PythonMutator: preserve normalize diagnostics (#1735)

## Changes
Preserve diagnostics if there are any errors or warnings when
PythonMutator normalizes output. If anything goes wrong during
conversion, diagnostics contain the relevant location and path.

## Tests
Unit tests

bundle/config/mutator/python/python_mutator.go

@@ -205,10 +205,8 @@ func (m *pythonMutator) runPythonMutator(ctx context.Context, cacheDir string, r
 		return dyn.InvalidValue, diag.Errorf("failed to load diagnostics: %s", pythonDiagnosticsErr)
 	}
 
-	output, err := loadOutputFile(rootPath, outputPath)
+	output, outputDiags := loadOutputFile(rootPath, outputPath)
-	if err != nil {
+	pythonDiagnostics = pythonDiagnostics.Extend(outputDiags)
-		return dyn.InvalidValue, diag.Errorf("failed to load Python mutator output: %s", err)
-	}
 
 	// we pass through pythonDiagnostic because it contains warnings
 	return output, pythonDiagnostics
@@ -225,10 +223,10 @@ func writeInputFile(inputPath string, input dyn.Value) error {
 	return os.WriteFile(inputPath, rootConfigJson, 0600)
 }
 
-func loadOutputFile(rootPath string, outputPath string) (dyn.Value, error) {
+func loadOutputFile(rootPath string, outputPath string) (dyn.Value, diag.Diagnostics) {
 	outputFile, err := os.Open(outputPath)
 	if err != nil {
-		return dyn.InvalidValue, fmt.Errorf("failed to open output file: %w", err)
+		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to open output file: %w", err))
 	}
 
 	defer outputFile.Close()
@@ -243,27 +241,34 @@ func loadOutputFile(rootPath string, outputPath string) (dyn.Value, error) {
 	// for that, we pass virtualPath instead of outputPath as file location
 	virtualPath, err := filepath.Abs(filepath.Join(rootPath, "__generated_by_pydabs__.yml"))
 	if err != nil {
-		return dyn.InvalidValue, fmt.Errorf("failed to get absolute path: %w", err)
+		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to get absolute path: %w", err))
 	}
 
 	generated, err := yamlloader.LoadYAML(virtualPath, outputFile)
 	if err != nil {
-		return dyn.InvalidValue, fmt.Errorf("failed to parse output file: %w", err)
+		return dyn.InvalidValue, diag.FromErr(fmt.Errorf("failed to parse output file: %w", err))
 	}
 
-	normalized, diagnostic := convert.Normalize(config.Root{}, generated)
+	return strictNormalize(config.Root{}, generated)
-	if diagnostic.Error() != nil {
-		return dyn.InvalidValue, fmt.Errorf("failed to normalize output: %w", diagnostic.Error())
 }
 
+func strictNormalize(dst any, generated dyn.Value) (dyn.Value, diag.Diagnostics) {
+	normalized, diags := convert.Normalize(dst, generated)
+
 	// warnings shouldn't happen because output should be already normalized
 	// when it happens, it's a bug in the mutator, and should be treated as an error
 
-	for _, d := range diagnostic.Filter(diag.Warning) {
+	strictDiags := diag.Diagnostics{}
-		return dyn.InvalidValue, fmt.Errorf("failed to normalize output: %s", d.Summary)
+
+	for _, d := range diags {
+		if d.Severity == diag.Warning {
+			d.Severity = diag.Error
 		}
 
-	return normalized, nil
+		strictDiags = strictDiags.Append(d)
+	}
+
+	return normalized, strictDiags
 }
 
 // loadDiagnosticsFile loads diagnostics from a file.

bundle/config/mutator/python/python_mutator_test.go

@@ -10,6 +10,8 @@ import (
 	"runtime"
 	"testing"
 
+	"github.com/databricks/cli/libs/dyn/convert"
+
 	"github.com/databricks/cli/libs/dyn/merge"
 
 	"github.com/databricks/cli/bundle/env"
@@ -255,7 +257,7 @@ func TestPythonMutator_badOutput(t *testing.T) {
 	mutator := PythonMutator(PythonMutatorPhaseLoad)
 	diag := bundle.Apply(ctx, b, mutator)
 
-	assert.EqualError(t, diag.Error(), "failed to load Python mutator output: failed to normalize output: unknown field: unknown_property")
+	assert.EqualError(t, diag.Error(), "unknown field: unknown_property")
 }
 
 func TestPythonMutator_disabled(t *testing.T) {
@@ -546,6 +548,22 @@ func TestInterpreterPath(t *testing.T) {
 	}
 }
 
+func TestStrictNormalize(t *testing.T) {
+	// NB: there is no way to trigger diag.Error, so we don't test it
+
+	type TestStruct struct {
+		A int `json:"a"`
+	}
+
+	value := dyn.NewValue(map[string]dyn.Value{"A": dyn.NewValue("abc", nil)}, nil)
+
+	_, diags := convert.Normalize(TestStruct{}, value)
+	_, strictDiags := strictNormalize(TestStruct{}, value)
+
+	assert.False(t, diags.HasError())
+	assert.True(t, strictDiags.HasError())
+}
+
 func withProcessStub(t *testing.T, args []string, output string, diagnostics string) context.Context {
 	ctx := context.Background()
 	ctx, stub := process.WithStub(ctx)