tfprotov5+tfprotov6: Support for Protocol Version 5.3 and 6.3 (#205)

Reference: #204

.changelog/205.txt

@@ -0,0 +1,11 @@
+```release-note:feature
+Added support for protocol version 5.3 and 6.3, which allows providers to opt into the `PlanResourceChange` RPC for resource destruction
+```
+
+```release-note:enhancement
+tfprotov5: Added `ServerCapabilities` type and `ServerCapabilities` field to `GetProviderSchemaResponse`
+```
+
+```release-note:enhancement
+tfprotov6: Added `ServerCapabilities` type and `ServerCapabilities` field to `GetProviderSchemaResponse`
+```

tfprotov5/internal/tfplugin5/tfplugin5.proto

@@ -1,6 +1,6 @@
-// Terraform Plugin RPC protocol version 5.2
+// Terraform Plugin RPC protocol version 5.3
 //
-// This file defines version 5.2 of the RPC protocol. To implement a plugin
+// This file defines version 5.3 of the RPC protocol. To implement a plugin
 // against this protocol, copy this definition into your own codebase and
 // use protoc to generate stubs for your target language.
 //
@@ -13,7 +13,7 @@
 // official protocol releases. Proto files taken from other commits may include
 // incomplete changes or features that did not make it into a final release.
 // In all reasonable cases, plugin developers should take the proto file from
-// the tag of the most recent release of Terraform, and not from the master
+// the tag of the most recent release of Terraform, and not from the main
 // branch or any other development branch.
 //
 syntax = "proto3";
@@ -118,7 +118,7 @@ message Schema {
 
     // The version of the schema.
     // Schemas are versioned, so that providers can upgrade a saved resource
-    // state when the schema is changed. 
+    // state when the schema is changed.
     int64 version = 1;
 
     // Block is the top level configuration block for this schema.
@@ -157,6 +157,18 @@ message GetProviderSchema {
         map<string, Schema> data_source_schemas = 3;
         repeated Diagnostic diagnostics = 4;
         Schema provider_meta = 5;
+        ServerCapabilities server_capabilities = 6;
+    }
+
+
+    // ServerCapabilities allows providers to communicate extra information
+    // regarding supported protocol features. This is used to indicate
+    // availability of certain forward-compatible changes which may be optional
+    // in a major protocol version, but cannot be tested for directly.
+    message ServerCapabilities {
+        // The plan_destroy capability signals that a provider expects a call
+        // to PlanResourceChange when a resource is going to be destroyed.
+        bool plan_destroy = 1;
     }
 }
 
@@ -247,14 +259,14 @@ message PlanResourceChange {
         DynamicValue prior_state = 2;
         DynamicValue proposed_new_state = 3;
         DynamicValue config = 4;
-        bytes prior_private = 5; 
+        bytes prior_private = 5;
         DynamicValue provider_meta = 6;
     }
 
     message Response {
         DynamicValue planned_state = 1;
         repeated AttributePath requires_replace = 2;
-        bytes planned_private = 3; 
+        bytes planned_private = 3;
         repeated Diagnostic diagnostics = 4;
 
 
@@ -279,12 +291,12 @@ message ApplyResourceChange {
         DynamicValue prior_state = 2;
         DynamicValue planned_state = 3;
         DynamicValue config = 4;
-        bytes planned_private = 5; 
+        bytes planned_private = 5;
         DynamicValue provider_meta = 6;
     }
     message Response {
         DynamicValue new_state = 1;
-        bytes private = 2; 
+        bytes private = 2;
         repeated Diagnostic diagnostics = 3;
 
         // This may be set only by the helper/schema "SDK" in the main Terraform
@@ -365,5 +377,5 @@ message ProvisionResource {
     message Response {
         string output  = 1;
         repeated Diagnostic diagnostics = 2;
-    }   
+    }
 }

tfprotov5/internal/toproto/provider.go

@@ -12,7 +12,12 @@ func GetProviderSchema_Request(in *tfprotov5.GetProviderSchemaRequest) (*tfplugi
 }
 
 func GetProviderSchema_Response(in *tfprotov5.GetProviderSchemaResponse) (*tfplugin5.GetProviderSchema_Response, error) {
-	var resp tfplugin5.GetProviderSchema_Response
+	if in == nil {
+		return nil, nil
+	}
+	resp := tfplugin5.GetProviderSchema_Response{
+		ServerCapabilities: GetProviderSchema_ServerCapabilities(in.ServerCapabilities),
+	}
 	if in.Provider != nil {
 		schema, err := Schema(in.Provider)
 		if err != nil {

tfprotov5/internal/toproto/server_capabilities.go

@@ -0,0 +1,16 @@
+package toproto
+
+import (
+	"github.com/hashicorp/terraform-plugin-go/tfprotov5"
+	"github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/tfplugin5"
+)
+
+func GetProviderSchema_ServerCapabilities(in *tfprotov5.ServerCapabilities) *tfplugin5.GetProviderSchema_ServerCapabilities {
+	if in == nil {
+		return nil
+	}
+
+	return &tfplugin5.GetProviderSchema_ServerCapabilities{
+		PlanDestroy: in.PlanDestroy,
+	}
+}

tfprotov5/provider.go

@@ -46,6 +46,10 @@ type GetProviderSchemaRequest struct{}
 // GetProviderSchemaResponse represents a Terraform RPC response containing the
 // provider's schemas.
 type GetProviderSchemaResponse struct {
+	// ServerCapabilities defines optionally supported protocol features,
+	// such as forward-compatible Terraform behavior changes.
+	ServerCapabilities *ServerCapabilities
+
 	// Provider defines the schema for the provider configuration, which
 	// will be specified in the provider block of the user's configuration.
 	Provider *Schema

tfprotov5/server_capabilities.go

@@ -0,0 +1,14 @@
+package tfprotov5
+
+// ServerCapabilities allows providers to communicate optionally supported
+// protocol features, such as forward-compatible Terraform behavior changes.
+//
+// This information is used in GetProviderSchemaResponse as capabilities are
+// static features which must be known upfront in the provider server.
+type ServerCapabilities struct {
+	// PlanDestroy signals that a provider expects a call to
+	// PlanResourceChange when a resource is going to be destroyed. This is
+	// opt-in to prevent unexpected errors or panics since the
+	// ProposedNewState in PlanResourceChangeRequest will be a null value.
+	PlanDestroy bool
+}

tfprotov5/tf5server/server.go

@@ -45,7 +45,7 @@ const (
 	//
 	// In the future, it may be possible to include this information directly
 	// in the protocol buffers rather than recreating a constant here.
-	protocolVersionMinor uint = 2
+	protocolVersionMinor uint = 3
 )
 
 // protocolVersion represents the combined major and minor version numbers of