diff --git a/terraform/eval_read_data_apply.go b/terraform/eval_read_data_apply.go
index 179fe368d..c9e235250 100644
--- a/terraform/eval_read_data_apply.go
+++ b/terraform/eval_read_data_apply.go
@@ -15,7 +15,7 @@ type evalReadDataApply struct {
 	evalReadData
 }
 
-func (n *evalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
+func (n *evalReadDataApply) Eval(ctx EvalContext) tfdiags.Diagnostics {
 	absAddr := n.Addr.Absolute(ctx.Path())
 
 	var diags tfdiags.Diagnostics
@@ -26,22 +26,25 @@ func (n *evalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	if n.ProviderSchema == nil || *n.ProviderSchema == nil {
-		return nil, fmt.Errorf("provider schema not available for %s", n.Addr)
+		diags = diags.Append(fmt.Errorf("provider schema not available for %s", n.Addr))
+		return diags
 	}
 
 	if planned != nil && planned.Action != plans.Read {
 		// If any other action gets in here then that's always a bug; this
 		// EvalNode only deals with reading.
-		return nil, fmt.Errorf(
+		diags = diags.Append(fmt.Errorf(
 			"invalid action %s for %s: only Read is supported (this is a bug in Terraform; please report it!)",
 			planned.Action, absAddr,
-		)
+		))
+		return diags
 	}
 
-	if err := ctx.Hook(func(h Hook) (HookAction, error) {
+	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
 		return h.PreApply(absAddr, states.CurrentGen, planned.Action, planned.Before, planned.After)
-	}); err != nil {
-		return nil, err
+	}))
+	if diags.HasErrors() {
+		return diags
 	}
 
 	config := *n.Config
@@ -49,7 +52,8 @@ func (n *evalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 	schema, _ := providerSchema.SchemaForResourceAddr(n.Addr.ContainingResource())
 	if schema == nil {
 		// Should be caught during validation, so we don't bother with a pretty error here
-		return nil, fmt.Errorf("provider %q does not support data source %q", n.ProviderAddr.Provider.String(), n.Addr.Resource.Type)
+		diags = diags.Append(fmt.Errorf("provider %q does not support data source %q", n.ProviderAddr.Provider.String(), n.Addr.Resource.Type))
+		return diags
 	}
 
 	forEach, _ := evaluateForEachExpression(config.ForEach, ctx)
@@ -58,13 +62,13 @@ func (n *evalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 	configVal, _, configDiags := ctx.EvaluateBlock(config.Config, schema, nil, keyData)
 	diags = diags.Append(configDiags)
 	if configDiags.HasErrors() {
-		return nil, diags.ErrWithWarnings()
+		return diags
 	}
 
 	newVal, readDiags := n.readDataSource(ctx, configVal)
 	diags = diags.Append(readDiags)
 	if diags.HasErrors() {
-		return nil, diags.ErrWithWarnings()
+		return diags
 	}
 
 	*n.State = &states.ResourceInstanceObject{
@@ -72,11 +76,9 @@ func (n *evalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 		Status: states.ObjectReady,
 	}
 
-	if err := ctx.Hook(func(h Hook) (HookAction, error) {
+	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
 		return h.PostApply(absAddr, states.CurrentGen, newVal, diags.Err())
-	}); err != nil {
-		diags = diags.Append(err)
-	}
+	}))
 
-	return nil, diags.ErrWithWarnings()
+	return diags
 }
diff --git a/terraform/eval_read_data_plan.go b/terraform/eval_read_data_plan.go
index 226594299..a1d7ccce6 100644
--- a/terraform/eval_read_data_plan.go
+++ b/terraform/eval_read_data_plan.go
@@ -21,14 +21,15 @@ type evalReadDataPlan struct {
 	evalReadData
 }
 
-func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
+func (n *evalReadDataPlan) Eval(ctx EvalContext) tfdiags.Diagnostics {
 	absAddr := n.Addr.Absolute(ctx.Path())
 
 	var diags tfdiags.Diagnostics
 	var configVal cty.Value
 
 	if n.ProviderSchema == nil || *n.ProviderSchema == nil {
-		return nil, fmt.Errorf("provider schema not available for %s", n.Addr)
+		diags = diags.Append(fmt.Errorf("provider schema not available for %s", n.Addr))
+		return diags
 	}
 
 	config := *n.Config
@@ -36,7 +37,8 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 	schema, _ := providerSchema.SchemaForResourceAddr(n.Addr.ContainingResource())
 	if schema == nil {
 		// Should be caught during validation, so we don't bother with a pretty error here
-		return nil, fmt.Errorf("provider %q does not support data source %q", n.ProviderAddr.Provider.String(), n.Addr.Resource.Type)
+		diags = diags.Append(fmt.Errorf("provider %q does not support data source %q", n.ProviderAddr.Provider.String(), n.Addr.Resource.Type))
+		return diags
 	}
 
 	objTy := schema.ImpliedType()
@@ -52,7 +54,7 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 	configVal, _, configDiags = ctx.EvaluateBlock(config.Config, schema, nil, keyData)
 	diags = diags.Append(configDiags)
 	if configDiags.HasErrors() {
-		return nil, diags.ErrWithWarnings()
+		return diags
 	}
 
 	configKnown := configVal.IsWhollyKnown()
@@ -69,11 +71,11 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 
 		proposedNewVal := objchange.PlannedDataResourceObject(schema, configVal)
 
