Add GetMetadata RPC to provider protocol

docs/plugin-protocol/tfplugin5.4.proto

@@ -128,8 +128,34 @@ message Schema {
     Block block = 2;
 }
 
+// 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;
+
+    // The get_provider_schema_optional capability indicates that this
+    // provider does not require calling GetProviderSchema to operate
+    // normally, and the caller can used a cached copy of the provider's
+    // schema.
+    bool get_provider_schema_optional = 2;
+}
+
 service Provider {
     //////// Information about what a provider supports/expects
+
+    // GetMetadata returns upfront information about server capabilities and
+    // supported resource types without requiring the server to instantiate all
+    // schema information, which may be memory intensive. This RPC is optional,
+    // where clients may receive an unimplemented RPC error. Clients should
+    // ignore the error and call the GetSchema RPC as a fallback.
+    rpc GetMetadata(GetMetadata.Request) returns (GetMetadata.Response);
+
+    // GetSchema returns schema information for the provider, data resources,
+    // and managed resources.
     rpc GetSchema(GetProviderSchema.Request) returns (GetProviderSchema.Response);
     rpc PrepareProviderConfig(PrepareProviderConfig.Request) returns (PrepareProviderConfig.Response);
     rpc ValidateResourceTypeConfig(ValidateResourceTypeConfig.Request) returns (ValidateResourceTypeConfig.Response);
@@ -151,6 +177,26 @@ service Provider {
     rpc Stop(Stop.Request) returns (Stop.Response);
 }
 
+message GetMetadata {
+    message Request {
+    }
+
+    message Response {
+        ServerCapabilities server_capabilities = 1;
+        repeated Diagnostic diagnostics = 2;
+        repeated DataSourceMetadata data_sources = 3;
+        repeated ResourceMetadata resources = 4;
+    }
+
+    message DataSourceMetadata {
+        string type_name = 1;
+    }
+
+    message ResourceMetadata {
+        string type_name = 1;
+    }
+}
+
 message GetProviderSchema {
     message Request {
     }
@@ -162,23 +208,6 @@ message GetProviderSchema {
         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;
-
-        // The get_provider_schema_optional capability indicates that this
-        // provider does not require calling GetProviderSchema to operate
-        // normally, and the caller can used a cached copy of the provider's
-        // schema.
-        bool get_provider_schema_optional = 2;
-    }
 }
 
 message PrepareProviderConfig {

docs/plugin-protocol/tfplugin6.4.proto

@@ -147,8 +147,34 @@ message Schema {
     Block block = 2;
 }
 
+// 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;
+
+    // The get_provider_schema_optional capability indicates that this
+    // provider does not require calling GetProviderSchema to operate
+    // normally, and the caller can used a cached copy of the provider's
+    // schema.
+    bool get_provider_schema_optional = 2;
+}
+
 service Provider {
     //////// Information about what a provider supports/expects
+
+    // GetMetadata returns upfront information about server capabilities and
+    // supported resource types without requiring the server to instantiate all
+    // schema information, which may be memory intensive. This RPC is optional,
+    // where clients may receive an unimplemented RPC error. Clients should
+    // ignore the error and call the GetProviderSchema RPC as a fallback.
+    rpc GetMetadata(GetMetadata.Request) returns (GetMetadata.Response);
+
+    // GetSchema returns schema information for the provider, data resources,
+    // and managed resources.
     rpc GetProviderSchema(GetProviderSchema.Request) returns (GetProviderSchema.Response);
     rpc ValidateProviderConfig(ValidateProviderConfig.Request) returns (ValidateProviderConfig.Response);
     rpc ValidateResourceConfig(ValidateResourceConfig.Request) returns (ValidateResourceConfig.Response);
@@ -170,6 +196,26 @@ service Provider {
     rpc StopProvider(StopProvider.Request) returns (StopProvider.Response);
 }
 
