Refactor out backend code (#198)

* Refactor out backend code

Having the backend intermediate type for instantiating and using Client
adds complexity, code length, and unnecessary error paths.

This commit fully removes backend without breaking any existing
funcitonality.

Signed-off-by: Will Beason <willbeason@google.com>

* Fix lint errors

Signed-off-by: Will Beason <willbeason@google.com>

constraint/pkg/client/client.go

@@ -33,7 +33,7 @@ type templateEntry struct {
 }
 
 type Client struct {
-	backend *Backend
+	driver  drivers.Driver
 	targets map[string]handler.TargetHandler
 
 	// mtx guards access to both templates and constraints.
@@ -92,7 +92,7 @@ func (c *Client) AddData(ctx context.Context, data interface{}) (*types.Response
 		// paths passed to driver must be specific to the target to prevent key
 		// collisions.
 		driverPath := createDataPath(target, relPath)
-		err = c.backend.driver.PutData(ctx, driverPath, processedData)
+		err = c.driver.PutData(ctx, driverPath, processedData)
 		if err != nil {
 			errMap[target] = err
 
@@ -127,7 +127,7 @@ func (c *Client) RemoveData(ctx context.Context, data interface{}) (*types.Respo
 			continue
 		}
 
-		if _, err := c.backend.driver.DeleteData(ctx, createDataPath(target, relPath)); err != nil {
+		if _, err := c.driver.DeleteData(ctx, createDataPath(target, relPath)); err != nil {
 			errMap[target] = err
 			continue
 		}
@@ -307,11 +307,11 @@ func (c *Client) ValidateConstraintTemplate(templ *templates.ConstraintTemplate)
 	if _, _, err := c.ValidateConstraintTemplateBasic(templ); err != nil {
 		return err
 	}
-	if dr, ok := c.backend.driver.(*local.Driver); ok {
+	if dr, ok := c.driver.(*local.Driver); ok {
 		_, _, err := dr.ValidateConstraintTemplate(templ)
 		return err
 	}
-	return fmt.Errorf("driver %T is not supported", c.backend.driver)
+	return fmt.Errorf("driver %T is not supported", c.driver)
 }
 
 // AddTemplate adds the template source code to OPA and registers the CRD with the client for
@@ -334,7 +334,7 @@ func (c *Client) AddTemplate(templ *templates.ConstraintTemplate) (*types.Respon
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
 
-	if err = c.backend.driver.AddTemplate(templ); err != nil {
+	if err = c.driver.AddTemplate(templ); err != nil {
 		return resp, err
 	}
 	cpy := templ.DeepCopy()
@@ -380,7 +380,7 @@ func (c *Client) RemoveTemplate(ctx context.Context, templ *templates.Constraint
 		return resp, err
 	}
 
-	if err := c.backend.driver.RemoveTemplate(templ); err != nil {
+	if err := c.driver.RemoveTemplate(templ); err != nil {
 		return resp, err
 	}
 
@@ -392,7 +392,7 @@ func (c *Client) RemoveTemplate(ctx context.Context, templ *templates.Constraint
 	delete(c.constraints, artifacts.gk)
 	// Also clean up root path to avoid memory leaks
 	constraintRoot := createConstraintGKPath(artifacts.targetHandler.GetName(), artifacts.gk)
-	if _, err := c.backend.driver.DeleteData(ctx, constraintRoot); err != nil {
+	if _, err := c.driver.DeleteData(ctx, constraintRoot); err != nil {
 		return resp, err
 	}
 	delete(c.templates, artifacts.Key())
@@ -523,7 +523,7 @@ func (c *Client) AddConstraint(ctx context.Context, constraint *unstructured.Uns
 	if err := c.validateConstraint(constraint, false); err != nil {
 		return resp, err
 	}
-	if err := c.backend.driver.AddConstraint(ctx, constraint); err != nil {
+	if err := c.driver.AddConstraint(ctx, constraint); err != nil {
 		return resp, err
 	}
 	for _, target := range entry.Targets {
@@ -552,7 +552,7 @@ func (c *Client) removeConstraintNoLock(ctx context.Context, constraint *unstruc
 	if err != nil {
 		return resp, err
 	}
-	if err := c.backend.driver.RemoveConstraint(ctx, constraint); err != nil {
+	if err := c.driver.RemoveConstraint(ctx, constraint); err != nil {
 		return resp, err
 	}
 	for _, target := range entry.Targets {
@@ -623,7 +623,7 @@ func (c *Client) init() error {
 		}
 
 		builtinPath := fmt.Sprintf("%s.hooks_builtin", hooks)
-		err := c.backend.driver.PutModule(builtinPath, libBuiltin.String())
+		err := c.driver.PutModule(builtinPath, libBuiltin.String())
 		if err != nil {
 			return err
 		}
@@ -672,20 +672,20 @@ func (c *Client) init() error {
 				ErrCreatingClient, err)
 		}
 
