Make plugin-framework provider configuration code treat empty values like the SDK

.changelog/8798.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+provider: fixed the provider so it resumes ignoring empty strings set in the `provider` block
+```

google/fwtransport/framework_config.go

@@ -18,6 +18,7 @@ import (
 	"google.golang.org/grpc"
 
 	"github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/terraform-plugin-framework/attr"
 	"github.com/hashicorp/terraform-plugin-framework/diag"
 	"github.com/hashicorp/terraform-plugin-framework/types"
 	"github.com/hashicorp/terraform-plugin-log/tflog"
@@ -151,6 +152,15 @@ type FrameworkProviderConfig struct {
 // LoadAndValidateFramework handles the bulk of configuring the provider
 // it is pulled out so that we can manually call this from our testing provider as well
 func (p *FrameworkProviderConfig) LoadAndValidateFramework(ctx context.Context, data *fwmodels.ProviderModel, tfVersion string, diags *diag.Diagnostics, providerversion string) {
+
+	// Make the plugin framwork code behave like the SDK by ignoring zero values. This means re-setting zero values to null.
+	// This is added to fix https://github.com/hashicorp/terraform-provider-google/issues/14255 in a v4.x.x release
+	// TODO(SarahFrench) remove as part of https://github.com/hashicorp/terraform-provider-google/issues/14447 in 5.0.0
+	p.HandleZeroValues(ctx, data, diags)
+	if diags.HasError() {
+		return
+	}
+
 	// Set defaults if needed
 	p.HandleDefaults(ctx, data, diags)
 	if diags.HasError() {
@@ -295,6 +305,77 @@ func (p *FrameworkProviderConfig) LoadAndValidateFramework(ctx context.Context,
 	p.RequestBatcherIam = transport_tpg.NewRequestBatcher("IAM", ctx, batchingConfig)
 }
 
+// HandleZeroValues will make the plugin framework act like the SDK; zero value, particularly empty strings, are converted to null.
+// This causes the plugin framework to treat the field as unset, just like how the SDK ignores empty strings.
+func (p *FrameworkProviderConfig) HandleZeroValues(ctx context.Context, data *fwmodels.ProviderModel, diags *diag.Diagnostics) {
+
+	// Change empty strings to null values
+	if data.AccessToken.Equal(types.StringValue("")) {
+		data.AccessToken = types.StringNull()
+	}
+	if data.BillingProject.Equal(types.StringValue("")) {
+		data.BillingProject = types.StringNull()
+	}
+	if data.Credentials.Equal(types.StringValue("")) {
+		data.Credentials = types.StringNull()
+	}
+	if data.ImpersonateServiceAccount.Equal(types.StringValue("")) {
+		data.ImpersonateServiceAccount = types.StringNull()
+	}
+	if data.Project.Equal(types.StringValue("")) {
+		data.Project = types.StringNull()
+	}
+	if data.Region.Equal(types.StringValue("")) {
+		data.Region = types.StringNull()
+	}
+	if data.RequestReason.Equal(types.StringValue("")) {
+		data.RequestReason = types.StringNull()
+	}
+	if data.RequestTimeout.Equal(types.StringValue("")) {
+		data.RequestTimeout = types.StringNull()
+	}
+	if data.Zone.Equal(types.StringValue("")) {
+		data.Zone = types.StringNull()
+	}
+
+	// Change lists that aren't null or unknown with length of zero to null lists
+	if !data.Scopes.IsNull() && !data.Scopes.IsUnknown() && (len(data.Scopes.Elements()) == 0) {
+		data.Scopes = types.ListNull(types.StringType)
+	}
+	if !data.ImpersonateServiceAccountDelegates.IsNull() && !data.ImpersonateServiceAccountDelegates.IsUnknown() && (len(data.ImpersonateServiceAccountDelegates.Elements()) == 0) {
+		data.ImpersonateServiceAccountDelegates = types.ListNull(types.StringType)
+	}
+
+	// Batching implementation will change in future, but this code will be removed in 5.0.0 so may be unaffected
+	if !data.Batching.IsNull() && !data.Batching.IsUnknown() && (len(data.Batching.Elements()) > 0) {
+		var pbConfigs []fwmodels.ProviderBatching
+		d := data.Batching.ElementsAs(ctx, &pbConfigs, true)
+		diags.Append(d...)
+		if diags.HasError() {
+			return
+		}
+		if pbConfigs[0].SendAfter.Equal(types.StringValue("")) {
+			pbConfigs[0].SendAfter = types.StringNull() // Convert empty string to null
+		}
+		b, _ := types.ObjectValue(
+			map[string]attr.Type{
+				"enable_batching": types.BoolType,
+				"send_after":      types.StringType,
+			},
+			map[string]attr.Value{
+				"enable_batching": pbConfigs[0].EnableBatching,
+				"send_after":      pbConfigs[0].SendAfter,
+			},
+		)
+		newBatching, d := types.ListValue(types.ObjectType{}.WithAttributeTypes(fwmodels.ProviderBatchingAttributes), []attr.Value{b})
+		diags.Append(d...)
+		if diags.HasError() {
+			return
+		}
+		data.Batching = newBatching
+	}
+}
+
 // HandleDefaults will handle all the defaults necessary in the provider
 func (p *FrameworkProviderConfig) HandleDefaults(ctx context.Context, data *fwmodels.ProviderModel, diags *diag.Diagnostics) {
 	if data.AccessToken.IsNull() && data.Credentials.IsNull() {