Merge pull request #30 from 0x-buidl/feat/interface_inheritance

feat: integrate interface inheritance

.gitignore

@@ -16,4 +16,4 @@
 
 examples/time
 examples/tygo
-examples/http
+examples/http

README.md

@@ -4,7 +4,7 @@ Tygo is a tool for generating Typescript typings from Golang source files that j
 
 It preserves comments, understands constants and also supports non-struct `type` expressions. It's perfect for generating equivalent types for a Golang REST API to be used in your front-end codebase.
 
-**🚀 Now supports Golang 1.18 generic types**
+**🚀 Now supports Golang 1.18 generic types, struct inheritance**
 
 ## Installation
 
@@ -223,7 +223,7 @@ export interface Nicknames {
 
 ### Readonly fields
 
-Sometimes a field should be immutable, you can `,readonly` to the `tstype` tag to mark a field as `readonly`.
+Sometimes a field should be immutable, you can add `,readonly` to the `tstype` tag to mark a field as `readonly`.
 
 ```golang
 // Golang input
@@ -241,6 +241,42 @@ export interface Cat {
 }
 ```
 
+## Inheritance
+
+Tygo supports interface inheritance. To extend an `inlined` struct, use the tag `tstype:,extends` on struct fields you wish to extend. Only `struct` types can be extended.
+
+Example usage [here](examples/inheritance)
+
+```go
+// Golang input
+import "example.com/external"
+
+type Base struct {
+	Name string `json:"name"`
+}
+
+type Base2[T string | int] struct {
+	ID T `json:"id"`
+}
+
+type Other[T int] struct {
+	Base                   `       tstype:",extends"`
+	Base2[T]               `       tstype:",extends"`
+	external.AnotherStruct `       tstype:",extends"`
+	OtherValue             string `                  json:"other_value"`
+}
+```
+
+```typescript
+// Typescript output
+export interface Other<T extends number /* int */>
+  extends Base,
+    Base2<T>,
+    external.AnotherStruct {
+  other_value: string;
+}
+```
+
 ## Generics
 
