Merge 96a6cef0d6 into b323703c1b

## Changes
This PR adds a warning validating that the configuration for a single
node cluster is valid for interactive, job, job-task, and pipeline
clusters.

Note: We skip the validation if a cluster policy is configured because
the policy is likely to configure `spark_conf` / `custom_tags` itself.

Note: Terrform originally only had validation for interactive, job, and
job-task clusters. This PR adding the validation for pipeline clusters
as well is new.

This PR follows the same logic as we used to have in Terraform. The
validation was removed from Terraform because we had no way to demote
the error to a warning:
https://github.com/databricks/terraform-provider-databricks/pull/4222

### Background
Single-node clusters require `spark_conf` and `custom_tags` to be
correctly set in the cluster definition for them to function optimally.
The cluster will be created even if incorrectly configured, but its
performance will not be great.

For example, if both `spark_conf` and `custom_tags` are not set and
`num_workers` is 0, then only the driver process will be launched on the
cluster compute instance thus leading to sub-optimal utilization of
available compute resources and no parallelization across worker
processes when processing a spark query.

### Issue

This PR addresses some issues reported in
https://github.com/databricks/cli/issues/1546

## Tests
Unit tests and manually.

Example output of the warning:
```
➜  bundle-playground git:(master) ✗ cli bundle validate
Warning: Single node cluster is not correctly configured
  at resources.pipelines.bar.clusters[0]
  in databricks.yml:29:11

num_workers should be 0 only for single-node clusters. To create a
valid single node cluster please ensure that the following properties
are correctly set in the cluster specification:

  spark_conf:
    spark.databricks.cluster.profile: singleNode
    spark.master: local[*]

  custom_tags:
    ResourceClass: SingleNode
  

Name: foobar
Target: default
Workspace:
  User: shreyas.goenka@databricks.com
  Path: /Workspace/Users/shreyas.goenka@databricks.com/.bundle/foobar/default

Found 1 warning
```

bundle/config/experimental.go

@@ -45,6 +45,12 @@ type PyDABs struct {
 	// These packages are imported to discover resources, resource generators, and mutators.
 	// This list can include namespace packages, which causes the import of nested packages.
 	Import []string `json:"import,omitempty"`
+
+	// LoadLocations is a flag to enable loading Python source locations from the PyDABs.
+	//
+	// Locations are only supported since PyDABs 0.6.0, and because of that,
+	// this flag is disabled by default.
+	LoadLocations bool `json:"load_locations,omitempty"`
 }
 
 type Command string

bundle/config/mutator/apply_presets.go

@@ -225,9 +225,21 @@ func (m *applyPresets) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagnos
 	if config.IsExplicitlyEnabled((b.Config.Presets.SourceLinkedDeployment)) {
 		isDatabricksWorkspace := dbr.RunsOnRuntime(ctx) && strings.HasPrefix(b.SyncRootPath, "/Workspace/")
 		if !isDatabricksWorkspace {
+			target := b.Config.Bundle.Target
+			path := dyn.NewPath(dyn.Key("targets"), dyn.Key(target), dyn.Key("presets"), dyn.Key("source_linked_deployment"))
+			diags = diags.Append(
+				diag.Diagnostic{
+					Severity: diag.Warning,
+					Summary:  "source-linked deployment is available only in the Databricks Workspace",
+					Paths: []dyn.Path{
+						path,
+					},
+					Locations: b.Config.GetLocations(path[2:].String()),
+				},
+			)
+
 			disabled := false
 			b.Config.Presets.SourceLinkedDeployment = &disabled
-			diags = diags.Extend(diag.Warningf("source-linked deployment is available only in the Databricks Workspace"))
 		}
 	}
 

bundle/config/mutator/apply_presets_test.go

@@ -9,7 +9,9 @@ import (
 	"github.com/databricks/cli/bundle/config"
 	"github.com/databricks/cli/bundle/config/mutator"
 	"github.com/databricks/cli/bundle/config/resources"
+	"github.com/databricks/cli/bundle/internal/bundletest"
 	"github.com/databricks/cli/libs/dbr"
+	"github.com/databricks/cli/libs/dyn"
 	"github.com/databricks/databricks-sdk-go/service/catalog"
 	"github.com/databricks/databricks-sdk-go/service/jobs"
 	"github.com/stretchr/testify/require"
@@ -435,6 +437,7 @@ func TestApplyPresetsSourceLinkedDeployment(t *testing.T) {
 				},
 			}
 
+			bundletest.SetLocation(b, "presets.source_linked_deployment", []dyn.Location{{File: "databricks.yml"}})
 			diags := bundle.Apply(tt.ctx, b, mutator.ApplyPresets())
 			if diags.HasError() {
 				t.Fatalf("unexpected error: %v", diags)
@@ -442,6 +445,7 @@ func TestApplyPresetsSourceLinkedDeployment(t *testing.T) {
 
 			if tt.expectedWarning != "" {
 				require.Equal(t, tt.expectedWarning, diags[0].Summary)
+				require.NotEmpty(t, diags[0].Locations)
 			}
 
 			require.Equal(t, tt.expectedValue, b.Config.Presets.SourceLinkedDeployment)

bundle/config/mutator/python/python_diagnostics.go

@@ -9,6 +9,7 @@ import (
 	"github.com/databricks/cli/libs/dyn"
 )
 
