flexibleconfig

tmpfile, err := ioutil.TempFile("", "KrakenD_parsed_config_template_1_")
if err != nil {
	fmt.Println(err.Error())
	return
}

defer os.Remove(tmpfile.Name())
if _, err := tmpfile.Write(originalTemplate); err != nil {
	fmt.Println(err.Error())
	return
}
if err := tmpfile.Close(); err != nil {
	fmt.Println(err.Error())
	return
}

includeTmpfile, err := ioutil.TempFile("", "KrakenD_parsed_config_template_2_")
if err != nil {
	fmt.Println(err.Error())
	return
}

defer os.Remove(includeTmpfile.Name())
if _, err := includeTmpfile.Write([]byte(fmt.Sprintf("{{ include \"%s\" }}", tmpfile.Name()))); err != nil {
	fmt.Println(err.Error())
	return
}
if err := includeTmpfile.Close(); err != nil {
	fmt.Println(err.Error())
	return
}

expectedCfg := config.ServiceConfig{
	Port:    1234,
	Version: 42,
}
tmpl := TemplateParser{
	Vars: map[string]interface{}{},
	Parser: config.ParserFunc(func(tmpPath string) (config.ServiceConfig, error) {
		data, err := ioutil.ReadFile(tmpPath)
		fmt.Println(string(data))
		if err != nil {
			fmt.Println(err)
			return expectedCfg, err
		}
		return expectedCfg, nil
	}),
}

tmpl.funcMap = template.FuncMap{
	"include": tmpl.include,
}

res, err := tmpl.Parse(includeTmpfile.Name())
if err != nil {
	fmt.Println(err.Error())
}
if res.Port != expectedCfg.Port {
	fmt.Println("unexpected cfg")
}
if res.Version != expectedCfg.Version {
	fmt.Println("unexpected cfg")
}

Output:
{
    "version": {{ add 40 2 }},
    "port": {{ .Port }},
    "endpoints": [
        {
            "endpoint": "/combination/{id}",
            "backend": [
                {
                    "host": [
                        "{{ .Jsonplaceholder }}"
                    ],
                    "url_pattern": "/posts?userId={id}",
                    "is_collection": true,
                    "mapping": {
                        "collection": "posts"
                    },
                    "disable_host_sanitize": true,
                    "extra_config": {
                    	"namespace1": {{ marshal .Namespace1 }}
				    }
                },
                {
                    "host": [
                        "{{ .Jsonplaceholder }}"
                    ],
                    "url_pattern": "/users/{id}",
                    "mapping": {
                        "email": "personal_email"
                    },
                    "disable_host_sanitize": true,
                    "extra_config": {
                    	"namespace1": {{ marshal .Namespace1 }},
                    	"namespace2": {{ marshal .Namespace2 }}
				    }
                }
            ],
            "extra_config": {
            	"namespace3": { "supu": "tupu" },
            	"namespace2": {{ marshal .Namespace2 }}
		    }
        }
    ],
    "extra_config": {
        "namespace2": {{ marshal .Namespace2 }}
    }
}

tmpfile, err := ioutil.TempFile("", "KrakenD_parsed_config_template_0_")
if err != nil {
	fmt.Println(err.Error())
	return
}

defer os.Remove(tmpfile.Name())
if _, err := tmpfile.Write(originalTemplate); err != nil {
	fmt.Println(err.Error())
	return
}
if err := tmpfile.Close(); err != nil {
	fmt.Println(err.Error())
	return
}

expectedCfg := config.ServiceConfig{
	Port:    1234,
	Version: 42,
}
tmpl := TemplateParser{
	Vars: map[string]interface{}{
		"Namespace1": map[string]interface{}{
			"Namespace1-key1": "value1",
			"Namespace1-key2": 2,
		},
		"Namespace2": map[string]interface{}{
			"Namespace2-key1": "value1000",
			"Namespace2-key2": 2000,
		},
		"Jsonplaceholder": "http://example.com",
		"Port":            1234,
	},
	Parser: config.ParserFunc(func(tmpPath string) (config.ServiceConfig, error) {
		data, err := ioutil.ReadFile(tmpPath)
		fmt.Println(string(data))
		if err != nil {
			fmt.Println(err.Error())
			return expectedCfg, err
		}
		return expectedCfg, nil
	}),
}

tmpl.funcMap = sprig.GenericFuncMap()
tmpl.funcMap["marshal"] = tmpl.marshal

res, err := tmpl.Parse(tmpfile.Name())
if err != nil {
	fmt.Println(err.Error())
}
if res.Port != expectedCfg.Port {
	fmt.Println("unexpected cfg")
}
if res.Version != expectedCfg.Version {
	fmt.Println("unexpected cfg")
}

Output:
{
    "version": 42,
    "port": 1234,
    "endpoints": [
        {
            "endpoint": "/combination/{id}",
            "backend": [
                {
                    "host": [
                        "http://example.com"
                    ],
                    "url_pattern": "/posts?userId={id}",
                    "is_collection": true,
                    "mapping": {
                        "collection": "posts"
                    },
                    "disable_host_sanitize": true,
                    "extra_config": {
                    	"namespace1": {"Namespace1-key1":"value1","Namespace1-key2":2}
				    }
                },
                {
                    "host": [
                        "http://example.com"
                    ],
                    "url_pattern": "/users/{id}",
                    "mapping": {
                        "email": "personal_email"
                    },
                    "disable_host_sanitize": true,
                    "extra_config": {
                    	"namespace1": {"Namespace1-key1":"value1","Namespace1-key2":2},
                    	"namespace2": {"Namespace2-key1":"value1000","Namespace2-key2":2000}
				    }
                }
            ],
            "extra_config": {
            	"namespace3": { "supu": "tupu" },
            	"namespace2": {"Namespace2-key1":"value1000","Namespace2-key2":2000}
		    }
        }
    ],
    "extra_config": {
        "namespace2": {"Namespace2-key1":"value1000","Namespace2-key2":2000}
    }
}