Allow choosing OPA evaluator

This just creates the option to use OPA by
setting the EC_USE_OPA env variable. It will
return an emtpy.

https://issues.redhat.com/browse/EC-1044

cmd/validate/image.go

@@ -45,6 +45,7 @@ import (
 type imageValidationFunc func(context.Context, app.SnapshotComponent, *app.SnapshotSpec, policy.Policy, []evaluator.Evaluator, bool) (*output.Output, error)
 
 var newConftestEvaluator = evaluator.NewConftestEvaluator
+var newOPAEvaluator = evaluator.NewOPAEvaluator
 
 func validateImageCmd(validate imageValidationFunc) *cobra.Command {
 	data := struct {
@@ -318,7 +319,14 @@ func validateImageCmd(validate imageValidationFunc) *cobra.Command {
 					log.Debugf("policySource: %#v", policySource)
 				}
 
-				c, err := newConftestEvaluator(cmd.Context(), policySources, data.policy, sourceGroup)
+				var c evaluator.Evaluator
+				var err error
+				if utils.IsOpaEnabled() {
+					c, err = newOPAEvaluator()
+				} else {
+					c, err = newConftestEvaluator(cmd.Context(), policySources, data.policy, sourceGroup)
+				}
+
 				if err != nil {
 					log.Debug("Failed to initialize the conftest evaluator!")
 					return err

internal/evaluator/opa_evaluator.go

@@ -0,0 +1,49 @@
+// Copyright The Enterprise Contract Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package evaluator
+
+import (
+	"context"
+	"os"
+	"path"
+
+	"github.com/spf13/afero"
+)
+
+// not sure what the properties will be yet, so setting the minimum.
+type opaEvaluator struct {
+	workDir string
+	fs      afero.Fs
+}
+
+func NewOPAEvaluator() (Evaluator, error) {
+	return opaEvaluator{}, nil
+}
+
+func (o opaEvaluator) Evaluate(ctx context.Context, target EvaluationTarget) ([]Outcome, Data, error) {
+	return []Outcome{}, Data{}, nil
+}
+
+func (o opaEvaluator) Destroy() {
+	if o.workDir != "" && os.Getenv("EC_DEBUG") == "" {
+		_ = o.fs.RemoveAll(o.workDir)
+	}
+}
+
+func (o opaEvaluator) CapabilitiesPath() string {
+	return path.Join(o.workDir, "capabilities.json")
+}

internal/evaluator/opa_evaluator_test.go

@@ -0,0 +1,115 @@
+// Copyright The Enterprise Contract Contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package evaluator
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+)
+
+// TestNewOPAEvaluator tests the constructor NewOPAEvaluator.
+func TestNewOPAEvaluator(t *testing.T) {
+	evaluator, err := NewOPAEvaluator()
+	assert.NoError(t, err, "Expected no error from NewOPAEvaluator")
+	assert.Equal(t, evaluator, opaEvaluator{})
+}
+
+func TestEvaluate(t *testing.T) {
+	opaEval := opaEvaluator{}
+
+	outcomes, data, err := opaEval.Evaluate(context.Background(), EvaluationTarget{})
+	assert.NoError(t, err, "Expected no error from Evaluate")
+	assert.Equal(t, []Outcome{}, outcomes)
+	assert.Equal(t, data, Data{})
+}
+
+// Test Destroy method of opaEvaluator.
+func TestDestroy(t *testing.T) {
+	// Setup an in-memory filesystem
+	fs := afero.NewMemMapFs()
+	workDir := "/tmp/workdir"
+
+	// Define test cases
+	testCases := []struct {
+		name         string
+		workDir      string
+		EC_DEBUG     bool
+		expectRemove bool
+	}{
+		{
+			name:         "Empty workDir, EC_DEBUG not set",
+			workDir:      "",
+			EC_DEBUG:     false,
+			expectRemove: false,
+		},
+		{
+			name:         "Non-empty workDir, EC_DEBUG not set",
+			workDir:      workDir,
+			EC_DEBUG:     false,
+			expectRemove: true,
+		},
+		{
+			name:         "Non-empty workDir, EC_DEBUG set",
+			workDir:      workDir,
+			EC_DEBUG:     true,
+			expectRemove: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Set up the environment
+			if tc.workDir != "" {
+				err := fs.MkdirAll(tc.workDir, 0755)
+				assert.NoError(t, err, "Failed to create workDir in in-memory filesystem")
+			}
+
+			if tc.EC_DEBUG {
+				os.Setenv("EC_DEBUG", "true")
+			} else {
+				os.Unsetenv("EC_DEBUG")
+			}
+
+			// Initialize the evaluator
+			opaEval := opaEvaluator{
+				workDir: tc.workDir,
+				fs:      fs,
+			}
+
+			// Call Destroy
+			opaEval.Destroy()
+
+			// Verify the result
+			exists, err := afero.DirExists(fs, tc.workDir)
+			assert.NoError(t, err, "Error checking if workDir exists after Destroy")
+
+			if tc.expectRemove {
+				assert.False(t, exists, "workDir should be removed")
+			} else {
+				assert.True(t, exists, "workDir should not be removed")
+			}
+
+			// Clean up for next test
+			_ = fs.RemoveAll(tc.workDir)
+			os.Unsetenv("EC_DEBUG")
+		})
+	}
+}

internal/utils/helpers.go

@@ -98,6 +98,10 @@ func Experimental() bool {
 	return os.Getenv("EC_EXPERIMENTAL") == "1"
 }
 
+func IsOpaEnabled() bool {
+	return os.Getenv("EC_USE_OPA") == "1"
+}
+
 // detect if the string is json
 func IsJson(data string) bool {
 	var jsMsg json.RawMessage