Merge pull request #17 from v-yarotsky/vy-yaml

Add YAML support

README.md

@@ -276,6 +276,36 @@ export interface ABCD<
 }
 ```
 
+## YAML support
+
+Tygo supports generating typings for YAML-serializable objects that can be understood by Go apps.
+By default, Tygo will respect `yaml` Go struct tags, in addition to `json`, but it will not apply any transformations to untagged fields.
+However, the default behavior of the popular `gopkg.in/yaml.v2` package for Go structs without tags is to downcase the struct field names.
+To emulate this behavior, one can use the `flavor` configuration option:
+
+```yaml
+packages:
+  - path: "github.com/my/package"
+    output_path: "webapp/api/types.ts"
+    flavor: "yaml"
+```
+
+```go
+// Golang input
+type Foo struct {
+	TaggedField string `yaml:"custom_field_name_in_yaml"`
+        UntaggedField string
+}
+```
+
+```typescript
+// Typescript output
+export interface Foo {
+  custom_field_name_in_yaml: string;
+  untaggedfield: string;
+}
+```
+
 ## Related projects
 
 - [**typescriptify-golang-structs**](https://github.com/tkrajina/typescriptify-golang-structs): Probably the most popular choice. The downside of this package is that it relies on reflection rather than parsing, which means that certain things can't be kept such as comments without adding a bunch of tags to your structs. The CLI generates a Go file which is then executed and reflected on, and its library requires you to manually specify all types that should be converted.

examples/yaml/index.ts

@@ -0,0 +1,14 @@
+// Code generated by tygo. DO NOT EDIT.
+
+//////////
+// source: yaml.go
+
+export interface YAMLTest {
+  id: string;
+  prefs: { [key: string]: {
+    foo: number /* uint32 */;
+  }};
+  address?: string;
+  nickname?: string;
+  thiswillgetlowercased: string;
+}

examples/yaml/yaml.go

@@ -0,0 +1,16 @@
+package yaml
+
+type YAMLTest struct {
+	ID string `yaml:"id"`
+
+	Preferences map[string]struct {
+		Foo uint32 `yaml:"foo"`
+	} `yaml:"prefs"`
+
+	MaybeFieldWithStar *string `yaml:"address"`
+	Nickname           string  `yaml:"nickname,omitempty"`
+
+	ThisWillGetLowercased string
+
+	unexported bool // Unexported fields won't be in the output
+}

tygo.yaml

@@ -25,3 +25,6 @@ packages:
   # Generate the "time" output example, note the output is in gitignore as it's pretty big
   - path: "time"
     output_path: "./examples/time/index.ts"
+  - path: "github.com/gzuidhof/tygo/examples/yaml"
+    output_path: "./examples/yaml/index.ts"
+    flavor: "yaml"

tygo/config.go

@@ -1,6 +1,7 @@
 package tygo
 
 import (
+	"fmt"
 	"log"
 	"path/filepath"
 	"strings"
@@ -35,6 +36,12 @@ type PackageConfig struct {
 
 	// FallbackType defines the Typescript type used as a fallback for unknown Go types.
 	FallbackType string `yaml:"fallback_type"`
+
+	// Flavor defines what the key names of the output types will look like.
+	// Supported values: "default", "" (same as "default"), "yaml".
+	// In "default" mode, `json` and `yaml` tags are respected, but otherwise keys are unchanged.
+	// In "yaml" mode, keys are lowercased to emulate gopkg.in/yaml.v2.
+	Flavor string `yaml:"flavor"`
 }
 
 type Config struct {
@@ -56,13 +63,30 @@ func (c Config) PackageConfig(packagePath string) *PackageConfig {
 			if pc.Indent == "" {
 				pc.Indent = "  "
 			}
+
+			var err error
+			pc.Flavor, err = normalizeFlavor(pc.Flavor)
+			if err != nil {
+				log.Fatalf("Invalid config for package %s: %s", packagePath, err)
+			}
 			return pc
 		}
 	}
 	log.Fatalf("Config not found for package %s", packagePath)
 	return nil
 }
 
+func normalizeFlavor(flavor string) (string, error) {
+	switch flavor {
+	case "", "default":
+		return "default", nil
+	case "yaml":
+		return "yaml", nil
+	default:
+		return "", fmt.Errorf("Unsupported flavor: %s", flavor)
+	}
+}
+
 func (c PackageConfig) IsFileIgnored(pathToFile string) bool {
 	basename := filepath.Base(pathToFile)
 	for _, ef := range c.ExcludeFiles {

tygo/write.go

@@ -200,6 +200,16 @@ func (g *PackageGenerator) writeStructFields(s *strings.Builder, fields []*ast.F
 
 				optional = jsonTag.HasOption("omitempty")
 			}
+			yamlTag, err := tags.Get("yaml")
+			if err == nil {
+				name = yamlTag.Name
+				if name == "-" {
+					continue
+				}
+
+				optional = yamlTag.HasOption("omitempty")
+			}
+
 			tstypeTag, err := tags.Get("tstype")
 			if err == nil {
 				tstype = tstypeTag.Name
@@ -212,7 +222,11 @@ func (g *PackageGenerator) writeStructFields(s *strings.Builder, fields []*ast.F
 		}
 
 		if len(name) == 0 {
-			name = fieldName
+			if g.conf.Flavor == "yaml" {
+				name = strings.ToLower(fieldName)
+			} else {
+				name = fieldName
+			}
 		}
 
 		g.writeCommentGroupIfNotNil(s, f.Doc, depth+1)