github_repository_custom_property: avoid panic on empty property_value

github/resource_github_repository_custom_property.go

@@ -69,6 +69,9 @@ func resourceGithubRepositoryCustomPropertyCreate(d *schema.ResourceData, meta a
 	// The propertyValue can either be a list of strings or a string
 	switch propertyType {
 	case github.PropertyValueTypeString, github.PropertyValueTypeSingleSelect, github.PropertyValueTypeURL, github.PropertyValueTypeTrueFalse:
+		if len(propertyValue) == 0 {
+			return fmt.Errorf("property_value must contain at least one element for property_type %q", propertyType)
+		}
 		customProperty.Value = propertyValue[0]
 	case github.PropertyValueTypeMultiSelect:
 		customProperty.Value = propertyValue

github/resource_github_repository_custom_property_unit_test.go

@@ -0,0 +1,50 @@
+package github
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/google/go-github/v85/github"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+// TestResourceGithubRepositoryCustomPropertyCreate_EmptyValueRejectsCleanly
+// pins the panic guard for #3358: when property_value resolves to an empty
+// list at apply time (which can happen despite the schema's MinItems=1 when
+// the value comes from a dynamic block whose source is empty), the Create
+// path used to index propertyValue[0] and crash the provider with
+// "index out of range [0] with length 0". The fix returns a clear error
+// for the single-value property types instead. This unit test reaches that
+// branch without going through the GitHub API by passing a nil v3client
+// in the meta, the guard fires before any client call.
+func TestResourceGithubRepositoryCustomPropertyCreate_EmptyValueRejectsCleanly(t *testing.T) {
+	singleValueTypes := []github.PropertyValueType{
+		github.PropertyValueTypeString,
+		github.PropertyValueTypeSingleSelect,
+		github.PropertyValueTypeURL,
+		github.PropertyValueTypeTrueFalse,
+	}
+
+	res := resourceGithubRepositoryCustomProperty()
+
+	for _, pt := range singleValueTypes {
+		t.Run(string(pt), func(t *testing.T) {
+			d := schema.TestResourceDataRaw(t, res.Schema, map[string]any{
+				"repository":     "some-repo",
+				"property_name":  "test-property",
+				"property_type":  string(pt),
+				"property_value": []any{},
+			})
+
+			meta := &Owner{name: "test-owner"}
+			err := resourceGithubRepositoryCustomPropertyCreate(d, meta)
+
+			if err == nil {
+				t.Fatalf("expected error for empty property_value with type %q, got nil", pt)
+			}
+			if !strings.Contains(err.Error(), "property_value") {
+				t.Errorf("expected error to mention property_value, got: %v", err)
+			}
+		})
+	}
+}