Insert default values into provider config

Add any top-level default attributes from the provider schema into Null
config values.

helper/plugin/grpc_provider.go

@@ -6,6 +6,7 @@ import (
 	"strconv"
 
 	"github.com/zclconf/go-cty/cty"
+	ctyconvert "github.com/zclconf/go-cty/cty/convert"
 	"github.com/zclconf/go-cty/cty/msgpack"
 	context "golang.org/x/net/context"
 
@@ -88,13 +89,67 @@ func (s *GRPCProviderServer) PrepareProviderConfig(_ context.Context, req *proto
 		return resp, nil
 	}
 
+	// lookup any required, top-level attributes that are Null, and see if we
+	// have a Default value available.
+	configVal, _ = cty.Transform(configVal, func(path cty.Path, val cty.Value) (cty.Value, error) {
+		// we're only looking for top-level attributes
+		if len(path) != 1 {
+			return val, nil
+		}
+
+		// nothing to do if we already have a value
+		if !val.IsNull() {
+			return val, nil
+		}
+
+		// get the Schema definition for this attribute
+		getAttr, ok := path[0].(cty.GetAttrStep)
+		// these should all exist, but just ignore anything strange
+		if !ok {
+			return val, nil
+		}
+
+		attrSchema := s.provider.Schema[getAttr.Name]
+		// continue to ignore anything that doesn't match
+		if attrSchema == nil {
+			return val, nil
+		}
+
+		// find a default value if it exists
+		def, err := attrSchema.DefaultValue()
+		if err != nil {
+			return val, err
+		}
+
+		// no default
+		if def == nil {
+			return val, err
+		}
+
+		// create a cty.Value and make sure it's the correct type
+		tmpVal := hcl2shim.HCL2ValueFromConfigValue(def)
+		val, err = ctyconvert.Convert(tmpVal, val.Type())
+		return val, err
+	})
+
+	configVal, err = block.CoerceValue(configVal)
+	if err != nil {
+		resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
+		return resp, nil
+	}
+
 	config := terraform.NewResourceConfigShimmed(configVal, block)
 
 	warns, errs := s.provider.Validate(config)
 	resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, convert.WarnsAndErrsToProto(warns, errs))
 
-	// TODO: set defaults
+	preparedConfigMP, err := msgpack.Marshal(configVal, block.ImpliedType())
-	resp.PreparedConfig = req.Config
+	if err != nil {
+		resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
+		return resp, nil
+	}
+
+	resp.PreparedConfig = &proto.DynamicValue{Msgpack: preparedConfigMP}
 
 	return resp, nil
 }

helper/plugin/grpc_provider_test.go

@@ -3,6 +3,7 @@ package plugin
 import (
 	"context"
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -425,3 +426,155 @@ func TestApplyResourceChange(t *testing.T) {
 		t.Fatalf("incorrect final state: %#v\n", newStateVal)
 	}
 }
+
+func TestPrepareProviderConfig(t *testing.T) {
+	for _, tc := range []struct {
+		Name         string
+		Schema       map[string]*schema.Schema
+		ConfigVal    cty.Value
+		ExpectError  string
+		ExpectConfig cty.Value
+	}{
+		{
+			Name: "test prepare",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Optional: true,
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("bar"),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("bar"),
+			}),
+		},
+		{
+			Name: "test default",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Optional: true,
+					Default:  "default",
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NullVal(cty.String),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("default"),
+			}),
+		},
+		{
+			Name: "test defaultfunc",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Optional: true,
+					DefaultFunc: func() (interface{}, error) {
+						return "defaultfunc", nil
+					},
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NullVal(cty.String),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("defaultfunc"),
+			}),
+		},
+		{
+			Name: "test default required",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Required: true,
+					DefaultFunc: func() (interface{}, error) {
+						return "defaultfunc", nil
+					},
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NullVal(cty.String),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("defaultfunc"),
+			}),
+		},
+		{
+			Name: "test incorrect type",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Required: true,
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NumberIntVal(3),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("3"),
+			}),
+		},
+		{
+			Name: "test incorrect default type",
+			Schema: map[string]*schema.Schema{
+				"foo": &schema.Schema{
+					Type:     schema.TypeString,
+					Required: true,
+					Default:  true,
+				},
+			},
+			ConfigVal: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NullVal(cty.String),
+			}),
+			ExpectConfig: cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.StringVal("true"),
+			}),
+		},
+	} {
+		t.Run(tc.Name, func(t *testing.T) {
+			server := &GRPCProviderServer{
+				provider: &schema.Provider{
+					Schema: tc.Schema,
+				},
+			}
+
+			block := schema.InternalMap(tc.Schema).CoreConfigSchema()
+
+			rawConfig, err := msgpack.Marshal(tc.ConfigVal, block.ImpliedType())
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			testReq := &proto.PrepareProviderConfig_Request{
+				Config: &proto.DynamicValue{
+					Msgpack: rawConfig,
+				},
+			}
+
+			resp, err := server.PrepareProviderConfig(nil, testReq)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if tc.ExpectError == "" && len(resp.Diagnostics) > 0 {
+				for _, d := range resp.Diagnostics {
+					if !strings.Contains(d.Summary, tc.ExpectError) {
+						t.Fatalf("Unexpected error: %s/%s", d.Summary, d.Detail)
+					}
+				}
+			}
+
+			val, err := msgpack.Unmarshal(resp.PreparedConfig.Msgpack, block.ImpliedType())
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if tc.ExpectConfig.GoString() != val.GoString() {
+				t.Fatalf("\nexpected: %#v\ngot: %#v", tc.ExpectConfig, val)
+			}
+		})
+	}
+}