Change backend.ValidateConfig to PrepareConfig

This mirrors the change made for providers, so that default values can
be inserted into the config by the backend implementation. This is only
the interface and method name changes, it does not yet add any default
values.

backend/atlas/backend.go

@@ -12,7 +12,6 @@ import (
 
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/configs/configschema"
-	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/state/remote"
 	"github.com/hashicorp/terraform/terraform"
@@ -43,9 +42,6 @@ type Backend struct {
 	// stateClient is the legacy state client, setup in Configure
 	stateClient *stateClient
 
-	// schema is the schema for configuration, set by init
-	schema *schema.Backend
-
 	// opLock locks operations
 	opLock sync.Mutex
 }
@@ -79,7 +75,7 @@ func (b *Backend) ConfigSchema() *configschema.Block {
 	}
 }
 
-func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Backend) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 
 	name := obj.GetAttr("name").AsString()
@@ -105,7 +101,7 @@ func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		}
 	}
 
-	return diags
+	return obj, diags
 }
 
 func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
@@ -116,7 +112,7 @@ func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
 		RunId: os.Getenv("ATLAS_RUN_ID"),
 	}
 
-	name := obj.GetAttr("name").AsString() // assumed valid due to ValidateConfig method
+	name := obj.GetAttr("name").AsString() // assumed valid due to PrepareConfig method
 	slashIdx := strings.Index(name, "/")
 	client.User = name[:slashIdx]
 	client.Name = name[slashIdx+1:]
@@ -139,7 +135,7 @@ func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
 		addr := v.AsString()
 		addrURL, err := url.Parse(addr)
 		if err != nil {
-			// We already validated the URL in ValidateConfig, so this shouldn't happen
+			// We already validated the URL in PrepareConfig, so this shouldn't happen
 			panic(err)
 		}
 		client.Server = addr

backend/backend.go

@@ -59,9 +59,10 @@ type Backend interface {
 	// be safely used before configuring.
 	ConfigSchema() *configschema.Block
 
-	// ValidateConfig checks the validity of the values in the given
+	// PrepareConfig checks the validity of the values in the given
-	// configuration, assuming that its structure has already been validated
+	// configuration, and inserts any missing defaults, assuming that its
-	// per the schema returned by ConfigSchema.
+	// structure has already been validated per the schema returned by
+	// ConfigSchema.
 	//
 	// This method does not have any side-effects for the backend and can
 	// be safely used before configuring. It also does not consult any
@@ -76,14 +77,14 @@ type Backend interface {
 	// as tfdiags.AttributeValue, and so the caller should provide the
 	// necessary context via the diags.InConfigBody method before returning
 	// diagnostics to the user.
-	ValidateConfig(cty.Value) tfdiags.Diagnostics
+	PrepareConfig(cty.Value) (cty.Value, tfdiags.Diagnostics)
 
 	// Configure uses the provided configuration to set configuration fields
 	// within the backend.
 	//
 	// The given configuration is assumed to have already been validated
 	// against the schema returned by ConfigSchema and passed validation
-	// via ValidateConfig.
+	// via PrepareConfig.
 	//
 	// This method may be called only once per backend instance, and must be
 	// called before all other methods except where otherwise stated.

backend/init/deprecate_test.go

@@ -14,7 +14,7 @@ func TestDeprecateBackend(t *testing.T) {
 		deprecateMessage,
 	)
 
-	diags := deprecatedBackend.ValidateConfig(cty.EmptyObjectVal)
+	_, diags := deprecatedBackend.PrepareConfig(cty.EmptyObjectVal)
 	if len(diags) != 1 {
 		t.Errorf("got %d diagnostics; want 1", len(diags))
 		for _, diag := range diags {

backend/init/init.go

@@ -108,11 +108,11 @@ type deprecatedBackendShim struct {
 	Message string
 }
 
-// ValidateConfig delegates to the wrapped backend to validate its config
+// PrepareConfig delegates to the wrapped backend to validate its config
 // and then appends shim's deprecation warning.
-func (b deprecatedBackendShim) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b deprecatedBackendShim) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
-	diags := b.Backend.ValidateConfig(obj)
+	newObj, diags := b.Backend.PrepareConfig(obj)
-	return diags.Append(tfdiags.SimpleWarning(b.Message))
+	return newObj, diags.Append(tfdiags.SimpleWarning(b.Message))
 }
 
