stacks: move the RPCAPI and deferred actions out of experimental

.changes/footer-with-experiments.md

@@ -1,9 +1,3 @@
-EXPERIMENTS:
-
-Experiments are only enabled in alpha releases of Terraform CLI. The following features are not yet available in stable releases.
-
-- The new command `terraform rpcapi` exposes some Terraform Core functionality through an RPC interface compatible with [`go-plugin`](https://github.com/hashicorp/go-plugin). The exact RPC API exposed here is currently subject to change at any time, because it's here primarily as a vehicle to support the [Terraform Stacks](https://www.hashicorp.com/blog/terraform-stacks-explained) private preview and so will be broken if necessary to respond to feedback from private preview participants, or possibly for other reasons. Do not use this mechanism yet outside of Terraform Stacks private preview.
-- The experimental "deferred actions" feature, enabled by passing the `-allow-deferral` option to `terraform plan`, permits `count` and `for_each` arguments in `module`, `resource`, and `data` blocks to have unknown values and allows providers to react more flexibly to unknown values. This experiment is under active development, and so it's not yet useful to participate in this experiment
 
 ## Previous Releases
 

.changes/v1.13/NEW FEATURES-20250515-151904.yaml

@@ -0,0 +1,5 @@
+kind: NEW FEATURES
+body: 'Deferred actions: The `plan`, `apply`, and `refresh` commands now support the `-allow-deferral` flag. The flag enables Terraform and Terraform Providers to defer changes with unresolvable unknown values to future plans instead of failing the entire plan.'
+time: 2025-05-15T15:19:04.603403+02:00
+custom:
+    Issue: "37067"

.changes/v1.13/NOTES-20250515-151922.yaml

@@ -0,0 +1,5 @@
+kind: NOTES
+body: The command `terraform rpcapi` is now generally available. It is not intended for public consumption, but exposes certain Terraform operations through an RPC interface compatible with [go-plugin](https://github.com/hashicorp/go-plugin).
+time: 2025-05-15T15:19:22.219798+02:00
+custom:
+    Issue: "37067"

commands.go

@@ -282,6 +282,17 @@ func initCommands(
 			}, nil
 		},
 
+		// "rpcapi" is handled a bit differently because the whole point of
+		// this interface is to bypass the CLI layer so wrapping automation can
+		// get as-direct-as-possible access to Terraform Core functionality,
+		// without interference from behaviors that are intended for CLI
+		// end-user convenience. We bypass the "command" package entirely
+		// for this command in particular.
+		"rpcapi": rpcapi.CLICommandFactory(rpcapi.CommandFactoryOpts{
+			ExperimentsAllowed: meta.AllowExperimentalFeatures,
+			ShutdownCh:         meta.ShutdownCh,
+		}),
+
 		"show": func() (cli.Command, error) {
 			return &command.ShowCommand{
 				Meta: meta,
@@ -439,17 +450,6 @@ func initCommands(
 				Meta: meta,
 			}, nil
 		}
-
-		// "rpcapi" is handled a bit differently because the whole point of
-		// this interface is to bypass the CLI layer so wrapping automation can
-		// get as-direct-as-possible access to Terraform Core functionality,
-		// without interference from behaviors that are intended for CLI
-		// end-user convenience. We bypass the "command" package entirely
-		// for this command in particular.
-		Commands["rpcapi"] = rpcapi.CLICommandFactory(rpcapi.CommandFactoryOpts{
-			ExperimentsAllowed: meta.AllowExperimentalFeatures,
-			ShutdownCh:         meta.ShutdownCh,
-		})
 	}
 
 	PrimaryCommands = []string{

internal/command/apply.go

@@ -274,20 +274,7 @@ func (c *ApplyCommand) OperationRequest(
 	opReq.Type = backendrun.OperationTypeApply
 	opReq.View = view.Operation()
 	opReq.StatePersistInterval = c.Meta.StatePersistInterval()
-
-	// EXPERIMENTAL: maybe enable deferred actions
-	if c.AllowExperimentalFeatures {
-		opReq.DeferralAllowed = args.DeferralAllowed
-	} else if args.DeferralAllowed {
-		// Belated flag parse error, since we don't know about experiments
-		// support at actual parse time.
-		diags = diags.Append(tfdiags.Sourceless(
-			tfdiags.Error,
-			"Failed to parse command-line flags",
-			"The -allow-deferral flag is only valid in experimental builds of Terraform.",
-		))
-		return nil, diags
-	}
+	opReq.DeferralAllowed = args.DeferralAllowed
 
