feat: add validation for cron spec

Author: evgeniy-scherbina

provider/workspace_preset.go

@@ -3,13 +3,17 @@ package provider
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
 	"github.com/mitchellh/mapstructure"
+	rbcron "github.com/robfig/cron/v3"
 )
 
+var PrebuildsCRONParser = rbcron.NewParser(rbcron.Minute | rbcron.Hour | rbcron.Dom | rbcron.Month | rbcron.Dow)
+
 type WorkspacePreset struct {
 	Name       string            `mapstructure:"name"`
 	Parameters map[string]string `mapstructure:"parameters"`
@@ -149,6 +153,21 @@ func workspacePresetDataSource() *schema.Resource {
 												"cron": {
 													Type:     schema.TypeString,
 													Required: true,
+													ValidateFunc: func(val interface{}, key string) ([]string, []error) {
+														cronSpec := val.(string)
+
+														err := validatePrebuildsCronSpec(cronSpec)
+														if err != nil {
+															return nil, []error{fmt.Errorf("cron spec failed validation: %w", err)}
+														}
+
+														_, err = PrebuildsCRONParser.Parse(cronSpec)
+														if err != nil {
+															return nil, []error{fmt.Errorf("failed to parse cron spec: %w", err)}
+														}
+
+														return nil, nil
+													},
 												},
 												"instances": {
 													Type:     schema.TypeInt,
@@ -166,3 +185,16 @@ func workspacePresetDataSource() *schema.Resource {
 		},
 	}
 }
+
+// validatePrebuildsCronSpec ensures that the minute, day-of-month and month options of spec are all set to *
+func validatePrebuildsCronSpec(spec string) error {
+	parts := strings.Fields(spec)
+	if len(parts) != 5 {
+		return fmt.Errorf("cron specification should consist of 5 fields")
+	}
+	if parts[0] != "*" || parts[2] != "*" || parts[3] != "*" {
+		return fmt.Errorf("minute, day-of-month and month should be *")
+	}
+
+	return nil
+}

provider/workspace_preset_test.go

@@ -426,6 +426,42 @@ func TestWorkspacePreset(t *testing.T) {
 				return nil
 			},
 		},
+		{
+			Name: "Prebuilds is set with an autoscaling.schedule field, but the cron includes a disallowed minute field",
+			Config: `
+			data "coder_workspace_preset" "preset_1" {
+				name = "preset_1"
+				prebuilds {
+					instances = 1
+					autoscaling {
+						timezone = "UTC"
+						schedule {
+							cron = "30 8-18 * * 1-5"
+							instances = "1"
+					  	}
+					}
+				}
+			}`,
+			ExpectError: regexp.MustCompile(`cron spec failed validation: minute, day-of-month and month should be *`),
+		},
+		{
+			Name: "Prebuilds is set with an autoscaling.schedule field, but the cron hour field is invalid",
+			Config: `
+			data "coder_workspace_preset" "preset_1" {
+				name = "preset_1"
+				prebuilds {
+					instances = 1
+					autoscaling {
+						timezone = "UTC"
+						schedule {
+							cron = "* 25-26 * * 1-5"
+							instances = "1"
+					  	}
+					}
+				}
+			}`,
+			ExpectError: regexp.MustCompile(`failed to parse cron spec: end of range \(26\) above maximum \(23\): 25-26`),
+		},
 	}
 
 	for _, testcase := range testcases {