Metadata API produces invalid subscription rule match value when it's nil

[antontroshin]

In what area(s)?

/area runtime

/area operator

/area placement

/area docs

/area test-and-release

What version of Dapr?

1.1.x
1.0.x
edge: output of git describe --dirty

Expected Behavior

Rule match value to be empty or nil (not returned in the response)

Actual Behavior

Prints an invalid match value string which is produced by Go's fmt.Sprintf function.

 "subscriptions": [
    {
      "pubsubname": "orderpubsub",
      "topic": "orders",
      "rules": [
        {
          "match": "%!s(<nil>)", // <--- The value is a product of `fmt.Sprintf("%s", nil)`

Steps to Reproduce the Problem

1. Clone quickstart git clone https://github.com/dapr/quickstarts.git
2. go to pub sub quickstart cd pub_sub/go/sdk/order-processor
3. run app dapr run --app-port 6001 --app-id order-processor --app-protocol http --dapr-http-port 3501 --components-path ../../../components -- go run app.go
4. Observe the log app is subscribed to the following topics: [orders] through pubsub=orderpubsub
5. Run curl http://localhost:3501/v1.0/metadata | jq
6. The response will show the programmatic subscription orderpubsub with rule's match field as "%!s(<nil>)"

➜  curl http://localhost:3501/v1.0/metadata |jq
{
  "id": "order-processor",
  "runtimeVersion": "1.12.0",
  "components": [
   ...
  ],
  ...
  "subscriptions": [
    {
      "pubsubname": "orderpubsub",
      "topic": "orders",
      "rules": [
        {
          "match": "%!s(<nil>)", // <--- The value is a product of `fmt.Sprintf("%s", nil)`
          "path": "/orders"
        }
      ],
      "deadLetterTopic": ""
    }
  ],
...
}

Release Note

RELEASE NOTE: FIX Metadata API programmatic subscription rule's match field, marshal invalid nil value format

[Taction]

/assign

[antontroshin]

Note: the place where this happens is here

dapr/pkg/grpc/universalapi/api_metadata.go

Line 148 in bf9e425

Match: fmt.Sprintf("%s", r.Match),

[Taction]

@antontroshin Thanks for reporting this issue and pointing out the code where it happens!