terraform: new Graph API that can return the graph for each op

terraform/context.go

@@ -189,13 +189,55 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 }
 
 type ContextGraphOpts struct {
+	// If true, validates the graph structure (checks for cycles).
 	Validate bool
-	Verbose  bool
+
+	// Legacy graphs only: won't prune the graph
+	Verbose bool
 }
 
-// Graph returns the graph for this config.
-func (c *Context) Graph(g *ContextGraphOpts) (*Graph, error) {
-	return c.graphBuilder(g).Build(RootModulePath)
+// Graph returns the graph used for the given operation type.
+//
+// The most extensive or complex graph type is GraphTypePlan.
+func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
+	if opts == nil {
+		opts = &ContextGraphOpts{Validate: true}
+	}
+
+	switch typ {
+	case GraphTypeApply:
+		return (&ApplyGraphBuilder{
+			Module:       c.module,
+			Diff:         c.diff,
+			State:        c.state,
+			Providers:    c.components.ResourceProviders(),
+			Provisioners: c.components.ResourceProvisioners(),
+			Destroy:      c.destroy,
+			Validate:     opts.Validate,
+		}).Build(RootModulePath)
+
+	case GraphTypePlan:
+		return (&PlanGraphBuilder{
+			Module:    c.module,
+			State:     c.state,
+			Providers: c.components.ResourceProviders(),
+			Targets:   c.targets,
+			Validate:  opts.Validate,
+		}).Build(RootModulePath)
+
+	case GraphTypePlanDestroy:
+		return (&DestroyPlanGraphBuilder{
+			Module:   c.module,
+			State:    c.state,
+			Targets:  c.targets,
+			Validate: opts.Validate,
+		}).Build(RootModulePath)
+
+	case GraphTypeLegacy:
+		return c.graphBuilder(opts).Build(RootModulePath)
+	}
+
+	return nil, fmt.Errorf("unknown graph type: %s", typ)
 }
 
 // GraphBuilder returns the GraphBuilder that will be used to create
@@ -360,7 +402,7 @@ func (c *Context) Input(mode InputMode) error {
 
 	if mode&InputModeProvider != 0 {
 		// Build the graph
-		graph, err := c.Graph(&ContextGraphOpts{Validate: true})
+		graph, err := c.Graph(GraphTypeLegacy, nil)
 		if err != nil {
 			return err
 		}
@@ -390,20 +432,11 @@ func (c *Context) Apply() (*State, error) {
 	X_legacyGraph := experiment.Enabled(experiment.X_legacyGraph)
 
 	// Build the graph.
-	var graph *Graph
-	var err error
+	graphType := GraphTypeLegacy
 	if !X_legacyGraph {
-		graph, err = (&ApplyGraphBuilder{
-			Module:       c.module,
-			Diff:         c.diff,
-			State:        c.state,
-			Providers:    c.components.ResourceProviders(),
-			Provisioners: c.components.ResourceProvisioners(),
-			Destroy:      c.destroy,
-		}).Build(RootModulePath)
-	} else {
-		graph, err = c.Graph(&ContextGraphOpts{Validate: true})
+		graphType = GraphTypeApply
 	}
+	graph, err := c.Graph(graphType, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -475,26 +508,15 @@ func (c *Context) Plan() (*Plan, error) {
 	X_legacyGraph := experiment.Enabled(experiment.X_legacyGraph)
 
 	// Build the graph.
-	var graph *Graph
-	var err error
+	graphType := GraphTypeLegacy
 	if !X_legacyGraph {
 		if c.destroy {
-			graph, err = (&DestroyPlanGraphBuilder{
-				Module:  c.module,
-				State:   c.state,
-				Targets: c.targets,
-			}).Build(RootModulePath)
+			graphType = GraphTypePlanDestroy
 		} else {
-			graph, err = (&PlanGraphBuilder{
-				Module:    c.module,
-				State:     c.state,
-				Providers: c.components.ResourceProviders(),
-				Targets:   c.targets,
-			}).Build(RootModulePath)
+			graphType = GraphTypePlan
 		}
-	} else {
-		graph, err = c.Graph(&ContextGraphOpts{Validate: true})
 	}
+	graph, err := c.Graph(graphType, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -522,7 +544,7 @@ func (c *Context) Plan() (*Plan, error) {
 	if X_legacyGraph {
 		// Now that we have a diff, we can build the exact graph that Apply will use
 		// and catch any possible cycles during the Plan phase.
-		if _, err := c.Graph(&ContextGraphOpts{Validate: true}); err != nil {
+		if _, err := c.Graph(GraphTypeLegacy, nil); err != nil {
 			return nil, err
 		}
 	}
@@ -548,7 +570,7 @@ func (c *Context) Refresh() (*State, error) {
 	c.state = c.state.DeepCopy()
 
