Decode action blocks and action_triggers inside resource blocks. (hashicorp#37030)

* Decode action blocks and action_triggers inside resource blocks.

This commit adds decoding of action and action_triggers inside terraform configuration. I added an Actions experiment as a hacky way of keeping the functionality out of main until we're ready for the alpha; this may never be an experiment but it's a handy feature flag so we don't have to do all the work in a long-lived feature branch.

* remove legacy shim handling
* validate that the referenced entry in actions is indeed an action

Author: mildwonkey

internal/configs/action.go

@@ -0,0 +1,277 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package configs
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/hclsyntax"
+
+	"github.com/hashicorp/terraform/internal/addrs"
+)
+
+// Action represents an "action" block inside a configuration
+type Action struct {
+	Name      string
+	Type      string
+	Config    hcl.Body
+	Count     hcl.Expression
+	ForEach   hcl.Expression
+	DependsOn []hcl.Traversal
+
+	ProviderConfigRef *ProviderConfigRef
+	Provider          addrs.Provider
+
+	DeclRange hcl.Range
+	TypeRange hcl.Range
+}
+
+// ActionTrigger represents a configured "action_trigger" inside the lifecycle
+// block of a managed resource.
+type ActionTrigger struct {
+	Condition hcl.Expression
+	Events    []ActionTriggerEvent
+	Actions   []ActionRef
+
+	DeclRange hcl.Range
+}
+
+// ActionTriggerEvent is an enum for valid values for events for action
+// triggers.
+type ActionTriggerEvent int
+
+//go:generate go tool golang.org/x/tools/cmd/stringer -type ActionTriggerEvent
+
+const (
+	BeforeCreate ActionTriggerEvent = iota
+	AfterCreate
+	BeforeUpdate
+	AfterUpdate
+	BeforeDestroy
+	AfterDestroy
+)
+
+// ActionRef represents a reference to a configured Action
+// copypasta of providerconfigref; not sure what's needed.
+type ActionRef struct {
+	Traversal hcl.Traversal
+	Range     hcl.Range
+}
+
+func decodeActionTriggerBlock(block *hcl.Block) (*ActionTrigger, hcl.Diagnostics) {
+	var diags hcl.Diagnostics
+	a := &ActionTrigger{
+		Events:    []ActionTriggerEvent{},
+		Actions:   []ActionRef{},
+		Condition: nil,
+	}
+
+	content, bodyDiags := block.Body.Content(actionTriggerSchema)
+	diags = append(diags, bodyDiags...)
+
+	if attr, exists := content.Attributes["condition"]; exists {
+		a.Condition = attr.Expr
+	}
+
+	// this is parsing events like expressions, so it's angry when there's quotes
+	// needs to parse strings:
+	// Quoted references are deprecated; In this context, references are expected literally rather than in quotes.
+	if attr, exists := content.Attributes["events"]; exists {
+		exprs, ediags := hcl.ExprList(attr.Expr)
+		diags = append(diags, ediags...)
+
+		events := []ActionTriggerEvent{}
+
+		for _, expr := range exprs {
+			var event ActionTriggerEvent
+			switch hcl.ExprAsKeyword(expr) {
+			case "before_create":
+				event = BeforeCreate
+			case "after_create":
+				event = AfterCreate
+			case "before_update":
+				event = BeforeUpdate
+			case "after_update":
+				event = AfterUpdate
+			case "before_destroy":
+				event = BeforeDestroy
+			case "after_destroy":
+				event = AfterDestroy
+			default:
+				diags = append(diags, &hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  fmt.Sprintf("Invalid \"event\" value %s", hcl.ExprAsKeyword(expr)),
+					Detail:   "The \"event\" argument supports the following values: before_create, after_create, before_update, after_update, before_destroy, after_destroy.",
+					Subject:  expr.Range().Ptr(),
+				})
+			}
+			events = append(events, event)
+		}
+		a.Events = events
+	}
+
+	if attr, exists := content.Attributes["actions"]; exists {
+		exprs, ediags := hcl.ExprList(attr.Expr)
+		diags = append(diags, ediags...)
+		actions := []ActionRef{}
+		for _, expr := range exprs {
+			traversal, travDiags := hcl.AbsTraversalForExpr(expr)
+			diags = append(diags, travDiags...)
+			// verify that the traversal is an action
+			if traversal.RootName() != "action" {
+				diags = append(diags, &hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Invalid actions argument inside action_triggers",
