pkg/cdi: split out Spec JSON Schema validation.

Don't forcibly pull in the Spec JSON Schema validation
bits, since the external package we depend on for that
is huge. For instance in cmd/cdi it results in a size
increase of cc. 3000 kB.

We neither want nor can force such a penalty on anybody
who imports CDI. To avoid this, we split out the Schema-
validation glue code bits to a validate subpackage and
add an externally settable Spec validation function.

Using this new setup, simply importing pkg/cdi keeps the
offending bits at bay. Yet it allows a willing client to
enable automatic validation by JSON Schema using only a
few lines of code.

Signed-off-by: Krisztian Litkey <[email protected]>

Author: klihub

pkg/cdi/schema.go

@@ -35,6 +35,9 @@ var (
 		"0.2.0": {},
 		"0.3.0": {},
 	}
+
+	// Externally set CDI Spec validation function.
+	specValidator func(*cdi.Spec) error
 )
 
 // Spec represents a single CDI Spec. It is usually loaded from a
@@ -85,7 +88,7 @@ func ReadSpec(path string, priority int) (*Spec, error) {
 // priority. If Spec data validation fails NewSpec returns a nil
 // Spec and an error.
 func NewSpec(raw *cdi.Spec, path string, priority int) (*Spec, error) {
-	err := validateWithSchema(raw)
+	err := validateSpec(raw)
 	if err != nil {
 		return nil, err
 	}
@@ -188,3 +191,22 @@ func parseSpec(data []byte) (*cdi.Spec, error) {
 	}
 	return raw, nil
 }
+
+// SetSpecValidator sets a CDI Spec validator function. This function
+// is used for extra CDI Spec content validation whenever a Spec file
+// loaded (using ReadSpec() or NewSpec()) or written (Spec.Write()).
+func SetSpecValidator(fn func(*cdi.Spec) error) {
+	specValidator = fn
+}
+
+// validateSpec validates the Spec using the extneral validator.
+func validateSpec(raw *cdi.Spec) error {
+	if specValidator == nil {
+		return nil
+	}
+	err := specValidator(raw)
+	if err != nil {
+		return errors.Wrap(err, "Spec validation failed")
+	}
+	return nil
+}

pkg/cdi/spec.go

@@ -0,0 +1,58 @@
+/*
+   Copyright © 2022 The CDI Authors
+
+   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.
+*/
+
+package validate
+
+import (
+	"github.com/container-orchestrated-devices/container-device-interface/schema"
+	raw "github.com/container-orchestrated-devices/container-device-interface/specs-go"
+)
+
+const (
+	// DefaultExternalSchema is the default JSON schema to load for validation.
+	DefaultExternalSchema = "/etc/cdi/schema/schema.json"
+)
+
+// WithSchema returns a CDI Spec validator that uses the given Schema.
+func WithSchema(s *schema.Schema) func(*raw.Spec) error {
+	if s == nil {
+		return func(*raw.Spec) error {
+			return nil
+		}
+	}
+	return func(spec *raw.Spec) error {
+		return s.ValidateType(spec)
+	}
+}
+
+// WithNamedSchema loads the named JSON schema and returns a CDI Spec
+// validator for it. If loading the schema fails a dummy validator is
+// returned.
+func WithNamedSchema(name string) func(*raw.Spec) error {
+	s, _ := schema.Load(name)
+	return WithSchema(s)
+}
+
+// WithDefaultSchema returns a CDI Spec validator that uses the default
+// external JSON schema, or the default builtin one if the external one
+// fails to load.
+func WithDefaultSchema() func(*raw.Spec) error {
+	s, err := schema.Load(DefaultExternalSchema)
+	if err == nil {
+		return WithSchema(s)
+	}
+	return WithSchema(schema.BuiltinSchema())
+}