Cannot compose insecure credential: combinedChannelCredentials w/ createFromMetadataGenerator + createInsecure

[willyyang]

Problem description

Error: Cannot compose insecure credential

Reproduction steps

const metadataUpdater = (_, cb) => {
    const metadata = new grpc.Metadata()
    metadata.set('key', 'test11')
    cb(null, metadata)
  }
  const metadataCreds = grpc.credentials.createFromMetadataGenerator(
    metadataUpdater
  )
  const insecureSSL = grpc.credentials.createInsecure()

  obClient = new serviceProto(
    `${host:port}`,
    grpc.credentials.combineChannelCredentials(insecureSSL, metadataCreds)
  )

Environment

• OS name, version and architecture: macOS 10.13.6
• Node version: 9.2.0
• Node installation method : nvm
• Package name and version: gRPC@1.9.1

[murgatroid99]

Please see #543 for an explanation of this behavior.