IAC tool cli building improvements by denis256 · Pull Request #5448 · gruntwork-io/terragrunt

denis256 · 2026-01-28T19:57:00Z

Description

Improved building of CLI arguments for IAC tool
Added error throwing when report extension is not supported
Simplified handling of boolean flags
Added more test to track parsing of boolean arguments

TODOs

Read the Gruntwork contribution guidelines.

I authored this code entirely myself
I am submitting code based on open source software (e.g. MIT, MPL-2.0, Apache)]
I am adding or upgrading a dependency or adapted code and confirm it has a compatible open source license
Update the docs.
Run the relevant tests successfully, including pre-commit checks.
Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes (draft)

Added / Removed / Updated [X].

Migration Guide

Summary by CodeRabbit

Bug Fixes
- Added nil-safety to argument handling to avoid panics.
Improvements
- More robust CLI flag and argument parsing (handles -flag, --flag, -flag=value, space-separated values).
- Smarter merging/normalization of commands, subcommands, flags, and arguments.
- Lazier initialization for CLI argument builders to support incremental construction.
Refactor
- Internal argument/flag handling reorganized for clarity and safer slice operations.
Tests
- Expanded unit tests covering flag removal, boolean flags, subcommand handling, and nil/edge cases.

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vercel · 2026-01-28T19:57:05Z

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Project	Deployment	Actions	Updated (UTC)
terragrunt-docs	Ready	Preview, Comment	Jan 29, 2026 8:10pm

coderabbitai · 2026-01-28T19:57:12Z

📝 Walkthrough

Walkthrough

Refactors CLI argument handling with flag normalization and robust flag/value parsing, adds new IacArgs builder helpers and tests (including boolean flag edge cases), introduces minor nil-guards and capacity-constant tweaks, and updates Terraform CLI args merging behavior with lazy initialization and new subcommand-merge logic.

Changes

Cohort / File(s)	Summary
CLI argument parsing & tests `internal/clihelper/args.go`, `internal/clihelper/args_test.go`, `internal/clihelper/boolean_args_test.go`	Added flag normalization/validation (`minFlagLen`, `normalizeFlag`, `isFlag`), enhanced flag handling (`HasFlag`, `RemoveFlag`, `MergeFlags`, `hasFlagWithValue`) to support `-f value` and `-f=value` forms, introduced argument builder helpers (`AppendArgument`, `InsertArgument(s)`, `AppendSubCommand`), exported `IsKnownSubCommand`, replaced ad-hoc slice ops with utilities, and expanded table-driven tests covering many edge cases.
Run command flags `internal/cli/commands/run/flags.go`	Renamed local `flags` variable to `cmdFlags` and updated subsequent chained calls to use `cmdFlags.Add(...)` and `cmdFlags.Sort()`; no behavioral changes.
Runner nil-safety `internal/runner/runnerpool/runner.go`	Added nil-check in `isDestroyCommand` to avoid nil dereference when `args` is nil.
Terraform run writers & dependency args `internal/tf/run_cmd.go`, `pkg/config/dependency.go`	Introduced `defaultWriterOptionsLen` constant for writer-options slice capacity initialization; switched dependency output arg construction to fluent builder pattern (`NewIacArgs().SetCommand(...).AppendFlag(...)`).
Terraform CLI args merging & tests `pkg/options/options.go`, `pkg/options/options_test.go`	Lazy-initialize `TerraformCliArgs`, added internal `mergeCommandAndSubCommand` to merge parsed Command/SubCommand (last-writer-wins for subcommands), adjusted `InsertTerraformCliArgs`/`AppendTerraformCliArgs` flows, and added tests for subcommand replacement and nil-guards.

Sequence Diagram(s)

(Skipped — changes are parsing/refactor-focused and do not introduce a new multi-component sequential flow requiring visualization.)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

IaC tool CLI arguments re-ordering #5414: Modifies IacArgs and CLI argument parsing/usage; directly related to internal/clihelper changes.
fix: Fixing exit codes for run --all #5385: Touches internal/runner/runnerpool/runner.go and runner behavior; related to the nil-guard change.
feat: Implementation of --all --graph flags #3944: Changes internal/cli/commands/run/flags.go (NewFlags); overlaps with run flags edits.

