gopherpolicy: remove explicit YAML dependency

gopherpolicy/pkg.go

@@ -28,13 +28,13 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"strings"
 	"time"
 
 	policy "github.com/databus23/goslo.policy"
 	"github.com/gophercloud/gophercloud/v2"
 	"github.com/gophercloud/gophercloud/v2/openstack"
 	"github.com/gophercloud/gophercloud/v2/openstack/identity/v3/tokens"
-	"gopkg.in/yaml.v2"
 
 	"github.com/sapcc/go-bits/logg"
 )
@@ -72,13 +72,28 @@ type TokenValidator struct {
 }
 
 // LoadPolicyFile creates v.Enforcer from the given policy file.
-func (v *TokenValidator) LoadPolicyFile(path string) error {
+//
+// The second argument must be set to `yaml.Unmarshal` if you want to support
+// policy.yaml files. This explicit dependency injection slot allows you to choose
+// whether to use gopkg.in/yaml.v2 or gopkg.in/yaml.v3 or anything else.
+//
+// If `yamlUnmarshal` is given as nil, `json.Unmarshal` from the standard
+// library will be used, so only policy.json files will be understood.
+func (v *TokenValidator) LoadPolicyFile(path string, yamlUnmarshal func(in []byte, out any) error) error {
+	unmarshal := yamlUnmarshal
+	if yamlUnmarshal == nil {
+		unmarshal = json.Unmarshal
+		if strings.HasSuffix(path, ".yaml") {
+			return fmt.Errorf("LoadPolicyFile cannot parse %s because YAML support is not available", path)
+		}
+	}
+
 	bytes, err := os.ReadFile(path)
 	if err != nil {
 		return err // no fmt.Errorf() necessary, errors from package os are already very descriptive
 	}
 	var rules map[string]string
-	err = yaml.Unmarshal(bytes, &rules)
+	err = unmarshal(bytes, &rules)
 	if err != nil {
 		return fmt.Errorf("while parsing structure of %s: %w", path, err)
 	}

liquidapi/liquidapi.go

@@ -84,6 +84,11 @@ type RunOpts struct {
 	// the Logic instance to supply configuration to it, before Init() is called.
 	TakesConfiguration bool
 
+	// If set, when the runtime loads its oslo.policy from $LIQUID_POLICY_PATH,
+	// YAML will be supported in addition to JSON. This is an explicit dependency
+	// injection slot to allow the caller to choose their YAML library.
+	YAMLUnmarshal func(in []byte, out any) error
+
 	// How often the runtime will call BuildServiceInfo() to refresh the
 	// ServiceInfo of the liquid. The zero value can be used for liquids with
 	// static ServiceInfo; no polling will be performed then.
@@ -177,7 +182,7 @@ func Run(ctx context.Context, logic Logic, opts RunOpts) error {
 	if err != nil {
 		return err
 	}
-	err = tv.LoadPolicyFile(policyPath)
+	err = tv.LoadPolicyFile(policyPath, opts.YAMLUnmarshal)
 	if err != nil {
 		return err
 	}