Enable target overrides for pipeline clusters (#792)

## Changes

This is a follow-up to #658 and #779 for jobs.

This change applies label normalization the same way the backend does.

## Tests

Unit and config loading tests.

bundle/config/resources.go

@@ -131,24 +131,23 @@ func (r *Resources) SetConfigFilePath(path string) {
 	}
 }
 
-// MergeJobClusters iterates over all jobs and merges their job clusters.
-// This is called after applying the target overrides.
-func (r *Resources) MergeJobClusters() error {
+// Merge iterates over all resources and merges chunks of the
+// resource configuration that can be merged. For example, for
+// jobs, this merges job cluster definitions and tasks that
+// use the same `job_cluster_key`, or `task_key`, respectively.
+func (r *Resources) Merge() error {
 	for _, job := range r.Jobs {
 		if err := job.MergeJobClusters(); err != nil {
 			return err
 		}
-	}
-	return nil
-}
-
-// MergeTasks iterates over all jobs and merges their tasks.
-// This is called after applying the target overrides.
-func (r *Resources) MergeTasks() error {
-	for _, job := range r.Jobs {
 		if err := job.MergeTasks(); err != nil {
 			return err
 		}
 	}
+	for _, pipeline := range r.Pipelines {
+		if err := pipeline.MergeClusters(); err != nil {
+			return err
+		}
+	}
 	return nil
 }

bundle/config/resources/pipeline.go

@@ -1,8 +1,11 @@
 package resources
 
 import (
+	"strings"
+
 	"github.com/databricks/cli/bundle/config/paths"
 	"github.com/databricks/databricks-sdk-go/service/pipelines"
+	"github.com/imdario/mergo"
 )
 
 type Pipeline struct {
@@ -13,3 +16,50 @@ type Pipeline struct {
 
 	*pipelines.PipelineSpec
 }
+
+// MergeClusters merges cluster definitions with same label.
+// The clusters field is a slice, and as such, overrides are appended to it.
+// We can identify a cluster by its label, however, so we can use this label
+// to figure out which definitions are actually overrides and merge them.
+//
+// Note: the cluster label is optional and defaults to 'default'.
+// We therefore ALSO merge all clusters without a label.
+func (p *Pipeline) MergeClusters() error {
+	clusters := make(map[string]*pipelines.PipelineCluster)
+	output := make([]pipelines.PipelineCluster, 0, len(p.Clusters))
+
+	// Normalize cluster labels.
+	// If empty, this defaults to "default".
+	// To make matching case insensitive, labels are lowercased.
+	for i := range p.Clusters {
+		label := p.Clusters[i].Label
+		if label == "" {
+			label = "default"
+		}
+		p.Clusters[i].Label = strings.ToLower(label)
+	}
+
+	// Target overrides are always appended, so we can iterate in natural order to
+	// first find the base definition, and merge instances we encounter later.
+	for i := range p.Clusters {
+		label := p.Clusters[i].Label
+
+		// Register pipeline cluster with label if not yet seen before.
+		ref, ok := clusters[label]
+		if !ok {
+			output = append(output, p.Clusters[i])
+			clusters[label] = &output[len(output)-1]
+			continue
+		}
+
+		// Merge this instance into the reference.
+		err := mergo.Merge(ref, &p.Clusters[i], mergo.WithOverride, mergo.WithAppendSlice)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Overwrite resulting slice.
+	p.Clusters = output
+	return nil
+}