+// pythonDiagnostic is a single entry in diagnostics.json
 type pythonDiagnostic struct {
 	Severity pythonSeverity           `json:"severity"`
 	Summary  string                   `json:"summary"`

bundle/config/mutator/python/python_locations.go

@@ -0,0 +1,181 @@
+package python
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"path/filepath"
+
+	"github.com/databricks/cli/libs/dyn"
+)
+
+// generatedFileName is used as the virtual file name for YAML generated by PyDABs.
+//
+// mergePythonLocations replaces dyn.Location with generatedFileName with locations loaded
+// from locations.json
+const generatedFileName = "__generated_by_pydabs__.yml"
+
+// pythonLocations is data structure for efficient location lookup for a given path
+//
+// Locations form a tree, and we assign locations of the closest ancestor to each dyn.Value based on its path.
+// We implement it as a trie (prefix tree) where keys are components of the path. With that, lookups are O(n)
+// where n is the number of components in the path.
+//
+// For example, with locations.json:
+//
+//	{"path": "resources.jobs.job_0", "file": "src/examples/job_0.py", "line": 3, "column": 5}
+//	{"path": "resources.jobs.job_0.tasks[0].task_key", "file": "src/examples/job_0.py", "line": 10, "column": 5}
+//	{"path": "resources.jobs.job_1", "file": "src/examples/job_1.py", "line": 5, "column": 7}
+//
+// - resources.jobs.job_0.tasks[0].task_key is located at job_0.py:10:5
+//
+//   - resources.jobs.job_0.tasks[0].email_notifications is located at job_0.py:3:5,
+//     because we use the location of the job as the most precise approximation.
+type pythonLocations struct {
+	// descendants referenced by index, e.g. '.foo'
+	keys map[string]*pythonLocations
+
+	// descendants referenced by key, e.g. '[0]'
+	indexes map[int]*pythonLocations
+
+	// location for the current node if it exists
+	location dyn.Location
+
+	// if true, location is present
+	exists bool
+}
+
+// pythonLocationEntry is a single entry in locations.json
+type pythonLocationEntry struct {
+	Path   string `json:"path"`
+	File   string `json:"file"`
+	Line   int    `json:"line"`
+	Column int    `json:"column"`
+}
+
+// mergePythonLocations applies locations from Python mutator into given dyn.Value
+//
+// The primary use-case is to merge locations.json with output.json, so that any
+// validation errors will point to Python source code instead of generated YAML.
+func mergePythonLocations(value dyn.Value, locations *pythonLocations) (dyn.Value, error) {
+	return dyn.Walk(value, func(path dyn.Path, value dyn.Value) (dyn.Value, error) {
+		newLocation, ok := findPythonLocation(locations, path)
+		if !ok {
+			return value, nil
+		}
+
+		var newLocations []dyn.Location
+
+		// the first item in the list is the "last" location used for error reporting
+		newLocations = append(newLocations, newLocation)
+
+		for _, location := range value.Locations() {
+			// When loaded, dyn.Value created by PyDABs use the virtual file path as their location,
+			// we replace it with newLocation.
+			if filepath.Base(location.File) == generatedFileName {
+				continue
+			}
+
+			newLocations = append(newLocations, location)
+		}
+
+		return value.WithLocations(newLocations), nil
+	})
+}
+
+// parsePythonLocations parses locations.json from the Python mutator.
+//
+// locations file is newline-separated JSON objects with pythonLocationEntry structure.
+func parsePythonLocations(input io.Reader) (*pythonLocations, error) {
+	decoder := json.NewDecoder(input)
+	locations := newPythonLocations()
+
+	for decoder.More() {
+		var entry pythonLocationEntry
+
+		err := decoder.Decode(&entry)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse python location: %s", err)
+		}
+
+		path, err := dyn.NewPathFromString(entry.Path)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse python location: %s", err)
+		}
+
+		location := dyn.Location{
+			File:   entry.File,
+			Line:   entry.Line,
+			Column: entry.Column,
+		}
+
+		putPythonLocation(locations, path, location)
+	}
+
+	return locations, nil
+}
+
+// putPythonLocation puts the location to the trie for the given path
+func putPythonLocation(trie *pythonLocations, path dyn.Path, location dyn.Location) {
+	var currentNode = trie
+
+	for _, component := range path {
+		if key := component.Key(); key != "" {
+			if _, ok := currentNode.keys[key]; !ok {
+				currentNode.keys[key] = newPythonLocations()
+			}
+
+			currentNode = currentNode.keys[key]
+		} else {
+			index := component.Index()
+			if _, ok := currentNode.indexes[index]; !ok {
+				currentNode.indexes[index] = newPythonLocations()
+			}
+
+			currentNode = currentNode.indexes[index]
+		}
+	}
+
+	currentNode.location = location
+	currentNode.exists = true
+}
+
+// newPythonLocations creates a new trie node
+func newPythonLocations() *pythonLocations {
+	return &pythonLocations{
+		keys:    make(map[string]*pythonLocations),
+		indexes: make(map[int]*pythonLocations),
+	}
+}
+
+// findPythonLocation finds the location or closest ancestor location in the trie for the given path
+// if no ancestor or exact location is found, false is returned.
+func findPythonLocation(locations *pythonLocations, path dyn.Path) (dyn.Location, bool) {
+	var currentNode = locations
+	var lastLocation = locations.location
+	var exists = locations.exists
+
+	for _, component := range path {
+		if key := component.Key(); key != "" {
+			if _, ok := currentNode.keys[key]; !ok {
+				break
+			}
+
+			currentNode = currentNode.keys[key]
+		} else {
+			index := component.Index()
+			if _, ok := currentNode.indexes[index]; !ok {
+				break
+			}
+
+			currentNode = currentNode.indexes[index]
+		}
+
+		if currentNode.exists {
+			lastLocation = currentNode.location
+			exists = true
+		}
+	}
+
+	return lastLocation, exists
+}