 	var err error
 	opReq.ConfigLoader, err = c.initConfigLoader()

internal/command/plan.go

@@ -164,20 +164,7 @@ func (c *PlanCommand) OperationRequest(
 	opReq.ForceReplace = args.ForceReplace
 	opReq.Type = backendrun.OperationTypePlan
 	opReq.View = view.Operation()
-
-	// EXPERIMENTAL: maybe enable deferred actions
-	if c.AllowExperimentalFeatures {
-		opReq.DeferralAllowed = args.DeferralAllowed
-	} else if args.DeferralAllowed {
-		// Belated flag parse error, since we don't know about experiments
-		// support at actual parse time.
-		diags = diags.Append(tfdiags.Sourceless(
-			tfdiags.Error,
-			"Failed to parse command-line flags",
-			"The -allow-deferral flag is only valid in experimental builds of Terraform.",
-		))
-		return nil, diags
-	}
+	opReq.DeferralAllowed = args.DeferralAllowed
 
 	var err error
 	opReq.ConfigLoader, err = c.initConfigLoader()

internal/command/refresh.go

@@ -146,20 +146,7 @@ func (c *RefreshCommand) OperationRequest(be backendrun.OperationsBackend, view
 	opReq.Targets = args.Targets
 	opReq.Type = backendrun.OperationTypeRefresh
 	opReq.View = view.Operation()
-
-	// EXPERIMENTAL: maybe enable deferred actions
-	if c.AllowExperimentalFeatures {
-		opReq.DeferralAllowed = args.DeferralAllowed
-	} else if args.DeferralAllowed {
-		// Belated flag parse error, since we don't know about experiments
-		// support at actual parse time.
-		diags = diags.Append(tfdiags.Sourceless(
-			tfdiags.Error,
-			"Failed to parse command-line flags",
-			"The -allow-deferral flag is only valid in experimental builds of Terraform.",
-		))
-		return nil, diags
-	}
+	opReq.DeferralAllowed = args.DeferralAllowed
 
 	var err error
 	opReq.ConfigLoader, err = c.initConfigLoader()

internal/terraform/eval_for_each.go

@@ -219,8 +219,8 @@ func (ev *forEachEvaluator) ensureKnownForImport(forEachVal cty.Value) tfdiags.D
 func (ev *forEachEvaluator) ensureKnownForResource(forEachVal cty.Value) tfdiags.Diagnostics {
 	var diags tfdiags.Diagnostics
 	ty := forEachVal.Type()
-	const errInvalidUnknownDetailMap = "The \"for_each\" map includes keys derived from resource attributes that cannot be determined until apply, and so Terraform cannot determine the full set of keys that will identify the instances of this resource.\n\nWhen working with unknown values in for_each, it's better to define the map keys statically in your configuration and place apply-time results only in the map values.\n\nAlternatively, you could use the -target planning option to first apply only the resources that the for_each value depends on, and then apply a second time to fully converge."
-	const errInvalidUnknownDetailSet = "The \"for_each\" set includes values derived from resource attributes that cannot be determined until apply, and so Terraform cannot determine the full set of keys that will identify the instances of this resource.\n\nWhen working with unknown values in for_each, it's better to use a map value where the keys are defined statically in your configuration and where only the values contain apply-time results.\n\nAlternatively, you could use the -target planning option to first apply only the resources that the for_each value depends on, and then apply a second time to fully converge."
+	const errInvalidUnknownDetailMap = "The \"for_each\" map includes keys derived from resource attributes that cannot be determined until apply, and so Terraform cannot determine the full set of keys that will identify the instances of this resource.\n\nWhen working with unknown values in for_each, it's better to define the map keys statically in your configuration and place apply-time results only in the map values.\n\nAlternatively, you could either use the -target planning option or the -allow-deferrals planning option to first apply only the resources that the for_each value depends on, and then apply a second time to fully converge."
+	const errInvalidUnknownDetailSet = "The \"for_each\" set includes values derived from resource attributes that cannot be determined until apply, and so Terraform cannot determine the full set of keys that will identify the instances of this resource.\n\nWhen working with unknown values in for_each, it's better to use a map value where the keys are defined statically in your configuration and where only the values contain apply-time results.\n\nAlternatively, you could either use the -target planning option or the -allow-deferrals planning option to first apply only the resources that the for_each value depends on, and then apply a second time to fully converge."
 
 	if !forEachVal.IsKnown() {
 		var detailMsg string