+					Detail:   "action_triggers.actions accepts a list of one or more actions",
+					Subject:  block.DefRange.Ptr(),
+				})
+			}
+			if len(traversal) != 0 {
+				actionRef := ActionRef{
+					Traversal: traversal,
+					Range:     expr.Range(),
+				}
+				actions = append(actions, actionRef)
+			}
+		}
+		a.Actions = actions
+	}
+
+	if len(a.Actions) == 0 {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "No actions specified",
+			Detail:   "At least one action must be specified for an action_trigger.",
+			Subject:  block.DefRange.Ptr(),
+		})
+	}
+
+	if len(a.Events) == 0 {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "No events specified",
+			Detail:   "At least one event must be specified for an action_trigger.",
+			Subject:  block.DefRange.Ptr(),
+		})
+	}
+	return a, diags
+}
+
+func decodeActionBlock(block *hcl.Block) (*Action, hcl.Diagnostics) {
+	var diags hcl.Diagnostics
+	a := &Action{
+		Type:      block.Labels[0],
+		Name:      block.Labels[1],
+		DeclRange: block.DefRange,
+		TypeRange: block.LabelRanges[0],
+	}
+
+	if !hclsyntax.ValidIdentifier(a.Type) {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid action type name",
+			Detail:   badIdentifierDetail,
+			Subject:  &block.LabelRanges[0],
+		})
+	}
+	if !hclsyntax.ValidIdentifier(a.Name) {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid action name",
+			Detail:   badIdentifierDetail,
+			Subject:  &block.LabelRanges[1],
+		})
+	}
+
+	content, remain, moreDiags := block.Body.PartialContent(actionBlockSchema)
+	diags = append(diags, moreDiags...)
+	a.Config = remain
+
+	if attr, exists := content.Attributes["count"]; exists {
+		a.Count = attr.Expr
+	}
+
+	if attr, exists := content.Attributes["for_each"]; exists {
+		a.ForEach = attr.Expr
+		// Cannot have count and for_each on the same action block
+		if a.Count != nil {
+			diags = append(diags, &hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  `Invalid combination of "count" and "for_each"`,
+				Detail:   `The "count" and "for_each" meta-arguments are mutually-exclusive, only one should be used.`,
+				Subject:  &attr.NameRange,
+			})
+		}
+	}
+
+	if attr, exists := content.Attributes["provider"]; exists {
+		var providerDiags hcl.Diagnostics
+		a.ProviderConfigRef, providerDiags = decodeProviderConfigRef(attr.Expr, "provider")
+		diags = append(diags, providerDiags...)
+	}
+
+	if attr, exists := content.Attributes["depends_on"]; exists {
+		deps, depsDiags := DecodeDependsOn(attr)
+		diags = append(diags, depsDiags...)
+		a.DependsOn = append(a.DependsOn, deps...)
+	}
+
+	return a, diags
+}
+
+// actionBlockSchema is the schema for an action type within terraform.
+var actionBlockSchema = &hcl.BodySchema{
+	Attributes: commonResourceAttributes,
+}
+
+var actionTriggerSchema = &hcl.BodySchema{
+	Attributes: []hcl.AttributeSchema{
+		{
+			Name:     "events",
+			Required: true,
+		},
+		{
+			Name:     "condition",
+			Required: false,
+		},
+		{
+			Name:     "actions",
+			Required: true,
+		},
+	},
+}
+
+func (a *Action) moduleUniqueKey() string {
+	return a.Addr().String()
+}
+
+// Addr returns a resource address for the receiver that is relative to the
+// resource's containing module.
+func (a *Action) Addr() addrs.Action {
+	return addrs.Action{
+		Type: a.Type,
+		Name: a.Name,
+	}
+}
+
+// ProviderConfigAddr returns the address for the provider configuration that
+// should be used for this action. This function returns a default provider
+// config addr if an explicit "provider" argument was not provided.
+func (a *Action) ProviderConfigAddr() addrs.LocalProviderConfig {
+	if a.ProviderConfigRef == nil {
+		// If no specific "provider" argument is given, we want to look up the
+		// provider config where the local name matches the implied provider
+		// from the resource type. This may be different from the resource's
+		// provider type.
+		return addrs.LocalProviderConfig{
+			LocalName: a.Addr().ImpliedProvider(),
+		}
+	}
+
+	return addrs.LocalProviderConfig{
+		LocalName: a.ProviderConfigRef.Name,
+		Alias:     a.ProviderConfigRef.Alias,
+	}
+}

