fixed panic in path validation (issue #264) (#266)

Co-authored-by: Samuel Monderer <samuelmo@radware.com>

openapi3/paths.go

@@ -16,6 +16,11 @@ func (paths Paths) Validate(c context.Context) error {
 			return fmt.Errorf("path %q does not start with a forward slash (/)", path)
 		}
 
+		if pathItem == nil {
+			paths[path] = &PathItem{}
+			pathItem = paths[path]
+		}
+
 		normalizedPath, pathParamsCount := normalizeTemplatedPath(path)
 		if oldPath, ok := normalizedPaths[normalizedPath]; ok {
 			return fmt.Errorf("conflicting paths %q and %q", path, oldPath)

openapi3/paths_test.go

@@ -0,0 +1,28 @@
+package openapi3
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var emptyPathSpec = `
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+servers:
+  - url: http://petstore.swagger.io/v1
+paths:
+  /pets:
+`
+
+func TestPathValidate(t *testing.T) {
+	swagger, err := NewSwaggerLoader().LoadSwaggerFromData([]byte(emptyPathSpec))
+	require.NoError(t, err)
+	err = swagger.Paths.Validate(context.Background())
+	require.NoError(t, err)
+}