Suggested reviewers

ThisGuyCodes
yhakbar

🚥 Pre-merge checks | ❌ 3

❌ Failed checks (1 warning, 2 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 47.37% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Title check	❓ Inconclusive	The title is partially related to the changeset but lacks specificity. While 'IAC tool cli building improvements' refers to real changes in the CLI argument handling code, it is overly broad and generic, not highlighting the main focus such as flag normalization, argument refactoring, or boolean flag handling.	Consider a more specific title such as 'Refactor IacArgs API and flag handling utilities' or 'Improve CLI argument parsing with normalized flags' to better convey the primary technical changes.
Description check	❓ Inconclusive	The description covers the main improvements but lacks detail and specificity. It mentions bullet points about CLI argument building, error throwing for report extensions, boolean flag handling, and tests, but does not provide sufficient context about what aspects were improved or why.	Enhance the description with more details about the specific improvements: explain the refactoring of IacArgs API (new methods, flag normalization), what the report extension error addresses, and how boolean flag handling was simplified. Add the issue number to the 'Fixes `#000`' line.

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…li-improvements

- prevent false positives in flag matching by checking for dash prefix - reintroduce nil guards for TerraformCliArgs in options - improve subcommand replacement logic in InsertTerraformCliArgs - restore fixture counter cleanup in run-cmd tests

…li-improvements

yhakbar · 2026-01-29T19:37:51Z


 				if ext != ".csv" && ext != ".json" {
-					return nil
+					return fmt.Errorf("unsupported report file extension: %s (supported: .csv, .json)", ext)


Why is this an error now? Users should be able to use whatever extension they want, we just won't auto-detect the right report format automatically if they don't use .csv or .json.

In the old version it is just returning out, so silently, no report format will be set

The docs say the default is CSV if it can't work it out based on extension or flag:
https://terragrunt.gruntwork.io/docs/features/run-report/#run-report

It must have been working at some point.

yhakbar · 2026-01-29T19:41:56Z

+	newFlags := make([]string, 0, len(a.Flags))
+	target := normalizeFlag(name)
+
+	for i := 0; i < len(a.Flags); i++ {


NIT: You can use the modern range syntax here.

Ah, maybe you run into issues if you're manually manipulating the iterator on line 318?

yhakbar · 2026-01-29T19:45:09Z

-	"-write-out",
+// valueTakingFlags contains flags that require space-separated values.
+// Only flags that commonly use a space-separated format need to be listed here.
+var valueTakingFlags = []string{


Are we keeping this because there's no way around having knowledge of OpenTofu/Terraform CLI arguments?

Yes, we need wha to take as "next parameter"

yhakbar · 2026-01-29T19:47:04Z

@@ -991,7 +991,7 @@ func (r *Runner) SetReport(rpt *report.Report) {
 // isDestroyCommand checks if the current command is a destroy operation
 func isDestroyCommand(cmd string, args *clihelper.IacArgs) bool {


If we move IaCArgs out of clihelper (which is pretty bloated right now), we can put stuff like this as methods on IaCArgs.

yhakbar · 2026-01-29T19:47:30Z

 	targetOptions.CheckDependentUnits = false
 	targetOptions.TerraformCommand = "output"
-	targetOptions.TerraformCliArgs = clihelper.NewIacArgs("output", "-json")
+	targetOptions.TerraformCliArgs = clihelper.NewIacArgs().SetCommand("output").AppendFlag("-json")


yhakbar · 2026-01-29T19:49:48Z

+
+	// Subcommands: replace or append
+	if len(parsed.SubCommand) > 0 {
+		// For "providers lock", if we insert "providers mirror", we want "providers mirror".


