[Feature] Add data source databricks_notification_destinations (#4087)

## Changes
<!-- Summary of your changes that are easy to understand -->
Added `databricks_notification_destinations` data source as requested in
#3950 to retrieve notification destinations that are created out-of-band
or in other terraform templates.
## Tests
<!-- 
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [x] `make test` run locally
- [x] relevant change in `docs/` folder
- [x] covered with integration tests in `internal/acceptance`
- [x] relevant acceptance tests are passing
- [x] using Go SDK

---------

Co-authored-by: Alex Ott <[email protected]>

Author: dgomez04

docs/data-sources/notification_destinations.md

@@ -0,0 +1,62 @@
+---
+subcategory: "Workspace"
+---
+# databricks_notification_destinations Data Source
+
+This data source allows you to retrieve information about [Notification Destinations](https://docs.databricks.com/api/workspace/notificationdestinations). Notification Destinations are used to send notifications for query alerts and jobs to external systems such as email, Slack, Microsoft Teams, PagerDuty, or generic webhooks. 
+
+## Example Usage
+
+
+```hcl
+resource "databricks_notification_destination" "email" {
+  display_name = "Email Destination"
+  config {
+    email {
+      addresses = ["[email protected]"]
+    }
+  }
+}
+
+resource "databricks_notification_destination" "slack" {
+  display_name = "Slack Destination"
+  config {
+    slack {
+      url = "https://hooks.slack.com/services/..."
+    }
+  }
+}
+
+# Lists all notification desitnations
+data "databricks_notification_destinations" "this" {}
+
+# List destinations of specific type and name
+data "databricks_notification_destinations" "filtered_notification" {
+  display_name_contains = "Destination"
+  type                  = "EMAIL"
+}
+```
+
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `display_name_contains` - (Optional) A **case-insensitive** substring to filter Notification Destinations by their display name. 
+* `type` - (Optional) The type of the Notification Destination to filter by. Valid values are: 
+  * `EMAIL` - Filters Notification Destinations of type Email. 
+  * `MICROSOFT_TEAMS` - Filters Notification Destinations of type Microsoft Teams. 
+  * `PAGERDUTY` - Filters Notification Destinations of type PagerDuty.
+  * `SLACK` - Filters Notification Destinations of type Slack. 
+  * `WEBHOOK` - Filters Notification Destinations of type Webhook. 
+
+## Attribute Reference
+
+In addition to all arguments above, the following attributes are exported:
+
+* `notification_destinations` - A list of Notification Destinations matching the specified criteria. Each element contains the following attributes: 
+    * `id` - The unique ID of the Notification Destination.
+    * `display_name` - The display name of the Notification Destination.
+    * `destination_type` - The type of the notification destination. Possible values are `EMAIL`, `MICROSOFT_TEAMS`, `PAGERDUTY`, `SLACK`, or `WEBHOOK`.
+
+If no matches are found, an empty list will be returned.

internal/providers/pluginfw/pluginfw.go

@@ -18,6 +18,7 @@ import (
 	providercommon "github.com/databricks/terraform-provider-databricks/internal/providers/common"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/cluster"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/library"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/notificationdestinations"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/qualitymonitor"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/registered_model"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/volume"
@@ -54,6 +55,7 @@ func (p *DatabricksProviderPluginFramework) DataSources(ctx context.Context) []f
 		cluster.DataSourceCluster,
 		volume.DataSourceVolumes,
 		registered_model.DataSourceRegisteredModel,
+		notificationdestinations.DataSourceNotificationDestinations,
 	}
 }
 

internal/providers/pluginfw/resources/notificationdestinations/data_notification_destinations.go

