remove PreDiff and PostDiff hook calls

PreDiff and PostDiff hooks were designed to be called immediately before
and after the PlanResourceChange calls to the provider. Probably due to
the confusing legacy naming of the hooks, these were scattered about the
nodes involved with planning, causing the hooks to be called in a number
of places where they were designed, including data sources and destroy
plans. Since these hooks are not used at all any longer anyway, we can
removed the extra calls with no effect.

If we choose in the future to call PlanResourceChange for resource
destroy plans, the hooks can be re-inserted (even though they currently
are unused) into the new code path which must diverge from the current
combined path of managed and data sources.

internal/terraform/context_apply_test.go

@@ -1512,10 +1512,8 @@ func TestContext2Apply_destroyData(t *testing.T) {
 	}
 
 	wantHookCalls := []*testHookCall{
-		{"PreDiff", "data.null_data_source.testing"},
-		{"PostDiff", "data.null_data_source.testing"},
-		{"PreDiff", "data.null_data_source.testing"},
-		{"PostDiff", "data.null_data_source.testing"},
+		{"PreApply", "data.null_data_source.testing"},
+		{"PostApply", "data.null_data_source.testing"},
 		{"PostStateUpdate", ""},
 	}
 	if !reflect.DeepEqual(hook.Calls, wantHookCalls) {

internal/terraform/node_resource_abstract_instance.go

@@ -410,18 +410,6 @@ func (n *NodeAbstractResourceInstance) planDestroy(ctx EvalContext, currentState
 		return noop, nil
 	}
 
-	// Call pre-diff hook
-	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PreDiff(
-			absAddr, deposedKey.Generation(),
-			currentState.Value,
-			cty.NullVal(cty.DynamicPseudoType),
-		)
-	}))
-	if diags.HasErrors() {
-		return nil, diags
-	}
-
 	// Plan is always the same for a destroy. We don't need the provider's
 	// help for this one.
 	plan := &plans.ResourceInstanceChange{
@@ -437,17 +425,6 @@ func (n *NodeAbstractResourceInstance) planDestroy(ctx EvalContext, currentState
 		ProviderAddr: n.ResolvedProvider,
 	}
 
-	// Call post-diff hook
-	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostDiff(
-			absAddr,
-			deposedKey.Generation(),
-			plan.Action,
-			plan.Before,
-			plan.After,
-		)
-	}))
-
 	return plan, diags
 }
 
@@ -1567,13 +1544,6 @@ func (n *NodeAbstractResourceInstance) planDataSource(ctx EvalContext, currentSt
 		}
 
 		proposedNewVal := objchange.PlannedDataResourceObject(schema, unmarkedConfigVal)
-
-		diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PreDiff(n.Addr, states.CurrentGen, priorVal, proposedNewVal)
-		}))
-		if diags.HasErrors() {
-			return nil, nil, keyData, diags
-		}
 		proposedNewVal = proposedNewVal.MarkWithPaths(configMarkPaths)
 
 		// Apply detects that the data source will need to be read by the After
@@ -1601,13 +1571,6 @@ func (n *NodeAbstractResourceInstance) planDataSource(ctx EvalContext, currentSt
 		return plannedChange, plannedNewState, keyData, diags
 	}
 
-	// While this isn't a "diff", continue to call this for data sources.
-	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PreDiff(n.Addr, states.CurrentGen, priorVal, configVal)
-	}))
-	if diags.HasErrors() {
-		return nil, nil, keyData, diags
-	}
 	// We have a complete configuration with no dependencies to wait on, so we
 	// can read the data source into the state.
 	newVal, readDiags := n.readDataSource(ctx, configVal)
@@ -1643,9 +1606,6 @@ func (n *NodeAbstractResourceInstance) planDataSource(ctx EvalContext, currentSt
 		Status: states.ObjectReady,
 	}
 
-	diags = diags.Append(ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostDiff(n.Addr, states.CurrentGen, plans.Update, priorVal, newVal)
-	}))
 	return nil, plannedNewState, keyData, diags
 }