Custom suppress diff for storage in databricks_pipeline

When the `storage` option isn't provided, DLT generates a temp one in the form of
`dbfs:/pipelines/<uuid>`.  But in the sequential apply the drift was detected, and
pipeline was recreated.  Marking it with `computed` or `suppress_diff` doesn't help
because it prevents the pipeline from the detection of change of `storage` from value
to null.

pipelines/resource_pipeline.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"regexp"
 	"time"
 
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
@@ -254,6 +255,17 @@ func (a PipelinesAPI) waitForState(id string, timeout time.Duration, desiredStat
 		})
 }
 
+func suppressStorageDiff(k, old, new string, d *schema.ResourceData) bool {
+	defaultStorageRegex := regexp.MustCompile(
+		`^dbfs:/pipelines/[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$`)
+	res := defaultStorageRegex.MatchString(old)
+	if new == "" && res {
+		log.Printf("[DEBUG] Suppressing diff for %v: platform=%#v config=%#v", k, old, new)
+		return true
+	}
+	return false
+}
+
 func adjustPipelineResourceSchema(m map[string]*schema.Schema) map[string]*schema.Schema {
 	cluster, _ := m["cluster"].Elem.(*schema.Resource)
 	clustersSchema := cluster.Schema
@@ -284,6 +296,8 @@ func adjustPipelineResourceSchema(m map[string]*schema.Schema) map[string]*schem
 	m["channel"].ValidateFunc = validation.StringInSlice([]string{"current", "preview"}, true)
 	m["edition"].ValidateFunc = validation.StringInSlice([]string{"pro", "core", "advanced"}, true)
 
+	m["storage"].DiffSuppressFunc = suppressStorageDiff
+
 	return m
 }
 

pipelines/resource_pipeline_test.go

@@ -591,3 +591,11 @@ func TestListPipelinesWithFilter(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, 1, len(data))
 }
+
+func TestStorageSuppressDiff(t *testing.T) {
+	k := "storage"
+	generated := "dbfs:/pipelines/c609bbb0-2e42-4bc8-bb4e-a1c26d6e9403"
+	require.True(t, suppressStorageDiff(k, generated, "", nil))
+	require.False(t, suppressStorageDiff(k, generated, "/tmp/abc", nil))
+	require.False(t, suppressStorageDiff(k, "/tmp/abc", "", nil))
+}