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config: add yaml flag #3069

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merged 1 commit into from
May 8, 2024
Merged

config: add yaml flag #3069

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42 changes: 42 additions & 0 deletions config/yamlflag.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
package config

import (
"fmt"

"gopkg.in/yaml.v2"
)

type yamlFlag[T any] struct {
Ptr **T
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ouch :)
But I see why

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The usage looks like

type Config struct {
  OpenTelemetry *otel.Options `yaml:"open-telemetry"`
  ...
}
...
flag.Var(newYamlFlag(&cfg.OpenTelemetry), "open-telemetry", "OpenTelemetry configuration in YAML format, use flow-style for convenience")
...

if o.OpenTelemetry != nil {
...
}

The value is allocated when flag is set and stays nil when it is not, i.e. this allows to tell if flag was provided.

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Yes I saw it, all good :)

value string // only for Set
}

func newYamlFlag[T any](ptr **T) *yamlFlag[T] {
return &yamlFlag[T]{Ptr: ptr}
}

func (yf *yamlFlag[T]) Set(value string) error {
var opts T
if err := yaml.Unmarshal([]byte(value), &opts); err != nil {
return fmt.Errorf("failed to parse yaml: %w", err)
}
*yf.Ptr = &opts
yf.value = value
return nil
}

func (yf *yamlFlag[T]) UnmarshalYAML(unmarshal func(interface{}) error) error {
var opts T
if err := unmarshal(&opts); err != nil {
return err
}
*yf.Ptr = &opts
return nil
}

func (yf *yamlFlag[T]) String() string {
if yf == nil {
return ""
}
return yf.value
}
108 changes: 108 additions & 0 deletions config/yamlflag_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,108 @@
package config

import (
"testing"

"gopkg.in/yaml.v2"

"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)

type yamlFlagTestConfig struct {
Foo string
Bar []string
Baz int
Qux *yamlFlagTestConfig
}

func TestYamlFlag(t *testing.T) {
t.Run("set", func(t *testing.T) {
cfg := struct {
Field *yamlFlagTestConfig
}{}

f := newYamlFlag(&cfg.Field)
v := `{foo: hello, bar: [world, "1"], baz: 2, qux: {baz: 3}}`
err := f.Set(v)

require.NoError(t, err)
assert.Equal(t, "hello", cfg.Field.Foo)
assert.Equal(t, []string{"world", "1"}, cfg.Field.Bar)
assert.Equal(t, 2, cfg.Field.Baz)
assert.Equal(t, 3, cfg.Field.Qux.Baz)

assert.Equal(t, v, f.String())
})

t.Run("set empty", func(t *testing.T) {
cfg := struct {
Field *yamlFlagTestConfig
}{}

f := newYamlFlag(&cfg.Field)
err := f.Set("")

require.NoError(t, err)
assert.Equal(t, &yamlFlagTestConfig{}, cfg.Field)
assert.Equal(t, "", f.String())
})

t.Run("set empty object", func(t *testing.T) {
cfg := struct {
Field *yamlFlagTestConfig
}{}

f := newYamlFlag(&cfg.Field)
err := f.Set("{}")

require.NoError(t, err)
assert.Equal(t, &yamlFlagTestConfig{}, cfg.Field)
assert.Equal(t, "{}", f.String())
})

t.Run("set invalid yaml", func(t *testing.T) {
cfg := struct {
Field *yamlFlagTestConfig
}{}

f := newYamlFlag(&cfg.Field)
v := `This is not a valid YAML`
err := f.Set(v)

assert.Error(t, err)
})

t.Run("unmarshal YAML", func(t *testing.T) {
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cfg := struct {
Field *yamlFlagTestConfig
}{}

err := yaml.Unmarshal([]byte(`
field:
foo: hello
bar:
- world
- "1"
baz: 2
qux:
baz: 3
`), &cfg)

require.NoError(t, err)
assert.Equal(t, "hello", cfg.Field.Foo)
assert.Equal(t, []string{"world", "1"}, cfg.Field.Bar)
assert.Equal(t, 2, cfg.Field.Baz)
assert.Equal(t, 3, cfg.Field.Qux.Baz)
})

t.Run("unmarshal invalid YAML", func(t *testing.T) {
cfg := struct {
Field *yamlFlagTestConfig
}{}

err := yaml.Unmarshal([]byte(`This is not a valid YAML`), &cfg)

assert.Error(t, err)
})
}
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