Expose engine logging to Go SDK (#4069)

* expose engine logging to Go SDK

* added comments

sdk/go/pulumi/context.go

@@ -50,6 +50,8 @@ type Context struct {
 	rpcsDone    *sync.Cond  // an event signaling completion of RPCs.
 	rpcsLock    *sync.Mutex // a lock protecting the RPC count and event.
 	rpcError    error       // the first error (if any) encountered during an RPC.
+
+	Log Log // the logging interface for the Pulumi log stream.
 }
 
 // NewContext creates a fresh run context out of the given metadata.
@@ -83,6 +85,10 @@ func NewContext(ctx context.Context, info RunInfo) (*Context, error) {
 	}
 
 	mutex := &sync.Mutex{}
+	log := &logState{
+		engine: engine,
+		ctx:    ctx,
+	}
 	return &Context{
 		ctx:         ctx,
 		info:        info,
@@ -94,6 +100,7 @@ func NewContext(ctx context.Context, info RunInfo) (*Context, error) {
 		rpcs:        0,
 		rpcsLock:    mutex,
 		rpcsDone:    sync.NewCond(mutex),
+		Log:         log,
 	}, nil
 }
 

sdk/go/pulumi/log.go

@@ -0,0 +1,76 @@
+// Copyright 2016-2020, Pulumi Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// The log module logs messages in a way that tightly integrates with the resource engine's interface.
+
+package pulumi
+
+import (
+	pulumirpc "github.com/pulumi/pulumi/sdk/proto/go"
+	"golang.org/x/net/context"
+)
+
+// Log is a group of logging functions that can be called from a Go application that will be logged
+// to the Pulumi log stream.  These events will be printed in the terminal while the Pulumi app
+// runs, and will be available from the Web console afterwards.
+type Log interface {
+	Debug(msg string, resource Resource, streamID int32, ephemeral bool) error
+	Info(msg string, resource Resource, streamID int32, ephemeral bool) error
+	Warn(msg string, resource Resource, streamID int32, ephemeral bool) error
+	Error(msg string, resource Resource, streamID int32, ephemeral bool) error
+}
+
+type logState struct {
+	engine pulumirpc.EngineClient
+	ctx    context.Context
+}
+
+// Debug logs a debug-level message that is generally hidden from end-users.
+func (log *logState) Debug(msg string, resource Resource, streamID int32, ephemeral bool) error {
+	return _log(log.ctx, log.engine, pulumirpc.LogSeverity_DEBUG, msg, resource, streamID, ephemeral)
+}
+
+// Logs an informational message that is generally printed to stdout during resource
+func (log *logState) Info(msg string, resource Resource, streamID int32, ephemeral bool) error {
+	return _log(log.ctx, log.engine, pulumirpc.LogSeverity_INFO, msg, resource, streamID, ephemeral)
+}
+
+// Logs a warning to indicate that something went wrong, but not catastrophically so.
+func (log *logState) Warn(msg string, resource Resource, streamID int32, ephemeral bool) error {
+	return _log(log.ctx, log.engine, pulumirpc.LogSeverity_WARNING, msg, resource, streamID, ephemeral)
+}
+
+// Logs a fatal error to indicate that the tool should stop processing resource
+func (log *logState) Error(msg string, resource Resource, streamID int32, ephemeral bool) error {
+	return _log(log.ctx, log.engine, pulumirpc.LogSeverity_ERROR, msg, resource, streamID, ephemeral)
+}
+
+func _log(ctx context.Context, engine pulumirpc.EngineClient, severity pulumirpc.LogSeverity,
+	message string, resource Resource, streamID int32, ephemeral bool) error {
+
+	resolvedUrn, _, _, err := resource.URN().awaitURN(ctx)
+	if err != nil {
+		return err
+	}
+
+	logRequest := &pulumirpc.LogRequest{
+		Severity:  severity,
+		Message:   message,
+		Urn:       string(resolvedUrn),
+		StreamId:  streamID,
+		Ephemeral: ephemeral,
+	}
+	_, err = engine.Log(ctx, logRequest)
+	return err
+}