Allow hcl format from stdin

cli/commands/hclfmt/action.go

@@ -4,8 +4,10 @@
 package hclfmt
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -27,6 +29,16 @@ import (
 func Run(opts *options.TerragruntOptions) error {
 	workingDir := opts.WorkingDir
 	targetFile := opts.HclFile
+	stdIn := opts.HclFromStdin
+
+	if stdIn {
+		if targetFile != "" {
+			opts.Logger.Debugf("Both stdin and path flags are specified")
+			return fmt.Errorf("both stdin and path flags are specified")
+		}
+
+		return formatFromStdin(opts)
+	}
 
 	// handle when option specifies a particular file
 	if targetFile != "" {
@@ -74,6 +86,39 @@ func Run(opts *options.TerragruntOptions) error {
 	return formatErrors.ErrorOrNil()
 }
 
+func formatFromStdin(opts *options.TerragruntOptions) error {
+
+	contents, err := io.ReadAll(os.Stdin)
+
+	if err != nil {
+		opts.Logger.Errorf("Error reading from stdin: %s", err)
+		return err
+	}
+
+	err = checkErrors(opts.Logger, opts.DisableLogColors, contents, "stdin")
+	if err != nil {
+		opts.Logger.Errorf("Error parsing hcl from stdin")
+		return err
+	}
+
+	newContents := hclwrite.Format(contents)
+
+	buf := bufio.NewWriter(os.Stdout)
+	_, err = buf.Write(newContents)
+	if err != nil {
+		opts.Logger.Errorf("Failed to write to stdout")
+		return err
+	}
+
+	err = buf.Flush()
+	if err != nil {
+		opts.Logger.Errorf("Failed to flush to stdout")
+		return err
+	}
+
+	return nil
+}
+
 // formatTgHCL uses the hcl2 library to format the hcl file. This will attempt to parse the HCL file first to
 // ensure that there are no syntax errors, before attempting to format it.
 func formatTgHCL(opts *options.TerragruntOptions, tgHclFile string) error {

cli/commands/hclfmt/action_test.go

@@ -258,6 +258,38 @@ func TestHCLFmtFile(t *testing.T) {
 	}
 }
 
+func TestHCLFmtStdin(t *testing.T) {
+
+	realStdin := os.Stdin
+	realStdout := os.Stdout
+
+	tempStdoutFile, err := os.CreateTemp(os.TempDir(), "stdout-*.hcl")
+	require.NoError(t, err)
+	defer os.Remove(tempStdoutFile.Name())
+
+	os.Stdout = tempStdoutFile
+	defer func() { os.Stdout = realStdout }()
+
+	os.Stdin, err = os.Open("../../../test/fixture-hclfmt-stdin/terragrunt.hcl")
+	defer func() { os.Stdin = realStdin }()
+	require.NoError(t, err)
+
+	expected, err := os.ReadFile("../../../test/fixture-hclfmt-stdin/expected.hcl")
+	require.NoError(t, err)
+
+	tgOptions, err := options.NewTerragruntOptionsForTest("")
+	require.NoError(t, err)
+
+	// format hcl froms tdin
+	tgOptions.HclFromStdin = true
+	err = Run(tgOptions)
+	require.NoError(t, err)
+
+	formatted, err := os.ReadFile(tempStdoutFile.Name())
+	require.NoError(t, err)
+	assert.Equal(t, expected, formatted)
+}
+
 func TestHCLFmtHeredoc(t *testing.T) {
 	t.Parallel()
 

cli/commands/hclfmt/command.go

@@ -8,9 +8,10 @@ import (
 const (
 	CommandName = "hclfmt"
 