 Tygo supports generic types (Go version >= 1.18) out of the box.
@@ -294,7 +330,7 @@ packages:
 // Golang input
 type Foo struct {
 	TaggedField string `yaml:"custom_field_name_in_yaml"`
-        UntaggedField string
+  UntaggedField string
 }
 ```
 

cmd/root.go

@@ -11,13 +11,14 @@ import (
 )
 
 func Execute() {
-	var rootCmd = &cobra.Command{
+	rootCmd := &cobra.Command{
 		Use:   "tygo",
 		Short: "Tool for generating Typescript from Go types",
 		Long:  `Tygo generates Typescript interfaces and constants from Go files by parsing them.`,
 	}
 
-	rootCmd.PersistentFlags().String("config", "tygo.yaml", "config file to load (default is tygo.yaml in the current folder)")
+	rootCmd.PersistentFlags().
+		String("config", "tygo.yaml", "config file to load (default is tygo.yaml in the current folder)")
 	rootCmd.Version = Version() + " " + Target() + " (" + CommitDate() + ") " + Commit()
 	rootCmd.PersistentFlags().BoolP("debug", "D", false, "Debug mode (prints debug messages)")
 

examples/bookstore/author.go

@@ -4,3 +4,7 @@ type AuthorBookListing struct {
 	AuthorName   string `json:"author_name"`
 	WrittenBooks []Book `json:"written_books"`
 }
+
+type AuthorWithInheritance[T int] struct {
+	ID T `json:"id"`
+}

examples/bookstore/book.go

@@ -22,8 +22,13 @@ type Book struct {
 	// ISBN identifier of the book, null if not known.
 	ISBN ISBN `json:"isbn"`
 
-	Genre    string    `json:"genre" tstype:"'novel' | 'crime' | 'fantasy'"`
+	Genre    string    `json:"genre"    tstype:"'novel' | 'crime' | 'fantasy'"`
 	Chapters []Chapter `json:"chapters"`
 
 	PublishedAt *time.Time `json:"published_at"`
 }
+
+type TextBook[T int] struct {
+	Book  `  tstype:",inline"`
+	Pages T `                 json:"pages"`
+}

examples/bookstore/index.ts

@@ -7,6 +7,9 @@ export interface AuthorBookListing {
   author_name: string;
   written_books: Book[];
 }
+export interface AuthorWithInheritance<T extends number /* int */> {
+  id: T;
+}
 
 //////////
 // source: book.go
@@ -33,3 +36,6 @@ export interface Book {
   chapters: Chapter[];
   published_at?: string /* RFC 3339 formatted */;
 }
+export interface TextBook<T extends number /* int */> {
+  pages: T;
+}

examples/inheritance/index.ts

@@ -0,0 +1,22 @@
+// Code generated by tygo. DO NOT EDIT.
+import * as bookapp from "../bookstore"
+
+//////////
+// source: inheritance.go
+
+export interface Base {
+  name: string;
+}
+export interface Base2<T extends string | number /* int */> {
+  id: T;
+}
+export interface Base3<T extends string, X extends number /* int */> {
+  class: T;
+  level: X;
+}
+export interface Other<T extends number /* int */, X extends string> extends Base, Base2<T>, Base3<X, T>, bookapp.Book, bookapp.TextBook<T> {
+  otherWithBase: Base;
+  otherWithBase2: Base2<X>;
+  otherValue: string;
+  author: bookapp.AuthorWithInheritance<T>;
+}

examples/inheritance/inheritance.go

@@ -0,0 +1,28 @@
+package inheritance
+
+import bookapp "github.com/gzuidhof/tygo/examples/bookstore"
+
+type Base struct {
+	Name string `json:"name"`
+}
+
+type Base2[T string | int] struct {
+	ID T `json:"id"`
+}
+
+type Base3[T string, X int] struct {
+	Class T `json:"class"`
+	Level X `json:"level"`
+}
+
+type Other[T int, X string] struct {
+	Base                `tstype:",extends"`
+	Base2[T]            `tstype:",extends"`
+	Base3[X, T]         `tstype:",extends"`
+	OtherWithBase       Base                             `                                          json:"otherWithBase"`
+	OtherWithBase2      Base2[X]                         `                                          json:"otherWithBase2"`
+	OtherValue          string                           `                                          json:"otherValue"`
+	Author              bookapp.AuthorWithInheritance[T] `tstype:"bookapp.AuthorWithInheritance<T>" json:"author"`
+	bookapp.Book        `tstype:",extends"`
+	bookapp.TextBook[T] `tstype:",extends"`
+}

tygo.yaml

@@ -11,10 +11,16 @@ packages:
     indent: "  "
     exclude_files:
       - "excluded.go"
-    frontmatter: | # We can define some additional text to put at the start of the file.
+    frontmatter:
+      | # We can define some additional text to put at the start of the file.
       export type Something = string | number;
   - path: "github.com/gzuidhof/tygo/examples/simple"
     fallback_type: unknown
+  - path: "github.com/gzuidhof/tygo/examples/inheritance"
+    fallback_type: unknown
+    frontmatter:
+      | # We can define some additional text to put at the start of the file.
+      import * as bookapp from "../bookstore"
   - path: "github.com/gzuidhof/tygo/examples/generic"
     fallback_type: unknown
   - path: "github.com/gzuidhof/tygo/examples/preserveTypeComments"

tygo/write.go

@@ -2,11 +2,10 @@ package tygo
 
 import (
 	"fmt"
-	"regexp"
-	"strings"
-
 	"go/ast"
 	"go/token"
+	"regexp"
+	"strings"
 
 	"github.com/fatih/structtag"
 )
@@ -36,7 +35,12 @@ func (g *PackageGenerator) writeIndent(s *strings.Builder, depth int) {
 	}
 }
 
-func (g *PackageGenerator) writeType(s *strings.Builder, t ast.Expr, depth int, optionalParens bool) {
+func (g *PackageGenerator) writeType(
+	s *strings.Builder,
+	t ast.Expr,
+	depth int,
+	optionalParens bool,
+) {
 	switch t := t.(type) {
 	case *ast.StarExpr:
 		if optionalParens {
@@ -147,7 +151,11 @@ func (g *PackageGenerator) writeTypeParamsFields(s *strings.Builder, fields []*a