internal/configs/actiontriggerevent_string.go

@@ -49,6 +49,7 @@ type Module struct {
 	ManagedResources   map[string]*Resource
 	DataResources      map[string]*Resource
 	EphemeralResources map[string]*Resource
+	Actions            map[string]*Action
 
 	Moved   []*Moved
 	Removed []*Removed
@@ -95,7 +96,8 @@ type File struct {
 	Removed []*Removed
 	Import  []*Import
 
-	Checks []*Check
+	Checks  []*Check
+	Actions []*Action
 }
 
 // NewModuleWithTests matches NewModule except it will also load in the provided
@@ -131,6 +133,7 @@ func NewModule(primaryFiles, overrideFiles []*File) (*Module, hcl.Diagnostics) {
 		Checks:             map[string]*Check{},
 		ProviderMetas:      map[addrs.Provider]*ProviderMeta{},
 		Tests:              map[string]*TestFile{},
+		Actions:            map[string]*Action{},
 	}
 
 	// Process the required_providers blocks first, to ensure that all
@@ -491,6 +494,35 @@ func (m *Module) appendFile(file *File) hcl.Diagnostics {
 		m.Import = append(m.Import, i)
 	}
 
+	for _, a := range file.Actions {
+		key := a.moduleUniqueKey()
+		if existing, exists := m.Actions[key]; exists {
+			diags = append(diags, &hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  fmt.Sprintf("Duplicate action %q configuration", existing.Type),
+				Detail:   fmt.Sprintf("An action named %q was already declared at %s. Resource names must be unique per type in each module.", existing.Name, existing.DeclRange),
+				Subject:  &a.DeclRange,
+			})
+			continue
+		}
+		m.Actions[key] = a
+
+		// set the provider FQN for the action
+		if a.ProviderConfigRef != nil {
+			a.Provider = m.ProviderForLocalConfig(a.ProviderConfigAddr())
+		} else {
+			// an invalid resource name (for e.g. "null resource" instead of
+			// "null_resource") can cause a panic down the line in addrs:
+			// https://github.com/hashicorp/terraform/issues/25560
+			implied, err := addrs.ParseProviderPart(a.Addr().ImpliedProvider())
+			if err == nil {
+				a.Provider = m.ImpliedProviderForUnqualifiedType(implied)
+			}
+			// We don't return a diagnostic because the invalid resource name
+			// will already have been caught.
+		}
+	}
+
 	return diags
 }
 
@@ -681,6 +713,22 @@ func (m *Module) mergeFile(file *File) hcl.Diagnostics {
 		})
 	}
 
+	for _, a := range file.Actions {
+		key := a.moduleUniqueKey()
+		existing, exists := m.Actions[key]
+		if !exists {
+			diags = append(diags, &hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Missing resource to override",
+				Detail:   fmt.Sprintf("There is no action named %q. An override file can only override a resource block defined in a primary configuration file.", a.Name),
+				Subject:  &a.DeclRange,
+			})
+			continue
+		}
+		mergeDiags := existing.merge(a, m.ProviderRequirements.RequiredProviders)
+		diags = append(diags, mergeDiags...)
+	}
+
 	return diags
 }