chore: runner-pool tests fixes (#4823)

* chore: Added detection of custom HCL file in discovery and runner-pool

* Discovery fixes

* Documentation update

* Added handling of directories as config paths

* chore: review notes

Author: denis256

internal/discovery/discovery.go

@@ -341,8 +341,16 @@ func (c *DiscoveredConfig) Parse(ctx context.Context, l log.Logger, opts *option
 	parseOpts.ErrWriter = io.Discard
 	parseOpts.SkipOutput = true
 
+	// If the user provided a specific terragrunt config path and it is not a directory,
+	// use its base name as the file to parse. This allows users to run terragrunt with
+	// a specific config file instead of the default terragrunt.hcl.
+	// Otherwise, use the default terragrunt.hcl filename.
 	filename := config.DefaultTerragruntConfigPath
+	if opts.TerragruntConfigPath != "" && !util.IsDir(opts.TerragruntConfigPath) {
+		filename = filepath.Base(opts.TerragruntConfigPath)
+	}
 
+	// For stack configurations, always use the default stack config filename
 	if c.Type == ConfigTypeStack {
 		filename = config.DefaultStackFile
 	}

internal/runner/runnerpool/builder.go

@@ -2,6 +2,7 @@ package runnerpool
 
 import (
 	"context"
+	"path/filepath"
 
 	"github.com/gruntwork-io/terragrunt/config"
 	"github.com/gruntwork-io/terragrunt/internal/discovery"
@@ -21,7 +22,7 @@ func Build(ctx context.Context, l log.Logger, terragruntOptions *options.Terragr
 		WithParseExclude().
 		WithDiscoverDependencies().
 		WithSuppressParseErrors().
-		WithConfigFilenames([]string{config.DefaultTerragruntConfigPath}).
+		WithConfigFilenames([]string{filepath.Base(terragruntOptions.TerragruntConfigPath)}).
 		WithDiscoveryContext(&discovery.DiscoveryContext{Cmd: terragruntOptions.TerraformCommand})
 
 	// Pass parser options

internal/runner/runnerpool/runner.go

@@ -54,18 +54,30 @@ func NewRunnerPoolStack(ctx context.Context, l log.Logger, terragruntOptions *op
 
 	// Collect all terragrunt.hcl paths for resolution.
 	unitPaths := make([]string, 0, len(discovered))
+
 	for _, cfg := range discovered {
 		if cfg.Parsed == nil {
 			// Skip configurations that could not be parsed
 			l.Warnf("Skipping unit at %s due to parse error", cfg.Path)
 			continue
 		}
 
-		terragruntConfigPath := config.GetDefaultConfigPath(cfg.Path)
+		// Determine per-unit config filename
+		var fname string
+		if cfg.Type == discovery.ConfigTypeStack {
+			fname = config.DefaultStackFile
+		} else {
+			fname = config.DefaultTerragruntConfigPath
+			if terragruntOptions.TerragruntConfigPath != "" && !util.IsDir(terragruntOptions.TerragruntConfigPath) {
+				fname = filepath.Base(terragruntOptions.TerragruntConfigPath)
+			}
+		}
+
+		terragruntConfigPath := filepath.Join(cfg.Path, fname)
 		unitPaths = append(unitPaths, terragruntConfigPath)
 	}
 
-	// Resolve units (this applies include/exclude logic and sets FlagExcluded accordingly).
+	// Resolve units (this applies to include/exclude logic and sets FlagExcluded accordingly).
 	unitResolver, err := common.NewUnitResolver(ctx, runner.Stack)
 	if err != nil {
 		return nil, err

test/integration_test.go

@@ -860,16 +860,12 @@ func TestTerragruntWorksWithNonDefaultConfigNamesAndRunAllCommand(t *testing.T)
 	tmpEnvPath := helpers.CopyEnvironment(t, testFixtureConfigWithNonDefaultNames)
 	tmpEnvPath = path.Join(tmpEnvPath, testFixtureConfigWithNonDefaultNames)
 
-	stdout := bytes.Buffer{}
-	stderr := bytes.Buffer{}
-
-	err := helpers.RunTerragruntCommand(t, "terragrunt run --all apply --config main.hcl --non-interactive --working-dir "+tmpEnvPath, &stdout, &stderr)
+	_, stderr, err := helpers.RunTerragruntCommandWithOutput(t, "terragrunt run --all apply --log-level debug --config main.hcl --non-interactive --working-dir "+tmpEnvPath)
 	require.NoError(t, err)
 
-	out := stdout.String()
-	assert.Equal(t, 1, strings.Count(out, "parent_hcl_file"))
-	assert.Equal(t, 1, strings.Count(out, "dependency_hcl"))
-	assert.Equal(t, 1, strings.Count(out, "common_hcl"))
+	assert.Contains(t, stderr, "run_cmd output: [parent_hcl_file]")
+	assert.Contains(t, stderr, "run_cmd output: [dependency_hcl]")
+	assert.Contains(t, stderr, "run_cmd output: [common_hcl]")
 }
 
 func TestTerragruntWorksWithNonDefaultConfigNames(t *testing.T) {