用 F# 手写 TypeScript 转 C# 类型绑定生成器

前言

我们经常会遇到这样的事情：有时候我们找到了一个库，但是这个库是用 TypeScript 写的，但是我们想在 C# 调用，于是我们需要设法将原来的 TypeScript 类型声明翻译成 C# 的代码，然后如果是 UI 组件的话，我们需要将其封装到一个 WebView 里面，然后通过 JavaScript 和 C# 的互操作功能来调用该组件的各种方法，支持该组件的各种事件等等。

但是这是一个苦力活，尤其是类型翻译这一步。

这个是我最近在帮助维护一个开源 UWP 项目 monaco-editor-uwp 所需要的，该项目将微软的 monaco 编辑器封装成了 UWP 组件。

然而它的 monaco.d.ts 足足有 1.5 mb，并且 API 经常会变化，如果人工翻译，不仅工作量十分大，还可能会漏掉新的变化，但是如果有一个自动生成器的话，那么人工的工作就会少很多。

目前 GitHub 上面有一个叫做 QuickType 的项目，但是这个项目对 TypeScript 的支持极其有限，仍然停留在 TypeScript 3.2，而且遇到不认识的类型就会报错，比如 DOM 类型等等。

因此我决定手写一个代码生成器 TypedocConverter：https://github.com/hez2010/TypedocConverter

构思

本来是打算从 TypeScript 词法和语义分析开始做的，但是发现有一个叫做 Typedoc 的项目已经帮我们完成了这一步，而且支持输出 JSON schema，那么剩下的事情就简单了：我们只需要将 TypeScript 的 AST 转换成 C# 的 AST，然后再将 AST 还原成代码即可。

那么话不多说，这就开写。

构建 Typescipt AST 类型绑定

借助于 F# 更加强大的类型系统，类型的声明和使用非常简单，并且具有完善的recursive pattern。pattern matching、option types 等支持，这也是该项目选用 F# 而不是 C# 的原因，虽然 C# 也支持这些，也有一定的 FP 能力，但是它还是偏 OOP，写起来会有很多的样板代码，非常的繁琐。

我们将 Typescipt 的类型绑定定义到 Definition.fs 中，这一步直接将 Typedoc 的定义翻译到 F# 即可：

首先是 ReflectionKind 枚举，该枚举表示了 JSON Schema 中各节点的类型：

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

然后是类型修饰标志 ReflectionFlags，注意该 record 所有的成员都是 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
}

然后到了我们的 Reflection，由于每一种类型的 Reflection 都可以由 ReflectionKind 来区分，因此我选择将所有类型的 Reflection 合并成为一个 record，而不是采用 Union Types，因为后者虽然看上去清晰，但是在实际 parse AST 的时候会需要大量 pattern matching 的代码。

由于部分 records 相互引用，因此我们使用 and 来定义 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
}

这样，我们就简单的完成了类型绑定的翻译，接下来要做的就是将 Typedoc 生成的 JSON 反序列化成我们所需要的东西即可。

反序列化

虽然想着好像一切都很顺利，但是实际上 System.Text.Json、Newtonsoft.JSON 等均不支持 F# 的 option types，所需我们还需要一个 JsonConverter 处理 option types。

本项目采用 Newtonsoft.Json，因为 System.Text.Json 目前尚不成熟。得益于 F# 对 OOP 的兼容，我们可以很容易的实现一个 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|])

这样所有的工作就完成了。

我们可以去 monaco-editor 仓库下载 monaco.d.ts 测试一下我们的 JSON Schema deserializer，可以发现 JSON Sechma 都被正确地反序列化了。

反序列化结果

构建 C# AST 类型

当然，此 "AST" 非彼 AST，我们没有必要其细化到语句层面，因为我们只是要写一个简单的代码生成器，我们只需要构建实体结构即可。

我们将实体结构定义到 Entity.fs 中，在此我们只需支持 interface、class、enum 即可，对于 class 和 interface，我们只需要支持 method、property 和 event 就足够了。