-		err = c.backend.driver.PutModule(modulePath, string(src))
+		err = c.driver.PutModule(modulePath, string(src))
 		if err != nil {
 			return fmt.Errorf("%w: error %s from compiled source:\n%s",
 				ErrCreatingClient, err, src)
 		}
 	}
-	if d, ok := c.backend.driver.(*local.Driver); ok {
+	if d, ok := c.driver.(*local.Driver); ok {
 		var externs []string
 		for _, field := range c.AllowedDataFields {
 			externs = append(externs, fmt.Sprintf("data.%s", field))
 		}
 		d.SetExterns(externs)
 	} else {
-		return fmt.Errorf("%w: driver %T is not supported", ErrCreatingClient, c.backend.driver)
+		return fmt.Errorf("%w: driver %T is not supported", ErrCreatingClient, c.driver)
 	}
 	return nil
 }
@@ -712,7 +712,7 @@ TargetLoop:
 			continue
 		}
 		input := map[string]interface{}{"review": review}
-		resp, err := c.backend.driver.Query(ctx, fmt.Sprintf(`hooks["%s"].violation`, name), input, drivers.Tracing(cfg.enableTracing))
+		resp, err := c.driver.Query(ctx, fmt.Sprintf(`hooks["%s"].violation`, name), input, drivers.Tracing(cfg.enableTracing))
 		if err != nil {
 			errMap[name] = err
 			continue
@@ -745,7 +745,7 @@ func (c *Client) Audit(ctx context.Context, opts ...QueryOpt) (*types.Responses,
 TargetLoop:
 	for name, target := range c.targets {
 		// Short-circuiting question applies here as well
-		resp, err := c.backend.driver.Query(ctx, fmt.Sprintf(`hooks["%s"].audit`, name), nil, drivers.Tracing(cfg.enableTracing))
+		resp, err := c.driver.Query(ctx, fmt.Sprintf(`hooks["%s"].audit`, name), nil, drivers.Tracing(cfg.enableTracing))
 		if err != nil {
 			errMap[name] = err
 			continue
@@ -767,7 +767,7 @@ TargetLoop:
 
 // Dump dumps the state of OPA to aid in debugging.
 func (c *Client) Dump(ctx context.Context) (string, error) {
-	return c.backend.driver.Dump(ctx)
+	return c.driver.Dump(ctx)
 }
 
 // knownTargets returns a sorted list of currently-known target names.

constraint/pkg/client/client_addtemplate_bench_test.go

@@ -4,10 +4,8 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/open-policy-agent/frameworks/constraint/pkg/client"
-	"github.com/open-policy-agent/frameworks/constraint/pkg/client/drivers/local"
+	"github.com/open-policy-agent/frameworks/constraint/pkg/client/clienttest"
 	"github.com/open-policy-agent/frameworks/constraint/pkg/core/templates"
-	"github.com/open-policy-agent/frameworks/constraint/pkg/handler/handlertest"
 )
 
 var modules = []struct {
@@ -80,24 +78,13 @@ func BenchmarkClient_AddTemplate(b *testing.B) {
 
 					for i := 0; i < b.N; i++ {
 						b.StopTimer()
-						targets := client.Targets(&handlertest.Handler{})
 
-						d := local.New()
-
-						backend, err := client.NewBackend(client.Driver(d))
-						if err != nil {
-							b.Fatal(err)
-						}
-
-						c, err := backend.NewClient(targets)
-						if err != nil {
-							b.Fatal(err)
-						}
+						c := clienttest.New(b)
 
 						b.StartTimer()
 
 						for _, ct := range cts {
-							_, err = c.AddTemplate(ct)
+							_, err := c.AddTemplate(ct)
 							if err != nil {
 								b.Fatal(err)
 							}