Add flag to include descriptions as comments

.gitignore

@@ -1,2 +1,3 @@
+/tfvar
 profile.cov
 dist/

cmd/cmd.go

@@ -12,14 +12,15 @@ import (
 )
 
 const (
-	flagAutoAssign = "auto-assign"
-	flagDebug      = "debug"
-	flagEnvVar     = "env-var"
-	flagNoDefault  = "ignore-default"
-	flagResource   = "resource"
-	flagVar        = "var"
-	flagVarFile    = "var-file"
-	flagWorkspace  = "workspace"
+	flagAutoAssign      = "auto-assign"
+	flagDebug           = "debug"
+	flagDescsAsComments = "descs-as-comments"
+	flagEnvVar          = "env-var"
+	flagNoDefault       = "ignore-default"
+	flagResource        = "resource"
+	flagVar             = "var"
+	flagVarFile         = "var-file"
+	flagWorkspace       = "workspace"
 )
 
 // New returns a new instance of cobra.Command for tfvar. Usage:
@@ -50,6 +51,7 @@ one would write it in variable definitions files (.tfvars).
 	rootCmd.PersistentFlags().BoolP(flagAutoAssign, "a", false, `Use values from environment variables TF_VAR_* and
 variable definitions files e.g. terraform.tfvars[.json] *.auto.tfvars[.json]`)
 	rootCmd.PersistentFlags().BoolP(flagDebug, "d", false, "Print debug log on stderr")
+	rootCmd.PersistentFlags().BoolP(flagDescsAsComments, "c", false, "Include variable descriptions as comments.")
 	rootCmd.PersistentFlags().BoolP(flagEnvVar, "e", false, "Print output in export TF_VAR_image_id=ami-abc123 format")
 	rootCmd.PersistentFlags().BoolP(flagResource, "r", false, "Print output in Terraform Enterprise (tfe) provider's tfe_variable resource format")
 	rootCmd.PersistentFlags().BoolP(flagWorkspace, "w", false, "Print output variables as payloads for Workspace Variables API")
@@ -179,21 +181,31 @@ func (r *runner) rootRunE(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	writer := tfvar.WriteAsTFVars
+	var writer func(w io.Writer, vars []tfvar.Variable) error
 
 	if isEnvVar {
 		r.log.Debug("Print outputs in environment variables format")
 		writer = tfvar.WriteAsEnvVars
-	}
-
-	if isWorkspace {
+	} else if isWorkspace {
 		r.log.Debug("Print outputs in Workspace API payload format")
 		writer = tfvar.WriteAsWorkspacePayload
-	}
-
-	if isResource {
+	} else if isResource {
 		r.log.Debug("Print outputs in tfe_resource format")
 		writer = tfvar.WriteAsTFEResource
+	} else {
+		r.log.Debug("Print outputs in tfvars format")
+		withComments, err := cmd.PersistentFlags().GetBool(flagDescsAsComments)
+		if err != nil {
+			return errors.Wrapf(err, "cmd: get flag --%s", flagDescsAsComments)
+		}
+		if withComments {
+			r.log.Debug("Including comments in tfvars output")
+		} else {
+			r.log.Debug("Not including comments in tfvars output")
+		}
+		writer = func(w io.Writer, vars []tfvar.Variable) error {
+			return tfvar.WriteAsTFVars(withComments, w, vars)
+		}
 	}
 	return writer(r.out, vars)
 }

pkg/tfvar/tfvar.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"strings"
 
 	"github.com/cockroachdb/errors"
 	"github.com/hashicorp/hcl/v2/hclsyntax"
@@ -101,18 +102,43 @@ func oneliner(original hclwrite.Tokens) hclwrite.Tokens {
 
 // WriteAsTFVars outputs the given vars in Terraform's variable definitions format, e.g.
 //    region = "ap-northeast-1"
-func WriteAsTFVars(w io.Writer, vars []Variable) error {
+func WriteAsTFVars(withComments bool, w io.Writer, vars []Variable) error {
 	f := hclwrite.NewEmptyFile()
 	rootBody := f.Body()
 
 	for _, v := range vars {
+		if withComments {
+			comment := strings.TrimSpace(v.Description)
+			if len(comment) > 0 {
+				rootBody.AppendUnstructuredTokens(commentToTokens(comment))
+			}
+		}
 		rootBody.SetAttributeValue(v.Name, v.Value)
 	}
 
 	_, err := f.WriteTo(w)
 	return errors.Wrap(err, "tfvar: failed to write as tfvars")
 }
 
+func commentToTokens(comment string) hclwrite.Tokens {
+	lines := strings.Split(comment, "\n")
+	newLine := hclwrite.Token{
+		Type:  hclsyntax.TokenNewline,
+		Bytes: []byte(string(hclsyntax.TokenNewline)),
+	}
+
+	var tokens hclwrite.Tokens
+	for _, line := range lines {
+		tokens = append(tokens, &hclwrite.Token{
+			Type:  hclsyntax.TokenComment,
+			Bytes: []byte(fmt.Sprintf("# %s", line)),
+		})
+		tokens = append(tokens, &newLine)
+	}
+
+	return tokens
+}
+
 type workspacePayload struct {
 	Data workspaceData `json:"data"`
 }

pkg/tfvar/tfvar_test.go

@@ -79,7 +79,7 @@ func TestWriteAsTFVars(t *testing.T) {
 	sort.Slice(vars, func(i, j int) bool { return vars[i].Name < vars[j].Name })
 
 	var buf bytes.Buffer
-	assert.NoError(t, WriteAsTFVars(&buf, vars))
+	assert.NoError(t, WriteAsTFVars(true, &buf, vars))
 
 	expected := `availability_zone_names = ["us-west-1a"]
 aws_amis = {
@@ -94,8 +94,9 @@ docker_ports = [{
   protocol = "tcp"
 }]
 instance_name = "my-instance"
-password      = null
-region        = null
+# the root password to use with the database
+password = null
+region   = null
 `
 	assert.Equal(t, expected, buf.String())
 }