Stack: detection of nested stacks (#4052)

* Netsted stack detection fixes

* Add test for multiple stacks generation

* Documentation update

* Docs sync

* Markdown update

* fixed lint issues

* Removed wrong character

Author: denis256

config/stack.go

@@ -64,7 +64,11 @@ func GenerateStacks(ctx context.Context, opts *options.TerragruntOptions) error
 	// stop worker pool on exit
 	defer wp.Stop()
 	// initial files setting as stack file
-	foundFiles := []string{opts.TerragruntStackConfigPath}
+
+	foundFiles, err := listStackFiles(opts, opts.WorkingDir)
+	if err != nil {
+		return errors.Errorf("Failed to list stack files in %s %v", opts.WorkingDir, err)
+	}
 
 	for {
 		// check if we have already processed the files

docs-starlight/src/data/commands/stack/generate.mdx

@@ -16,7 +16,7 @@ examples:
       terragrunt stack generate
 ---
 
-import { FileTree } from '@astrojs/starlight/components';
+import { Aside, FileTree } from '@astrojs/starlight/components';
 
 ## Generating a stack
 
@@ -67,3 +67,13 @@ Generates the following stack:
       - terragrunt.hcl
 
 </FileTree>
+
+<Aside type="note">
+Parallel Execution: Stack generation runs concurrently to improve performance. The number of parallel tasks is determined by the `GOMAXPROCS` environment variable and can be explicitly controlled using the `--parallelism` flag:
+
+```bash
+terragrunt stack generate --parallelism 4
+```
+
+Automatic Discovery: The command automatically discovers all `terragrunt.stack.hcl` files within the directory structure and generates them in parallel.
+</Aside>

docs/_docs/04_reference/02-cli-options.md

@@ -338,13 +338,16 @@ Will create the following directory structure:
     └── terragrunt.hcl
 ```
 
-**Note**: Stack generation is executed in parallel. By default, the number of parallel tasks is limited by the `GOMAXPROCS` environment variable.
-You can override this limit using the `--parallelism` CLI flag:
+**Notes**:
+
+- Parallel Execution: Stack generation runs concurrently to improve performance. The number of parallel tasks is determined by the `GOMAXPROCS` environment variable and can be explicitly controlled using the `--parallelism` flag:
 
 ```bash
-terragrunt stack generate --parallelism 4
+  terragrunt stack generate --parallelism 4
 ```
 
+- Automatic Discovery: The command automatically discovers all `terragrunt.stack.hcl` files within the directory structure and generates them in parallel.
+
 #### stack run
 
 The `stack run *` command allows users to execute IaC commands across all units defined in a `terragrunt.stack.hcl` file.

test/fixtures/stacks/multiple-stacks/dev/terragrunt.stack.hcl

@@ -0,0 +1,15 @@
+unit "v2-unit1" {
+	source = "../unit"
+	path   = "unit1"
+}
+
+unit "v2-unit2" {
+	source = "../unit"
+	path   = "unit2"
+}
+
+unit "v2-unit3" {
+	source = "../unit"
+	path   = "unit3"
+}
+

test/fixtures/stacks/multiple-stacks/live/terragrunt.stack.hcl

@@ -0,0 +1,15 @@
+unit "v1-unit1" {
+	source = "../unit"
+	path   = "unit1"
+}
+
+unit "v1-unit2" {
+	source = "../unit"
+	path   = "unit2"
+}
+
+unit "v1-unit3" {
+	source = "../unit"
+	path   = "unit3"
+}
+

test/fixtures/stacks/multiple-stacks/unit/main.tf

@@ -0,0 +1,4 @@
+
+output "output" {
+  value = "unit"
+}

test/fixtures/stacks/multiple-stacks/unit/terragrunt.hcl

@@ -36,6 +36,7 @@ const (
 	testFixtureNoStack             = "fixtures/stacks/no-stack"
 	testFixtureStackCycles         = "fixtures/stacks/errors/cycles"
 	testFixtureNoStackNoDir        = "fixtures/stacks/no-stack-dir"
+	testFixtureMultipleStacks      = "fixtures/stacks/multiple-stacks"
 )
 
 func TestStacksGenerateBasic(t *testing.T) {
@@ -892,6 +893,22 @@ func TestStacksNoStackDirNoTerragruntStackDirectoryCreated(t *testing.T) {
 	assert.NoDirExists(t, path)
 }
 
+func TestStacksGenerateMultipleStacks(t *testing.T) {
+	t.Parallel()
+
+	helpers.CleanupTerraformFolder(t, testFixtureMultipleStacks)
+	tmpEnvPath := helpers.CopyEnvironment(t, testFixtureMultipleStacks)
+	rootPath := util.JoinPath(tmpEnvPath, testFixtureMultipleStacks)
+
+	helpers.RunTerragrunt(t, "terragrunt stack generate --experiment stacks --terragrunt-working-dir "+rootPath)
+
+	devStack := util.JoinPath(rootPath, "dev", ".terragrunt-stack")
+	validateStackDir(t, devStack)
+
+	liveStack := util.JoinPath(rootPath, "live", ".terragrunt-stack")
+	validateStackDir(t, liveStack)
+}
+
 // validateNoStackDirs check if the directories outside of stack are created and contain test files
 func validateNoStackDirs(t *testing.T, rootPath string) {
 	t.Helper()