Get plan output with terraform 0.12 (#41)

This fixes issue #38 and adds 0.12.6 to the list of versions we test against.

Context: `terraform show` is broken since 0.12 (see hashicorp/terraform#21446), so I'm using regex on top of `terraform plan` to produce the plan output.

Tests were fixed to support changes in output in 0.12.

astro/terraform/terraform_plan.go

@@ -18,6 +18,7 @@ package terraform
 
 import (
 	"fmt"
+	"regexp"
 )
 
 // Plan runs a `terraform plan`
@@ -53,12 +54,27 @@ func (s *Session) Plan() (Result, error) {
 	// are changes (so there's no error).
 	if process.ExitCode() == 2 {
 		// Fetch changes
-		result, err := s.Show(fmt.Sprintf("%s.plan", s.id))
+		terraformVersion, err := s.versionCached()
 		if err != nil {
-			return result, err
+			return nil, err
+		}
+		if VersionMatches(terraformVersion, "<0.12") {
+			result, err := s.Show(fmt.Sprintf("%s.plan", s.id))
+			if err != nil {
+				return result, err
+			}
+			changes = result.Stdout()
+		} else {
+			rawPlanOutput := process.Stdout().String()
+			var re = regexp.MustCompile(`(?s)Terraform will perform the following actions:(.*)-{72}`)
+			if match := re.FindStringSubmatch(rawPlanOutput); len(match) == 2 {
+				changes = match[1]
+			} else {
+				return &terraformResult{
+					process: process,
+				}, fmt.Errorf("unable to parse terraform plan output")
+			}
 		}
-
-		changes = result.Stdout()
 	}
 
 	return &PlanResult{

astro/tests/base.go

@@ -45,6 +45,7 @@ var (
 		"0.9.11",
 		"0.10.8",
 		"0.11.5",
+		"0.12.6",
 	}
 )
 

astro/tests/integration_test.go

@@ -25,6 +25,9 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/uber/astro/astro/terraform"
+
+	version "github.com/burl/go-version"
 )
 
 // getSessionDirs returns a list of the sessions inside a session repository.
@@ -52,6 +55,12 @@ func getSessionDirs(sessionBaseDir string) ([]string, error) {
 	return sessionDirs, nil
 }
 
+// stringVersionMatches returns whether or not the version passed as string matches the constraint.
+// See terraform.VersionMatches for more info.
+func stringVersionMatches(v string, versionConstraint string) bool {
+	return terraform.VersionMatches(version.Must(version.NewVersion(v)), versionConstraint)
+}
+
 func TestProjectApplyChangesSuccess(t *testing.T) {
 	for _, version := range terraformVersionsToTest {
 		t.Run(version, func(t *testing.T) {
@@ -84,7 +93,11 @@ func TestProjectPlanSuccessChanges(t *testing.T) {
 		t.Run(version, func(t *testing.T) {
 			result := RunTest(t, []string{"plan"}, "fixtures/plan-success-changes", version)
 			assert.Contains(t, result.Stdout.String(), "foo: OK Changes")
-			assert.Regexp(t, `\+.*null_resource.foo`, result.Stdout.String())
+			addedResourceRe := `\+.*null_resource.foo`
+			if stringVersionMatches(version, ">=0.12") {
+				addedResourceRe = `null_resource.foo.*will be created`
+			}
+			assert.Regexp(t, addedResourceRe, result.Stdout.String())
 			assert.Equal(t, 0, result.ExitCode)
 		})
 	}
@@ -95,7 +108,11 @@ func TestProjectPlanError(t *testing.T) {
 		t.Run(version, func(t *testing.T) {
 			result := RunTest(t, []string{"plan"}, "fixtures/plan-error", version)
 			assert.Contains(t, result.Stderr.String(), "foo: ERROR")
-			assert.Contains(t, result.Stderr.String(), "Error parsing")
+			errorMessage := "Error parsing"
+			if stringVersionMatches(version, ">=0.12") {
+				errorMessage = "Argument or block definition required"
+			}
+			assert.Contains(t, result.Stderr.String(), errorMessage)
 			assert.Equal(t, 1, result.ExitCode)
 		})
 	}