add comment for priority loop

Author: lantoli

internal/convert/convert.go

@@ -33,6 +33,7 @@ const (
 	commentConfirmReferences = "Please review the changes and confirm that references to this resource are updated."
 	commentMovedBlock        = "Moved blocks"
 	commentRemovedOld        = "Note: Remember to remove or comment out the old cluster definitions."
+	commentPriorityFor       = "Regions must be sorted by priority in descending order."
 )
 
 var (
@@ -326,7 +327,8 @@ func fillRegionConfigsDynamicBlock(specbSrc *hclwrite.Body, root attrVals) (dyna
 	if err != nil {
 		return dynamicBlock{}, err
 	}
-	priorityFor := hcl.TokensFromExpr(fmt.Sprintf("for %s in range(%d, %d, -1) : ", nPriority, valMaxPriority, valMinPriority))
+	priorityFor := hcl.TokensComment(commentPriorityFor)
+	priorityFor = append(priorityFor, hcl.TokensFromExpr(fmt.Sprintf("for %s in range(%d, %d, -1) : ", nPriority, valMaxPriority, valMinPriority))...)
 	priorityFor = append(priorityFor, regionFor...)
 	repSpecb.SetAttributeRaw(nConfig, hcl.TokensFuncFlatten(priorityFor))
 

internal/convert/testdata/clu2adv/dynamic_regions_config_auto_scaling.out.tf

@@ -17,6 +17,7 @@ resource "mongodbatlas_advanced_cluster" "cluster" {
   replication_specs = [
     for i in range(var.replication_specs.num_shards) : {
       region_configs = flatten([
+        # Regions must be sorted by priority in descending order.
         for priority in range(7, 0, -1) : [
           for region in var.replication_specs.regions_config : {
             provider_name = var.provider_name

internal/convert/testdata/clu2adv/dynamic_regions_config_basic.out.tf

@@ -6,6 +6,7 @@ resource "mongodbatlas_advanced_cluster" "dynamic_regions_config" {
     for i in range(var.replication_specs.num_shards) : {
       zone_name = var.zone_name
       region_configs = flatten([
+        # Regions must be sorted by priority in descending order.
         for priority in range(7, 0, -1) : [
           for region in var.replication_specs.regions_config : {
             provider_name = "AWS"

internal/hcl/hcl.go

@@ -134,10 +134,14 @@ func RemoveLeadingNewline(tokens hclwrite.Tokens) hclwrite.Tokens {
 
 // AppendComment adds a comment at the end of the body.
 func AppendComment(body *hclwrite.Body, comment string) {
-	tokens := hclwrite.Tokens{
+	body.AppendUnstructuredTokens(TokensComment(comment))
+}
+
+// TokensComment returns the tokens for a comment.
+func TokensComment(comment string) hclwrite.Tokens {
+	return hclwrite.Tokens{
 		&hclwrite.Token{Type: hclsyntax.TokenComment, Bytes: []byte("# " + comment + "\n")},
 	}
-	body.AppendUnstructuredTokens(tokens)
 }
 
 // GetParser returns a parser for the given config and checks HCL syntax is valid