 	s.WriteByte('>')
 }
 
-func (g *PackageGenerator) writeInterfaceFields(s *strings.Builder, fields []*ast.Field, depth int) {
+func (g *PackageGenerator) writeInterfaceFields(
+	s *strings.Builder,
+	fields []*ast.Field,
+	depth int,
+) {
 	// Usually interfaces in Golang don't have fields, but generic (union) interfaces we can map to Typescript.
 
 	if len(fields) == 0 { // Type without any fields (probably only has methods)
@@ -161,7 +169,9 @@ func (g *PackageGenerator) writeInterfaceFields(s *strings.Builder, fields []*as
 			continue
 		}
 		if !didContainNonFuncFields {
-			s.WriteByte('\n') // We need to write a newline so comments of generic components render nicely.
+			s.WriteByte(
+				'\n',
+			) // We need to write a newline so comments of generic components render nicely.
 			didContainNonFuncFields = true
 		}
 
@@ -227,7 +237,7 @@ func (g *PackageGenerator) writeStructFields(s *strings.Builder, fields []*ast.F
 			tstypeTag, err := tags.Get("tstype")
 			if err == nil {
 				tstype = tstypeTag.Name
-				if tstype == "-" {
+				if tstype == "-" || tstypeTag.HasOption("extends") {
 					continue
 				}
 				required = tstypeTag.HasOption("required")

tygo/write_toplevel.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"go/ast"
 	"strings"
+
+	"github.com/fatih/structtag"
 )
 
 type groupContext struct {
@@ -67,8 +69,13 @@ func (g *PackageGenerator) writeSpec(s *strings.Builder, spec ast.Spec, group *g
 // `type X struct { ... }`
 // or
 // `type Bar = string`
-func (g *PackageGenerator) writeTypeSpec(s *strings.Builder, ts *ast.TypeSpec, group *groupContext) {
-	if ts.Doc != nil && g.PreserveTypeComments() { // The spec has its own comment, which overrules the grouped comment.
+func (g *PackageGenerator) writeTypeSpec(
+	s *strings.Builder,
+	ts *ast.TypeSpec,
+	group *groupContext,
+) {
+	if ts.Doc != nil &&
+		g.PreserveTypeComments() { // The spec has its own comment, which overrules the grouped comment.
 		g.writeCommentGroup(s, ts.Doc, 0)
 	} else if group.isGroupedDeclaration && g.PreserveTypeComments() {
 		g.writeCommentGroupIfNotNil(s, group.doc, 0)
@@ -83,6 +90,7 @@ func (g *PackageGenerator) writeTypeSpec(s *strings.Builder, ts *ast.TypeSpec, g
 			g.writeTypeParamsFields(s, ts.TypeParams.List)
 		}
 
+		g.writeTypeInheritanceSpec(s, st.Fields.List)
 		s.WriteString(" {\n")
 		g.writeStructFields(s, st.Fields.List, 0)
 		s.WriteString("}")
@@ -113,9 +121,43 @@ func (g *PackageGenerator) writeTypeSpec(s *strings.Builder, ts *ast.TypeSpec, g
 	}
 }
 
+// Writing of type inheritance specs, which are expressions like
+// `type X struct {  }`
+// `type Y struct { X `tstype:",extends"` }`
+// `export interface Y extends X { }`
+func (g *PackageGenerator) writeTypeInheritanceSpec(s *strings.Builder, fields []*ast.Field) {
+	inheritances := make([]string, 0)
+	for _, f := range fields {
+		if f.Type != nil && f.Tag != nil {
+			tags, err := structtag.Parse(f.Tag.Value[1 : len(f.Tag.Value)-1])
+			if err != nil {
+				panic(err)
+			}
+
+			tstypeTag, err := tags.Get("tstype")
+			if err != nil || !tstypeTag.HasOption("extends") {
+				continue
+			}
+
+			name, valid := getInheritedType(f.Type)
+			if valid {
+				inheritances = append(inheritances, name)
+			}
+		}
+	}
+	if len(inheritances) > 0 {
+		s.WriteString(" extends ")
+		s.WriteString(strings.Join(inheritances, ", "))
+	}
+}
+
 // Writing of value specs, which are exported const expressions like
 // const SomeValue = 3
-func (g *PackageGenerator) writeValueSpec(s *strings.Builder, vs *ast.ValueSpec, group *groupContext) {
+func (g *PackageGenerator) writeValueSpec(
+	s *strings.Builder,
+	vs *ast.ValueSpec,
+	group *groupContext,
+) {
 	for i, name := range vs.Names {
 		group.iotaValue = group.iotaValue + 1
 		if name.Name == "_" {
@@ -125,7 +167,8 @@ func (g *PackageGenerator) writeValueSpec(s *strings.Builder, vs *ast.ValueSpec,
 			continue
 		}
 
-		if vs.Doc != nil && g.PreserveTypeComments() { // The spec has its own comment, which overrules the grouped comment.
+		if vs.Doc != nil &&
+			g.PreserveTypeComments() { // The spec has its own comment, which overrules the grouped comment.
 			g.writeCommentGroup(s, vs.Doc, 0)
 		} else if group.isGroupedDeclaration && g.PreserveTypeComments() {
 			g.writeCommentGroupIfNotNil(s, group.doc, 0)
@@ -187,3 +230,40 @@ func (g *PackageGenerator) writeValueSpec(s *strings.Builder, vs *ast.ValueSpec,
 
 	}
 }
+
+func getInheritedType(f ast.Expr) (name string, valid bool) {
+	switch ft := f.(type) {
+	case *ast.Ident:
+		if ft.Obj != nil && ft.Obj.Decl != nil {
+			dcl, ok := ft.Obj.Decl.(*ast.TypeSpec)
+			if ok {
+				_, isStruct := dcl.Type.(*ast.StructType)
+				valid = isStruct && dcl.Name.IsExported()
+				name = dcl.Name.Name
+				break
+			}
+		}
+	case *ast.IndexExpr:
+		name, valid = getInheritedType(ft.X)
+		if valid {
+			generic := getIdent(ft.Index.(*ast.Ident).Name)
+			name += fmt.Sprintf("<%s>", generic)
+			break
+		}
+	case *ast.IndexListExpr:
+		name, valid = getInheritedType(ft.X)
+		if valid {
+			generic := ""
+			for _, index := range ft.Indices {
+				generic += fmt.Sprintf("%s, ", getIdent(index.(*ast.Ident).Name))
+			}
+			name += fmt.Sprintf("<%s>", generic[:len(generic)-2])
+			break
+		}
+	case *ast.SelectorExpr:
+		valid = ft.Sel.IsExported()
+		name = fmt.Sprintf("%s.%s", ft.X, ft.Sel)
+
+	}
+	return
+}