From 358797fb4f5cdbf3f00479fda5572c5f7cdd991c Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Thu, 11 Sep 2025 16:32:29 +0200
Subject: [PATCH 1/6] move out comment examples

---
 ...luster_with_count.in.tf => comments.in.tf} |  9 ++--
 ...ster_with_count.out.tf => comments.out.tf} |  9 ++--
 .../testdata/clu2adv/free_cluster.in.tf       | 22 ++++++++
 .../testdata/clu2adv/free_cluster.out.tf      | 52 +++++++++++++++++++
 .../free_cluster_missing_attribute.in.tf      | 21 ++------
 5 files changed, 89 insertions(+), 24 deletions(-)
 rename internal/convert/testdata/clu2adv/{free_cluster_with_count.in.tf => comments.in.tf} (83%)
 rename internal/convert/testdata/clu2adv/{free_cluster_with_count.out.tf => comments.out.tf} (88%)
 create mode 100644 internal/convert/testdata/clu2adv/free_cluster.in.tf
 create mode 100644 internal/convert/testdata/clu2adv/free_cluster.out.tf

diff --git a/internal/convert/testdata/clu2adv/free_cluster_with_count.in.tf b/internal/convert/testdata/clu2adv/comments.in.tf
similarity index 83%
rename from internal/convert/testdata/clu2adv/free_cluster_with_count.in.tf
rename to internal/convert/testdata/clu2adv/comments.in.tf
index 4702169..d3f38e8 100644
--- a/internal/convert/testdata/clu2adv/free_cluster_with_count.in.tf
+++ b/internal/convert/testdata/clu2adv/comments.in.tf
@@ -1,7 +1,3 @@
-resource "resource1" "res1" {
-  name = "name1"
-}
-
 resource "mongodbatlas_cluster" "free_cluster" { # comment in the resource
   # comment in own line in the beginning
   count      = local.use_free_cluster ? 1 : 0
@@ -14,3 +10,8 @@ resource "mongodbatlas_cluster" "free_cluster" { # comment in the resource
   provider_instance_size_name = "M0"
   # comment in own line at the end happens before replication_specs
 }
+
+resource "another_resource" "res1" {
+  # comment in own line in the middle is not deleted in unprocessed resource
+  name = "name1"
+}
diff --git a/internal/convert/testdata/clu2adv/free_cluster_with_count.out.tf b/internal/convert/testdata/clu2adv/comments.out.tf
similarity index 88%
rename from internal/convert/testdata/clu2adv/free_cluster_with_count.out.tf
rename to internal/convert/testdata/clu2adv/comments.out.tf
index c7dbdbf..8a689a4 100644
--- a/internal/convert/testdata/clu2adv/free_cluster_with_count.out.tf
+++ b/internal/convert/testdata/clu2adv/comments.out.tf
@@ -1,7 +1,3 @@
-resource "resource1" "res1" {
-  name = "name1"
-}
-
 resource "mongodbatlas_advanced_cluster" "free_cluster" { # comment in the resource
   # comment in own line in the beginning
   count      = local.use_free_cluster ? 1 : 0
@@ -28,3 +24,8 @@ resource "mongodbatlas_advanced_cluster" "free_cluster" { # comment in the resou
   # Generated by atlas-cli-plugin-terraform.
   # Please review the changes and confirm that references to this resource are updated.
 }
+
+resource "another_resource" "res1" {
+  # comment in own line in the middle is not deleted in unprocessed resource
+  name = "name1"
+}
diff --git a/internal/convert/testdata/clu2adv/free_cluster.in.tf b/internal/convert/testdata/clu2adv/free_cluster.in.tf
new file mode 100644
index 0000000..a317811
--- /dev/null
+++ b/internal/convert/testdata/clu2adv/free_cluster.in.tf
@@ -0,0 +1,22 @@
+resource "mongodbatlas_cluster" "free_cluster" {
+  project_id                  = var.project_id
+  name                        = var.cluster_name
+  provider_name               = "TENANT"
+  backing_provider_name       = "AWS"
+  provider_region_name        = var.region
+  provider_instance_size_name = "M0"