-		if err := ctx.Hook(func(h Hook) (HookAction, error) {
+		diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
 			return h.PreDiff(absAddr, states.CurrentGen, priorVal, proposedNewVal)
-		}); err != nil {
-			diags = diags.Append(err)
-			return nil, diags.ErrWithWarnings()
+		}))
+		if diags.HasErrors() {
+			return diags
 		}
 
 		// Apply detects that the data source will need to be read by the After
@@ -93,13 +95,11 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 			Status: states.ObjectPlanned,
 		}
 
-		if err := ctx.Hook(func(h Hook) (HookAction, error) {
+		diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
 			return h.PostDiff(absAddr, states.CurrentGen, plans.Read, priorVal, proposedNewVal)
-		}); err != nil {
-			diags = diags.Append(err)
-		}
+		}))
 
-		return nil, diags.ErrWithWarnings()
+		return diags
 	}
 
 	// We have a complete configuration with no dependencies to wait on, so we
@@ -107,7 +107,7 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 	newVal, readDiags := n.readDataSource(ctx, configVal)
 	diags = diags.Append(readDiags)
 	if diags.HasErrors() {
-		return nil, diags.ErrWithWarnings()
+		return diags
 	}
 
 	// if we have a prior value, we can check for any irregularities in the response
@@ -137,13 +137,10 @@ func (n *evalReadDataPlan) Eval(ctx EvalContext) (interface{}, error) {
 		Status: states.ObjectReady,
 	}
 
-	if err := ctx.Hook(func(h Hook) (HookAction, error) {
+	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
 		return h.PostDiff(absAddr, states.CurrentGen, plans.Update, priorVal, newVal)
-	}); err != nil {
-		return nil, err
-	}
-
-	return nil, diags.ErrWithWarnings()
+	}))
+	return diags
 }
 
 // forcePlanRead determines if we need to override the usual behavior of
diff --git a/terraform/node_resource_apply_instance.go b/terraform/node_resource_apply_instance.go
index 7a109855f..82f5b2f46 100644
--- a/terraform/node_resource_apply_instance.go
+++ b/terraform/node_resource_apply_instance.go
@@ -134,6 +134,7 @@ func (n *NodeApplyableResourceInstance) Execute(ctx EvalContext, op walkOperatio
 }
 
 func (n *NodeApplyableResourceInstance) dataResourceExecute(ctx EvalContext) error {
+	var diags tfdiags.Diagnostics
 	addr := n.ResourceInstanceAddr().Resource
 
 	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
@@ -166,9 +167,9 @@ func (n *NodeApplyableResourceInstance) dataResourceExecute(ctx EvalContext) err
 			State:          &state,
 		},
 	}
-	_, err = readDataApply.Eval(ctx)
-	if err != nil {
-		return err
+	diags = readDataApply.Eval(ctx)
+	if diags.HasErrors() {
+		return diags.ErrWithWarnings()
 	}
 
 	writeState := &EvalWriteState{
@@ -187,7 +188,7 @@ func (n *NodeApplyableResourceInstance) dataResourceExecute(ctx EvalContext) err
 		ProviderSchema: &providerSchema,
 		Change:         nil,
 	}
-	diags := writeDiff.Eval(ctx)
+	diags = writeDiff.Eval(ctx)
 	if diags.HasErrors() {
 		return diags.ErrWithWarnings()
 	}
diff --git a/terraform/node_resource_plan_instance.go b/terraform/node_resource_plan_instance.go
index 836f1328e..64ab930ec 100644
--- a/terraform/node_resource_plan_instance.go
+++ b/terraform/node_resource_plan_instance.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/hashicorp/terraform/plans"
 	"github.com/hashicorp/terraform/states"
+	"github.com/hashicorp/terraform/tfdiags"
 
 	"github.com/hashicorp/terraform/addrs"
 )
@@ -45,6 +46,7 @@ func (n *NodePlannableResourceInstance) Execute(ctx EvalContext, op walkOperatio
 }
 
 func (n *NodePlannableResourceInstance) dataResourceExecute(ctx EvalContext) error {
+	var diags tfdiags.Diagnostics
 	config := n.Config
 	addr := n.ResourceInstanceAddr()
 
@@ -84,9 +86,9 @@ func (n *NodePlannableResourceInstance) dataResourceExecute(ctx EvalContext) err
 			dependsOn:      n.dependsOn,
 		},
 	}
-	_, err = readDataPlan.Eval(ctx)
-	if err != nil {
-		return err
+	diags = readDataPlan.Eval(ctx)
+	if diags.HasErrors() {
+		return diags.ErrWithWarnings()
 	}
 
 	// write the data source into both the refresh state and the
@@ -119,7 +121,7 @@ func (n *NodePlannableResourceInstance) dataResourceExecute(ctx EvalContext) err
 		ProviderSchema: &providerSchema,
 		Change:         &change,
 	}
-	diags := writeDiff.Eval(ctx)
+	diags = writeDiff.Eval(ctx)
 	return diags.ErrWithWarnings()
 }