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feat: implement xyaml.UnmarshalStrict
Works like a normal `yaml.Unmarshal`, but also verifies that there are no extra fields in the provided YAML data, and provides a meaningful error back. Signed-off-by: Artem Chernyshev <[email protected]>
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6 files changed

+293
-2
lines changed

‎go.mod

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2,10 +2,12 @@ module github.com/siderolabs/gen
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go 1.24.0
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require github.com/stretchr/testify v1.9.0
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require (
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github.com/stretchr/testify v1.9.0
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gopkg.in/yaml.v3 v3.0.1
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)
69

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require (
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github.com/davecgh/go-spew v1.1.1 // indirect
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github.com/pmezard/go-difflib v1.0.0 // indirect
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gopkg.in/yaml.v3 v3.0.1 // indirect
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)

‎xyaml/testdata/invalid-nested.yaml

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@@ -0,0 +1,7 @@
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---
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field: a
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slice:
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- field: b
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this: shouldn't be there
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map:
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some: value

‎xyaml/testdata/invalid.yaml

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@@ -0,0 +1,3 @@
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---
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field: hi
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g: bye

‎xyaml/testdata/valid.yaml

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@@ -0,0 +1,6 @@
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---
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field: a
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slice:
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- field: b
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map:
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some: value

‎xyaml/xyaml.go

Lines changed: 200 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,200 @@
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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// Package xyaml contains utility functions for parsing YAML.
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package xyaml
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import (
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"errors"
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"fmt"
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"reflect"
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"strings"
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"gopkg.in/yaml.v3"
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)
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// UnmarshalStrict decodes YAML document validating that there are no extra fields found.
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func UnmarshalStrict[T any](data []byte, t T) error {
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var node yaml.Node
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if err := yaml.Unmarshal(data, &node); err != nil {
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return err
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}
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if err := checkUnknownKeys(t, &node); err != nil {
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return err
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}
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return node.Decode(t)
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}
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func checkUnknownKeys(t any, node *yaml.Node) error {
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if node.Kind == yaml.DocumentNode {
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if len(node.Content) == 0 {
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return nil
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}
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node = node.Content[0]
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}
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unknown, err := internalCheckUnknownKeys(reflect.TypeOf(t), node)
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if err != nil {
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return err
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}
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if unknown != nil {
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var data []byte
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if data, err = yaml.Marshal(unknown); err != nil {
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return fmt.Errorf("failed to marshal error summary %w", err)
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}
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return fmt.Errorf("unknown keys found during decoding:\n%s", string(data))
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}
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return nil
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}
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// structKeys builds a set of known YAML fields by name and their indexes in the struct.
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//
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//nolint:gocyclo
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func structKeys(typ reflect.Type) (map[string][]int, reflect.Type) {
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fields := reflect.VisibleFields(typ)
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availableKeys := make(map[string][]int, len(fields))
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for _, field := range fields {
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if tag := field.Tag.Get("yaml"); tag != "" {
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if tag == "-" {
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continue
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}
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idx := strings.IndexByte(tag, ',')
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inlined := false
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if idx >= 0 {
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options := strings.Split(tag[idx+1:], ",")
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for _, opt := range options {
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if opt == "inline" {
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inlined = true
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}
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}
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}
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// handle inlined `map` objects, inlining structs in general is not supported yet
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if inlined {
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inlinedTyp := field.Type
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if inlinedTyp.Kind() == reflect.Map {
92+
return nil, inlinedTyp
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}
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}
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if idx == -1 {
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availableKeys[tag] = field.Index
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} else if idx > 0 {
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availableKeys[tag[:idx]] = field.Index
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}
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} else {
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availableKeys[strings.ToLower(field.Name)] = field.Index
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}
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}
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return availableKeys, typ
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}
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var typeOfInterfaceAny = reflect.TypeOf((*any)(nil)).Elem()
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//nolint:gocyclo,cyclop
112+
func internalCheckUnknownKeys(typ reflect.Type, spec *yaml.Node) (unknown any, err error) {
113+
for typ.Kind() == reflect.Ptr {
114+
typ = typ.Elem()
115+
}
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// anything can be unmarshaled into `interface{}`
118+
if typ == typeOfInterfaceAny {
119+
return nil, nil
120+
}
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122+
switch spec.Kind { //nolint:exhaustive // not checking for scalar types
123+
case yaml.MappingNode:
124+
var availableKeys map[string][]int
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switch typ.Kind() { //nolint:exhaustive
127+
case reflect.Map:
128+
// any key is fine in the map
129+
case reflect.Struct:
130+
availableKeys, typ = structKeys(typ)
131+
default:
132+
return unknown, fmt.Errorf("unexpected type for yaml mapping: %s", typ)
133+
}
134+
135+
for i := 0; i < len(spec.Content); i += 2 {
136+
keyNode := spec.Content[i]
137+
138+
if keyNode.Kind != yaml.ScalarNode {
139+
return unknown, errors.New("unexpected mapping key type")
140+
}
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key := keyNode.Value
143+
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var elemType reflect.Type
145+
146+
switch typ.Kind() { //nolint:exhaustive
147+
case reflect.Struct:
148+
fieldIndex, ok := availableKeys[key]
149+
if !ok {
150+
if unknown == nil {
151+
unknown = map[string]any{}
152+
}
153+
154+
unknown.(map[string]any)[key] = spec.Content[i+1]
155+
156+
continue
157+
}
158+
159+
elemType = typ.FieldByIndex(fieldIndex).Type
160+
case reflect.Map:
161+
elemType = typ.Elem()
162+
}
163+
164+
// validate nested values
165+
innerUnknown, err := internalCheckUnknownKeys(elemType, spec.Content[i+1])
166+
if err != nil {
167+
return unknown, err
168+
}
169+
170+
if innerUnknown != nil {
171+
if unknown == nil {
172+
unknown = map[string]any{}
173+
}
174+
175+
unknown.(map[string]any)[key] = innerUnknown
176+
}
177+
}
178+
case yaml.SequenceNode:
179+
if typ.Kind() != reflect.Slice {
180+
return unknown, fmt.Errorf("unexpected type for yaml sequence: %s", typ)
181+
}
182+
183+
for i := range len(spec.Content) {
184+
innerUnknown, err := internalCheckUnknownKeys(typ.Elem(), spec.Content[i])
185+
if err != nil {
186+
return unknown, err
187+
}
188+
189+
if innerUnknown != nil {
190+
if unknown == nil {
191+
unknown = []any{}
192+
}
193+
194+
unknown = append(unknown.([]any), innerUnknown)
195+
}
196+
}
197+
}
198+
199+
return unknown, nil
200+
}

‎xyaml/xyaml_test.go

Lines changed: 73 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
1+
// This Source Code Form is subject to the terms of the Mozilla Public
2+
// License, v. 2.0. If a copy of the MPL was not distributed with this
3+
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
4+
5+
package xyaml_test
6+
7+
import (
8+
_ "embed"
9+
"testing"
10+
11+
"github.com/siderolabs/gen/xyaml"
12+
"github.com/stretchr/testify/require"
13+
)
14+
15+
type A struct {
16+
Field string `yaml:"field"`
17+
Map map[string]string `yaml:"map"`
18+
Slice []A `yaml:"slice"`
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}
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//go:embed testdata/valid.yaml
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var valid []byte
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24+
//go:embed testdata/invalid.yaml
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var invalid []byte
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27+
//go:embed testdata/invalid-nested.yaml
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var invalidNested []byte
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30+
func TestUnmarshalStrict(t *testing.T) {
31+
for _, tt := range []struct {
32+
name string
33+
err string
34+
data []byte
35+
}{
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{
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name: "valid",
38+
data: valid,
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},
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{
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name: "invalid",
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data: invalid,
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err: "unknown keys",
44+
},
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{
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name: "invalid nested",
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data: invalidNested,
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err: "this",
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},
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{
51+
name: "empty",
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data: []byte{},
53+
},
54+
} {
55+
t.Run(tt.name, func(t *testing.T) {
56+
var a A
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58+
err := xyaml.UnmarshalStrict(tt.data, &a)
59+
60+
if tt.err != "" {
61+
require.ErrorContains(t, err, tt.err)
62+
63+
return
64+
}
65+
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if len(tt.data) != 0 {
67+
require.NotEmpty(t, a)
68+
}
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require.NoError(t, err)
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})
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}
73+
}

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