+}
+
+resource "mongodbatlas_cluster" "count" {
+  count                       = local.use_free_cluster ? 1 : 0
+  project_id                  = var.project_id
+  name                        = var.cluster_name
+  provider_name               = "TENANT"
+  backing_provider_name       = "AWS"
+  provider_region_name        = var.region
+  provider_instance_size_name = "M0"
+}
+
+resource "another_resource" "res1" {
+  name = "name1"
+}
diff --git a/internal/convert/testdata/clu2adv/free_cluster.out.tf b/internal/convert/testdata/clu2adv/free_cluster.out.tf
new file mode 100644
index 0000000..9d40780
--- /dev/null
+++ b/internal/convert/testdata/clu2adv/free_cluster.out.tf
@@ -0,0 +1,52 @@
+resource "mongodbatlas_advanced_cluster" "free_cluster" {
+  project_id   = var.project_id
+  name         = var.cluster_name
+  cluster_type = "REPLICASET"
+  replication_specs = [
+    {
+      region_configs = [
+        {
+          priority              = 7
+          region_name           = var.region
+          provider_name         = "TENANT"
+          backing_provider_name = "AWS"
+          electable_specs = {
+            instance_size = "M0"
+          }
+        }
+      ]
+    }
+  ]
+
+  # Generated by atlas-cli-plugin-terraform.
+  # Please review the changes and confirm that references to this resource are updated.
+}
+
+resource "mongodbatlas_advanced_cluster" "count" {
+  count        = local.use_free_cluster ? 1 : 0
+  project_id   = var.project_id
+  name         = var.cluster_name
+  cluster_type = "REPLICASET"
+  replication_specs = [
+    {
+      region_configs = [
+        {
+          priority              = 7
+          region_name           = var.region
+          provider_name         = "TENANT"
+          backing_provider_name = "AWS"
+          electable_specs = {
+            instance_size = "M0"
+          }
+        }
+      ]
+    }
+  ]
+
+  # Generated by atlas-cli-plugin-terraform.
+  # Please review the changes and confirm that references to this resource are updated.
+}
+
+resource "another_resource" "res1" {
+  name = "name1"
+}
diff --git a/internal/convert/testdata/clu2adv/free_cluster_missing_attribute.in.tf b/internal/convert/testdata/clu2adv/free_cluster_missing_attribute.in.tf
index 2f17b21..50ed2c1 100644
--- a/internal/convert/testdata/clu2adv/free_cluster_missing_attribute.in.tf
+++ b/internal/convert/testdata/clu2adv/free_cluster_missing_attribute.in.tf
@@ -1,19 +1,8 @@
-resource "resource1" "res1" {
-  name = "name1"
-}
-
-resource "mongodbatlas_cluster" "free_cluster" { # comment in the resource
-  # comment in own line in the beginning
-  count      = local.use_free_cluster ? 1 : 0
-  project_id = var.project_id # inline comment kept
-  name       = var.cluster_name
-  # comment in own line in the middle is deleted
-  provider_name               = "TENANT" # inline comment for attribute moved is not kept
+resource "mongodbatlas_cluster" "free_cluster" {
+  project_id                  = var.project_id
+  name                        = var.cluster_name
+  provider_name               = "TENANT"
   provider_region_name        = var.region
   provider_instance_size_name = "M0"
-  # comment in own line at the end happens before replication_specs
-}
-
-data "mongodbatlas_cluster" "cluster2" {
-  name = "name4"
+  # missing backing_provider_name
 }

From 48eb5d056cf2342fe2aa9e990f2ce398bc505d38 Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Thu, 11 Sep 2025 16:43:59 +0200
Subject: [PATCH 2/6] failing tests with feature to implement

