Creating index pattern with Saved Objects API before matching indices exists throws misleading/vague error.

[A-Hall]

Kibana version: 7.6.0 and previous

Elasticsearch version: 7.6.0 and previous

Browser version: Chrome Version 79.0.3945.130 (Official Build) (64-bit)

Browser OS version: Windows 10

Original install method (e.g. download page, yum, from source, etc.): unpacked tarball

Describe the bug:

Vague/misleading error is thrown when index pattern created through the saved objects API matches no indices.

Steps to reproduce:

1. Create index pattern with API.

curl -X POST "localhost:5601/api/saved_objects/index-pattern/my-pattern" -H 'kbn-xsrf: true' -H 'Content-Type: application/json' -u elastic:changeme -d'
{
  "attributes": {
    "title": "my-pattern-*"
  }
}
'

2. Go to Discover tab and choose the newly created index pattern.

3. Unable to fetch fields error is generated.

Expected behavior:

Error message says something like: No indices exist that match the index pattern.

Screenshots (if relevant):

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[naveenspen14]

Hi Team,
In which version of kibana this fix will be available?.
We also facing same issue.

[mattkime]

We now have an API specifically for creating index patterns - https://www.elastic.co/guide/en/kibana/master/index-patterns-api-create.html

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

Closing since as @mattkime pointed out there's a dedicated API for that, an we improved handling of data views without indices recently e.g. by #151788