bundle/config/mutator/python/python_locations_test.go

@@ -0,0 +1,124 @@
+package python
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/databricks/cli/libs/dyn"
+	assert "github.com/databricks/cli/libs/dyn/dynassert"
+)
+
+func TestMergeLocations(t *testing.T) {
+	pythonLocation := dyn.Location{File: "foo.py", Line: 1, Column: 1}
+	generatedLocation := dyn.Location{File: generatedFileName, Line: 1, Column: 1}
+	yamlLocation := dyn.Location{File: "foo.yml", Line: 1, Column: 1}
+
+	locations := newPythonLocations()
+	putPythonLocation(locations, dyn.MustPathFromString("foo"), pythonLocation)
+
+	input := dyn.NewValue(
+		map[string]dyn.Value{
+			"foo": dyn.NewValue(
+				map[string]dyn.Value{
+					"baz": dyn.NewValue("baz", []dyn.Location{yamlLocation}),
+					"qux": dyn.NewValue("baz", []dyn.Location{generatedLocation, yamlLocation}),
+				},
+				[]dyn.Location{},
+			),
+			"bar": dyn.NewValue("baz", []dyn.Location{generatedLocation}),
+		},
+		[]dyn.Location{yamlLocation},
+	)
+
+	expected := dyn.NewValue(
+		map[string]dyn.Value{
+			"foo": dyn.NewValue(
+				map[string]dyn.Value{
+					// pythonLocation is appended to the beginning of the list if absent
+					"baz": dyn.NewValue("baz", []dyn.Location{pythonLocation, yamlLocation}),
+					// generatedLocation is replaced by pythonLocation
+					"qux": dyn.NewValue("baz", []dyn.Location{pythonLocation, yamlLocation}),
+				},
+				[]dyn.Location{pythonLocation},
+			),
+			// if location is unknown, we keep it as-is
+			"bar": dyn.NewValue("baz", []dyn.Location{generatedLocation}),
+		},
+		[]dyn.Location{yamlLocation},
+	)
+
+	actual, err := mergePythonLocations(input, locations)
+
+	assert.NoError(t, err)
+	assert.Equal(t, expected, actual)
+}
+
+func TestFindLocation(t *testing.T) {
+	location0 := dyn.Location{File: "foo.py", Line: 1, Column: 1}
+	location1 := dyn.Location{File: "foo.py", Line: 2, Column: 1}
+
+	locations := newPythonLocations()
+	putPythonLocation(locations, dyn.MustPathFromString("foo"), location0)
+	putPythonLocation(locations, dyn.MustPathFromString("foo.bar"), location1)
+
+	actual, exists := findPythonLocation(locations, dyn.MustPathFromString("foo.bar"))
+
+	assert.True(t, exists)
+	assert.Equal(t, location1, actual)
+}
+
+func TestFindLocation_indexPathComponent(t *testing.T) {
+	location0 := dyn.Location{File: "foo.py", Line: 1, Column: 1}
+	location1 := dyn.Location{File: "foo.py", Line: 2, Column: 1}
+	location2 := dyn.Location{File: "foo.py", Line: 3, Column: 1}
+
+	locations := newPythonLocations()
+	putPythonLocation(locations, dyn.MustPathFromString("foo"), location0)
+	putPythonLocation(locations, dyn.MustPathFromString("foo.bar"), location1)
+	putPythonLocation(locations, dyn.MustPathFromString("foo.bar[0]"), location2)
+
+	actual, exists := findPythonLocation(locations, dyn.MustPathFromString("foo.bar[0]"))
+
+	assert.True(t, exists)
+	assert.Equal(t, location2, actual)
+}
+
+func TestFindLocation_closestAncestorLocation(t *testing.T) {
+	location0 := dyn.Location{File: "foo.py", Line: 1, Column: 1}
+	location1 := dyn.Location{File: "foo.py", Line: 2, Column: 1}
+
+	locations := newPythonLocations()
+	putPythonLocation(locations, dyn.MustPathFromString("foo"), location0)
+	putPythonLocation(locations, dyn.MustPathFromString("foo.bar"), location1)
+
+	actual, exists := findPythonLocation(locations, dyn.MustPathFromString("foo.bar.baz"))
+
+	assert.True(t, exists)
+	assert.Equal(t, location1, actual)
+}
+
+func TestFindLocation_unknownLocation(t *testing.T) {
+	location0 := dyn.Location{File: "foo.py", Line: 1, Column: 1}
+	location1 := dyn.Location{File: "foo.py", Line: 2, Column: 1}
+
+	locations := newPythonLocations()
+	putPythonLocation(locations, dyn.MustPathFromString("foo"), location0)
+	putPythonLocation(locations, dyn.MustPathFromString("foo.bar"), location1)
+
+	_, exists := findPythonLocation(locations, dyn.MustPathFromString("bar"))
+
+	assert.False(t, exists)
+}
+
+func TestParsePythonLocations(t *testing.T) {
+	expected := dyn.Location{File: "foo.py", Line: 1, Column: 2}
+
+	input := `{"path": "foo", "file": "foo.py", "line": 1, "column": 2}`
+	reader := bytes.NewReader([]byte(input))
+	locations, err := parsePythonLocations(reader)
+
+	assert.NoError(t, err)
+
+	assert.True(t, locations.keys["foo"].exists)
+	assert.Equal(t, expected, locations.keys["foo"].location)
+}

bundle/config/mutator/python/python_mutator.go

@@ -7,9 +7,12 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 
+	"github.com/databricks/cli/bundle/config/mutator/paths"
+
 	"github.com/databricks/databricks-sdk-go/logger"
 	"github.com/fatih/color"
 
@@ -108,7 +111,12 @@ func (m *pythonMutator) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagno
 			return dyn.InvalidValue, fmt.Errorf("failed to create cache dir: %w", err)
 		}
 
-		rightRoot, diags := m.runPythonMutator(ctx, cacheDir, b.BundleRootPath, pythonPath, leftRoot)
+		rightRoot, diags := m.runPythonMutator(ctx, leftRoot, runPythonMutatorOpts{
+			cacheDir:       cacheDir,
+			bundleRootPath: b.BundleRootPath,
+			pythonPath:     pythonPath,
+			loadLocations:  experimental.PyDABs.LoadLocations,
+		})
 		mutateDiags = diags
 		if diags.HasError() {
 			return dyn.InvalidValue, mutateDiagsHasError
@@ -152,13 +160,21 @@ func createCacheDir(ctx context.Context) (string, error) {
 	return os.MkdirTemp("", "-pydabs")
 }
 
-func (m *pythonMutator) runPythonMutator(ctx context.Context, cacheDir string, rootPath string, pythonPath string, root dyn.Value) (dyn.Value, diag.Diagnostics) {
-	inputPath := filepath.Join(cacheDir, "input.json")
-	outputPath := filepath.Join(cacheDir, "output.json")
-	diagnosticsPath := filepath.Join(cacheDir, "diagnostics.json")
+type runPythonMutatorOpts struct {
+	cacheDir       string
+	bundleRootPath string
+	pythonPath     string
+	loadLocations  bool
+}
+
+func (m *pythonMutator) runPythonMutator(ctx context.Context, root dyn.Value, opts runPythonMutatorOpts) (dyn.Value, diag.Diagnostics) {
+	inputPath := filepath.Join(opts.cacheDir, "input.json")
+	outputPath := filepath.Join(opts.cacheDir, "output.json")
+	diagnosticsPath := filepath.Join(opts.cacheDir, "diagnostics.json")
+	locationsPath := filepath.Join(opts.cacheDir, "locations.json")
 
 	args := []string{
-		pythonPath,
+		opts.pythonPath,
 		"-m",
 		"databricks.bundles.build",
 		"--phase",
@@ -171,6 +187,10 @@ func (m *pythonMutator) runPythonMutator(ctx context.Context, cacheDir string, r
 		diagnosticsPath,
 	}
 
+	if opts.loadLocations {
+		args = append(args, "--locations", locationsPath)
+	}
+
 	if err := writeInputFile(inputPath, root); err != nil {
 		return dyn.InvalidValue, diag.Errorf("failed to write input file: %s", err)
 	}
@@ -185,7 +205,7 @@ func (m *pythonMutator) runPythonMutator(ctx context.Context, cacheDir string, r
 	_, processErr := process.Background(
 		ctx,
 		args,
-		process.WithDir(rootPath),
+		process.WithDir(opts.bundleRootPath),
 		process.WithStderrWriter(stderrWriter),
 		process.WithStdoutWriter(stdoutWriter),
 	)
@@ -221,7 +241,12 @@ func (m *pythonMutator) runPythonMutator(ctx context.Context, cacheDir string, r
 		return dyn.InvalidValue, diag.Errorf("failed to load diagnostics: %s", pythonDiagnosticsErr)
 	}
 
-	output, outputDiags := loadOutputFile(rootPath, outputPath)
+	locations, err := loadLocationsFile(locationsPath)
+	if err != nil {
+		return dyn.InvalidValue, diag.Errorf("failed to load locations: %s", err)
+	}
+
+	output, outputDiags := loadOutputFile(opts.bundleRootPath, outputPath, locations)
 	pythonDiagnostics = pythonDiagnostics.Extend(outputDiags)
 
 	// we pass through pythonDiagnostic because it contains warnings
@@ -266,7 +291,21 @@ func writeInputFile(inputPath string, input dyn.Value) error {
 	return os.WriteFile(inputPath, rootConfigJson, 0600)
 }
 
-func loadOutputFile(rootPath string, outputPath string) (dyn.Value, diag.Diagnostics) {
+// loadLocationsFile loads locations.json containing source locations for generated YAML.
+func loadLocationsFile(locationsPath string) (*pythonLocations, error) {
+	locationsFile, err := os.Open(locationsPath)
+	if errors.Is(err, fs.ErrNotExist) {
+		return newPythonLocations(), nil
+	} else if err != nil {
+		return nil, fmt.Errorf("failed to open locations file: %w", err)
+	}
+
+	defer locationsFile.Close()
+
+	return parsePythonLocations(locationsFile)
+}
+
+func loadOutputFile(rootPath string, outputPath string, locations *pythonLocations) (dyn.Value, diag.Diagnostics) {
 	outputFile, err := os.Open(outputPath)
 	if err != nil {
 		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to open output file: %w", err))
@@ -277,12 +316,12 @@ func loadOutputFile(rootPath string, outputPath string) (dyn.Value, diag.Diagnos
 	// we need absolute path because later parts of pipeline assume all paths are absolute
 	// and this file will be used as location to resolve relative paths.
 	//
-	// virtualPath has to stay in rootPath, because locations outside root path are not allowed:
+	// virtualPath has to stay in bundleRootPath, because locations outside root path are not allowed:
 	//
 	//   Error: path /var/folders/.../pydabs/dist/*.whl is not contained in bundle root path
 	//
 	// for that, we pass virtualPath instead of outputPath as file location
-	virtualPath, err := filepath.Abs(filepath.Join(rootPath, "__generated_by_pydabs__.yml"))
+	virtualPath, err := filepath.Abs(filepath.Join(rootPath, generatedFileName))
 	if err != nil {
 		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to get absolute path: %w", err))
 	}
@@ -292,7 +331,25 @@ func loadOutputFile(rootPath string, outputPath string) (dyn.Value, diag.Diagnos
 		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to parse output file: %w", err))
 	}
 
-	return strictNormalize(config.Root{}, generated)
+	// paths are resolved relative to locations of their values, if we change location
+	// we have to update each path, until we simplify that, we don't update locations
+	// for such values, so we don't change how paths are resolved
+	_, err = paths.VisitJobPaths(generated, func(p dyn.Path, kind paths.PathKind, v dyn.Value) (dyn.Value, error) {
+		putPythonLocation(locations, p, v.Location())
+		return v, nil
+	})
+	if err != nil {
+		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to update locations: %w", err))
+	}
+
+	// generated has dyn.Location as if it comes from generated YAML file
+	// earlier we loaded locations.json with source locations in Python code
+	generatedWithLocations, err := mergePythonLocations(generated, locations)
+	if err != nil {
+		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to update locations: %w", err))
+	}
+
+	return strictNormalize(config.Root{}, generatedWithLocations)
 }
 
 func strictNormalize(dst any, generated dyn.Value) (dyn.Value, diag.Diagnostics) {

bundle/config/mutator/python/python_mutator_test.go

@@ -6,7 +6,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"reflect"
 	"runtime"
 	"testing"
 
