Configuration not loaded when built with Docker

[lazynoda]

I'm trying to load the configuration (as explained in the docs) and it works well when running the service locally, but it fails when the service is built & executed via Docker image. Here is a basic encore project with the minimal stuff to test this issue: config-issue.zip

The service contains the following endpoint and config load

package config

import (
	"context"
	"encore.dev/config"
)

type Response struct {
	Data string `json:"data"`
}

type Configuration struct {
	PropertyName config.String
}

var cfg = config.Load[*Configuration]()

//encore:api public method=GET path=/config
func Invoke(ctx context.Context) (*Response, error) {
	return &Response{
		Data: cfg.PropertyName(),
	}, nil
}

And this is the configuration file

PropertyName: "Property value"

The service is built and executed via

encore build docker config-issue
docker run \
    -p 9999:8080 \
    -d \
    --name encore \
    config-issue:latest

Doing the request to http://localhost:9999/config results in panic because cfg is nil.

---

After further investigation, apparently the Docker image does not contain the environment variables ENCORE_CFG_{SERVICE_NAME} (took a bit to discover this). If I add that environment variable to the Docker container, then everything works again:

docker run \
    -p 9999:8080 \
    -e ENCORE_CFG_CONFIG='eyJQcm9wZXJ0eU5hbWUiOiJSYW5kb20gdmFsdWUifQ' \
    -d \
    --name encore \
    config-issue:latest

For anyone interested, the environment variable value is the configuration, JSON marshalled and then Base64 encoded.

encore/runtimes/go/config/manager_internal.go

Line 62 in b1001e9

cfgBytes, err := base64.RawURLEncoding.DecodeString(envVar)

encore/runtimes/go/config/pkgfn.go

Line 53 in b1001e9

return __unmarshaler(itr, nil)

---

I don't know if the problem is that encore build docker doesn't export that environment variables into the Docker image, or there is a lack in the documentation specifying how to set / override configs in Docker. Depending on the expected behaviour. If you ask me, I'd export the environment variables because the config can be configured depending on the meta Environment.Cloud and it can be docker.

[lazynoda]

Seems expected behaviour as the config is validated but not used

encore/cli/daemon/export/export.go

Lines 78 to 91 in b1001e9

	// Validate the service configs.
	_, err = bld.ServiceConfigs(ctx, builder.ServiceConfigsParams{
	Parse: parse,
	CueMeta: &cueutil.Meta{
	// Dummy data to satisfy config validation.
	APIBaseURL: "http://localhost:0",
	EnvName: "encore-eject",
	EnvType: cueutil.EnvType_Development,
	CloudType: cueutil.CloudType_Local,
	},
	})
	if err != nil {
	return false, err
	}

However, Meta is available at that point of the code because it's exported later

encore/cli/daemon/export/export.go

Lines 157 to 175 in b1001e9

	if !req.SkipInfraConf {
	cfg, infraCfgOutput, err := buildAndValidateInfraConfig(EmbeddedInfraConfigParams{
	File: dockerbuild.HostPath(req.InfraConfPath),
	Services: req.Services,
	Gateways: req.Gateways,
	GlobalCORS: cors,
	Meta: parse.Meta,
	})
	logResponse = infraCfgOutput
	if err != nil {
	return false, errors.Wrap(err, "build infra config")
	}
	data, err := json.Marshal(cfg)
	if err != nil {
	return false, errors.Wrap(err, "marshal infra config")
	}
	spec.WriteFiles[defaultInfraConfigPath] = data
	spec.Env = append(spec.Env, fmt.Sprintf("ENCORE_INFRA_CONFIG_PATH=%s", defaultInfraConfigPath))
	}