---
 .../testdata/clu2adv/free_cluster.in.tf       | 20 ++++++++
 .../testdata/clu2adv/free_cluster.out.tf      | 46 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/internal/convert/testdata/clu2adv/free_cluster.in.tf b/internal/convert/testdata/clu2adv/free_cluster.in.tf
index a317811..0e62d39 100644
--- a/internal/convert/testdata/clu2adv/free_cluster.in.tf
+++ b/internal/convert/testdata/clu2adv/free_cluster.in.tf
@@ -17,6 +17,26 @@ resource "mongodbatlas_cluster" "count" {
   provider_instance_size_name = "M0"
 }
 
+
+resource "mongodbatlas_cluster" "upgrade_from_free_cluster" {
+  # upgraded free cluster to dedicated
+  project_id                  = var.project_id
+  name                        = var.cluster_name
+  provider_name               = "AWS" # changed from TENANT to AWS
+  provider_instance_size_name = "M10" # changed from M0 to M10
+  # removed backing_provider_name = AWS"
+  provider_region_name = var.region
+}
+
+resource "mongodbatlas_cluster" "upgrade_from_free_cluster_with_variables" {
+  # upgraded free cluster to dedicated, using variables in all attributes
+  project_id                  = var.project_id
+  name                        = var.cluster_name
+  provider_name               = var.provider_name
+  provider_instance_size_name = var.instance_size
+  provider_region_name        = var.region
+}
+
 resource "another_resource" "res1" {
   name = "name1"
 }
diff --git a/internal/convert/testdata/clu2adv/free_cluster.out.tf b/internal/convert/testdata/clu2adv/free_cluster.out.tf
index 9d40780..7fece6a 100644
--- a/internal/convert/testdata/clu2adv/free_cluster.out.tf
+++ b/internal/convert/testdata/clu2adv/free_cluster.out.tf
@@ -47,6 +47,52 @@ resource "mongodbatlas_advanced_cluster" "count" {
   # Please review the changes and confirm that references to this resource are updated.
 }
 
+resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster" {
+  project_id   = var.project_id
+  name         = var.cluster_name
+  cluster_type = "REPLICASET"
+  replication_specs = [
+    {
+      region_configs = [
+        {
+          priority      = 7
+          region_name   = var.region
+          provider_name = "AWS"
+          electable_specs = {
+            instance_size = "M10"
+          }
+        }
+      ]
+    }
+  ]
+
+  # Generated by atlas-cli-plugin-terraform.
+  # Please review the changes and confirm that references to this resource are updated.
+}
+
+resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster_with_variables" {
+  project_id   = var.project_id
+  name         = var.cluster_name
+  cluster_type = "REPLICASET"
+  replication_specs = [
+    {
+      region_configs = [
+        {
+          priority      = 7
+          region_name   = var.region
+          provider_name = var.provider_name
+          electable_specs = {
+            instance_size = var.instance_size
+          }
+        }
+      ]
+    }
+  ]
+
+  # Generated by atlas-cli-plugin-terraform.
+  # Please review the changes and confirm that references to this resource are updated.
+}
+
 resource "another_resource" "res1" {
   name = "name1"
 }

From a80db2417f9a76f694da9b2860ac756b78654a91 Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Thu, 11 Sep 2025 16:47:33 +0200
Subject: [PATCH 3/6] free cluster if providerName == "TENANT"

---
 internal/convert/clu2adv.go                                 | 4 ++--
 internal/convert/const.go                                   | 1 +
 internal/convert/testdata/adv2v2/errors.json                | 1 -
 .../convert/testdata/adv2v2/missing_replication_specs.in.tf | 6 ------
 4 files changed, 3 insertions(+), 9 deletions(-)
 delete mode 100644 internal/convert/testdata/adv2v2/missing_replication_specs.in.tf

diff --git a/internal/convert/clu2adv.go b/internal/convert/clu2adv.go
index 914ef64..9ad5d35 100644
--- a/internal/convert/clu2adv.go
+++ b/internal/convert/clu2adv.go
@@ -69,8 +69,8 @@ func convertResource(block *hclwrite.Block) (bool, error) {
 }
 