@@ -47,6 +46,7 @@ func TestPythonMutator_load(t *testing.T) {
         pydabs:
           enabled: true
           venv_path: .venv
+          load_locations: true
       resources:
         jobs:
           job0:
@@ -65,7 +65,8 @@ func TestPythonMutator_load(t *testing.T) {
 			"experimental": {
 				"pydabs": {
 					"enabled": true,
-					"venv_path": ".venv"
+					"venv_path": ".venv",
+					"load_locations": true
 				}
 			},
 			"resources": {
@@ -80,6 +81,8 @@ func TestPythonMutator_load(t *testing.T) {
 			}
 		}`,
 		`{"severity": "warning", "summary": "job doesn't have any tasks", "location": {"file": "src/examples/file.py", "line": 10, "column": 5}}`,
+		`{"path": "resources.jobs.job0", "file": "src/examples/job0.py", "line": 3, "column": 5}
+		{"path": "resources.jobs.job1", "file": "src/examples/job1.py", "line": 5, "column": 7}`,
 	)
 
 	mutator := PythonMutator(PythonMutatorPhaseLoad)
@@ -97,6 +100,25 @@ func TestPythonMutator_load(t *testing.T) {
 		assert.Equal(t, "job_1", job1.Name)
 	}
 
+	// output of locations.json should be applied to underlying dyn.Value
+	err := b.Config.Mutate(func(v dyn.Value) (dyn.Value, error) {
+		name1, err := dyn.GetByPath(v, dyn.MustPathFromString("resources.jobs.job1.name"))
+		if err != nil {
+			return dyn.InvalidValue, err
+		}
+
+		assert.Equal(t, []dyn.Location{
+			{
+				File:   "src/examples/job1.py",
+				Line:   5,
+				Column: 7,
+			},
+		}, name1.Locations())
+
+		return v, nil
+	})
+	assert.NoError(t, err)
+
 	assert.Equal(t, 1, len(diags))
 	assert.Equal(t, "job doesn't have any tasks", diags[0].Summary)
 	assert.Equal(t, []dyn.Location{
@@ -106,7 +128,6 @@ func TestPythonMutator_load(t *testing.T) {
 			Column: 5,
 		},
 	}, diags[0].Locations)
-
 }
 
 func TestPythonMutator_load_disallowed(t *testing.T) {
@@ -146,7 +167,7 @@ func TestPythonMutator_load_disallowed(t *testing.T) {
 					}
 				}
 			}
-		}`, "")
+		}`, "", "")
 
 	mutator := PythonMutator(PythonMutatorPhaseLoad)
 	diag := bundle.Apply(ctx, b, mutator)
@@ -191,7 +212,7 @@ func TestPythonMutator_init(t *testing.T) {
 					}
 				}
 			}
-		}`, "")
+		}`, "", "")
 
 	mutator := PythonMutator(PythonMutatorPhaseInit)
 	diag := bundle.Apply(ctx, b, mutator)
@@ -252,7 +273,7 @@ func TestPythonMutator_badOutput(t *testing.T) {
 					}
 				}
 			}
-		}`, "")
+		}`, "", "")
 
 	mutator := PythonMutator(PythonMutatorPhaseLoad)
 	diag := bundle.Apply(ctx, b, mutator)
@@ -588,7 +609,7 @@ or activate the environment before running CLI commands:
 	assert.Equal(t, expected, out)
 }
 
-func withProcessStub(t *testing.T, args []string, output string, diagnostics string) context.Context {
+func withProcessStub(t *testing.T, args []string, output string, diagnostics string, locations string) context.Context {
 	ctx := context.Background()
 	ctx, stub := process.WithStub(ctx)
 
@@ -600,32 +621,51 @@ func withProcessStub(t *testing.T, args []string, output string, diagnostics str
 
 	inputPath := filepath.Join(cacheDir, "input.json")
 	outputPath := filepath.Join(cacheDir, "output.json")
+	locationsPath := filepath.Join(cacheDir, "locations.json")
 	diagnosticsPath := filepath.Join(cacheDir, "diagnostics.json")
 
-	args = append(args, "--input", inputPath)
-	args = append(args, "--output", outputPath)
-	args = append(args, "--diagnostics", diagnosticsPath)
-
 	stub.WithCallback(func(actual *exec.Cmd) error {
 		_, err := os.Stat(inputPath)
 		assert.NoError(t, err)
 
-		if reflect.DeepEqual(actual.Args, args) {
-			err := os.WriteFile(outputPath, []byte(output), 0600)
+		actualInputPath := getArg(actual.Args, "--input")
+		actualOutputPath := getArg(actual.Args, "--output")
+		actualDiagnosticsPath := getArg(actual.Args, "--diagnostics")
+		actualLocationsPath := getArg(actual.Args, "--locations")
+
+		require.Equal(t, inputPath, actualInputPath)
+		require.Equal(t, outputPath, actualOutputPath)
+		require.Equal(t, diagnosticsPath, actualDiagnosticsPath)
+
+		// locations is an optional argument
+		if locations != "" {
+			require.Equal(t, locationsPath, actualLocationsPath)
+
+			err = os.WriteFile(locationsPath, []byte(locations), 0600)
+			require.NoError(t, err)
+		}
+
+		err = os.WriteFile(outputPath, []byte(output), 0600)
 		require.NoError(t, err)
 
 		err = os.WriteFile(diagnosticsPath, []byte(diagnostics), 0600)
 		require.NoError(t, err)
 
 		return nil
-		} else {
-			return fmt.Errorf("unexpected command: %v", actual.Args)
-		}
 	})
 
 	return ctx
 }
 
+func getArg(args []string, name string) string {
+	for i := 0; i < len(args); i++ {
+		if args[i] == name {
+			return args[i+1]
+		}
+	}
+	return ""
+}
+
 func loadYaml(name string, content string) *bundle.Bundle {
 	v, diag := config.LoadFromBytes(name, []byte(content))
 

