fix: prevent crash for legacy provider lookups

internal/langserver/handlers/service.go

@@ -110,6 +110,7 @@ func (svc *service) Assigner() (jrpc2.Assigner, error) {
 	if err != nil {
 		return nil, err
 	}
+	store.SetLogger(svc.logger)
 
 	err = schemas.PreloadSchemasToStore(store.ProviderSchemas)
 	if err != nil {

internal/state/provider_schema.go

@@ -95,6 +95,7 @@ func updateProviderVersions(txn *memdb.Txn, modPath string, pv map[tfaddr.Provid
 }
 
 func (s *ProviderSchemaStore) AddLocalSchema(modPath string, addr tfaddr.Provider, schema *tfschema.ProviderSchema) error {
+	s.logger.Printf("PSS: adding local schema (%s, %s): %p", modPath, addr, schema)
 	txn := s.db.Txn(true)
 	defer txn.Abort()
 
@@ -190,6 +191,7 @@ func (s *ProviderSchemaStore) AddPreloadedSchema(addr tfaddr.Provider, pv *versi
 }
 
 func (s *ProviderSchemaStore) ProviderSchema(modPath string, addr tfaddr.Provider, vc version.Constraints) (*tfschema.ProviderSchema, error) {
+	s.logger.Printf("PSS: getting provider schema (%s, %s, %s)", modPath, addr, vc)
 	txn := s.db.Txn(false)
 
 	it, err := txn.Get(s.tableName, "id_prefix", addr)
@@ -233,7 +235,9 @@ func (s *ProviderSchemaStore) ProviderSchema(modPath string, addr tfaddr.Provide
 		}
 		if obj != nil {
 			ps := obj.(*ProviderSchema)
-			return ps.Schema, err
+			if ps.Schema != nil {
+				return ps.Schema, nil
+			}
 		}
 
 		// Last we just try to loosely match the provider type
@@ -264,7 +268,7 @@ func (s *ProviderSchemaStore) ProviderSchema(modPath string, addr tfaddr.Provide
 
 	sort.Stable(ss)
 
-	return ss.schemas[0].Schema, err
+	return ss.schemas[0].Schema, nil
 }
 
 type ModuleLookupFunc func(string) (*Module, error)

internal/state/provider_schema_test.go

@@ -44,6 +44,64 @@ func TestStateStore_AddPreloadedSchema_duplicate(t *testing.T) {
 	}
 }
 
+// Test a scenario where Terraform 0.13+ produced schema with non-legacy
+// addresses but lookup is still done via legacy address
+func TestStateStore_IncompleteSchema_legacyLookup(t *testing.T) {
+	s, err := NewStateStore()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	modPath := t.TempDir()
+	err = s.Modules.Add(modPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	addr := tfaddr.Provider{
+		Hostname:  tfaddr.DefaultRegistryHost,
+		Namespace: "hashicorp",
+		Type:      "aws",
+	}
+	pv := testVersion(t, "3.2.0")
+
+	pvs := map[tfaddr.Provider]*version.Version{
+		addr: pv,
+	}
+
+	// obtaining versions typically takes less time than schema itself
+	// so we test that "incomplete" state is handled correctly too
+
+	err = s.Modules.UpdateTerraformVersion(modPath, testVersion(t, "0.13.0"), pvs, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = s.ProviderSchemas.ProviderSchema(modPath, tfaddr.NewLegacyProvider("aws"), testConstraint(t, ">= 1.0"))
+	if err == nil {
+		t.Fatal("expected error when requesting incomplete schema")
+	}
+	expectedErr := &NoSchemaError{}
+	if !errors.As(err, &expectedErr) {
+		t.Fatalf("unexpected error: %#v", err)
+	}
+
+	// next attempt (after schema is actually obtained) should not fail
+
+	err = s.ProviderSchemas.AddLocalSchema(modPath, addr, &tfschema.ProviderSchema{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ps, err := s.ProviderSchemas.ProviderSchema(modPath, tfaddr.NewLegacyProvider("aws"), testConstraint(t, ">= 1.0"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ps == nil {
+		t.Fatal("expected provider schema not to be nil")
+	}
+}
+
 func TestStateStore_AddLocalSchema_duplicate(t *testing.T) {
 	s, err := NewStateStore()
 	if err != nil {

internal/state/state.go

@@ -1,6 +1,9 @@
 package state
 
 import (
+	"io/ioutil"
+	"log"
+
 	"github.com/hashicorp/go-memdb"
 	"github.com/hashicorp/go-version"
 	tfaddr "github.com/hashicorp/terraform-registry-address"
@@ -52,6 +55,7 @@ type StateStore struct {
 type ModuleStore struct {
 	db        *memdb.MemDB
 	tableName string
+	logger    *log.Logger
 }
 
 type ModuleReader interface {
@@ -63,6 +67,7 @@ type ModuleReader interface {
 type ProviderSchemaStore struct {
 	db        *memdb.MemDB
 	tableName string
+	logger    *log.Logger
 }
 
 type SchemaReader interface {
@@ -79,10 +84,19 @@ func NewStateStore() (*StateStore, error) {
 		Modules: &ModuleStore{
 			db:        db,
 			tableName: moduleTableName,
+			logger:    defaultLogger,
 		},
 		ProviderSchemas: &ProviderSchemaStore{
 			db:        db,
 			tableName: providerSchemaTableName,
+			logger:    defaultLogger,
 		},
 	}, nil
 }
+
+func (s *StateStore) SetLogger(logger *log.Logger) {
+	s.Modules.logger = logger
+	s.ProviderSchemas.logger = logger
+}
+
+var defaultLogger = log.New(ioutil.Discard, "", 0)