[BUG] analysis_* options not applied unless there's other settings present

[karaggeorge]

What is the bug?

Creating an index resource with only mappings and analysis_analyzer fails with 400 saying analyzers are not defined.

After a lot of debugging and looking through the source, I noticed that the analysis field does not get sent over the API unless there's at least one more setting passed.

The code that filters this out is here:

terraform-provider-opensearch/provider/resource_opensearch_index.go

Lines 449 to 451 in 59aec32

	if len(settings) > 0 {
	body["settings"] = settings
	}

For a simpler repro, you can just create an index with just analysis_analyzer. It'll pass, but the index will have no settings

As a workaround, adding any other setting like number_of_replicas = "0" fixes it

How can one reproduce the bug?

This resource block should work:

resource "opensearch_index" "test_index" {
  name = "test-index"

  mappings = jsonencode({
    "properties": {
      "name": {
        "type": "text",
        "search_analyzer": "name_search_analyzer"
      }
    }
  })

  analysis_analyzer = jsonencode({
    name_search_analyzer = {
      type = "custom"
      tokenizer = "standard"
      filter = ["lowercase"]
    }
  })
}

Currently, this errors:

opensearch_index.test-index: Creating...
╷
│ Error: elastic: Error 400 (Bad Request): OpenSearch exception [type=illegal_argument_exception, reason=analyzer [name_search_analyzer] has not been configured in mappings]- server : [envoy] [type=illegal_argument_exception]
│ 
│   with opensearch_index.test-index,
│   on init.tf line 117, in resource "opensearch_index" "test-index":
│  117: resource "opensearch_index" "test-index" {
│ 

What is the expected behavior?

It creates an index with the appropriate settings/mappings

What is your host/environment?

macOS Sequoia 15.3

Do you have any screenshots?

If applicable, add screenshots to help explain your problem.

Do you have any additional context?

Going through the code a bit, I'm 99% sure it's this statement here:

terraform-provider-opensearch/provider/resource_opensearch_index.go

Lines 449 to 451 in 59aec32

	if len(settings) > 0 {
	body["settings"] = settings
	}

If there's no settings in the keys defined above, the settings block just doesn't get attached to the body, so it doesn't get sent. After I added a setting in that list, it worked

[peterzhuamazon]

HI @prudhvigodithi could you take a look on this?

Thanks.