当然，代码中存在泛型的可能，这一点我们也需要考虑。

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
}

文档化注释生成器

文档化注释也是少不了的东西，能极大方便开发者后续使用生成的类型绑定，而无需参照原 typescript 类型声明上的注释。

代码很简单，只需要将文本处理成 xml 即可。

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

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

类型生成器

Typescript 的类型系统较为灵活，包括 union types、intersect types 等等，这些即使是目前的 C# 8 都不能直接表达，需要等到 C# 9 才行。当然我们可以生成一个 struct 并为其编写隐式转换操作符重载，支持 union types，但是目前尚未实现，我们就先用 union types 中的第一个类型代替，而对于 intersect types，我们姑且先使用 object。

然而 union types 有一个特殊情况：string literals types alias。就是这样的东西：

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

即纯 string 值组合的 type alias，这个我们还是有必要支持的，因为在 typescript 中用的非常广泛。

C# 在没有对应语法的时候要怎么支持呢？很简单，我们创建一个 enum，该 enum 包含该类型中的所有元素，然后我们为其编写 JsonConverter，这样就能确保序列化后，typescript 方能正确识别类型，而在 C# 又有 type sound 的编码体验。

另外，我们需要提供一些常用的类型转换：

• 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 类型
• 其他的数组类型如  Uint32Array  
• 对于  <void> ，我们需要解除泛型，即  T<void>  ->  T

那么实现如下：

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 = "" |})

当然，目前尚不支持生成泛型约束，如果以后有时间的话会考虑添加。

修饰生成器

例如 public 、 private 、 protected 、 static 等等。这一步很简单，直接将 ReflectionFlags 转换一下即可，个人觉得使用 mutable 代码会让代码变得非常不优雅，但是有的时候还是需要用一下的，不然会极大地提高代码的复杂度。

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

终于到 parse 实体的部分了，我们先从最简单的做起：枚举。 代码很简单，直接将原 AST 中的枚举部分转换一下即可。

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 = []
    }

你会注意到一个上面我有一处标了个 ????? ，这是在干什么呢？

其实，TypeScript 的 enum 是 recursive 的，也就意味着定义的时候，一个元素可以引用另一个元素，比如这样:

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

这个时候，我们需要查找它引用的枚举值，比如在上面的例子里面，处理 C 的时候，需要将它的值 A 用真实值 1 代替。所以我们还需要一个查找函数：

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

这样我们的 Enum parser 就完成了。

Interface 和 Class 生成器

下面到了重头戏，interface 和 class 才是类型绑定的关键。

我们的函数签名是这样的：

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

首先我们从 Reflection 节点中查找并生成注释、修饰、名称、泛型参数、继承关系、方法、属性和事件：

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)
    | _ -> []

有一点要注意，就是对于 interface 来说，子 interface 无需重复父 interface 的成员，因此需要排除。

然后我们直接返回一个 record，代表该节点的实体即可。

{
    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);
}

注意处理 event 的时候，委托的类型需要特殊处理一下。

Type alias 生诚器

还记得我们最上面说的一种特殊的 union types 吗？这里就是处理纯 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.")
            []
    | _ -> []

组合 Prasers

我们最后将以上 parsers 组合起来就 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，我们的 parse 工作全部搞定，完结撒花~~~

代码生成

有了 C# 的实体类型，代码生成还困难吗？

不过有一点要注意的是，我们需要将名称转换为 Pascal Case，还需要生成 string literals union types 的 JsonConverter。不过这些都是样板代码，非常简单。

这里就不放代码了，感兴趣的同学可以自行去我的 GitHub 仓库查看。

测试效果

原 typescipt 代码：

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 后，将其作为输入，生成 C# 代码：

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");
        }
    }
}

后记

有了这个 工具 后，妈妈再也不用担心我封装 TypeScript 的库了。有了 TypedocConverter，任何 TypeScript 的库都能轻而易举地转换成 C# 的类型绑定，然后进行封装，非常方便。

感谢大家看到这里，最后，欢迎大家使用 TypedocConverter 。当然，如果能 star 一波甚至贡献代码，我会非常感谢的！