providers: ignore "constraint providers"

Certain providers of Terraform are meant to specify constraint rather
than locations/regions, etc. In cases where a provider doesn't contain a
valid location, it will not be added to the list of valid providers, if
no providers at all exist an error will be returned mentioning it.

CHANGELOG.md

@@ -1,5 +1,19 @@
 ## [Unreleased]
 
+### Fixed
+
+- Ignore providers related to constraints
+  ([Pull #58](https://github.com/cycloidio/terracost/pull/58))
+- Unexpected error when using supported/unsupported providers
+  ([Pull #56](https://github.com/cycloidio/terracost/pull/56))
+
+## [0.4.3] _2021-08-30_
+
+### Changed
+
+- Improved error returned when using unknown providers, empty terraform
+  ([Pull #55](https://github.com/cycloidio/terracost/pull/55))
+
 ## [0.4.2] _2021-07-22_
 
 ### Fixed

aws/terraform_provider.go

@@ -13,7 +13,11 @@ const RegistryName = "registry.terraform.io/hashicorp/aws"
 var TerraformProviderInitializer = terraform.ProviderInitializer{
 	MatchNames: []string{ProviderName, RegistryName},
 	Provider: func(values map[string]string) (terraform.Provider, error) {
-		regCode := region.Code(values["region"])
+		r, ok := values["region"]
+		if !ok {
+			return nil, nil
+		}
+		regCode := region.Code(r)
 		return awstf.NewProvider(ProviderName, regCode)
 	},
 }

e2e/aws_estimation_test.go

@@ -28,7 +28,11 @@ import (
 var terraformAWSTestProviderInitializer = terraform.ProviderInitializer{
 	MatchNames: []string{"aws", "aws-test"},
 	Provider: func(config map[string]string) (terraform.Provider, error) {
-		regCode := region.Code(config["region"])
+		r, ok := config["region"]
+		if !ok {
+			return nil, nil
+		}
+		regCode := region.Code(r)
 		return awstf.NewProvider("aws-test", regCode)
 	},
 }
@@ -41,7 +45,11 @@ var terraformAWSTestProviderInitializer = terraform.ProviderInitializer{
 var terraformAWSProviderInitializer = terraform.ProviderInitializer{
 	MatchNames: []string{"aws"},
 	Provider: func(config map[string]string) (terraform.Provider, error) {
-		regCode := region.Code(config["region"])
+		r, ok := config["region"]
+		if !ok {
+			return nil, nil
+		}
+		regCode := region.Code(r)
 		return awstf.NewProvider("aws", regCode)
 	},
 }
@@ -227,6 +235,15 @@ func TestAWSEstimation(t *testing.T) {
 			}
 			assert.Equal(t, expected, rd.Errors())
 		})
+		t.Run("NoProvider", func(t *testing.T) {
+			f, err := os.Open("../testdata/aws/terraform-plan-noprovider.json")
+			require.NoError(t, err)
+			defer f.Close()
+
+			plan, err := costestimation.EstimateTerraformPlan(ctx, backend, f, terraformAWSTestProviderInitializer)
+			require.Error(t, err, terraform.ErrNoProviders)
+			require.Nil(t, plan)
+		})
 	})
 	t.Run("HCL", func(t *testing.T) {
 		t.Run("Success", func(t *testing.T) {

terraform/error.go

@@ -6,4 +6,5 @@ import "errors"
 var (
 	ErrNoQueries       = errors.New("no terraform entities found, looks empty")
 	ErrNoKnownProvider = errors.New("terraform providers are not yet supported")
+	ErrNoProviders     = errors.New("no valid providers found")
 )

terraform/plan.go

@@ -45,11 +45,7 @@ func (p *Plan) ExtractPlannedQueries() ([]query.Resource, error) {
 	if err != nil {
 		return nil, fmt.Errorf("unable to extract planned queries: %w", err)
 	}
-	queries, err := p.extractQueries(p.PlannedValues, providers), nil
-	if err != nil {
-		return nil, err
-	}
-	return queries, nil
+	return p.extractQueries(p.PlannedValues, providers), nil
 }
 
 // ExtractPriorQueries extracts a query.Resource slice from the `prior_state` part of the Plan.
@@ -77,9 +73,14 @@ func (p *Plan) extractProviders() (map[string]Provider, error) {
 			if err != nil {
 				return nil, err
 			}
-			providers[name] = prov
+			if prov != nil {
+				providers[name] = prov
+			}
 		}
 	}
+	if len(providers) == 0 {
+		return nil, ErrNoProviders
+	}
 	return providers, nil
 }
 

terraform/provider.go

@@ -24,6 +24,7 @@ type ProviderInitializer struct {
 	MatchNames []string
 
 	// Provider initializes a Provider instance given the values defined in the config and returns it.
+	// If a provider must be ignored (related to version constraints, etc), please return nil to avoid using it.
 	Provider func(values map[string]string) (Provider, error)
 }
 