bundle/config/validate/single_node_cluster.go

@@ -0,0 +1,137 @@
+package validate
+
+import (
+	"context"
+	"strings"
+
+	"github.com/databricks/cli/bundle"
+	"github.com/databricks/cli/libs/diag"
+	"github.com/databricks/cli/libs/dyn"
+	"github.com/databricks/cli/libs/dyn/convert"
+	"github.com/databricks/cli/libs/log"
+)
+
+// Validates that any single node clusters defined in the bundle are correctly configured.
+func SingleNodeCluster() bundle.ReadOnlyMutator {
+	return &singleNodeCluster{}
+}
+
+type singleNodeCluster struct{}
+
+func (m *singleNodeCluster) Name() string {
+	return "validate:SingleNodeCluster"
+}
+
+const singleNodeWarningDetail = `num_workers should be 0 only for single-node clusters. To create a
+valid single node cluster please ensure that the following properties
+are correctly set in the cluster specification:
+
+  spark_conf:
+    spark.databricks.cluster.profile: singleNode
+    spark.master: local[*]
+
+  custom_tags:
+    ResourceClass: SingleNode
+  `
+
+const singleNodeWarningSummary = `Single node cluster is not correctly configured`
+
+func showSingleNodeClusterWarning(ctx context.Context, v dyn.Value) bool {
+	// Check if the user has explicitly set the num_workers to 0. Skip the warning
+	// if that's not the case.
+	numWorkers, ok := v.Get("num_workers").AsInt()
+	if !ok || numWorkers > 0 {
+		return false
+	}
+
+	// Convenient type that contains the common fields from compute.ClusterSpec and
+	// pipelines.PipelineCluster that we are interested in.
+	type ClusterConf struct {
+		SparkConf  map[string]string `json:"spark_conf"`
+		CustomTags map[string]string `json:"custom_tags"`
+		PolicyId   string            `json:"policy_id"`
+	}
+
+	conf := &ClusterConf{}
+	err := convert.ToTyped(conf, v)
+	if err != nil {
+		return false
+	}
+
+	// If the policy id is set, we don't want to show the warning. This is because
+	// the user might have configured `spark_conf` and `custom_tags` correctly
+	// in their cluster policy.
+	if conf.PolicyId != "" {
+		return false
+	}
+
+	profile, ok := conf.SparkConf["spark.databricks.cluster.profile"]
+	if !ok {
+		log.Debugf(ctx, "spark_conf spark.databricks.cluster.profile not found in single-node cluster spec")
+		return true
+	}
+	if profile != "singleNode" {
+		log.Debugf(ctx, "spark_conf spark.databricks.cluster.profile is not singleNode in single-node cluster spec: %s", profile)
+		return true
+	}
+
+	master, ok := conf.SparkConf["spark.master"]
+	if !ok {
+		log.Debugf(ctx, "spark_conf spark.master not found in single-node cluster spec")
+		return true
+	}
+	if !strings.HasPrefix(master, "local") {
+		log.Debugf(ctx, "spark_conf spark.master does not start with local in single-node cluster spec: %s", master)
+		return true
+	}
+
+	resourceClass, ok := conf.CustomTags["ResourceClass"]
+	if !ok {
+		log.Debugf(ctx, "custom_tag ResourceClass not found in single-node cluster spec")
+		return true
+	}
+	if resourceClass != "SingleNode" {
+		log.Debugf(ctx, "custom_tag ResourceClass is not SingleNode in single-node cluster spec: %s", resourceClass)
+		return true
+	}
+
+	return false
+}
+
+func (m *singleNodeCluster) Apply(ctx context.Context, rb bundle.ReadOnlyBundle) diag.Diagnostics {
+	diags := diag.Diagnostics{}
+
+	patterns := []dyn.Pattern{
+		// Interactive clusters
+		dyn.NewPattern(dyn.Key("resources"), dyn.Key("clusters"), dyn.AnyKey()),
+		// Job clusters
+		dyn.NewPattern(dyn.Key("resources"), dyn.Key("jobs"), dyn.AnyKey(), dyn.Key("job_clusters"), dyn.AnyIndex(), dyn.Key("new_cluster")),
+		// Job task clusters
+		dyn.NewPattern(dyn.Key("resources"), dyn.Key("jobs"), dyn.AnyKey(), dyn.Key("tasks"), dyn.AnyIndex(), dyn.Key("new_cluster")),
+		// Job for each task clusters
+		dyn.NewPattern(dyn.Key("resources"), dyn.Key("jobs"), dyn.AnyKey(), dyn.Key("tasks"), dyn.AnyIndex(), dyn.Key("for_each_task"), dyn.Key("task"), dyn.Key("new_cluster")),
+		// Pipeline clusters
+		dyn.NewPattern(dyn.Key("resources"), dyn.Key("pipelines"), dyn.AnyKey(), dyn.Key("clusters"), dyn.AnyIndex()),
+	}
+
+	for _, p := range patterns {
+		_, err := dyn.MapByPattern(rb.Config().Value(), p, func(p dyn.Path, v dyn.Value) (dyn.Value, error) {
+			warning := diag.Diagnostic{
+				Severity:  diag.Warning,
+				Summary:   singleNodeWarningSummary,
+				Detail:    singleNodeWarningDetail,
+				Locations: v.Locations(),
+				Paths:     []dyn.Path{p},
+			}
+
+			if showSingleNodeClusterWarning(ctx, v) {
+				diags = append(diags, warning)
+			}
+			return v, nil
+		})
+		if err != nil {
+			log.Debugf(ctx, "Error while applying single node cluster validation: %s", err)
+		}
+	}
+	return diags
+}