 func isFreeTierCluster(resourceb *hclwrite.Body) bool {
-	d, _ := getDynamicBlock(resourceb, nRepSpecs, true)
-	return resourceb.FirstMatchingBlock(nRepSpecs, nil) == nil && !d.IsPresent()
+	providerName, _ := hcl.GetAttrString(resourceb.GetAttribute(nProviderName))
+	return providerName == nTenant
 }
 
 func convertDataSource(block *hclwrite.Block) bool {
diff --git a/internal/convert/const.go b/internal/convert/const.go
index 350f210..74670c5 100644
--- a/internal/convert/const.go
+++ b/internal/convert/const.go
@@ -80,4 +80,5 @@ const (
 	nSpec                       = "spec"
 	nFailIndexKeyTooLong        = "fail_index_key_too_long"
 	nDefaultReadConcern         = "default_read_concern"
+	nTenant                     = "TENANT"
 )
diff --git a/internal/convert/testdata/adv2v2/errors.json b/internal/convert/testdata/adv2v2/errors.json
index a744913..e956619 100644
--- a/internal/convert/testdata/adv2v2/errors.json
+++ b/internal/convert/testdata/adv2v2/errors.json
@@ -1,7 +1,6 @@
 {
 	"configuration_file_error": "failed to parse Terraform config file",
 	"replication_specs_missing_region_configs": "replication_specs must have at least one region_configs",
-	"missing_replication_specs": "must have at least one replication_specs",
 	"dynamic_unsupported_tag": "dynamic blocks are not supported for advanced_configuration",
 	"dynamic_regions_config_invalid_multiple_blocks": "dynamic block must be the only block",
 	"dynamic_replication_specs_invalid_multiple_blocks": "dynamic block must be the only block",
diff --git a/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf b/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf
deleted file mode 100644
index 247a176..0000000
--- a/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf
+++ /dev/null
@@ -1,6 +0,0 @@
-resource "mongodbatlas_advanced_cluster" "no_replication_specs" {
-  # missing replication_specs
-  project_id   = var.project_id
-  name         = "cluster-multi-region"
-  cluster_type = "REPLICASET"
-}

From 77d12d0724cbda9ad7de355023f67a4f214c8bf0 Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Thu, 11 Sep 2025 18:47:31 +0200
Subject: [PATCH 4/6] implementation

---
 internal/convert/clu2adv.go                   | 28 +++++++++++++++++-
 internal/convert/const.go                     | 29 ++++++++++---------
 .../testdata/clu2adv/free_cluster.out.tf      |  5 ++++
 3 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/internal/convert/clu2adv.go b/internal/convert/clu2adv.go
index 9ad5d35..9187f63 100644
--- a/internal/convert/clu2adv.go
+++ b/internal/convert/clu2adv.go
@@ -107,6 +107,32 @@ func fillMovedBlocks(body *hclwrite.Body, moveLabels []string) {
 	}
 }
 
