From 029a04c37d11126d182a46ba5d020de118b5442a Mon Sep 17 00:00:00 2001
From: Evan Lezar <elezar@nvidia.com>
Date: Thu, 24 Nov 2022 14:29:18 +0100
Subject: [PATCH] Use blank device hostPath if same as Path

The HostPath field was added in the v0.5.0 CDI specification.
The cdi package uses strict unmarshalling when loading specs
from file causing failures for unexpected fields.

Since the behaviour for HostPath == "" and HostPath == Path are
equivalent, we clear HostPath if it is equal to Path to ensure
compatibility with the widest range of specs.

This allows, for example, a v0.4.0 spec to be generated as required.

Signed-off-by: Evan Lezar <elezar@nvidia.com>
---
 internal/edits/device.go      | 11 +++++-
 internal/edits/device_test.go | 69 +++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 internal/edits/device_test.go

diff --git a/internal/edits/device.go b/internal/edits/device.go
index 8f5418de..72e6b06e 100644
--- a/internal/edits/device.go
+++ b/internal/edits/device.go
@@ -42,8 +42,17 @@ func (d device) toEdits() (*cdi.ContainerEdits, error) {
 // toSpec converts a discovered Device to a CDI Spec Device. Note
 // that missing info is filled in when edits are applied by querying the Device node.
 func (d device) toSpec() (*specs.DeviceNode, error) {
+	// The HostPath field was added in the v0.5.0 CDI specification.
+	// The cdi package uses strict unmarshalling when loading specs from file causing failures for
+	// unexpected fields.
+	// Since the behaviour for HostPath == "" and HostPath == Path are equivalent, we clear HostPath
+	// if it is equal to Path to ensure compatibility with the widest range of specs.
+	hostPath := d.HostPath
+	if hostPath == d.Path {
+		hostPath = ""
+	}
 	s := specs.DeviceNode{
-		HostPath: d.HostPath,
+		HostPath: hostPath,
 		Path:     d.Path,
 	}
 
diff --git a/internal/edits/device_test.go b/internal/edits/device_test.go
new file mode 100644
index 00000000..44c35098
--- /dev/null
+++ b/internal/edits/device_test.go
@@ -0,0 +1,69 @@
+/**
+# Copyright (c) NVIDIA CORPORATION.  All rights reserved.
+#
+# 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 edits
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/discover"
+	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDeviceToSpec(t *testing.T) {
+	testCases := []struct {
+		device   discover.Device
+		expected *specs.DeviceNode
+	}{
+		{
+			device: discover.Device{
+				Path: "/foo",
+			},
+			expected: &specs.DeviceNode{
+				Path: "/foo",
+			},
+		},
+		{
+			device: discover.Device{
+				Path:     "/foo",
+				HostPath: "/foo",
+			},
+			expected: &specs.DeviceNode{
+				Path: "/foo",
+			},
+		},
+		{
+			device: discover.Device{
+				Path:     "/foo",
+				HostPath: "/not/foo",
+			},
+			expected: &specs.DeviceNode{
+				Path:     "/foo",
+				HostPath: "/not/foo",
+			},
+		},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			spec, err := device(tc.device).toSpec()
+			require.NoError(t, err)
+			require.EqualValues(t, tc.expected, spec)
+		})
+	}
+}