testdata/aws/terraform-plan-noprovider.json

@@ -0,0 +1,190 @@
+{
+  "format_version": "0.1",
+  "terraform_version": "0.14.9",
+  "planned_values": {
+    "root_module": {
+      "child_modules": [
+        {
+          "resources": [
+            {
+              "address": "module.instance.aws_instance.example",
+              "mode": "managed",
+              "type": "aws_instance",
+              "name": "example",
+              "provider_name": "registry.terraform.io/hashicorp/aws",
+              "schema_version": 1,
+              "values": {
+                "ami": "ami-2757f631",
+                "availability_zone": "us-east-1e",
+                "instance_type": "t2.xlarge",
+                "root_block_device": [
+                  {
+                    "iops": 100,
+                    "volume_size": 8,
+                    "volume_type": "gp2"
+                  }
+                ],
+                "tenancy": "default"
+              }
+            }
+          ],
+          "address": "module.instance"
+        }
+      ],
+      "resources": [
+        {
+          "address": "aws_lb.example",
+          "mode": "managed",
+          "type": "aws_lb",
+          "name": "example",
+          "provider_name": "registry.terraform.io/hashicorp/aws",
+          "schema_version": 0,
+          "values": {
+            "load_balancer_type": "application"
+          }
+        }
+      ]
+    }
+  },
+  "resource_changes": [
+    {
+      "address": "module.instance.aws_instance.example",
+      "module_address": "module.instance",
+      "mode": "managed",
+      "type": "aws_instance",
+      "name": "example",
+      "provider_name": "aws",
+      "change": {
+        "actions": [
+          "update"
+        ],
+        "before": {
+          "ami": "ami-2757f631",
+          "availability_zone": "us-east-1e",
+          "instance_type": "t2.micro",
+          "root_block_device": [
+            {
+              "iops": 100,
+              "volume_size": 8,
+              "volume_type": "gp2"
+            }
+          ],
+          "tenancy": "default"
+        },
+        "after": {
+          "ami": "ami-2757f631",
+          "availability_zone": "us-east-1e",
+          "instance_type": "t2.xlarge",
+          "root_block_device": [
+            {
+              "iops": 100,
+              "volume_size": 8,
+              "volume_type": "gp2"
+            }
+          ],
+          "tenancy": "default"
+        },
+        "after_unknown": {}
+      }
+    },
+    {
+      "address": "aws_lb.example",
+      "mode": "managed",
+      "type": "aws_lb",
+      "name": "example",
+      "provider_name": "registry.terraform.io/hashicorp/aws",
+      "change": {
+        "actions": [
+          "create"
+        ],
+        "before": null,
+        "after": {
+          "load_balancer_type": "application"
+        },
+        "after_unknown": {}
+      }
+    }
+  ],
+  "prior_state": {
+    "format_version": "0.1",
+    "terraform_version": "0.12.28",
+    "values": {
+      "root_module": {
+        "child_modules": [
+          {
+            "resources": [
+              {
+                "address": "module.instance.aws_instance.example",
+                "mode": "managed",
+                "type": "aws_instance",
+                "name": "example",
+                "provider_name": "aws",
+                "schema_version": 1,
+                "values": {
+                  "ami": "ami-2757f631",
+                  "availability_zone": "us-east-1e",
+                  "instance_type": "t2.micro",
+                  "root_block_device": [
+                    {
+                      "iops": 100,
+                      "volume_size": 8,
+                      "volume_type": "gp2"
+                    }
+                  ],
+                  "tenancy": "default"
+                }
+              }
+            ],
+            "address": "module.instance"
+          }
+        ]
+      }
+    }
+  },
+  "configuration": {
+    "provider_config": {}
+    },
+    "root_module": {
+      "module_calls": {
+        "instance": {
+          "source": "./instance",
+          "module": {
+            "resources": [
+              {
+                "address": "aws_instance.example",
+                "mode": "managed",
+                "type": "aws_instance",
+                "name": "example",
+                "provider_config_key": "instance:aws",
+                "expressions": {
+                  "ami": {
+                    "constant_value": "ami-2757f631"
+                  },
+                  "instance_type": {
+                    "constant_value": "t2.xlarge"
+                  }
+                },
+                "schema_version": 1
+              }
+            ]
+          }
+        }
+      },
+      "resources": [
+        {
+          "address": "aws_lb.example",
+          "mode": "managed",
+          "type": "aws_lb",
+          "name": "example",
+          "provider_config_key": "aws.paris",
+          "expressions": {
+            "load_balancer_type": {
+              "constant_value": "application"
+            }
+          },
+          "schema_version": 1
+        }
+      ]
+    }
+  }
+}

testdata/aws/terraform-plan.json

@@ -164,6 +164,11 @@
             "constant_value": "eu-west-3"
           }
         }
+      },
+      "ignored": {
+        "name": "aws-constrain",
+        "version_constraint": ">= 1.1.1",
+        "module_address": "some-module"
       }
     },
     "root_module": {