+// createDefaultReplicationSpec creates a default replication_specs for clusters without any
+// (e.g. upgraded from free tier).
+func createDefaultReplicationSpec(resourceb *hclwrite.Body, root attrVals) error {
+	resourceb.SetAttributeValue(nClusterType, cty.StringVal(valClusterType))
+	configb := hclwrite.NewEmptyFile().Body()
+	hcl.SetAttrInt(configb, nPriority, valMaxPriority)
+	if err := hcl.MoveAttr(resourceb, configb, nRegionNameSrc, nRegionName, errRoot); err != nil {
+		return err
+	}
+	if providerNameTokens, found := root.req[nProviderName]; found {
+		configb.SetAttributeRaw(nProviderName, providerNameTokens)
+	}
+
+	electableSpecb := hclwrite.NewEmptyFile().Body()
+	if instanceSizeTokens, found := root.req[nInstanceSizeSrc]; found {
+		electableSpecb.SetAttributeRaw(nInstanceSize, instanceSizeTokens)
+	}
+	electableSpecb.SetAttributeValue(nNodeCount, cty.NumberIntVal(valDefaultNodeCount))
+	configb.SetAttributeRaw(nElectableSpecs, hcl.TokensObject(electableSpecb))
+
+	repSpecsb := hclwrite.NewEmptyFile().Body()
+	repSpecsb.SetAttributeRaw(nConfig, hcl.TokensArraySingle(configb))
+	resourceb.SetAttributeRaw(nRepSpecs, hcl.TokensArraySingle(repSpecsb))
+	return nil
+}
+
 // fillFreeTierCluster is the entry point to convert clusters in free tier
 func processFreeTierCluster(resourceb *hclwrite.Body) error {
 	resourceb.SetAttributeValue(nClusterType, cty.StringVal(valClusterType))
@@ -160,7 +186,7 @@ func processRepSpecsCluster(resourceb *hclwrite.Body, root attrVals) error {
 	}
 	repSpecBlocks := collectBlocks(resourceb, nRepSpecs)
 	if len(repSpecBlocks) == 0 {
-		return fmt.Errorf("must have at least one replication_specs")
+		return createDefaultReplicationSpec(resourceb, root)
 	}
 	dConfig, err := processConfigsWithDynamicRegion(repSpecBlocks[0].Body(), root, false)
 	if err != nil {
diff --git a/internal/convert/const.go b/internal/convert/const.go
index 74670c5..2337ea6 100644
--- a/internal/convert/const.go
+++ b/internal/convert/const.go
@@ -1,20 +1,21 @@
 package convert
 
 const (
-	resourceType     = "resource"
-	dataSourceType   = "data"
-	cluster          = "mongodbatlas_cluster"
-	advCluster       = "mongodbatlas_advanced_cluster"
-	clusterPlural    = "mongodbatlas_clusters"
-	advClusterPlural = "mongodbatlas_advanced_clusters"
-	valClusterType   = "REPLICASET"
-	valMaxPriority   = 7
-	valMinPriority   = 0
-	errFreeCluster   = "free cluster (because no " + nRepSpecs + ")"
-	errRepSpecs      = "setting " + nRepSpecs
-	errPriority      = "setting " + nPriority
-	errNumShards     = "setting " + nNumShards
-	errRoot          = "setting root attributes"
+	resourceType        = "resource"
+	dataSourceType      = "data"
+	cluster             = "mongodbatlas_cluster"
+	advCluster          = "mongodbatlas_advanced_cluster"
+	clusterPlural       = "mongodbatlas_clusters"
+	advClusterPlural    = "mongodbatlas_advanced_clusters"
+	valClusterType      = "REPLICASET"
+	valMaxPriority      = 7
+	valMinPriority      = 0
+	valDefaultNodeCount = 3
+	errFreeCluster      = "free cluster (because no " + nRepSpecs + ")"
+	errRepSpecs         = "setting " + nRepSpecs
+	errPriority         = "setting " + nPriority
+	errNumShards        = "setting " + nNumShards
+	errRoot             = "setting root attributes"
 
 	commentGeneratedBy       = "Generated by atlas-cli-plugin-terraform."
 	commentConfirmReferences = "Please review the changes and confirm that references to this resource are updated."
diff --git a/internal/convert/testdata/clu2adv/free_cluster.out.tf b/internal/convert/testdata/clu2adv/free_cluster.out.tf
index 7fece6a..6cd06ee 100644
--- a/internal/convert/testdata/clu2adv/free_cluster.out.tf
+++ b/internal/convert/testdata/clu2adv/free_cluster.out.tf
@@ -47,7 +47,9 @@ resource "mongodbatlas_advanced_cluster" "count" {
   # Please review the changes and confirm that references to this resource are updated.
 }
 
+
 resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster" {
+  # upgraded free cluster to dedicated
   project_id   = var.project_id
   name         = var.cluster_name
   cluster_type = "REPLICASET"
@@ -60,6 +62,7 @@ resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster" {
           provider_name = "AWS"
           electable_specs = {
             instance_size = "M10"
+            node_count    = 3
           }
         }
       ]
@@ -71,6 +74,7 @@ resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster" {
 }
 
 resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster_with_variables" {
+  # upgraded free cluster to dedicated, using variables in all attributes
   project_id   = var.project_id
   name         = var.cluster_name
   cluster_type = "REPLICASET"
@@ -83,6 +87,7 @@ resource "mongodbatlas_advanced_cluster" "upgrade_from_free_cluster_with_variabl
           provider_name = var.provider_name
           electable_specs = {
             instance_size = var.instance_size
+            node_count    = 3
           }
         }
       ]

