Merge pull request #52 from pdhammond42/main

Add ability to emit literal Typescript from with Go file

Author: gzuidhof

README.md

@@ -197,6 +197,60 @@ export interface Book {
 
 You could use the `frontmatter` field in the config to inject `export type Genre = "novel" | "crime" | "fantasy"` at the top of the file, and use `tstype:"Genre"`. I personally prefer that as we may use the `Genre` type more than once.
 
+**`tygo:emit` directive**
+
+Another way to generate types that cannot be directly represented in Go is to use a `//tygo:emit` directive to 
+directly emit literal TS code.
+The directive can be used in two ways. A `tygo:emit` directive on a struct will emit the remainder of the directive 
+text before the struct.
+```golang
+// Golang input
+
+//tygo:emit export type Genre = "novel" | "crime" | "fantasy"
+type Book struct {
+	Title    string    `json:"title"`
+	Genre    string    `json:"genre" tstype:"Genre"`
+}
+```
+
+```typescript
+export type Genre = "novel" | "crime" | "fantasy"
+
+export interface Book {
+  title: string;
+  genre: Genre;
+}
+```
+
+A `//tygo:emit` directive on a string var will emit the contents of the var, useful for multi-line content.
+```golang
+//tygo:emit
+var _ = `export type StructAsTuple=[
+  a:number, 
+  b:number, 
+  c:string,
+]
+`
+type CustomMarshalled struct {
+  Content []StructAsTuple `json:"content"`
+}
+```
+
+```typescript
+export type StructAsTuple=[
+  a:number, 
+  b:number, 
+  c:string,
+]
+
+export interface CustomMarshalled {
+  content: StructAsTuple[];
+}
+
+```
+
+Generating types this way is particularly useful for tuple types, because a comma cannot be used in the `tstype` tag.
+
 ### Required fields
 
 Pointer type fields usually become optional in the Typescript output, but sometimes you may want to require it regardless.

examples/emit/custom.go

@@ -0,0 +1,34 @@
+package emit
+
+// emit directive on a string literal emits that value.
+//
+//tygo:emit
+var _ = `export type OtherStructAsTuple=[
+  a:number, 
+  b:number, 
+  c:string,
+]
+`
+
+//tygo:emit This has no effect, only strings.
+var _ = 12
+
+// a non-string var is ignored. A var with no comment is ignored.
+
+var foo = " "
+
+// CustomMarshalled illustrates getting tygo to emit literal text
+// This solves the problem of a struct field being marshalled into a tuple.
+//
+// emit directive on a struct emits the remainder of the directive line
+//
+//tygo:emit export type StructAsTuple=[a:number, b:number, c:string]
+type CustomMarshalled struct {
+	Content []StructAsTuple `json:"content"`
+}
+
+//tygo:emit export type Genre = "novel" | "crime" | "fantasy"
+type Book struct {
+	Title string `json:"title"`
+	Genre string `json:"genre" tstype:"Genre"`
+}

examples/emit/excluded.go

@@ -0,0 +1,7 @@
+package emit
+
+type StructAsTuple struct {
+	A int
+	B float64
+	C string
+}

examples/emit/index.ts

@@ -0,0 +1,26 @@
+// Code generated by tygo. DO NOT EDIT.
+
+//////////
+// source: custom.go
+
+export type OtherStructAsTuple=[
+  a:number, 
+  b:number, 
+  c:string,
+]
+
+export type StructAsTuple=[a:number, b:number, c:string]
+/**
+ * CustomMarshalled illustrates getting tygo to emit literal text
+ * This solves the problem of a struct field being marshalled into a tuple.
+ * emit directive on a struct emits the remainder of the directive line
+ */
+export interface CustomMarshalled {
+  content: StructAsTuple[];
+}
+export type Genre = "novel" | "crime" | "fantasy"
+
+export interface Book {
+  title: string;
+  genre: Genre;
+}

tygo.yaml

@@ -50,5 +50,8 @@ packages:
     flavor: "yaml"
   - path: "github.com/gzuidhof/tygo/examples/interface"
   - path: "github.com/gzuidhof/tygo/examples/directive"
+  - path: "github.com/gzuidhof/tygo/examples/emit"
+    exclude_files: 
+      - "excluded.go"
 
 

tygo/package_generator.go

@@ -26,15 +26,25 @@ func (g *PackageGenerator) Generate() (string, error) {
 
 			// GenDecl can be an import, type, var, or const expression
 			case *ast.GenDecl:
-				if x.Tok == token.VAR || x.Tok == token.IMPORT {
+				if x.Tok == token.IMPORT {
 					return false
 				}
+				isEmit := false
+				if x.Tok == token.VAR {
+					isEmit = g.isEmitVar(x)
+					if !isEmit {
+						return false
+					}
+				}
 
 				if first {
 					g.writeFileSourceHeader(s, filepaths[i], file)
 					first = false
 				}
-
+				if isEmit {
+					g.emitVar(s, x)
+					return false
+				}
 				g.writeGroupDecl(s, x)
 				return false
 			}

tygo/write_comment.go

@@ -19,9 +19,20 @@ func (g *PackageGenerator) writeCommentGroupIfNotNil(s *strings.Builder, f *ast.
 	}
 }
 
+func (c *PackageGenerator) writeDirective(s *strings.Builder, cg *ast.CommentGroup) {
+	for _, cm := range cg.List {
+		if strings.HasPrefix(cm.Text, "//tygo:emit") {
+			// remove the separator whitespace but leave extra whitespace for indentation
+			s.WriteString(strings.TrimPrefix(cm.Text, "//tygo:emit")[1:])
+			s.WriteString("\n")
+		}
+	}
+}
+
 func (g *PackageGenerator) writeCommentGroup(s *strings.Builder, cg *ast.CommentGroup, depth int) {
 	docLines := strings.Split(cg.Text(), "\n")
 
+	g.writeDirective(s, cg)
 	if len(cg.List) > 0 && cg.Text() == "" { // This is a directive comment like //go:embed
 		s.WriteByte('\n')
 		return

tygo/write_toplevel.go

@@ -17,6 +17,34 @@ type groupContext struct {
 	iotaValue            int
 }
 
+// isEmitVar returns true if dec is a string var with a tygo:emit directive.
+func (g *PackageGenerator) isEmitVar(dec *ast.GenDecl) bool {
+	if dec.Tok != token.VAR || dec.Doc == nil {
+		return false
+	}
+
+	for _, c := range dec.Doc.List {
+		if strings.HasPrefix(c.Text, "//tygo:emit") {
+			// we know it's VAR so asserting *ast.ValueSpec is OK.
+			v, ok := dec.Specs[0].(*ast.ValueSpec).Values[0].(*ast.BasicLit)
+			if !ok {
+				return false
+			}
+			return v.Kind == token.STRING
+		}
+	}
+	return false
+}
+
+// emitVar emits the text associated with dec, which is assumes to be a string var with a
+// tygo:emit directive, as tested by isEmitVar.
+func (g *PackageGenerator) emitVar(s *strings.Builder, dec *ast.GenDecl) {
+	v := dec.Specs[0].(*ast.ValueSpec).Values[0].(*ast.BasicLit).Value
+	if len(v) < 2 {
+		return
+	}
+	s.WriteString(v[1:len(v)-1] + "\n")
+}
 func (g *PackageGenerator) writeGroupDecl(s *strings.Builder, decl *ast.GenDecl) {
 	// This checks whether the declaration is a group declaration like:
 	// const (