feat(test): Enable inter-query cache (#1073)

This improves performance for some Rego policies, such as those that use
the http.send builtin. This is only enabled for the "conftest test"
comamnd to avoid introducing flaky unit tests with "conftest verify" due
to the caching.

Signed-off-by: James Alseth <[email protected]>

Author: jalseth

policy/engine.go

@@ -19,19 +19,21 @@ import (
 	"github.com/open-policy-agent/opa/storage"
 	"github.com/open-policy-agent/opa/storage/inmem"
 	"github.com/open-policy-agent/opa/topdown"
+	"github.com/open-policy-agent/opa/topdown/cache"
 	"github.com/open-policy-agent/opa/topdown/print"
 	"github.com/open-policy-agent/opa/version"
 )
 
 // Engine represents the policy engine.
 type Engine struct {
-	trace         bool
-	builtinErrors bool
-	modules       map[string]*ast.Module
-	compiler      *ast.Compiler
-	store         storage.Store
-	policies      map[string]string
-	docs          map[string]string
+	trace                 bool
+	builtinErrors         bool
+	modules               map[string]*ast.Module
+	compiler              *ast.Compiler
+	store                 storage.Store
+	policies              map[string]string
+	docs                  map[string]string
+	enableInterQueryCache bool
 }
 
 // CompilerOptions defines the options for the Rego compiler.
@@ -171,6 +173,10 @@ func (e *Engine) ShowBuiltinErrors() {
 	e.builtinErrors = true
 }
 
+func (e *Engine) EnableInterQueryCache() {
+	e.enableInterQueryCache = true
+}
+
 // Check executes all of the loaded policies against the input and returns the results.
 func (e *Engine) Check(ctx context.Context, configs map[string]interface{}, namespace string) (output.CheckResults, error) {
 	var checkResults output.CheckResults
@@ -454,6 +460,9 @@ func (e *Engine) query(ctx context.Context, input any, query string) (output.Que
 		rego.PrintHook(ph),
 		rego.BuiltinErrorList(builtInErrors),
 	}
+	if e.enableInterQueryCache {
+		options = append(options, rego.InterQueryBuiltinCache(cache.NewInterQueryCacheWithContext(ctx, nil)))
+	}
 
 	regoInstance := rego.New(options...)
 	resultSet, err := regoInstance.Eval(ctx)

runner/test.go

@@ -76,6 +76,7 @@ func (t *TestRunner) Run(ctx context.Context, fileList []string) (output.CheckRe
 	if err != nil {
 		return nil, fmt.Errorf("load: %w", err)
 	}
+	engine.EnableInterQueryCache()
 
 	if t.Trace {
 		engine.EnableTracing()