(writer, null); return; }
            var value = (UnionStr)untypedValue;
            switch (value)
            {
                case UnionStr.A: serializer.Serialize(writer, "A"); return;
                case UnionStr.B: serializer.Serialize(writer, "B"); return;
                case UnionStr.C: serializer.Serialize(writer, "C"); return;
                case UnionStr.Other: serializer.Serialize(writer, "Other"); return;
                default: break;
            }
            throw new System.Exception("Cannot marshal type UnionStr");
        }
    }
}

後記

有了這個工具後，媽媽再也不用擔心我封裝 TypeScript 的庫了。有了 TypedocConverter，任何 TypeScript 的庫都能輕而易舉地轉換成 C# 的類型綁定，然後進行封裝，非常友善。

感謝大家看到這裡，最後，歡迎大家使用 TypedocConverter。當然，如果能 star 一波甚至貢獻代碼，我會非常感謝的！

用 F# 手寫 TypeScript 轉 C# 類型綁定生成器

前言

構思

建構 Typescipt AST 類型綁定

反序列化

建構 C# AST 類型

文檔化注釋生成器

類型生成器

修飾生成器

Enum 生成器

Interface 和 Class 生成器

Type alias 生誠器

組合 Prasers

代碼生成

測試效果

後記

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