I don't really understand what this means. Why are we overwriting this?

yhakbar · 2026-01-29T19:50:46Z

+//   - If parsed.Command matches opts command, do nothing (idempotent)
+//   - If parsed.Command is a known subcommand, add to SubCommand
+//   - Otherwise treat parsed.Command as positional argument
+func (opts *TerragruntOptions) mergeCommand(parsed *clihelper.IacArgs) {


I'm nervous about adding another method to TerragruntOptions. I feel like we're giving more responsibility to something we should be slimming down.

denis256 added 2 commits January 28, 2026 19:47

CLI parsing improvements

67e82e1

output fetching improvements

819fbf9

vercel bot deployed to Preview January 28, 2026 19:57 View deployment

options simplifications

658f5f7

vercel bot deployed to Preview January 28, 2026 20:02 View deployment

Args tests fixes

dd1de91

vercel bot deployed to Preview January 28, 2026 20:21 View deployment

Merge branch 'main' into iac-cli-improvements

a01a918

vercel bot deployed to Preview January 28, 2026 20:23 View deployment

denis256 added 2 commits January 29, 2026 15:20

Simplified CLI arguments parsing

112883e

Merge remote-tracking branch 'origin/iac-cli-improvements' into iac-c…

7c6bf76

…li-improvements

vercel bot deployed to Preview January 29, 2026 15:22 View deployment

cli parsing simplificaiton

20409c0

vercel bot deployed to Preview January 29, 2026 16:32 View deployment

args cleanup

765bc24

vercel bot deployed to Preview January 29, 2026 16:46 View deployment

vercel bot deployed to Preview January 29, 2026 16:58 View deployment

denis256 added 2 commits January 29, 2026 17:01

tests cleanup

8d191a6

Merge remote-tracking branch 'origin/iac-cli-improvements' into iac-c…

369897a

…li-improvements

vercel bot deployed to Preview January 29, 2026 17:09 View deployment

args simplification

f168c4e

vercel bot deployed to Preview January 29, 2026 17:15 View deployment

flags cleanup

a15ca95

vercel bot deployed to Preview January 29, 2026 17:26 View deployment

test fixes

c44764f

vercel bot deployed to Preview January 29, 2026 17:34 View deployment

cli cleanup

0c42d92

vercel bot deployed to Preview January 29, 2026 18:23 View deployment

Merge remote-tracking branch 'origin/main' into iac-cli-improvements

695675e

vercel bot deployed to Preview January 29, 2026 18:28 View deployment

flags simplificaion

b44e45d

vercel bot deployed to Preview January 29, 2026 18:44 View deployment

args update

923b256

vercel bot deployed to Preview January 29, 2026 18:52 View deployment

conditions simplifications

9fe81fc

vercel bot deployed to Preview January 29, 2026 19:05 View deployment

args cleanup

3e18426

vercel bot deployed to Preview January 29, 2026 19:10 View deployment

denis256 marked this pull request as ready for review January 29, 2026 19:33

denis256 requested review from thisguycodes and yhakbar as code owners January 29, 2026 19:33

yhakbar reviewed Jan 29, 2026

View reviewed changes

options cleanup

8c2ec6b

vercel bot deployed to Preview January 29, 2026 19:58 View deployment

Default extension handling for reports

a2e1668

vercel bot deployed to Preview January 29, 2026 20:10 View deployment

yhakbar approved these changes Jan 29, 2026

View reviewed changes

denis256 merged commit b6da3f0 into main Jan 29, 2026
51 of 52 checks passed

denis256 deleted the iac-cli-improvements branch January 29, 2026 20:53

coderabbitai bot mentioned this pull request Jan 30, 2026

chore: iac cli package #5462

Merged

6 tasks

BrewTestBot mentioned this pull request Mar 31, 2026

terragrunt 1.0.0 Homebrew/homebrew-core#275297

Merged

		@@ -991,7 +991,7 @@ func (r Runner) SetReport(rpt report.Report) {
		// isDestroyCommand checks if the current command is a destroy operation
		func isDestroyCommand(cmd string, args *clihelper.IacArgs) bool {

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Description

TODOs

Release Notes (draft)

Migration Guide

Summary by CodeRabbit

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Walkthrough

Changes

Sequence Diagram(s)

Estimated code review effort

Possibly related PRs

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denis256 commented Jan 28, 2026 •

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