[Fix] Do not send run_as when updating databricks_pipeline when not specified (#4470)

## Changes
A recent change to add support for `run_as` in pipelines causes pipeline
update requests to include the `run_as` field. The Get Pipeline always
returns the `run_as_user_name` for a pipeline, even for workspaces not
in the private preview. Some users may have `run_as` in their TF state
now, even if they did not specify it in their configuration. As we are
using SDKv2 for this resource, it isn't straightforward to see whether
the user actually included `run_as` in their configuration or if it is
only in the state because of the change to the `Read` method.

This PR addresses this by only sending `run_as` if there is a planned
change in the `run_as` field. If the user doesn't set `run_as`
explicitly (as in existing customers not in the private preview), or if
it is set to the same value as the `run_as_user_name` field, the
provider does not need to set `run_as`, so it can be removed from the
request.

Resolves #4469.

## Tests

- [x] Created & updated a pipeline in a workspace without run_as preview
enabled; succeeded.
- [x] Created & updated a pipeline in a workspace with run_as preview
enabled; succeeded.

Author: mgyucht

NEXT_CHANGELOG.md

@@ -1,11 +1,13 @@
 # NEXT CHANGELOG
 
-## Release v1.66.0
+## Release v1.65.1
 
 ### New Features and Improvements
 
 ### Bug Fixes
 
+ * Do not send `run_as` when updating `databricks_pipeline` resource if no change is planned.
+
 ### Documentation
 
 ### Exporter

pipelines/pipeline_test.go

@@ -96,6 +96,9 @@ func TestAccPipelineResource_CreatePipeline(t *testing.T) {
 }
 
 func pipelineRunAsTemplate(runAs string) string {
+	if runAs != "" {
+		runAs = `run_as { ` + runAs + ` }`
+	}
 	return `
 	data "databricks_current_user" "me" {}
 
@@ -135,9 +138,7 @@ func pipelineRunAsTemplate(runAs string) string {
 
 		continuous = false
 
-		run_as {
-			` + runAs + `
-		}
+		` + runAs + `
 	}
 	` + dltNotebookResource
 }
@@ -180,6 +181,10 @@ func TestUcAccPipelineRunAsMutations(t *testing.T) {
 		acceptance.Step{
 			Template: pipelineRunAsTemplate(`service_principal_name = "` + spId + `"`),
 		},
+		// Remove run_as, and there should be no change.
+		acceptance.Step{
+			Template: pipelineRunAsTemplate(""),
+		},
 	)
 }
 

pipelines/resource_pipeline.go

@@ -71,6 +71,12 @@ func Update(w *databricks.WorkspaceClient, ctx context.Context, d *schema.Resour
 	common.DataToStructPointer(d, pipelineSchema, &updatePipelineRequest)
 	updatePipelineRequest.EditPipeline.PipelineId = d.Id()
 	adjustForceSendFields(&updatePipelineRequest.Clusters)
+	// Workspaces not enrolled in the private preview must not send run_as in the update request.
+	// If run_as was persisted in state because of a `terraform refresh`, there will not be a planned change
+	// as long as the user hasn't specified a value.
+	if !d.HasChange("run_as") {
+		updatePipelineRequest.RunAs = nil
+	}
 
 	err := w.Pipelines.Update(ctx, updatePipelineRequest.EditPipeline)
 	if err != nil {