chore: support -j N syntax for parallel flag and remove default value (…

…#1524)

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## What this PR does / why we need it:

This PR adds support for supplying a parameter to the short form of the
`--parallel`flag, i.e. `-j N`.
It also removes the default value, so the long version always needs a
value.

## Which issue(s) this PR fixes:
<!--
*Automatically closes linked issue when PR is merged.
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
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issues/tests in a comment and do not use `Fixes`_*
Keep it empty if not applicable.
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## Special notes for your reviewer:

## Does this PR introduce a user-facing change?
<!--
If no, just write "no" in the block below.
If yes, please explain the change and update documentation and the
CHANGELOG.md file accordingly.
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no
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CHANGELOG.md

@@ -41,8 +41,7 @@ Given a version number `MAJOR.MINOR.PATCH`, we increment the:
 - Improve user experience when using Terramate with existing Terragrunt projects.
   - Add  `terramate create --all-terragrunt` option, which will automatically create Terramate stacks for each Terraform module.
 - Allow to run independent stacks in parallel for faster deployments and better utilization of system resources in general.
-  - Add `--parallel` (short `-j`) option to `terramate run` and `terramate script run`.
-  - `--parallel=N` limits the number of concurrent runs to `N`, otherwise a sensible default limit is chosen.
+  - Add `--parallel=N` (short `-j N`) option to `terramate run` and `terramate script run` to allow running up to `N` stacks in parallel.
   - Ordering constraints between stacks are still respected, i.e. `before`/`after`, parent before sub-folders.
 - Add `cloud_sync_drift_status` option to `script` block commands. It allows for synchronizing the
   stack drift details from script jobs.

cmd/terramate/cli/cli.go

@@ -11,8 +11,6 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"reflect"
-	"strconv"
 	"strings"
 	"time"
 
@@ -102,12 +100,6 @@ const (
 // UIMode defines different modes of operation for the cli.
 type UIMode int
 
-type kongParallelFlag struct {
-	Value int
-}
-
-const defaultParallelRunCount = 5
-
 type cliSpec struct {
 	VersionFlag    bool     `hidden:"true" name:"version" help:"Show Terramate version."`
 	Chdir          string   `short:"C" optional:"true" predictor:"file" help:"Set working directory."`
@@ -171,7 +163,7 @@ type cliSpec struct {
 		// Note: 0 is not the real default value here, this is just a workaround.
 		// Kong doesn't support having 0 as the default value in case the flag isn't set, but K in case it's set without a value.
 		// The K case is handled in the custom decoder.
-		Parallel kongParallelFlag `short:"j" optional:"true" default:"0" help:"Run independent stacks in parallel."`
+		Parallel int `short:"j" optional:"true" help:"Run independent stacks in parallel."`
 
 		runSafeguardsCliSpec
 
@@ -196,7 +188,7 @@ type cliSpec struct {
 			Cmds []string `arg:"" optional:"true" passthrough:"" help:"Script to execute."`
 
 			// See above comment regarding for run --parallel.
-			Parallel kongParallelFlag `short:"j" optional:"true" default:"0" help:"Run independent stacks in parallel"`
+			Parallel int `short:"j" optional:"true" help:"Run independent stacks in parallel."`
 
 			runSafeguardsCliSpec
 		} `cmd:"" help:"Run a Terramate Script in stacks."`
@@ -709,36 +701,6 @@ func (c *cli) run() {
 	}
 }
 
-func (s *kongParallelFlag) Decode(ctx *kong.DecodeContext) error {
-	if ctx.Scan.Peek().Type == kong.FlagValueToken {
-		t, err := ctx.Scan.PopValue("counter")
-		if err != nil {
-			return err
-		}
-
-		switch v := t.Value.(type) {
-		case string:
-			n, err := strconv.ParseInt(v, 10, 64)
-			if err != nil {
-				return stdfmt.Errorf("expected a counter but got %q (%T)", t, t.Value)
-			}
-			s.Value = int(n)
-
-		case int, int8, int16, int32, int64:
-			t := reflect.ValueOf(v)
-			s.Value = int(t.Int())
-
-		default:
-			return stdfmt.Errorf("expected a counter but got %q (%T)", t, t.Value)
-		}
-		return nil
-	}
-
-	s.Value = defaultParallelRunCount
-
-	return nil
-}
-
 func (c *cli) setupSafeguards(run runSafeguardsCliSpec) {
 	global := c.parsedArgs.deprecatedGlobalSafeguardsCliSpec
 