 // DeprecateBackend can be used to wrap a backend to retrun a deprecation

backend/local/backend.go

@@ -139,9 +139,9 @@ func (b *Local) ConfigSchema() *configschema.Block {
 	}
 }
 
-func (b *Local) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Local) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	if b.Backend != nil {
-		return b.Backend.ValidateConfig(obj)
+		return b.Backend.PrepareConfig(obj)
 	}
 
 	var diags tfdiags.Diagnostics
@@ -170,7 +170,7 @@ func (b *Local) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		}
 	}
 
-	return diags
+	return obj, diags
 }
 
 func (b *Local) Configure(obj cty.Value) tfdiags.Diagnostics {

backend/nil.go

@@ -17,8 +17,8 @@ func (Nil) ConfigSchema() *configschema.Block {
 	return &configschema.Block{}
 }
 
-func (Nil) ValidateConfig(cty.Value) tfdiags.Diagnostics {
+func (Nil) PrepareConfig(v cty.Value) (cty.Value, tfdiags.Diagnostics) {
-	return nil
+	return v, nil
 }
 
 func (Nil) Configure(cty.Value) tfdiags.Diagnostics {

backend/remote-state/s3/backend_test.go

@@ -76,7 +76,7 @@ func TestBackendConfig_invalidKey(t *testing.T) {
 		"dynamodb_table": "dynamoTable",
 	})
 
-	diags := New().ValidateConfig(cfg)
+	_, diags := New().PrepareConfig(cfg)
 	if !diags.HasErrors() {
 		t.Fatal("expected config validation error")
 	}

backend/remote/backend.go

@@ -139,8 +139,8 @@ func (b *Remote) ConfigSchema() *configschema.Block {
 	}
 }
 
-// ValidateConfig implements backend.Enhanced.
+// PrepareConfig implements backend.Backend.
-func (b *Remote) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Remote) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 
 	if val := obj.GetAttr("organization"); val.IsNull() || val.AsString() == "" {
@@ -182,7 +182,7 @@ func (b *Remote) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		))
 	}
 
-	return diags
+	return obj, diags
 }
 
 // Configure implements backend.Enhanced.

backend/remote/backend_test.go

@@ -117,7 +117,7 @@ func TestRemote_config(t *testing.T) {
 		b := New(testDisco(s))
 
 		// Validate
-		valDiags := b.ValidateConfig(tc.config)
+		_, valDiags := b.PrepareConfig(tc.config)
 		if (valDiags.Err() != nil || tc.valErr != "") &&
 			(valDiags.Err() == nil || !strings.Contains(valDiags.Err().Error(), tc.valErr)) {
 			t.Fatalf("%s: unexpected validation result: %v", name, valDiags.Err())
@@ -196,7 +196,7 @@ func TestRemote_versionConstraints(t *testing.T) {
 		version.Version = tc.version
 
 		// Validate
-		valDiags := b.ValidateConfig(tc.config)
+		_, valDiags := b.PrepareConfig(tc.config)
 		if valDiags.HasErrors() {
 			t.Fatalf("%s: unexpected validation result: %v", name, valDiags.Err())
 		}

backend/remote/testing.go

@@ -97,10 +97,11 @@ func testBackend(t *testing.T, obj cty.Value) (*Remote, func()) {
 	b := New(testDisco(s))
 