@@ -0,0 +1,116 @@
+package notificationdestinations
+
+import (
+	"context"
+	"fmt"
+	"slices"
+	"strings"
+
+	"github.com/databricks/databricks-sdk-go/service/settings"
+	"github.com/databricks/terraform-provider-databricks/common"
+	pluginfwcommon "github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/common"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/converters"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/tfschema"
+	"github.com/databricks/terraform-provider-databricks/internal/service/settings_tf"
+	"github.com/hashicorp/terraform-plugin-framework/datasource"
+	"github.com/hashicorp/terraform-plugin-framework/datasource/schema"
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+)
+
+func DataSourceNotificationDestinations() datasource.DataSource {
+	return &NotificationDestinationsDataSource{}
+}
+
+var _ datasource.DataSourceWithConfigure = &NotificationDestinationsDataSource{}
+
+type NotificationDestinationsDataSource struct {
+	Client *common.DatabricksClient
+}
+
+type NotificationDestinationsInfo struct {
+	DisplayNameContains      types.String                                     `tfsdk:"display_name_contains" tf:"optional"`
+	Type                     types.String                                     `tfsdk:"type" tf:"optional"`
+	NotificationDestinations []settings_tf.ListNotificationDestinationsResult `tfsdk:"notification_destinations" tf:"computed"`
+}
+
+func (d *NotificationDestinationsDataSource) Metadata(ctx context.Context, req datasource.MetadataRequest, resp *datasource.MetadataResponse) {
+	resp.TypeName = "databricks_notification_destinations"
+}
+
+func (d *NotificationDestinationsDataSource) Schema(ctx context.Context, req datasource.SchemaRequest, resp *datasource.SchemaResponse) {
+	attrs, blocks := tfschema.DataSourceStructToSchemaMap(NotificationDestinationsInfo{}, nil)
+	resp.Schema = schema.Schema{
+		Attributes: attrs,
+		Blocks:     blocks,
+	}
+}
+
+func (d *NotificationDestinationsDataSource) Configure(_ context.Context, req datasource.ConfigureRequest, resp *datasource.ConfigureResponse) {
+	if d.Client == nil {
+		d.Client = pluginfwcommon.ConfigureDataSource(req, resp)
+	}
+}
+
+func validateType(notificationType string) diag.Diagnostics {
+	validTypes := []string{
+		string(settings.DestinationTypeEmail),
+		string(settings.DestinationTypeMicrosoftTeams),
+		string(settings.DestinationTypePagerduty),
+		string(settings.DestinationTypeSlack),
+		string(settings.DestinationTypeWebhook),
+	}
+
+	if !slices.Contains(validTypes, notificationType) {
+		return diag.Diagnostics{diag.NewErrorDiagnostic(fmt.Sprintf("Invalid type '%s'; valid types are %s.", notificationType, strings.Join(validTypes, ", ")), "")}
+	}
+	return nil
+}
+
+func AppendDiagAndCheckErrors(resp *datasource.ReadResponse, diags diag.Diagnostics) bool {
+	resp.Diagnostics.Append(diags...)
+	return resp.Diagnostics.HasError()
+}
+
+func (d *NotificationDestinationsDataSource) Read(ctx context.Context, req datasource.ReadRequest, resp *datasource.ReadResponse) {
+	w, diags := d.Client.GetWorkspaceClient()
+	if AppendDiagAndCheckErrors(resp, diags) {
+		return
+	}
+
+	var notificationInfo NotificationDestinationsInfo
+	if AppendDiagAndCheckErrors(resp, req.Config.Get(ctx, &notificationInfo)) {
+		return
+	}
+
+	notificationType := notificationInfo.Type.ValueString()
+	notificationDisplayName := strings.ToLower(notificationInfo.DisplayNameContains.ValueString())
+
+	if notificationType != "" && AppendDiagAndCheckErrors(resp, validateType(notificationType)) {
+		return
+	}
+
+	notificationsGoSdk, err := w.NotificationDestinations.ListAll(ctx, settings.ListNotificationDestinationsRequest{})
+	if err != nil {
+		resp.Diagnostics.AddError("Failed to fetch Notification Destinations", err.Error())
+		return
+	}
+
+	var notificationsTfSdk []settings_tf.ListNotificationDestinationsResult
+	for _, notification := range notificationsGoSdk {
+		if (notificationType != "" && notification.DestinationType.String() != notificationType) ||
+			(notificationDisplayName != "" && !strings.Contains(strings.ToLower(notification.DisplayName), notificationDisplayName)) {
+			continue
+		}
+
+		var notificationDestination settings_tf.ListNotificationDestinationsResult
+		if AppendDiagAndCheckErrors(resp, converters.GoSdkToTfSdkStruct(ctx, notification, &notificationDestination)) {
+			return
+		}
+		notificationsTfSdk = append(notificationsTfSdk, notificationDestination)
+	}
+
+	notificationInfo.NotificationDestinations = notificationsTfSdk
+	resp.Diagnostics.Append(resp.State.Set(ctx, notificationInfo)...)
+
+}

internal/providers/pluginfw/resources/notificationdestinations/data_notification_destinations_acc_test.go

@@ -0,0 +1,63 @@
+package notificationdestinations_test
+
+import (
+	"testing"
+
+	"github.com/databricks/terraform-provider-databricks/internal/acceptance"
+	"github.com/hashicorp/terraform-plugin-testing/terraform"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func CheckDataSourceNotificationsPopulated(t *testing.T) func(s *terraform.State) error {
+	return func(s *terraform.State) error {
+		ds, ok := s.Modules[0].Resources["data.databricks_notification_destinations.this"]
+		require.True(t, ok, "data.databricks_notification_destinations.this has to be there")
+
+		notificationCount := ds.Primary.Attributes["notification_destinations.#"]
+		require.Equal(t, "2", notificationCount, "expected two notifications")
+
+		notificationIds := []string{
+			ds.Primary.Attributes["notification_destinations.0.id"],
+			ds.Primary.Attributes["notification_destinations.1.id"],
+		}
+
+		expectedNotificationIds := []string{
+			s.Modules[0].Resources["databricks_notification_destination.email_notification"].Primary.ID,
+			s.Modules[0].Resources["databricks_notification_destination.slack_notification"].Primary.ID,
+		}
+
+		assert.ElementsMatch(t, expectedNotificationIds, notificationIds, "expected notification_destination ids to match")
+
+		return nil
+	}
+}
+
+func TestAccNotificationsCreation(t *testing.T) {
+	acceptance.WorkspaceLevel(t, acceptance.Step{
+		Template: `
+			resource "databricks_notification_destination" "email_notification" {
+				display_name = "email notification destination"
+				config {
+					email {
+					addresses = ["[email protected]"]
+					}
+				}
+			}
+
+			resource "databricks_notification_destination" "slack_notification" {
+				display_name = "slack notification destination"
+				config {
+					slack {
+					url = "https://hooks.slack.com/services/..."
+					}
+				}
+			}
+
+			data "databricks_notification_destinations" "this" {
+				depends_on = [databricks_notification_destination.email_notification, databricks_notification_destination.slack_notification]
+			}
+		`,
+		Check: CheckDataSourceNotificationsPopulated(t),
+	})
+}

internal/providers/pluginfw/resources/notificationdestinations/data_notification_destinations_test.go

@@ -0,0 +1,15 @@
+package notificationdestinations
+
+import (
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestValidateType_InvalidType(t *testing.T) {
+	actualDiagnostics := validateType("INVALID")
+	expectedDiagnostics := diag.Diagnostics{diag.NewErrorDiagnostic("Invalid type 'INVALID'; valid types are EMAIL, MICROSOFT_TEAMS, PAGERDUTY, SLACK, WEBHOOK.", "")}
+	assert.True(t, actualDiagnostics.HasError())
+	assert.Equal(t, expectedDiagnostics, actualDiagnostics)
+}