+message GetMetadata {
+    message Request {
+    }
+
+    message Response {
+        ServerCapabilities server_capabilities = 1;
+        repeated Diagnostic diagnostics = 2;
+        repeated DataSourceMetadata data_sources = 3;
+        repeated ResourceMetadata resources = 4;
+    }
+
+    message DataSourceMetadata {
+        string type_name = 1;
+    }
+
+    message ResourceMetadata {
+        string type_name = 1;
+    }
+}
+
 message GetProviderSchema {
     message Request {
     }
@@ -181,23 +227,6 @@ message GetProviderSchema {
         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;
-
-        // The get_provider_schema_optional capability indicates that this
-        // provider does not require calling GetProviderSchema to operate
-        // normally, and the caller can used a cached copy of the provider's
-        // schema.
-        bool get_provider_schema_optional = 2;
-    }
 }
 
 message ValidateProviderConfig {

internal/grpcwrap/provider.go

@@ -12,6 +12,8 @@ import (
 	"github.com/zclconf/go-cty/cty"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 	"github.com/zclconf/go-cty/cty/msgpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 // New wraps a providers.Interface to implement a grpc ProviderServer.
@@ -29,6 +31,10 @@ type provider struct {
 	schema   providers.GetProviderSchemaResponse
 }
 
+func (p *provider) GetMetadata(_ context.Context, req *tfplugin5.GetMetadata_Request) (*tfplugin5.GetMetadata_Response, error) {
+	return nil, status.Error(codes.Unimplemented, "GetMetadata is not implemented by core")
+}
+
 func (p *provider) GetSchema(_ context.Context, req *tfplugin5.GetProviderSchema_Request) (*tfplugin5.GetProviderSchema_Response, error) {
 	resp := &tfplugin5.GetProviderSchema_Response{
 		ResourceSchemas:   make(map[string]*tfplugin5.Schema),
@@ -62,7 +68,7 @@ func (p *provider) GetSchema(_ context.Context, req *tfplugin5.GetProviderSchema
 		}
 	}
 
-	resp.ServerCapabilities = &tfplugin5.GetProviderSchema_ServerCapabilities{
+	resp.ServerCapabilities = &tfplugin5.ServerCapabilities{
 		PlanDestroy: p.schema.ServerCapabilities.PlanDestroy,
 	}
 

internal/grpcwrap/provider6.go

@@ -12,6 +12,8 @@ import (
 	"github.com/zclconf/go-cty/cty"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 	"github.com/zclconf/go-cty/cty/msgpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 // New wraps a providers.Interface to implement a grpc ProviderServer using
@@ -29,6 +31,10 @@ type provider6 struct {
 	schema   providers.GetProviderSchemaResponse
 }
 
+func (p *provider6) GetMetadata(_ context.Context, req *tfplugin6.GetMetadata_Request) (*tfplugin6.GetMetadata_Response, error) {
+	return nil, status.Error(codes.Unimplemented, "GetMetadata is not implemented by core")
+}
+
 func (p *provider6) GetProviderSchema(_ context.Context, req *tfplugin6.GetProviderSchema_Request) (*tfplugin6.GetProviderSchema_Response, error) {
 	resp := &tfplugin6.GetProviderSchema_Response{
 		ResourceSchemas:   make(map[string]*tfplugin6.Schema),
@@ -62,8 +68,9 @@ func (p *provider6) GetProviderSchema(_ context.Context, req *tfplugin6.GetProvi
 		}
 	}
 
-	resp.ServerCapabilities = &tfplugin6.GetProviderSchema_ServerCapabilities{
-		PlanDestroy: p.schema.ServerCapabilities.PlanDestroy,
+	resp.ServerCapabilities = &tfplugin6.ServerCapabilities{
+		GetProviderSchemaOptional: p.schema.ServerCapabilities.GetProviderSchemaOptional,
+		PlanDestroy:               p.schema.ServerCapabilities.PlanDestroy,
 	}
 
 	// include any diagnostics from the original GetSchema call