feat: add go omitempty json tag

docs/languages/Go.md

@@ -21,13 +21,21 @@ As you normally only need one library to do this, we developers can never get en
 Here are all the supported presets and the libraries they use for converting to and from JSON:
 
 - [JSON Tags](#json-tags)
+  - [omitempty tag](#omitempty-tag)
 
 #### JSON Tags
 
 To generate go models that work correctly with JSON marshal functions we need to generate appropriate JSON `struct-tags`, use the preset `GO_COMMON_PRESET` and provide the option `addJsonTag: true`.
 
 check out this [example for a live demonstration](../../examples/go-json-tags/)
 
+##### omitempty tag
+
+To add `omitempty` parameter to JSON `struct-tags`, use the preset `GO_COMMON_PRESET` and provide the option `addOmitEmpty: true` along with `addJsonTag: true`. 
+
+check out this [example for a live demonstration](../../examples/go-omitepty-tag/)
+
+
 ### To and from XML
 Currently not supported, [let everyone know you need it](https://github.com/asyncapi/modelina/issues/new?assignees=&labels=enhancement&template=enhancement.md)!
 

examples/go-omitepty-tag/README.md

@@ -0,0 +1,17 @@
+# go omitempty JSON struct tag
+
+`GO_COMMON_PRESET` to render `omitempty` parameter in JSON `struct-tags` in go struct.
+
+## How to run this example
+
+Run this example using:
+
+```sh
+npm i && npm run start
+```
+
+If you are on Windows, use the `start:windows` script instead:
+
+```sh
+npm i && npm run start:windows
+```

examples/go-omitepty-tag/__snapshots__/index.spec.ts.snap

@@ -0,0 +1,97 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Should be able to render TEMPLATE and should log expected output to console 1`] = `
+Array [
+  "// Root represents a Root model.
+type Root struct {
+  Cities *Cities \`json:\\"cities, omitempty\\"\`
+  Options *Options \`json:\\"options, omitempty\\"\`
+}",
+]
+`;
+
+exports[`Should be able to render TEMPLATE and should log expected output to console 2`] = `
+Array [
+  "// Cities represents an enum of Cities.
+type Cities uint
+
+const (
+  CitiesLondon Cities = iota
+  CitiesRome
+  CitiesBrussels
+)
+
+// Value returns the value of the enum.
+func (op Cities) Value() any {
+	if op >= Cities(len(CitiesValues)) {
+		return nil
+	}
+	return CitiesValues[op]
+}
+
+var CitiesValues = []any{\\"London\\",\\"Rome\\",\\"Brussels\\"}
+var ValuesToCities = map[any]Cities{
+  CitiesValues[CitiesLondon]: CitiesLondon,
+  CitiesValues[CitiesRome]: CitiesRome,
+  CitiesValues[CitiesBrussels]: CitiesBrussels,
+}
+
+ 
+func (op *Cities) UnmarshalJSON(raw []byte) error {
+  var v any
+  if err := json.Unmarshal(raw, &v); err != nil {
+  return err
+  }
+  *op = ValuesToCities[v]
+  return nil
+}
+
+func (op Cities) MarshalJSON() ([]byte, error) {
+  return json.Marshal(op.Value())
+}",
+]
+`;
+
+exports[`Should be able to render TEMPLATE and should log expected output to console 3`] = `
+Array [
+  "// Options represents an enum of Options.
+type Options uint
+
+const (
+  OptionsNumber_123 Options = iota
+  OptionsNumber_213
+  OptionsTrue
+  OptionsRun
+)
+
+// Value returns the value of the enum.
+func (op Options) Value() any {
+	if op >= Options(len(OptionsValues)) {
+		return nil
+	}
+	return OptionsValues[op]
+}
+
+var OptionsValues = []any{123,213,true,\\"Run\\"}
+var ValuesToOptions = map[any]Options{
+  OptionsValues[OptionsNumber_123]: OptionsNumber_123,
+  OptionsValues[OptionsNumber_213]: OptionsNumber_213,
+  OptionsValues[OptionsTrue]: OptionsTrue,
+  OptionsValues[OptionsRun]: OptionsRun,
+}
+
+ 
+func (op *Options) UnmarshalJSON(raw []byte) error {
+  var v any
+  if err := json.Unmarshal(raw, &v); err != nil {
+  return err
+  }
+  *op = ValuesToOptions[v]
+  return nil
+}
+
+func (op Options) MarshalJSON() ([]byte, error) {
+  return json.Marshal(op.Value())
+}",
+]
+`;

