fix #2072 make sure the generated code is formatted before writing …

…it to a file. (#3917)

codegen/generate.go

@@ -11,7 +11,6 @@ import (
 
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/hclsimple"
-
 	"github.com/hashicorp/hcl/v2/hclwrite"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 
@@ -87,6 +86,7 @@ type GenerateConfig struct {
 	Contents         string `cty:"contents"`
 	DisableSignature bool   `cty:"disable_signature"`
 	Disable          bool   `cty:"disable"`
+	HclFmt           *bool  `cty:"hcl_fmt"`
 }
 
 // WriteToFile will generate a new file at the given target path with the given contents. If a file already exists at
@@ -135,10 +135,30 @@ func WriteToFile(terragruntOptions *options.TerragruntOptions, basePath string,
 		prefix = fmt.Sprintf("%s%s\n", config.CommentPrefix, TerragruntGeneratedSignature)
 	}
 
-	contentsToWrite := fmt.Sprintf("%s%s", prefix, config.Contents)
+	fmtGeneratedCode := false
+
+	if config.HclFmt == nil {
+		var fmtExt = map[string]struct{}{
+			".hcl":  {},
+			".tf":   {},
+			".tofu": {},
+		}
+
+		ext := filepath.Ext(config.Path)
+		if _, ok := fmtExt[ext]; ok {
+			fmtGeneratedCode = true
+		}
+	} else {
+		fmtGeneratedCode = *config.HclFmt
+	}
+
+	contentsToWrite := []byte(fmt.Sprintf("%s%s", prefix, config.Contents))
+	if fmtGeneratedCode {
+		contentsToWrite = hclwrite.Format(contentsToWrite)
+	}
 
 	const ownerWriteGlobalReadPerms = 0644
-	if err := os.WriteFile(targetPath, []byte(contentsToWrite), ownerWriteGlobalReadPerms); err != nil {
+	if err := os.WriteFile(targetPath, contentsToWrite, ownerWriteGlobalReadPerms); err != nil {
 		return errors.New(err)
 	}
 

codegen/generate_test.go

@@ -3,6 +3,7 @@ package codegen_test
 import (
 	"bytes"
 	"fmt"
+	"os"
 	"testing"
 
 	"github.com/gruntwork-io/terragrunt/codegen"
@@ -144,6 +145,81 @@ func TestRemoteStateConfigToTerraformCode(t *testing.T) {
 	}
 }
 
+func TestFmtGeneratedFile(t *testing.T) {
+	t.Parallel()
+
+	testDir := t.TempDir()
+
+	bTrue := true
+	bFalse := false
+
+	tc := []struct {
+		name     string
+		disabled bool
+		fmt      *bool
+		path     string
+		contents string
+		expected string
+		ifExists codegen.GenerateConfigExists
+	}{
+		{
+			name:     "fmt-simple-hcl-file",
+			fmt:      &bTrue,
+			path:     fmt.Sprintf("%s/%s", testDir, "fmt_simple.hcl"),
+			contents: "variable \"msg\"{\ntype=string\n  default=\"hello\"\n}\n",
+			expected: "variable \"msg\" {\n  type    = string\n  default = \"hello\"\n}\n",
+			ifExists: codegen.ExistsError,
+		},
+		{
+			name:     "fmt-hcl-file-by-default",
+			path:     fmt.Sprintf("%s/%s", testDir, "fmt_hcl_file_by_default.hcl"),
+			contents: "variable \"msg\"{\ntype=string\n  default=\"hello\"\n}\n",
+			expected: "variable \"msg\" {\n  type    = string\n  default = \"hello\"\n}\n",
+			ifExists: codegen.ExistsError,
+		},
+		{
+			name:     "ignore-hcl-fmt",
+			fmt:      &bFalse,
+			path:     fmt.Sprintf("%s/%s", testDir, "ignore_hcl_fmt.hcl"),
+			contents: "variable \"msg\"{\ntype=string\n  default=\"hello\"\n}\n",
+			expected: "variable \"msg\"{\ntype=string\n  default=\"hello\"\n}\n",
+			ifExists: codegen.ExistsError,
+		},
+	}
+
+	for _, tt := range tc {
+		tt := tt
+
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			config := codegen.GenerateConfig{
+				Path:             tt.path,
+				IfExists:         tt.ifExists,
+				CommentPrefix:    "",
+				DisableSignature: true,
+				Contents:         tt.contents,
+				Disable:          tt.disabled,
+				HclFmt:           tt.fmt,
+			}
+
+			opts, err := options.NewTerragruntOptionsForTest("mock-path-for-test.hcl")
+			require.NoError(t, err)
+			assert.NotNil(t, opts)
+
+			err = codegen.WriteToFile(opts, "", config)
+			require.NoError(t, err)
+
+			assert.True(t, util.FileExists(tt.path))
+
+			fileContent, err := os.ReadFile(tt.path)
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.expected, string(fileContent))
+		})
+	}
+}
+
 func TestGenerateDisabling(t *testing.T) {
 	t.Parallel()
 

docs/_docs/04_reference/04-config-blocks-and-attributes.md

@@ -1301,6 +1301,8 @@ The `generate` block supports the following arguments:
   `false`. Optional.
 - `contents` (attribute): The contents of the generated file.
 - `disable` (attribute): Disables this generate block.
+- `hcl_fmt` (attribute): Unless disabled (set to `false`), files with `.hcl`, `.tf`, and `.tofu` extensions will be formatted before being written to disk.
+  If explicitly set to `true`, formatting will be applied to the generated files.
 
 Example: