WIP

internal/terraform/context_apply_target_test.go

@@ -0,0 +1,48 @@
+package terraform
+
+import (
+	"testing"
+
+	"github.com/hashicorp/terraform/internal/addrs"
+	provider "github.com/hashicorp/terraform/internal/providers"
+	"github.com/hashicorp/terraform/internal/states"
+	"github.com/hashicorp/terraform/internal/tfdiags"
+)
+
+func TestContextApply_TargetInstance(t *testing.T) {
+	testConfig := testModuleInline(t, map[string]string{
+		"main.tf": `
+	resource "test_object" "foo" {
+		count = 2
+		test_string = join("_", ["foo", count.index])
+	}	
+
+	resource "test_object" "bar" {
+		count = 2
+    	test_string = resource.test_object.foo[count.index].test_string
+	}
+`,
+	})
+
+	p := simpleMockProvider()
+	ctx := testContext2(
+		t,
+		&ContextOpts{
+			Providers: map[addrs.Provider]provider.Factory{
+				addrs.NewDefaultProvider("test"): testProviderFuncFixed(p),
+			},
+		},
+	)
+
+	testTarget := mustResourceInstanceAddr("test_object.bar[0]")
+	planOptions := DefaultPlanOpts
+	planOptions.Targets = []addrs.Targetable{
+		testTarget,
+	}
+	planOptions.SafeTargeting = true
+	pr, diags := ctx.Plan(testConfig, states.NewState(), planOptions)
+	tfdiags.AssertNoErrors(t, diags)
+
+	_ = pr.Changes.Resources
+	t.Log("test")
+}

internal/terraform/context_plan.go

@@ -67,6 +67,8 @@ type PlanOpts struct {
 	// warnings as part of the planning result.
 	Targets []addrs.Targetable
 
+	SafeTargeting bool
+
 	// ActionTargets represents the actions that should be triggered by this
 	// execution. This is incompatible with the `Targets` attribute, only one
 	// can be set. Also, Mode must be plans.RefreshOnly when using
@@ -1005,6 +1007,7 @@ func (c *Context) planGraph(config *configs.Config, prevRunState *states.State,
 			ExternalProviderConfigs:   externalProviderConfigs,
 			Plugins:                   c.plugins,
 			Targets:                   opts.Targets,
+			SafeTargeting:             opts.SafeTargeting,
 			ForceReplace:              opts.ForceReplace,
 			skipRefresh:               opts.SkipRefresh,
 			preDestroyRefresh:         opts.PreDestroyRefresh,

internal/terraform/graph_builder_plan.go

@@ -132,6 +132,9 @@ type PlanGraphBuilder struct {
 	// or test runtimes, where the root modules as Terraform sees them aren't
 	// the actual root modules.
 	AllowRootEphemeralOutputs bool
+
+	// TODO: Add comment
+	SafeTargeting bool
 }
 
 // See GraphBuilder
@@ -303,6 +306,10 @@ func (b *PlanGraphBuilder) Steps() []GraphTransformer {
 		// Target
 		&TargetsTransformer{Targets: b.Targets},
 
+		// TODO_SAMS: Check whether we can create a dummy safe target transformer
+		// which checks references and trims down the produce of targetsTransformer
+		// down to what instances are actually targeted by the defined target.
+
 		// Filter the graph to only include nodes that are relevant to the query operation.
 		&QueryTransformer{queryPlan: b.queryPlan, validate: b.Operation == walkValidate},
 

internal/terraform/transform_targets.go

@@ -197,13 +197,18 @@ func (t *TargetsTransformer) nodeIsTarget(v dag.Vertex, targets []addrs.Targetab
 	return false
 }
 
-// addVertexDependenciesToTargetedNodes adds dependencies of the targeted vertex to the
-// targetedNodes set. This includes all ancestors in the graph.
-// It also includes all action trigger nodes in the graph. Actions are planned after the
-// triggering node has planned so that we can ensure the actions are only planned if the triggering
-// resource has an action (Create / Update) corresponding to one of the events in the action trigger
-// blocks event list.
-func (t *TargetsTransformer) addVertexDependenciesToTargetedNodes(g *Graph, v dag.Vertex, targetedNodes dag.Set, addrs []addrs.Targetable) {
+// addVertexDependenciesToTargetedNodes adds dependencies of the targeted vertex
+// to the targetedNodes set. This includes all ancestors in the graph.
+// It also includes all action trigger nodes in the graph. Actions are planned
+// after the triggering node has planned so that we can ensure the actions are
+// only planned if the triggering resource has an action (Create / Update)
+// corresponding to one of the events in the action trigger blocks event list.
+func (t *TargetsTransformer) addVertexDependenciesToTargetedNodes(
+	g *Graph,
+	v dag.Vertex,
+	targetedNodes dag.Set,
+	addrs []addrs.Targetable,
+) {
 	if targetedNodes.Include(v) {
 		return
 	}