 	// Build the graph
-	graph, err := c.Graph(&ContextGraphOpts{Validate: true})
+	graph, err := c.Graph(GraphTypeLegacy, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -619,7 +641,7 @@ func (c *Context) Validate() ([]string, []error) {
 	// We also validate the graph generated here, but this graph doesn't
 	// necessarily match the graph that Plan will generate, so we'll validate the
 	// graph again later after Planning.
-	graph, err := c.Graph(&ContextGraphOpts{Validate: true})
+	graph, err := c.Graph(GraphTypeLegacy, nil)
 	if err != nil {
 		return nil, []error{err}
 	}

terraform/context_graph_type.go

@@ -0,0 +1,26 @@
+package terraform
+
+//go:generate stringer -type=GraphType context_graph_type.go
+
+// GraphType is an enum of the type of graph to create with a Context.
+// The values of the constants may change so they shouldn't be depended on;
+// always use the constant name.
+type GraphType byte
+
+const (
+	GraphTypeInvalid GraphType = 0
+	GraphTypeLegacy  GraphType = iota
+	GraphTypePlan
+	GraphTypePlanDestroy
+	GraphTypeApply
+)
+
+// GraphTypeMap is a mapping of human-readable string to GraphType. This
+// is useful to use as the mechanism for human input for configurable
+// graph types.
+var GraphTypeMap = map[string]GraphType{
+	"apply":        GraphTypeApply,
+	"plan":         GraphTypePlan,
+	"plan-destroy": GraphTypePlanDestroy,
+	"legacy":       GraphTypeLegacy,
+}

terraform/graph_builder_apply.go

@@ -33,13 +33,16 @@ type ApplyGraphBuilder struct {
 
 	// Destroy, if true, represents a pure destroy operation
 	Destroy bool
+
+	// Validate will do structural validation of the graph.
+	Validate bool
 }
 
 // See GraphBuilder
 func (b *ApplyGraphBuilder) Build(path []string) (*Graph, error) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
-		Validate: true,
+		Validate: b.Validate,
 		Name:     "ApplyGraphBuilder",
 	}).Build(path)
 }

terraform/graph_builder_destroy_plan.go

@@ -19,13 +19,16 @@ type DestroyPlanGraphBuilder struct {
 
 	// Targets are resources to target
 	Targets []string
+
+	// Validate will do structural validation of the graph.
+	Validate bool
 }
 
 // See GraphBuilder
 func (b *DestroyPlanGraphBuilder) Build(path []string) (*Graph, error) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
-		Validate: true,
+		Validate: b.Validate,
 		Name:     "DestroyPlanGraphBuilder",
 	}).Build(path)
 }

terraform/graph_builder_plan.go

@@ -31,13 +31,16 @@ type PlanGraphBuilder struct {
 
 	// DisableReduce, if true, will not reduce the graph. Great for testing.
 	DisableReduce bool
+
+	// Validate will do structural validation of the graph.
+	Validate bool
 }
 
 // See GraphBuilder
 func (b *PlanGraphBuilder) Build(path []string) (*Graph, error) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
-		Validate: true,
+		Validate: b.Validate,
 		Name:     "PlanGraphBuilder",
 	}).Build(path)
 }

terraform/graphtype_string.go

@@ -0,0 +1,16 @@
+// Code generated by "stringer -type=GraphType context_graph_type.go"; DO NOT EDIT
+
+package terraform
+
+import "fmt"
+
+const _GraphType_name = "GraphTypeInvalidGraphTypeLegacyGraphTypePlanGraphTypePlanDestroyGraphTypeApply"
+
+var _GraphType_index = [...]uint8{0, 16, 31, 44, 64, 78}
+
+func (i GraphType) String() string {
+	if i >= GraphType(len(_GraphType_index)-1) {
+		return fmt.Sprintf("GraphType(%d)", i)
+	}
+	return _GraphType_name[_GraphType_index[i]:_GraphType_index[i+1]]
+}