Support CSV indices in SLM policy definitions

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Fix authentication for fleet API (using ApiKey instead of Bearer keyword) ([#576](https://github.com/elastic/terraform-provider-elasticstack/pull/576))
 - Ensure all Kibana resources use the supplied `ca_certs` value. ([#585](https://github.com/elastic/terraform-provider-elasticstack/pull/585))
+- Don't panic when SLM indices are specified as a CSV string rather than an array ([#593](https://github.com/elastic/terraform-provider-elasticstack/pull/593))
 
 ## [0.11.1] - 2024-02-17
 

internal/models/models.go

@@ -1,6 +1,9 @@
 package models
 
 import (
+	"encoding/json"
+	"errors"
+	"strings"
 	"time"
 )
 
@@ -194,12 +197,38 @@ type SnapshotPolicyConfig struct {
 	ExpandWildcards    *string                `json:"expand_wildcards,omitempty"`
 	IgnoreUnavailable  *bool                  `json:"ignore_unavailable,omitempty"`
 	IncludeGlobalState *bool                  `json:"include_global_state,omitempty"`
-	Indices            []string               `json:"indices,omitempty"`
+	Indices            StringSliceOrCSV       `json:"indices,omitempty"`
 	FeatureStates      []string               `json:"feature_states,omitempty"`
 	Metadata           map[string]interface{} `json:"metadata,omitempty"`
 	Partial            *bool                  `json:"partial,omitempty"`
 }
 
+type StringSliceOrCSV []string
+
+var ErrInvalidStringSliceOrCSV = errors.New("expected array of strings, or a csv string")
+
+func (i *StringSliceOrCSV) UnmarshalJSON(data []byte) error {
+	// Ignore null, like in the main JSON package.
+	if string(data) == "null" || string(data) == `""` {
+		return nil
+	}
+
+	// First try to parse as an array
+	var sliceResult []string
+	if err := json.Unmarshal(data, &sliceResult); err == nil {
+		*i = StringSliceOrCSV(sliceResult)
+		return nil
+	}
+
+	var stringResult string
+	if err := json.Unmarshal(data, &stringResult); err == nil {
+		*i = StringSliceOrCSV(strings.Split(stringResult, ","))
+		return nil
+	}
+
+	return ErrInvalidStringSliceOrCSV
+}
+
 type Index struct {
 	Name     string                 `json:"-"`
 	Aliases  map[string]IndexAlias  `json:"aliases,omitempty"`

internal/models/models_test.go

@@ -0,0 +1,56 @@
+package models
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestStringSliceOrCSV_UnmarshalJSON9(t *testing.T) {
+	tests := []struct {
+		name           string
+		jsonString     string
+		expectedResult StringSliceOrCSV
+		expectedErr    error
+	}{
+		{
+			name:           "should handle json arrays",
+			jsonString:     `["a", "b", "c"]`,
+			expectedResult: StringSliceOrCSV{"a", "b", "c"},
+		},
+		{
+			name:           "should handle csv strings",
+			jsonString:     `"a,b,c"`,
+			expectedResult: StringSliceOrCSV{"a", "b", "c"},
+		},
+		{
+			name:       "should handle explicit nulls",
+			jsonString: `null`,
+		},
+		{
+			name:       "should handle empty strings",
+			jsonString: `""`,
+		},
+		{
+			name:        "should fail on invalid data",
+			jsonString:  "true",
+			expectedErr: ErrInvalidStringSliceOrCSV,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var actualModel StringSliceOrCSV
+			err := json.Unmarshal([]byte(tt.jsonString), &actualModel)
+
+			if tt.expectedErr == nil {
+				require.NoError(t, err)
+			} else {
+				require.ErrorIs(t, err, tt.expectedErr)
+			}
+
+			require.Equal(t, tt.expectedResult, actualModel)
+		})
+	}
+}