feat: performance improvement on -version execution (#4288)

* Version check fixes

* Version saving

* Add fetching of context cache

* Version caching fixes

* Add check for single version run

* Lint issues fixes

* extracted version files

* Added test to track that version is invoked in unit with custom version

Author: denis256

cli/app.go

@@ -7,6 +7,8 @@ import (
 	"os"
 	"strings"
 
+	"github.com/gruntwork-io/terragrunt/cli/commands/run"
+
 	"github.com/gruntwork-io/terragrunt/engine"
 	"github.com/gruntwork-io/terragrunt/internal/os/signal"
 	"github.com/gruntwork-io/terragrunt/telemetry"
@@ -106,6 +108,8 @@ func (app *App) RunContext(ctx context.Context, args []string) error {
 	// configure engine context
 	ctx = engine.WithEngineValues(ctx)
 
+	ctx = run.WithRunVersionCache(ctx)
+
 	defer func(ctx context.Context) {
 		if err := engine.Shutdown(ctx, app.opts); err != nil {
 			_, _ = app.ErrWriter.Write([]byte(err.Error()))

cli/commands/run/context.go

@@ -0,0 +1,25 @@
+package run
+
+import (
+	"context"
+
+	"github.com/gruntwork-io/terragrunt/internal/cache"
+)
+
+type configKey byte
+
+const (
+	versionCacheContextKey configKey = iota
+	versionCacheName                 = "versionCache"
+)
+
+// WithRunVersionCache initializes the version cache in the context for the run package.
+func WithRunVersionCache(ctx context.Context) context.Context {
+	ctx = context.WithValue(ctx, versionCacheContextKey, cache.NewCache[string](versionCacheName))
+	return ctx
+}
+
+// GetRunVersionCache retrieves the version cache from the context for the run package.
+func GetRunVersionCache(ctx context.Context) *cache.Cache[string] {
+	return cache.ContextCache[string](ctx, versionCacheContextKey)
+}

cli/commands/run/version_check.go

@@ -4,12 +4,16 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"path/filepath"
 	"regexp"
 	"strings"
 
+	"encoding/hex"
+
 	"github.com/gruntwork-io/terragrunt/internal/errors"
 	"github.com/gruntwork-io/terragrunt/options"
 	"github.com/gruntwork-io/terragrunt/tf"
+	"github.com/gruntwork-io/terragrunt/util"
 	"github.com/hashicorp/go-version"
 )
 
@@ -27,6 +31,8 @@ var TerraformVersionRegex = regexp.MustCompile(`^(\S+)\s(v?\d+\.\d+\.\d+)`)
 
 const versionParts = 3
 
+var versionFiles = []string{".terraform-version", ".tool-versions", "mise.toml", ".mise.toml"}
+
 // CheckVersionConstraints checks the version constraints of both terragrunt and terraform. Note that as a side effect this will set the
 // following settings on terragruntOptions:
 // - TerraformPath
@@ -85,18 +91,36 @@ func CheckVersionConstraints(ctx context.Context, terragruntOptions *options.Ter
 
 // PopulateTerraformVersion populates the currently installed version of Terraform into the given terragruntOptions.
 func PopulateTerraformVersion(ctx context.Context, terragruntOptions *options.TerragruntOptions) error {
-	// Discard all log output to make sure we don't pollute stdout or stderr with this extra call to '--version'
+	versionCache := GetRunVersionCache(ctx)
+	cacheKey := computeVersionFilesCacheKey(terragruntOptions.WorkingDir)
+
+	if cachedOutput, found := versionCache.Get(ctx, cacheKey); found {
+		terraformVersion, err := ParseTerraformVersion(cachedOutput)
+		if err != nil {
+			return err
+		}
+
+		tfImplementation, err := parseTerraformImplementationType(cachedOutput)
+
+		if err != nil {
+			return err
+		}
+
+		terragruntOptions.TerraformVersion = terraformVersion
+
+		terragruntOptions.TerraformImplementation = tfImplementation
+
+		return nil
+	}
+
 	terragruntOptionsCopy, err := terragruntOptions.CloneWithConfigPath(terragruntOptions.TerragruntConfigPath)
 	if err != nil {
 		return err
 	}
 
 	terragruntOptionsCopy.Writer = io.Discard
 	terragruntOptionsCopy.ErrWriter = io.Discard
-	// Remove any TF_CLI_ARGS before version checking. These are appended to
-	// the arguments supplied on the command line and cause issues when running
-	// the --version command.
-	// https://www.terraform.io/docs/commands/environment-variables.html#tf_cli_args-and-tf_cli_args_name
+
 	for key := range terragruntOptionsCopy.Env {
 		if strings.HasPrefix(key, "TF_CLI_ARGS") {
 			delete(terragruntOptionsCopy.Env, key)
@@ -108,6 +132,9 @@ func PopulateTerraformVersion(ctx context.Context, terragruntOptions *options.Te
 		return err
 	}
 
+	// Save output to cache
+	versionCache.Put(ctx, cacheKey, output.Stdout.String())
+
 	terraformVersion, err := ParseTerraformVersion(output.Stdout.String())
 	if err != nil {
 		return err
@@ -212,6 +239,29 @@ func parseTerraformImplementationType(versionCommandOutput string) (options.Terr
 	}
 }
 
+// Helper to compute a cache key from the checksums of .terraform-version and .tool-versions
+func computeVersionFilesCacheKey(workingDir string) string {
+	var hashes []string
+
+	for _, file := range versionFiles {
+		path := filepath.Join(workingDir, file)
+		if util.FileExists(path) {
+			hash, err := util.FileSHA256(path)
+			if err == nil {
+				hashes = append(hashes, file+":"+hex.EncodeToString(hash))
+			}
+		}
+	}
+
+	cacheKey := "no-version-files"
+
+	if len(hashes) != 0 {
+		cacheKey = strings.Join(hashes, "|")
+	}
+
+	return util.EncodeBase64Sha1(cacheKey)
+}
+
 // Custom error types
 
 type InvalidTerraformVersionSyntax string

test/fixtures/version-invocation/app/main.tf

@@ -0,0 +1,5 @@
+variable "input_value" {}
+
+output "output_value" {
+  value = var.input_value
+}

test/fixtures/version-invocation/app/terragrunt.hcl

@@ -0,0 +1,12 @@
+
+dependency "dependency" {
+  config_path = "../dependency"
+}
+
+dependency "dependency-with-custom-version" {
+  config_path = "../dependency-with-custom-version"
+}
+
+inputs = {
+  input_value = dependency.dependency.outputs.result
+}

test/fixtures/version-invocation/dependency-with-custom-version/.tool-versions

@@ -0,0 +1 @@
+tofu 1.9.4

test/fixtures/version-invocation/dependency-with-custom-version/main.tf

@@ -0,0 +1,4 @@
+output "result" {
+
+  value = "42"
+}

test/fixtures/version-invocation/dependency-with-custom-version/terragrunt.hcl

@@ -0,0 +1,4 @@
+output "result" {
+
+  value = "42"
+}