bundle/config/resources/pipeline_test.go

@@ -0,0 +1,76 @@
+package resources
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/databricks/databricks-sdk-go/service/pipelines"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPipelineMergeClusters(t *testing.T) {
+	p := &Pipeline{
+		PipelineSpec: &pipelines.PipelineSpec{
+			Clusters: []pipelines.PipelineCluster{
+				{
+					NodeTypeId: "i3.xlarge",
+					NumWorkers: 2,
+					PolicyId:   "1234",
+				},
+				{
+					Label:      "maintenance",
+					NodeTypeId: "i3.2xlarge",
+				},
+				{
+					NodeTypeId: "i3.2xlarge",
+					NumWorkers: 4,
+				},
+			},
+		},
+	}
+
+	err := p.MergeClusters()
+	require.NoError(t, err)
+
+	assert.Len(t, p.Clusters, 2)
+	assert.Equal(t, "default", p.Clusters[0].Label)
+	assert.Equal(t, "maintenance", p.Clusters[1].Label)
+
+	// The default cluster was merged with a subsequent one.
+	pc0 := p.Clusters[0]
+	assert.Equal(t, "i3.2xlarge", pc0.NodeTypeId)
+	assert.Equal(t, 4, pc0.NumWorkers)
+	assert.Equal(t, "1234", pc0.PolicyId)
+
+	// The maintenance cluster was left untouched.
+	pc1 := p.Clusters[1]
+	assert.Equal(t, "i3.2xlarge", pc1.NodeTypeId)
+}
+
+func TestPipelineMergeClustersCaseInsensitive(t *testing.T) {
+	p := &Pipeline{
+		PipelineSpec: &pipelines.PipelineSpec{
+			Clusters: []pipelines.PipelineCluster{
+				{
+					Label:      "default",
+					NumWorkers: 2,
+				},
+				{
+					Label:      "DEFAULT",
+					NumWorkers: 4,
+				},
+			},
+		},
+	}
+
+	err := p.MergeClusters()
+	require.NoError(t, err)
+
+	assert.Len(t, p.Clusters, 1)
+
+	// The default cluster was merged with a subsequent one.
+	pc0 := p.Clusters[0]
+	assert.Equal(t, "default", strings.ToLower(pc0.Label))
+	assert.Equal(t, 4, pc0.NumWorkers)
+}

bundle/config/root.go

@@ -238,12 +238,7 @@ func (r *Root) MergeTargetOverrides(target *Target) error {
 			return err
 		}
 
-		err = r.Resources.MergeJobClusters()
-		if err != nil {
-			return err
-		}
-
-		err = r.Resources.MergeTasks()
+		err = r.Resources.Merge()
 		if err != nil {
 			return err
 		}

bundle/tests/override_pipeline_cluster/databricks.yml

@@ -0,0 +1,33 @@
+bundle:
+  name: override_pipeline_cluster
+
+workspace:
+  host: https://acme.cloud.databricks.com/
+
+resources:
+  pipelines:
+    foo:
+      name: job
+      clusters:
+        - label: default
+          spark_conf:
+            foo: bar
+
+targets:
+  development:
+    resources:
+      pipelines:
+        foo:
+          clusters:
+            - label: default
+              node_type_id: i3.xlarge
+              num_workers: 1
+
+  staging:
+    resources:
+      pipelines:
+        foo:
+          clusters:
+            - label: default
+              node_type_id: i3.2xlarge
+              num_workers: 4

bundle/tests/override_pipeline_cluster_test.go

@@ -0,0 +1,29 @@
+package config_tests
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOverridePipelineClusterDev(t *testing.T) {
+	b := loadTarget(t, "./override_pipeline_cluster", "development")
+	assert.Equal(t, "job", b.Config.Resources.Pipelines["foo"].Name)
+	assert.Len(t, b.Config.Resources.Pipelines["foo"].Clusters, 1)
+
+	c := b.Config.Resources.Pipelines["foo"].Clusters[0]
+	assert.Equal(t, map[string]string{"foo": "bar"}, c.SparkConf)
+	assert.Equal(t, "i3.xlarge", c.NodeTypeId)
+	assert.Equal(t, 1, c.NumWorkers)
+}
+
+func TestOverridePipelineClusterStaging(t *testing.T) {
+	b := loadTarget(t, "./override_pipeline_cluster", "staging")
+	assert.Equal(t, "job", b.Config.Resources.Pipelines["foo"].Name)
+	assert.Len(t, b.Config.Resources.Pipelines["foo"].Clusters, 1)
+
+	c := b.Config.Resources.Pipelines["foo"].Clusters[0]
+	assert.Equal(t, map[string]string{"foo": "bar"}, c.SparkConf)
+	assert.Equal(t, "i3.2xlarge", c.NodeTypeId)
+	assert.Equal(t, 4, c.NumWorkers)
+}