Call configure in sequence (instead of in parallel) (#2738)

It looks like GCP has [introduced a
dependency](hashicorp/terraform-provider-google-beta#8747)
on configuring SDK and then PF into their provider. This commit is being
used to check if ordering will fix the panics that the GCP upgrade is
seeing in tests.

pulumi/pulumi-gcp#2733 shows that this is a
necessary change.

pkg/x/muxer/muxer.go

@@ -291,14 +291,6 @@ func (m *muxer) DiffConfig(ctx context.Context, req *pulumirpc.DiffRequest) (*pu
 func (m *muxer) Configure(ctx context.Context, req *pulumirpc.ConfigureRequest) (*pulumirpc.ConfigureResponse, error) {
 	// Configure determines what the values the provider understands. We take the
 	// `and` of configure values.
-	subs := make([]func() tuple[*pulumirpc.ConfigureResponse, error], len(m.servers))
-	for i, s := range m.servers {
-		i, s := i, s
-		subs[i] = func() tuple[*pulumirpc.ConfigureResponse, error] {
-			req := proto.Clone(req).(*pulumirpc.ConfigureRequest)
-			return newTuple(s.Configure(ctx, req))
-		}
-	}
 	response := &pulumirpc.ConfigureResponse{
 		AcceptSecrets:                   true,
 		SupportsPreview:                 true,
@@ -307,17 +299,20 @@ func (m *muxer) Configure(ctx context.Context, req *pulumirpc.ConfigureRequest)
 		SupportsAutonamingConfiguration: true,
 	}
 	errs := new(multierror.Error)
-	for _, r := range asyncJoin(subs) {
-		if r.B != nil {
-			errs.Errors = append(errs.Errors, r.B)
+
+	for _, s := range m.servers {
+		req := proto.Clone(req).(*pulumirpc.ConfigureRequest)
+		r, err := s.Configure(ctx, req)
+		if err != nil {
+			errs.Errors = append(errs.Errors, err)
 			continue
 		}
-		response.AcceptOutputs = response.AcceptOutputs && r.A.GetAcceptOutputs()
-		response.AcceptResources = response.AcceptResources && r.A.GetAcceptResources()
-		response.AcceptSecrets = response.AcceptSecrets && r.A.GetAcceptSecrets()
-		response.SupportsPreview = response.SupportsPreview && r.A.GetSupportsPreview()
+		response.AcceptOutputs = response.AcceptOutputs && r.GetAcceptOutputs()
+		response.AcceptResources = response.AcceptResources && r.GetAcceptResources()
+		response.AcceptSecrets = response.AcceptSecrets && r.GetAcceptSecrets()
+		response.SupportsPreview = response.SupportsPreview && r.GetSupportsPreview()
 		response.SupportsAutonamingConfiguration = response.SupportsAutonamingConfiguration &&
-			r.A.GetSupportsAutonamingConfiguration()
+			r.GetSupportsAutonamingConfiguration()
 	}
 	return response, m.muxedErrors(errs)
 }

pkg/x/muxer/muxer_test.go

@@ -17,6 +17,7 @@ package muxer
 import (
 	"context"
 	"fmt"
+	"sync/atomic"
 	"testing"
 
 	"github.com/pulumi/pulumi/sdk/v3/go/common/diag"
@@ -200,3 +201,37 @@ func (s diffConfigServer) DiffConfig(
 	}
 	return s.UnimplementedResourceProviderServer.DiffConfig(ctx, req)
 }
+
+func TestConfigureInSequence(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+
+	for i := 0; i < 1000; i++ {
+		var count atomic.Uint32
+		m := &muxer{
+			host: &host{},
+			servers: []server{
+				configure{t: t, expect: 0, counter: &count},
+				configure{t: t, expect: 1, counter: &count},
+				configure{t: t, expect: 2, counter: &count},
+				configure{t: t, expect: 3, counter: &count},
+			},
+		}
+		_, err := m.Configure(ctx, &pulumirpc.ConfigureRequest{})
+		require.NoError(t, err)
+
+		assert.Equal(t, uint32(4), count.Load())
+	}
+}
+
+type configure struct {
+	pulumirpc.UnimplementedResourceProviderServer
+	t       *testing.T
+	expect  uint32
+	counter *atomic.Uint32
+}
+
+func (c configure) Configure(context.Context, *pulumirpc.ConfigureRequest) (*pulumirpc.ConfigureResponse, error) {
+	assert.True(c.t, c.counter.CompareAndSwap(c.expect, c.expect+1), "")
+	return &pulumirpc.ConfigureResponse{}, nil
+}