add dependsOn to evalDataRead

this is also needed during refresh, so move it into the base struct type

terraform/eval_read_data.go

@@ -52,6 +52,12 @@ type evalReadData struct {
 	// - If planned action is plans.Update, it indicates that the data source
 	// was read, and the result needs to be stored in state during apply.
 	OutputChange **plans.ResourceInstanceChange
+
+	// dependsOn stores the list of transitive resource addresses that any
+	// configuration depends_on references may resolve to. This is used to
+	// determine if there are any changes that will force this data sources to
+	// be deferred to apply.
+	dependsOn []addrs.ConfigResource
 }
 
 // readDataSource handles everything needed to call ReadDataSource on the provider.
@@ -235,7 +241,7 @@ func (n *evalReadDataRefresh) Eval(ctx EvalContext) (interface{}, error) {
 	// refresh, that we can read this resource. If there are dependency updates
 	// in the config, they we be discovered in plan and the data source will be
 	// read again.
-	if !configKnown || (priorVal.IsNull() && len(n.Config.DependsOn) > 0) {
+	if !configKnown || (priorVal.IsNull() && n.forcePlanRead()) {
 		if configKnown {
 			log.Printf("[TRACE] evalReadDataRefresh: %s configuration is fully known, but we're forcing a read plan to be created", absAddr)
 		} else {
@@ -291,3 +297,10 @@ func (n *evalReadDataRefresh) Eval(ctx EvalContext) (interface{}, error) {
 
 	return nil, diags.ErrWithWarnings()
 }
+
+// forcePlanRead determines if we need to override the usual behavior of
+// immediately reading from the data source where possible, instead forcing us
+// to generate a plan.
+func (n *evalReadDataRefresh) forcePlanRead() bool {
+	return len(n.Config.DependsOn) > 0 || len(n.dependsOn) > 0
+}

terraform/eval_read_data_plan.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/zclconf/go-cty/cty"
 
-	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/plans"
 	"github.com/hashicorp/terraform/plans/objchange"
 	"github.com/hashicorp/terraform/states"
@@ -18,12 +17,6 @@ import (
 // or generating a plan to do so.
 type evalReadDataPlan struct {
 	evalReadData
-
-	// dependsOn stores the list of transitive resource addresses that any
-	// configuration depends_on references may resolve to. This is used to
-	// determine if there are any changes that will force this data sources to
-	// be deferred to apply.
-	dependsOn []addrs.ConfigResource
 }
 
 func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {

terraform/graph_builder_refresh.go

@@ -171,6 +171,7 @@ func (b *RefreshGraphBuilder) Steps() []GraphTransformer {
 		// have to connect again later for providers and so on.
 		&ReferenceTransformer{},
 		&AttachDependenciesTransformer{},
+		&attachDataResourceDependenciesTransformer{},
 
 		// Target
 		&TargetsTransformer{

terraform/node_data_refresh.go

@@ -121,6 +121,7 @@ func (n *NodeRefreshableDataResource) DynamicExpand(ctx EvalContext) (*Graph, er
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 		a.ProviderMetas = n.ProviderMetas
+		a.dependsOn = n.dependsOn
 
 		return &NodeRefreshableDataResourceInstance{
 			NodeAbstractResourceInstance: a,
@@ -227,6 +228,7 @@ func (n *NodeRefreshableDataResourceInstance) EvalTree() EvalNode {
 					ProviderSchema: &providerSchema,
 					OutputChange:   &change,
 					State:          &state,
+					dependsOn:      n.dependsOn,
 				},
 			},
 

terraform/node_resource_plan_instance.go

@@ -83,9 +83,9 @@ func (n *NodePlannableResourceInstance) evalTreeDataResource(addr addrs.AbsResou
 					ProviderSchema: &providerSchema,
 					OutputChange:   &change,
 					State:          &state,
-				},
 					dependsOn:      n.dependsOn,
 				},
+			},
 
 			&EvalWriteState{
 				Addr:           addr.Resource,