bundle/config/validate/single_node_cluster_test.go

@@ -0,0 +1,566 @@
+package validate
+
+import (
+	"context"
+	"testing"
+
+	"github.com/databricks/cli/bundle"
+	"github.com/databricks/cli/bundle/config"
+	"github.com/databricks/cli/bundle/config/resources"
+	"github.com/databricks/cli/bundle/internal/bundletest"
+	"github.com/databricks/cli/libs/diag"
+	"github.com/databricks/cli/libs/dyn"
+	"github.com/databricks/databricks-sdk-go/service/compute"
+	"github.com/databricks/databricks-sdk-go/service/jobs"
+	"github.com/databricks/databricks-sdk-go/service/pipelines"
+	"github.com/stretchr/testify/assert"
+)
+
+func failCases() []struct {
+	name       string
+	sparkConf  map[string]string
+	customTags map[string]string
+} {
+	return []struct {
+		name       string
+		sparkConf  map[string]string
+		customTags map[string]string
+	}{
+		{
+			name: "no tags or conf",
+		},
+		{
+			name: "no tags",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+				"spark.master":                     "local[*]",
+			},
+		},
+		{
+			name:       "no conf",
+			customTags: map[string]string{"ResourceClass": "SingleNode"},
+		},
+		{
+			name: "invalid spark cluster profile",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "invalid",
+				"spark.master":                     "local[*]",
+			},
+			customTags: map[string]string{"ResourceClass": "SingleNode"},
+		},
+		{
+			name: "invalid spark.master",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+				"spark.master":                     "invalid",
+			},
+			customTags: map[string]string{"ResourceClass": "SingleNode"},
+		},
+		{
+			name: "invalid tags",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+				"spark.master":                     "local[*]",
+			},
+			customTags: map[string]string{"ResourceClass": "invalid"},
+		},
+		{
+			name: "missing ResourceClass tag",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+				"spark.master":                     "local[*]",
+			},
+			customTags: map[string]string{"what": "ever"},
+		},
+		{
+			name: "missing spark.master",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+			},
+			customTags: map[string]string{"ResourceClass": "SingleNode"},
+		},
+		{
+			name: "missing spark.databricks.cluster.profile",
+			sparkConf: map[string]string{
+				"spark.master": "local[*]",
+			},
+			customTags: map[string]string{"ResourceClass": "SingleNode"},
+		},
+	}
+}
+
+func TestValidateSingleNodeClusterFailForInteractiveClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range failCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Clusters: map[string]*resources.Cluster{
+							"foo": {
+								ClusterSpec: &compute.ClusterSpec{
+									SparkConf:  tc.sparkConf,
+									CustomTags: tc.customTags,
+								},
+							},
+						},
+					},
+				},
+			}
+
+			bundletest.SetLocation(b, "resources.clusters.foo", []dyn.Location{{File: "a.yml", Line: 1, Column: 1}})
+
+			// We can't set num_workers to 0 explicitly in the typed configuration.
+			// Do it on the dyn.Value directly.
+			bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+				return dyn.Set(v, "resources.clusters.foo.num_workers", dyn.V(0))
+			})
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Equal(t, diag.Diagnostics{
+				{
+					Severity:  diag.Warning,
+					Summary:   singleNodeWarningSummary,
+					Detail:    singleNodeWarningDetail,
+					Locations: []dyn.Location{{File: "a.yml", Line: 1, Column: 1}},
+					Paths:     []dyn.Path{dyn.NewPath(dyn.Key("resources"), dyn.Key("clusters"), dyn.Key("foo"))},
+				},
+			}, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterFailForJobClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range failCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									JobClusters: []jobs.JobCluster{
+										{
+											NewCluster: compute.ClusterSpec{
+												ClusterName: "my_cluster",
+												SparkConf:   tc.sparkConf,
+												CustomTags:  tc.customTags,
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			bundletest.SetLocation(b, "resources.jobs.foo.job_clusters[0].new_cluster", []dyn.Location{{File: "b.yml", Line: 1, Column: 1}})
+
+			// We can't set num_workers to 0 explicitly in the typed configuration.
+			// Do it on the dyn.Value directly.
+			bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+				return dyn.Set(v, "resources.jobs.foo.job_clusters[0].new_cluster.num_workers", dyn.V(0))
+			})
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Equal(t, diag.Diagnostics{
+				{
+					Severity:  diag.Warning,
+					Summary:   singleNodeWarningSummary,
+					Detail:    singleNodeWarningDetail,
+					Locations: []dyn.Location{{File: "b.yml", Line: 1, Column: 1}},
+					Paths:     []dyn.Path{dyn.MustPathFromString("resources.jobs.foo.job_clusters[0].new_cluster")},
+				},
+			}, diags)
+
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterFailForJobTaskClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range failCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									Tasks: []jobs.Task{
+										{
+											NewCluster: &compute.ClusterSpec{
+												ClusterName: "my_cluster",
+												SparkConf:   tc.sparkConf,
+												CustomTags:  tc.customTags,
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			bundletest.SetLocation(b, "resources.jobs.foo.tasks[0].new_cluster", []dyn.Location{{File: "c.yml", Line: 1, Column: 1}})
+
+			// We can't set num_workers to 0 explicitly in the typed configuration.
+			// Do it on the dyn.Value directly.
+			bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+				return dyn.Set(v, "resources.jobs.foo.tasks[0].new_cluster.num_workers", dyn.V(0))
+			})
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Equal(t, diag.Diagnostics{
+				{
+					Severity:  diag.Warning,
+					Summary:   singleNodeWarningSummary,
+					Detail:    singleNodeWarningDetail,
+					Locations: []dyn.Location{{File: "c.yml", Line: 1, Column: 1}},
+					Paths:     []dyn.Path{dyn.MustPathFromString("resources.jobs.foo.tasks[0].new_cluster")},
+				},
+			}, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterFailForPipelineClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range failCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Pipelines: map[string]*resources.Pipeline{
+							"foo": {
+								PipelineSpec: &pipelines.PipelineSpec{
+									Clusters: []pipelines.PipelineCluster{
+										{
+											SparkConf:  tc.sparkConf,
+											CustomTags: tc.customTags,
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			bundletest.SetLocation(b, "resources.pipelines.foo.clusters[0]", []dyn.Location{{File: "d.yml", Line: 1, Column: 1}})
+
+			// We can't set num_workers to 0 explicitly in the typed configuration.
+			// Do it on the dyn.Value directly.
+			bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+				return dyn.Set(v, "resources.pipelines.foo.clusters[0].num_workers", dyn.V(0))
+			})
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Equal(t, diag.Diagnostics{
