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https://github.com/romshark/yamagiconf
The magic YAML configuration framework for Go
https://github.com/romshark/yamagiconf
config configuration go golang parser yaml yaml-configuration
Last synced: 14 days ago
JSON representation
The magic YAML configuration framework for Go
- Host: GitHub
- URL: https://github.com/romshark/yamagiconf
- Owner: romshark
- License: mit
- Created: 2024-05-09T13:25:53.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2024-10-16T00:22:44.000Z (24 days ago)
- Last Synced: 2024-10-17T11:52:41.101Z (23 days ago)
- Topics: config, configuration, go, golang, parser, yaml, yaml-configuration
- Language: Go
- Homepage:
- Size: 314 KB
- Stars: 16
- Watchers: 1
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# yamagiconf
The heavily opinionated **YA**ML **Magi**c **Conf**iguration framework for Go
keeps your configs simple and consistent
by being *more restrictive than your regular YAML parser* 🚷 allowing only a subset of YAML
and enforcing some restrictions to the target Go type.
If you hate [YAML](https://yaml.org/), and you're afraid of
[YAML documents from hell](https://ruudvanasseldonk.com/2023/01/11/the-yaml-document-from-hell),
and you can't stand complex, unexplorable and unintuitive configurations then yamagiconf is for you!
🪄 It's magic because it uses [reflect](https://pkg.go.dev/reflect) to find recursively all
values of types that implement `interface { Validate() error }` and calls them reporting
an error annotated with line and column in the YAML file if necessary.
## (anti-)Features
- Go restrictions:
- 🚫 Forbids recursive Go types.
- 🚫 Forbids the use of `any`, `int` & `uint` (unspecified width), and other types.
Only maps, slices, arrays and deterministic primitives are allowed.
- ❗️ Requires `yaml` struct tags on all exported fields.
- ❗️ Requires `env` struct tags to be POSIX-style.
- 🚫 Forbids the use of `env` struct tag on non-primitive fields.
Allows only floats, ints, strings, bool and types that implement the
[`encoding.TextUnmarshaler`](https://pkg.go.dev/encoding#TextUnmarshaler) interface.
- 🚫 Forbids the use of `env` on primitive fields implementing
the [`yaml.Unmarshaler`](https://pkg.go.dev/gopkg.in/yaml.v3#Unmarshaler) interface.
- 🚫 Forbids the use of `yaml` and `env` struct tags within implementations of
[`encoding.TextUnmarshaler`](https://pkg.go.dev/encoding#TextUnmarshaler) and/or
[`yaml.Unmarshaler`](https://pkg.go.dev/gopkg.in/yaml.v3#Unmarshaler).
- 🚫 Forbids the use of YAML struct tag option `"inline"` for non-embedded structs and
requires embedded structs to use option `"inline"`.
- YAML restrictions:
- 🚫 Forbids the use of `no`, `yes`, `on` and `off` for `bool`,
allows only `true` and `false`.
- 🚫 Forbids the use of `~`, `Null` and other variations, allows only `null` for nilables.
- 🚫 Forbids assigning `null` to non-nilables (which normally would assign zero value).
- 🚫 Forbids fields in the YAML file that aren't specified by the Go type.
- 🚫 Forbids the use of [YAML tags](https://yaml.org/spec/1.2.2/#3212-tags).
- 🚫 Forbids redeclaration of anchors.
- 🚫 Forbids unused anchors.
- 🚫 Forbids anchors with implicit `null` value (no value) like `foo: &bar`.
- ❗️ Requires fields specified in the configuration type to be present in the YAML file.
- 🚫 Forbids assigning non-string values to Go types that implement
the [`encoding.TextUnmarshaler`](https://pkg.go.dev/encoding#TextUnmarshaler) interface.
- 🚫 Forbids empty array items ([see rationale](#why-are-empty-array-items-forbidden)).
- 🚫 Forbids multi-document files.
- 🚫 Forbids [YAML merge keys](https://yaml.org/type/merge.html).
- Features:
- 🪄 If any type within your configuration struct implements the `Validate` interface,
then its validation method will be called using reflection
(doesn't apply to unexported fields which are invisible to `reflect`).
If it returns an error - the error will be reported.
Keeps your validation logic close to your configuration type definitions.
- Reports errors by `line:column` when possible.
- Supports [github.com/go-playground/validator](https://github.com/go-playground/validator)
validation struct tags.
- Implements `env` struct tags to overwrite fields from env vars if provided.
- Supports [`encoding.TextUnmarshaler`](https://pkg.go.dev/encoding#TextUnmarshaler)
and [`yaml.Unmarshaler`](https://pkg.go.dev/gopkg.in/yaml.v3#Unmarshaler)
(except for the root struct type).
- Supports `time.Duration`.
## Example
https://go.dev/play/p/PjV0aG7uIUH
```yaml
list:
- foo: valid
bar: valid
- foo: valid
bar: valid
map:
valid: valid
secret: 'this will be overwritten from env var SECRET'
required: 'this must not be empty'
```
```go
package main
import (
"fmt"
"github.com/romshark/yamagiconf"
)
type Config struct {
List []Struct `yaml:"list"`
Map map[ValidatedString]ValidatedString `yaml:"map"`
// Secret will be overwritten if env var SECRET is set.
Secret string `yaml:"secret" env:"SECRET"`
// See https://github.com/go-playground/validator
// for all available validation tags
Required string `yaml:"required" validate:"required"`
}
type Struct struct {
Foo string `yaml:"foo"`
Bar ValidatedString `yaml:"bar"`
}
// Validate will automatically be called by yamagiconf
func (v *Struct) Validate() error {
if v.Foo == "invalid" {
return fmt.Errorf("invalid foo")
}
if v.Bar == "invalid" {
return fmt.Errorf("invalid bar")
}
return nil
}
type ValidatedString string
// Validate will automatically be called by yamagiconf
func (v ValidatedString) Validate() error {
if v == "invalid" {
return fmt.Errorf("string is invalid")
}
return nil
}
func main() {
var c Config
if err := yamagiconf.LoadFile("./config.yaml", &c); err != nil {
fmt.Println("Whoops, something is wrong with your config!", err)
}
fmt.Printf("%#v\n", c)
}
```
## FAQ
###
### Why are empty array items forbidden?
Consider the following YAML array:
```yaml
array:
-
- ''
- ""
- x
```
Even though this YAML array works as expect with a Go array:
`[4]string{"", "", "", "x"}`, parsing the same YAML into a Go slice will result in
the empty item being ommited: `[]string{"", "", "x"}` which is counterintuitive.
Therefore, yamagiconf forbids empty array items in general to keep behavior
consistent and intuitive independent of the Go target type.