From 8f784c3969f1458f80d39f256bd48b9e7383bc69 Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Thu, 11 Sep 2025 18:54:22 +0200
Subject: [PATCH 5/6] undo changes in adv2v2

---
 internal/convert/testdata/adv2v2/errors.json                | 1 +
 .../convert/testdata/adv2v2/missing_replication_specs.in.tf | 6 ++++++
 2 files changed, 7 insertions(+)
 create mode 100644 internal/convert/testdata/adv2v2/missing_replication_specs.in.tf

diff --git a/internal/convert/testdata/adv2v2/errors.json b/internal/convert/testdata/adv2v2/errors.json
index e956619..a744913 100644
--- a/internal/convert/testdata/adv2v2/errors.json
+++ b/internal/convert/testdata/adv2v2/errors.json
@@ -1,6 +1,7 @@
 {
 	"configuration_file_error": "failed to parse Terraform config file",
 	"replication_specs_missing_region_configs": "replication_specs must have at least one region_configs",
+	"missing_replication_specs": "must have at least one replication_specs",
 	"dynamic_unsupported_tag": "dynamic blocks are not supported for advanced_configuration",
 	"dynamic_regions_config_invalid_multiple_blocks": "dynamic block must be the only block",
 	"dynamic_replication_specs_invalid_multiple_blocks": "dynamic block must be the only block",
diff --git a/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf b/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf
new file mode 100644
index 0000000..247a176
--- /dev/null
+++ b/internal/convert/testdata/adv2v2/missing_replication_specs.in.tf
@@ -0,0 +1,6 @@
+resource "mongodbatlas_advanced_cluster" "no_replication_specs" {
+  # missing replication_specs
+  project_id   = var.project_id
+  name         = "cluster-multi-region"
+  cluster_type = "REPLICASET"
+}

From 7331af6dd96998b1a25c5fde025ceca6d5537667 Mon Sep 17 00:00:00 2001
From: Leo Antoli <430982+lantoli@users.noreply.github.com>
Date: Fri, 12 Sep 2025 07:06:18 +0200
Subject: [PATCH 6/6] rename

---
 internal/convert/clu2adv.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/internal/convert/clu2adv.go b/internal/convert/clu2adv.go
index 9187f63..63862ee 100644
--- a/internal/convert/clu2adv.go
+++ b/internal/convert/clu2adv.go
@@ -107,9 +107,9 @@ func fillMovedBlocks(body *hclwrite.Body, moveLabels []string) {
 	}
 }
 
-// createDefaultReplicationSpec creates a default replication_specs for clusters without any
+// createDefaultRepSpec creates a default replication_specs for clusters without any
 // (e.g. upgraded from free tier).
-func createDefaultReplicationSpec(resourceb *hclwrite.Body, root attrVals) error {
+func createDefaultRepSpec(resourceb *hclwrite.Body, root attrVals) error {
 	resourceb.SetAttributeValue(nClusterType, cty.StringVal(valClusterType))
 	configb := hclwrite.NewEmptyFile().Body()
 	hcl.SetAttrInt(configb, nPriority, valMaxPriority)
@@ -186,7 +186,7 @@ func processRepSpecsCluster(resourceb *hclwrite.Body, root attrVals) error {
 	}
 	repSpecBlocks := collectBlocks(resourceb, nRepSpecs)
 	if len(repSpecBlocks) == 0 {
-		return createDefaultReplicationSpec(resourceb, root)
+		return createDefaultRepSpec(resourceb, root)
 	}
 	dConfig, err := processConfigsWithDynamicRegion(repSpecBlocks[0].Body(), root, false)
 	if err != nil {