+				{
+					Severity:  diag.Warning,
+					Summary:   singleNodeWarningSummary,
+					Detail:    singleNodeWarningDetail,
+					Locations: []dyn.Location{{File: "d.yml", Line: 1, Column: 1}},
+					Paths:     []dyn.Path{dyn.MustPathFromString("resources.pipelines.foo.clusters[0]")},
+				},
+			}, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterFailForJobForEachTaskCluster(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range failCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									Tasks: []jobs.Task{
+										{
+											ForEachTask: &jobs.ForEachTask{
+												Task: jobs.Task{
+													NewCluster: &compute.ClusterSpec{
+														ClusterName: "my_cluster",
+														SparkConf:   tc.sparkConf,
+														CustomTags:  tc.customTags,
+													},
+												},
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			bundletest.SetLocation(b, "resources.jobs.foo.tasks[0].for_each_task.task.new_cluster", []dyn.Location{{File: "e.yml", Line: 1, Column: 1}})
+
+			// We can't set num_workers to 0 explicitly in the typed configuration.
+			// Do it on the dyn.Value directly.
+			bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+				return dyn.Set(v, "resources.jobs.foo.tasks[0].for_each_task.task.new_cluster.num_workers", dyn.V(0))
+			})
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Equal(t, diag.Diagnostics{
+				{
+					Severity:  diag.Warning,
+					Summary:   singleNodeWarningSummary,
+					Detail:    singleNodeWarningDetail,
+					Locations: []dyn.Location{{File: "e.yml", Line: 1, Column: 1}},
+					Paths:     []dyn.Path{dyn.MustPathFromString("resources.jobs.foo.tasks[0].for_each_task.task.new_cluster")},
+				},
+			}, diags)
+		})
+	}
+}
+
+func passCases() []struct {
+	name       string
+	numWorkers *int
+	sparkConf  map[string]string
+	customTags map[string]string
+	policyId   string
+} {
+	zero := 0
+	one := 1
+
+	return []struct {
+		name       string
+		numWorkers *int
+		sparkConf  map[string]string
+		customTags map[string]string
+		policyId   string
+	}{
+		{
+			name: "single node cluster",
+			sparkConf: map[string]string{
+				"spark.databricks.cluster.profile": "singleNode",
+				"spark.master":                     "local[*]",
+			},
+			customTags: map[string]string{
+				"ResourceClass": "SingleNode",
+			},
+			numWorkers: &zero,
+		},
+		{
+			name:       "num workers is not zero",
+			numWorkers: &one,
+		},
+		{
+			name: "num workers is not set",
+		},
+		{
+			name:       "policy id is not empty",
+			policyId:   "policy-abc",
+			numWorkers: &zero,
+		},
+	}
+}
+
+func TestValidateSingleNodeClusterPassInteractiveClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range passCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Clusters: map[string]*resources.Cluster{
+							"foo": {
+								ClusterSpec: &compute.ClusterSpec{
+									SparkConf:  tc.sparkConf,
+									CustomTags: tc.customTags,
+									PolicyId:   tc.policyId,
+								},
+							},
+						},
+					},
+				},
+			}
+
+			if tc.numWorkers != nil {
+				bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+					return dyn.Set(v, "resources.clusters.foo.num_workers", dyn.V(*tc.numWorkers))
+				})
+			}
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Empty(t, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterPassJobClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range passCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									JobClusters: []jobs.JobCluster{
+										{
+											NewCluster: compute.ClusterSpec{
+												ClusterName: "my_cluster",
+												SparkConf:   tc.sparkConf,
+												CustomTags:  tc.customTags,
+												PolicyId:    tc.policyId,
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			if tc.numWorkers != nil {
+				bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+					return dyn.Set(v, "resources.jobs.foo.job_clusters[0].new_cluster.num_workers", dyn.V(*tc.numWorkers))
+				})
+			}
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Empty(t, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterPassJobTaskClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range passCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									Tasks: []jobs.Task{
+										{
+											NewCluster: &compute.ClusterSpec{
+												ClusterName: "my_cluster",
+												SparkConf:   tc.sparkConf,
+												CustomTags:  tc.customTags,
+												PolicyId:    tc.policyId,
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			if tc.numWorkers != nil {
+				bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+					return dyn.Set(v, "resources.jobs.foo.tasks[0].new_cluster.num_workers", dyn.V(*tc.numWorkers))
+				})
+			}
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Empty(t, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterPassPipelineClusters(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range passCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Pipelines: map[string]*resources.Pipeline{
+							"foo": {
+								PipelineSpec: &pipelines.PipelineSpec{
+									Clusters: []pipelines.PipelineCluster{
+										{
+											SparkConf:  tc.sparkConf,
+											CustomTags: tc.customTags,
+											PolicyId:   tc.policyId,
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			if tc.numWorkers != nil {
+				bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+					return dyn.Set(v, "resources.pipelines.foo.clusters[0].num_workers", dyn.V(*tc.numWorkers))
+				})
+			}
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Empty(t, diags)
+		})
+	}
+}
+
+func TestValidateSingleNodeClusterPassJobForEachTaskCluster(t *testing.T) {
+	ctx := context.Background()
+
+	for _, tc := range passCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			b := &bundle.Bundle{
+				Config: config.Root{
+					Resources: config.Resources{
+						Jobs: map[string]*resources.Job{
+							"foo": {
+								JobSettings: &jobs.JobSettings{
+									Tasks: []jobs.Task{
+										{
+											ForEachTask: &jobs.ForEachTask{
+												Task: jobs.Task{
+													NewCluster: &compute.ClusterSpec{
+														ClusterName: "my_cluster",
+														SparkConf:   tc.sparkConf,
+														CustomTags:  tc.customTags,
+														PolicyId:    tc.policyId,
+													},
+												},
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			}
+
+			if tc.numWorkers != nil {
+				bundletest.Mutate(t, b, func(v dyn.Value) (dyn.Value, error) {
+					return dyn.Set(v, "resources.jobs.foo.tasks[0].for_each_task.task.new_cluster.num_workers", dyn.V(*tc.numWorkers))
+				})
+			}
+
+			diags := bundle.ApplyReadOnly(ctx, bundle.ReadOnly(b), SingleNodeCluster())
+			assert.Empty(t, diags)
+		})
+	}
+}

bundle/config/validate/validate.go

@@ -36,6 +36,7 @@ func (v *validate) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagnostics
 		ValidateSyncPatterns(),
 		JobTaskClusterSpec(),
 		ValidateFolderPermissions(),
+		SingleNodeCluster(),
 	))
 }