-	FlagNameTerragruntHCLFmt = "terragrunt-hclfmt-file"
-	FlagNameTerragruntCheck  = "terragrunt-check"
-	FlagNameTerragruntDiff   = "terragrunt-diff"
+	FlagNameTerragruntHCLFmt      = "terragrunt-hclfmt-file"
+	FlagNameTerragruntCheck       = "terragrunt-check"
+	FlagNameTerragruntDiff        = "terragrunt-diff"
+	FlagNameTerragruntHCLFmtStdin = "terragrunt-hclfmt-stdin"
 )
 
 func NewFlags(opts *options.TerragruntOptions) cli.Flags {
@@ -32,6 +33,12 @@ func NewFlags(opts *options.TerragruntOptions) cli.Flags {
 			EnvVar:      "TERRAGRUNT_DIFF",
 			Usage:       "Print diff between original and modified file versions when running with 'hclfmt'.",
 		},
+		&cli.BoolFlag{
+			Name:        FlagNameTerragruntHCLFmtStdin,
+			Destination: &opts.HclFromStdin,
+			EnvVar:      "TERRAGRUNT_HCLFMT_STDIN",
+			Usage:       "Format HCL from stdin and print result to stdout.",
+		},
 	}
 }
 

docs/_docs/04_reference/cli-options.md

@@ -63,6 +63,7 @@ This page documents the CLI commands and options available with Terragrunt:
   - [terragrunt-check](#terragrunt-check)
   - [terragrunt-diff](#terragrunt-diff)
   - [terragrunt-hclfmt-file](#terragrunt-hclfmt-file)
+  - [terragrunt-hclfmt-stdin](#terragrunt-hclfmt-stdin)
   - [terragrunt-hclvalidate-json](#terragrunt-hclvalidate-json)
   - [terragrunt-hclvalidate-invalid](#terragrunt-hclvalidate-invalid)
   - [terragrunt-override-attr](#terragrunt-override-attr)
@@ -763,6 +764,7 @@ prefix `--terragrunt-` (e.g., `--terragrunt-config`). The currently available op
   - [terragrunt-check](#terragrunt-check)
   - [terragrunt-diff](#terragrunt-diff)
   - [terragrunt-hclfmt-file](#terragrunt-hclfmt-file)
+  - [terragrunt-hclfmt-stdin](#terragrunt-hclfmt-stdin)
   - [terragrunt-hclvalidate-json](#terragrunt-hclvalidate-json)
   - [terragrunt-hclvalidate-invalid](#terragrunt-hclvalidate-invalid)
   - [terragrunt-override-attr](#terragrunt-override-attr)
@@ -1118,7 +1120,15 @@ When passed in, running `hclfmt` will print diff between original and modified f
 
 - [hclfmt](#hclfmt)
 
-When passed in, run `hclfmt` only on specified hcl file.
+### terragrunt-hclfmt-stdin
+
+**CLI Arg**: `--terragrunt-hclfmt-stdin`<br/>
+**Environment Variable**: `TERRAGRUNT_HCLFMT_STDIN` (set to `true`)<br/>
+**Commands**:
+
+- [hclfmt](#hclfmt)
+
+When passed in, run `hclfmt` only on hcl passed to `stdin`, result is printed to `stdout`.
 
 ### terragrunt-hclvalidate-json
 

options/options.go

@@ -218,6 +218,9 @@ type TerragruntOptions struct {
 	// The file which hclfmt should be specifically run on
 	HclFile string
 
+	// If True then HCL from StdIn must should be formatted.
+	HclFromStdin bool
+
 	// The file path that terragrunt should use when rendering the terragrunt.hcl config as json.
 	JSONOut string
 

test/fixture-hclfmt-stdin/expected.hcl

@@ -0,0 +1,13 @@
+inputs = {
+  # comments
+  foo = "bar"
+  bar = "baz"
+
+  inputs   = "disjoint"
+  disjoint = true
+
+  listInput = [
+    "foo",
+    "bar",
+  ]
+}

test/fixture-hclfmt-stdin/terragrunt.hcl

@@ -0,0 +1,13 @@
+inputs = {
+# comments
+  foo =                               "bar"
+  bar="baz"
+
+  inputs = "disjoint"
+  disjoint = true
+
+  listInput = [
+"foo",
+"bar",
+]
+}