cmd/terramate/cli/run.go

@@ -187,7 +187,7 @@ func (c *cli) runOnStacks() {
 		Reverse:         c.parsedArgs.Run.Reverse,
 		ScriptRun:       false,
 		ContinueOnError: c.parsedArgs.Run.ContinueOnError,
-		Parallel:        c.parsedArgs.Run.Parallel.Value,
+		Parallel:        c.parsedArgs.Run.Parallel,
 	})
 	if err != nil {
 		fatal("one or more commands failed", err)

cmd/terramate/cli/script_run.go

@@ -118,7 +118,7 @@ func (c *cli) runScript() {
 		DryRun:          c.parsedArgs.Script.Run.DryRun,
 		ScriptRun:       true,
 		ContinueOnError: false,
-		Parallel:        c.parsedArgs.Script.Run.Parallel.Value,
+		Parallel:        c.parsedArgs.Script.Run.Parallel,
 	})
 	if err != nil {
 		fatal("one or more commands failed", err)

cmd/terramate/e2etests/cloud/run_cloud_deployment_test.go

@@ -407,7 +407,7 @@ func TestCLIRunWithCloudSyncDeployment(t *testing.T) {
 					"--cloud-sync-deployment",
 				}
 				if isParallel {
-					runflags = append(runflags, "--parallel")
+					runflags = append(runflags, "--parallel", "5")
 					tc.want.run.IgnoreStdout = true
 					tc.want.run.IgnoreStderr = true
 				}

cmd/terramate/e2etests/cloud/run_cloud_drift_test.go

@@ -531,7 +531,7 @@ func TestCLIRunWithCloudSyncDriftStatus(t *testing.T) {
 					"--cloud-sync-drift-status",
 				}
 				if isParallel {
-					runflags = append(runflags, "--parallel")
+					runflags = append(runflags, "-j", "5")
 					tc.want.run.IgnoreStdout = true
 					tc.want.run.IgnoreStderr = true
 				}

cmd/terramate/e2etests/cloud/run_cloud_signal_test.go

@@ -120,7 +120,7 @@ func TestCLIRunWithCloudSyncDeploymentWithSignals(t *testing.T) {
 					"--cloud-sync-deployment",
 				}
 				if isParallel {
-					runflags = append(runflags, "--parallel")
+					runflags = append(runflags, "--parallel", "5")
 					tc.want.run.IgnoreStdout = true
 					tc.want.run.IgnoreStderr = true
 				}
@@ -220,7 +220,7 @@ func TestCLIRunWithCloudSyncDriftStatusWithSignals(t *testing.T) {
 					"--cloud-sync-drift-status",
 				}
 				if isParallel {
-					runflags = append(runflags, "--parallel")
+					runflags = append(runflags, "--parallel=5")
 					tc.want.run.IgnoreStdout = true
 					tc.want.run.IgnoreStderr = true
 				}

cmd/terramate/e2etests/cloud/run_script_cloud_deployment_test.go

@@ -236,7 +236,7 @@ func TestCLIScriptRunWithCloudSyncDeployment(t *testing.T) {
 
 				scriptArgs := []string{"--quiet", "--disable-safeguards=git-out-of-sync"}
 				if isParallel {
-					scriptArgs = append(scriptArgs, "--parallel")
+					scriptArgs = append(scriptArgs, "--parallel=5")
 					// For the parallel test, we ignore output validation, since the print order is non-deterministic.
 					tc.want.run.IgnoreStderr = true
 					tc.want.run.IgnoreStdout = true

cmd/terramate/e2etests/cloud/run_script_cloud_drift_test.go

@@ -512,7 +512,7 @@ func TestScriptRunDriftStatus(t *testing.T) {
 					"--quiet",
 				}
 				if isParallel {
-					runflags = append(runflags, "--parallel")
+					runflags = append(runflags, "--parallel", "5")
 					tc.want.run.IgnoreStdout = true
 					tc.want.run.IgnoreStderr = true
 				}

cmd/terramate/e2etests/core/run_parallel_test.go

@@ -39,7 +39,7 @@ func TestParallelFibonacci(t *testing.T) {
 
 			tmcli := NewCLI(t, s.RootDir())
 
-			res := tmcli.Run("run", "--quiet", "--parallel", "--", HelperPath, "fibonacci")
+			res := tmcli.Run("run", "--quiet", "--parallel=5", "--", HelperPath, "fibonacci")
 			AssertRunResult(t, res, RunExpected{})
 
 			b, err := os.ReadFile(s.RootDir() + fmt.Sprintf("/fib.%v/fib.txt", tc.FibN))