examples/go-omitepty-tag/index.spec.ts

@@ -0,0 +1,17 @@
+const spy = jest.spyOn(global.console, 'log').mockImplementation(() => {
+  return;
+});
+import { generate } from './index';
+
+describe('Should be able to render TEMPLATE', () => {
+  afterAll(() => {
+    jest.restoreAllMocks();
+  });
+  test('and should log expected output to console', async () => {
+    await generate();
+    expect(spy.mock.calls.length).toEqual(3);
+    expect(spy.mock.calls[0]).toMatchSnapshot();
+    expect(spy.mock.calls[1]).toMatchSnapshot();
+    expect(spy.mock.calls[2]).toMatchSnapshot();
+  });
+});

examples/go-omitepty-tag/index.ts

@@ -0,0 +1,37 @@
+import {
+  GoGenerator,
+  GO_COMMON_PRESET,
+  GoCommonPresetOptions
+} from '../../src';
+
+const options: GoCommonPresetOptions = { addJsonTag: true, addOmitEmpty: true };
+const generator = new GoGenerator({
+  presets: [{ preset: GO_COMMON_PRESET, options }]
+});
+const jsonSchemaDraft7 = {
+  $schema: 'http://json-schema.org/draft-07/schema#',
+  type: 'object',
+  additionalProperties: false,
+  properties: {
+    cities: {
+      $id: 'cities',
+      type: 'string',
+      enum: ['London', 'Rome', 'Brussels']
+    },
+    options: {
+      $id: 'options',
+      type: ['integer', 'boolean', 'string'],
+      enum: [123, 213, true, 'Run']
+    }
+  }
+};
+
+export async function generate(): Promise<void> {
+  const models = await generator.generate(jsonSchemaDraft7);
+  for (const model of models) {
+    console.log(model.result);
+  }
+}
+if (require.main === module) {
+  generate();
+}

examples/go-omitepty-tag/package.json

@@ -0,0 +1,10 @@
+{
+  "config" : { "example_name" : "go omitempty json tag" },
+  "scripts": {
+    "install": "cd ../.. && npm i",
+    "start": "../../node_modules/.bin/ts-node --cwd ../../ ./examples/$npm_package_config_example_name/index.ts",
+    "start:windows": "..\\..\\node_modules\\.bin\\ts-node --cwd ..\\..\\ .\\examples\\%npm_package_config_example_name%\\index.ts",
+    "test": "../../node_modules/.bin/jest --config=../../jest.config.js ./examples/$npm_package_config_example_name/index.spec.ts",
+    "test:windows": "..\\..\\node_modules\\.bin\\jest --config=..\\..\\jest.config.js examples/%npm_package_config_example_name%/index.spec.ts"
+  }
+}

src/generators/go/presets/CommonPreset.ts

@@ -8,20 +8,25 @@ import {
 
 export interface GoCommonPresetOptions {
   addJsonTag: boolean;
+  addOmitEmpty?: boolean;
 }
 
 function renderJSONTag({
-  field
+  field,
+  omitempty
 }: {
   field: ConstrainedObjectPropertyModel;
+  omitempty?: boolean;
 }): string {
   if (
     field.property instanceof ConstrainedDictionaryModel &&
     field.property.serializationType === 'unwrap'
   ) {
     return `json:"-"`;
   }
-  return `json:"${field.unconstrainedPropertyName}"`;
+  return `json:"${field.unconstrainedPropertyName}${
+    omitempty ? ', omitempty' : ''
+  }"`;
 }
 
 function renderMarshallingFunctions({
@@ -52,7 +57,7 @@ export const GO_COMMON_PRESET: GoPreset<GoCommonPresetOptions> = {
     field: ({ content, field, options }) => {
       const blocks: string[] = [];
       if (options.addJsonTag) {
-        blocks.push(renderJSONTag({ field }));
+        blocks.push(renderJSONTag({ field, omitempty: options.addOmitEmpty }));
       }
       return `${content} \`${blocks.join(' ')}\``;
     }

test/generators/go/presets/CommonPreset.spec.ts

@@ -7,7 +7,10 @@ import {
 describe('GO_COMMON_PRESET', () => {
   let generator: GoGenerator;
   beforeEach(() => {
-    const options: GoCommonPresetOptions = { addJsonTag: true };
+    const options: GoCommonPresetOptions = {
+      addJsonTag: true,
+      addOmitEmpty: true
+    };
     generator = new GoGenerator({
       presets: [{ preset: GO_COMMON_PRESET, options }]
     });

test/generators/go/presets/__snapshots__/CommonPreset.spec.ts.snap

@@ -3,9 +3,9 @@
 exports[`GO_COMMON_PRESET should render json tags for structs 1`] = `
 "// Root represents a Root model.
 type Root struct {
-  StringProp string \`json:\\"stringProp\\"\`
-  NumberProp float64 \`json:\\"numberProp\\"\`
-  BooleanProp bool \`json:\\"booleanProp\\"\`
+  StringProp string \`json:\\"stringProp, omitempty\\"\`
+  NumberProp float64 \`json:\\"numberProp, omitempty\\"\`
+  BooleanProp bool \`json:\\"booleanProp, omitempty\\"\`
 }"
 `;