 	// Configure the backend so the client is created.
-	valDiags := b.ValidateConfig(obj)
+	newObj, valDiags := b.PrepareConfig(obj)
 	if len(valDiags) != 0 {
 		t.Fatal(valDiags.ErrWithWarnings())
 	}
+	obj = newObj
 
 	confDiags := b.Configure(obj)
 	if len(confDiags) != 0 {

backend/testing.go

@@ -39,13 +39,15 @@ func TestBackendConfig(t *testing.T, b Backend, c hcl.Body) Backend {
 	obj, decDiags := hcldec.Decode(c, spec, nil)
 	diags = diags.Append(decDiags)
 
-	valDiags := b.ValidateConfig(obj)
+	newObj, valDiags := b.PrepareConfig(obj)
 	diags = diags.Append(valDiags.InConfigBody(c))
 
 	if len(diags) != 0 {
 		t.Fatal(diags.ErrWithWarnings())
 	}
 
+	obj = newObj
+
 	confDiags := b.Configure(obj)
 	if len(confDiags) != 0 {
 		confDiags = confDiags.InConfigBody(c)

builtin/providers/terraform/data_source_state.go

@@ -92,11 +92,12 @@ func dataSourceRemoteStateRead(d *cty.Value) (cty.Value, tfdiags.Diagnostics) {
 		return cty.NilVal, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return cty.NilVal, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	if configureDiags.HasErrors() {

command/init.go

@@ -446,6 +446,7 @@ func (c *InitCommand) initBackend(root *configs.Module, extraConfig rawFlags) (b
 		ConfigOverride: backendConfigOverride,
 		Init:           true,
 	}
+
 	back, backDiags := c.Backend(opts)
 	diags = diags.Append(backDiags)
 	return back, true, diags

command/meta_backend.go

@@ -180,11 +180,12 @@ func (m *Meta) BackendForPlan(settings plans.Backend) (backend.Enhanced, tfdiags
 		return nil, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags)
@@ -917,11 +918,13 @@ func (m *Meta) backend_C_r_S_unchanged(c *configs.Backend, cHash int, sMgr *stat
 	}
 
 	// Validate the config and then configure the backend
-	validDiags := b.ValidateConfig(configVal)
+	newVal, validDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validDiags)
 	if validDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
+
 	configDiags := b.Configure(configVal)
 	diags = diags.Append(configDiags)
 	if configDiags.HasErrors() {
@@ -1037,11 +1040,12 @@ func (m *Meta) backendInitFromConfig(c *configs.Backend) (backend.Backend, cty.V
 		}
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags.InConfigBody(c.Config))
 	if validateDiags.HasErrors() {
 		return nil, cty.NilVal, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags.InConfigBody(c.Config))
@@ -1067,11 +1071,12 @@ func (m *Meta) backendInitFromSaved(s *terraform.BackendState) (backend.Backend,
 		return nil, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags)

helper/schema/backend.go

@@ -49,9 +49,9 @@ func (b *Backend) ConfigSchema() *configschema.Block {
 	return b.CoreConfigSchema()
 }
 
-func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Backend) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	if b == nil {
-		return nil
+		return obj, nil
 	}
 
 	var diags tfdiags.Diagnostics
@@ -63,7 +63,7 @@ func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 	for _, err := range errs {
 		diags = diags.Append(err)
 	}
-	return diags
+	return obj, diags
 }
 
 func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {

helper/schema/backend_test.go

@@ -48,7 +48,7 @@ func TestBackendValidate(t *testing.T) {
 
 	for i, tc := range cases {
 		t.Run(fmt.Sprintf("%d-%s", i, tc.Name), func(t *testing.T) {
-			diags := tc.B.ValidateConfig(cty.ObjectVal(tc.Config))
+			_, diags := tc.B.PrepareConfig(cty.ObjectVal(tc.Config))
 			if diags.HasErrors() != tc.Err {
 				t.Errorf("wrong number of diagnostics")
 			}